WO2014153265A1

WO2014153265A1 - Spectrum analysis of coronary artery turbulent blood flow

Info

Publication number: WO2014153265A1
Application number: PCT/US2014/029833
Authority: WO
Inventors: Norman Lee OWSLEY; Roger Paul NORRIS; Ralph Walter ZAORSKI
Original assignee: PhonoFlow Medical, LLC
Priority date: 2013-03-18
Filing date: 2014-03-14
Publication date: 2014-09-25
Also published as: EP2976016A1; CA2907400A1; EP2976016A4

Abstract

Methods and apparatuses are described to obtain, cardiac data, which includes acquiring vibrational field cardiac data from a transducer wherein the transducer measures vibration over a surface of a human's body. An unwanted coronary event is separated from vibrational cardiac data. A transient event is extracted from the vibrational cardiac heart cycle data. The transient event occurs during a diastolic interval within a heart cycle. The transient event is evaluated for a condition of coronary artery blood flow turbulence and a condition of health of a coronary artery is assessed from a feature in the vibrational frequency power spectrum estimate.

Description

SPECTRUM ANALYSIS OF CORONARY ARTERY TURBULENT BLOOD FLOW

RELATED APPLICATIONS

[0001 J This application claims priority .from United States Non-Provisional

Patent Application titled "Spectrum Analysis Of Coronary Artery Turbulent Blood Flow," filed on March 18, 2013, Serial Number 13/815,961. United States Nort- PiOvisioiia Patent Application titled "Spectrum Analysts Of Coronary Artery Turbulent Blood Flow," filed on March 1 , 2013, Serial Number 13/815,961 is a continuation-in-part of United States Patent Application Serial No. 12/228,058 filed o« August 9, 2008.

BACKGROUND OF TEIE INVENTION 1· FIELD OF INVENTION

[0002J The invention relates generally to detecting and processing vibrational cardiac data, and more specifically to apparatuses and methods used to detect vibrational cardiac data related to coronary artery disease.

2. ART BACKGROUND

[00031 Coronary artery disease is a primary precursor of heart attacks, which is a leading cause of death i n the United States. Coronary artery disease is characterized by a deposition of plaque within the coronary arteries, resulting in a condition referred to as stenosis, in which case blood flow is restricted and the oxygen supply to the heart muscle is decreased. Such a deposition of plaque is also referred to as an occlusion. Coronary artery disease can result in heart attack and subsequent physical injury and possible death. This can present a problem.

[0004| It is known thai the blood Row can become turbulent as the blood passes through an area of stenosis. Turbulent blood flow provides a source of vibrational excitation within the body. The vibrational excitation causes energy to propagate through the body and provides a field that can be measured at the surface of the body. Normal body functions such as breathing and the opening and closing of the heart's valves provide high levels of background noise relati ve to the magnitude of the vibrational energy resulting from excitation at areas of stenosis. Such high levels of background noise can frustrate detection. This can present a problem.

(000SJ The body is made up of structures that have very different physical properties which, are distributed as a function of space throughout the body cavity. Some of these structures are lungs, ribs, organs, blood, arteries, fat, etc. These structures present a non-homogeneous media to the propagation of vibrational energy. Such a non-homogenous media can make it difficult to characterize the media sufficiently to f m: focused listening beams while processing the vibrational energy emitted f om the areas of stenosis during a parametric analysis that assumes a known vibrational wave speed. This can present a problem.

[0006] Currently, coronary artery disease is treated post symptomatically with an invasive procedure called an angiogram. The angiogram is costly, invasi ve, and places the patient at risk of injury due to complications that can arise during the procedure. All of this can present problems. BRIEF .DESCRIPTION OF THE .DRAWINGS

(0007) The invention may best be understood by referring to the following description and accompanying drawings that are used to illustrate embodiments of the invention. The invention is illustrated by way of example in the embodiments and is not limited in the figures of the accompanying drawings, in which like references indicate similar elements.

(0008| Figure A illustrates an apparatus, according to one embodiment of the invention.

(0009J Figure IB illustrates a block diagram of a computer system (data acquisition system) in which embodiments of the invention may be used.

[0010] Figure 2 illustrates a plot, representational of vibrational cardiac data as a function of time for two heart cycles, according to one embodiment of the invention.

(0011) Figure 3 illustrates a method for processing vibrational cardiac data, according to embodiments of the invention.

(0012) Figure 4 illustrates several channels of vibrational cardiac data, according to an embodiment of the invention,

(0013) Figure 5 illustrates master replica selection according to an embodiment of the invention.

{0014) Figure 6 illustrates, in one embodiment,, a correlation scan.

[0015) Figure 7 illustrates, in one embodiment, assembling multiple heart cycles.

10 16) Figure 8 illustrates, in one embodiment, diastolic intervals selected for further processing. |0 17J Figure 9 illustrates a two-dimensional space-time frequency power spectrum (orthogonal vibration mode decomposition of the cross-channel power spectral density matrix "CSDM") of vibrational cardiac data, according to one embodiment of the invention.

(^'0018| Figure 10 illustrates a two-dimensional space-time frequency power spectrum processed for Equivalent Rectangular Bandwidth, according to one embodiment of the invention.

(001 | Figure 11 illustrates a phantom constructed to simulate b!ood flow through an area of stenosis, according to one embodiment of the invention.

(0020) Figure 12 illustrates detection of stenosis in a phantom, according to embodiments of the invention.

[0021) Figure 13 illustrates an Equivalent Rectangular bandwidth (ERB) display of vibrational energy resulting from fluid flow with occluder present in a phantom (area of stenosis), according to one embodiment of the invention,

[0022) Figure 14 illustrates an Equivalent Rectangular bandwidth (ERB) estimate of vibrational energy resulting from fluid flow without occluder in a phantom (healthy condition without stenosis), according to one embodiment of the invention.

(0023) Figure 15 illustrates an apparatus according to embodiments of the invention.

(0024) Figure 16 illustrates a method to obtain vibrational cardiac data according embodiments of the invention.

[0025) Figure 17 illustrates time series plots of vibrational cardiac data, according to embodiments of the invention. [0026) Figure 18 illustrates another set of time series plots of vibrational cardiac data collected from a human whose coronary arteries are in a healthy condition, according to embodiments of the invention.

{0027 j Figure 19 illustrates vibrational frequency power spectra estimates corresponding to a time slot 181 shown in Figure 18, according to embodiments of the invention.

(0028) Figure 20 illustrates a method for averaging vibrational frequency cardiac data, according to embodiments of the invention.

(0029 j Figure 21 illustrates an overlay of space-time a veraged vibrational frequency power spectra estimates corresponding to data from Figure IS, according to embodiments of the invention.

(0030) Figure 22 illustrate a set of time series plots of vibrational cardiac data collected from a human with coronary artery disease, according to embodiments of the invention.

(00311 Figure 23 illustrates a set of vibrational frequency power spectra estimates corresponding to the time serie trora Figure 22, according to embodiments of the invention.

(0032] Figure 24 illustrates an overlay of vibrational frequency power spectra estimates from multiple slots corresponding to the human's data shown in Figure 22, according to embodiments of the invention.

(0033] Figure 25 illustrates a method for identifying a feature related to coronary artery blood flow turbulence using a single human, according to embodiments of the invention.

(0034] Figure 26 illustrates a comparison of vibrational cardiac data from muitipie humans, according to embodiments of the invention. j0 35j Figure 27 iliostraies a method for idcntifymg a feature related, to coronary artery blood flow turbulence using multiple humans, according to embodiments of the in ventioo..

[00361 DET AILED DESCRIPTION

[0037J In the following detailed description of embodiments of die invention, reference is made to the accompanying drawings m which tike references indicate similar elements,, and in which is shown by wa of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those of skill in the art to practice the invention.. In other instances, well-known circuits, structures, and techniques have not been shown in detail in order not to obscure the understanding of this description. The folio wing detailed description is, therefore, not to be taken in a limiting sense, and the scope of the invention is defined only by the appended claims.

[O038J Apparatuses and methods are described for detecting and processing vibrational cardiac data in a human. In one or more embodiments, the vibrational cardiac data arises from stenosis in a coronary artery. In one embodiment, vibrational cardiac data is measured and processed from a phantom with and without stenosis. (0039J Figure 1A illustrates an apparatus generally at 100, according to one embodiment of the invention. With reference to Figure 1A, a cross-section 1 12 of a human body contains coronary artery 102 ha ving a flow of blood 1 4 passing therethrough. The flow of blood 1 4 can interact with a coronary artery lesion 10B and cause an excitation of the artery wall by known physical means, which include transition to turbulent flow and the corresponding application of forces normal to the surface of the coronary artery. Such excitation of the coronary artery wall results in vibrational energy 110 propagating to the surface of the ^'human 1 1 1 .

|OO40J In this description of embodiments, the term "sensor" is synonymous with the terms "channel" or "sensor channel," whereby a separate measurement is contemplated. Additionally,, the term "sensor" is synonymous with the terms

'transducer" or ''sensing transducer;^' Thus, a first sensor's output (a first channel) and a second sensor's output (a second channel) are each available for analysis and each represents a separate measurement of a field quantity of interest, such as the vibration field in a human's body. As will be noted by those of skill in the art, in some instances, it might be advantageous to electrically combine together, in series or parallel, several sensors into a single channel. Such combinations can be made within the scope of the descriptions provided herein. However to simplify the discussion, "sensor" will be understood to be synonymous with the terms "sensor channel," "channel," "transducer," or "sensing transducer,"

[0041] An array of sensors 1 16 measures the vibration of the surface 1 1 and collects vibrational cardiac data thereby. The array of sensors ! 16 is made up of a genera! number of N sensors (sensing transducers or transducers), in one

embodiment, the number N equals 14 and the spacing between adjacent transducers is one-quarter inch (0.25"). ^"Those of skill in the art will recognize that the array of N sensors 1 16 can be configured wi th; a different number of sensors, a different sensor width, and or sensor spacing. The example given herein is provided merely for illustration and does not 1 im.it embodiments of the invention.

[0042] The cross section 1 1 2 of the human presents a non-homogeneous media through which the vibrational energy 1 10 propagates and contains various structures such as ribs, lungs, organs interfaces, muscles, fat, and skin tissue indicated generally by 1 14. The vibrational energy propagates through the non-homogeneous media and is measured on ⁽he surface 1 1 1 by the array of N sensors 1 16, in one embodiment, it can be desirable to place the array of sensors 1 1 ⁽> over a person's heart and above a space between adjacent ribs to facilitate detection of the vibrational energy.

[00431 iii one embodiment, each sensor of the array of sensors 1 16 is made from a strip of polyvinylidene fluoride (PVDF) film. In one example, each strip of PVDF film measures 0.75 inches long, between attachments to a chassis 122, and 0.1 875 inches wide. Each strip of PVDF film is stretched into a flat plane and is anchored at each end by the chassis 122. At the midpoint of each strip of PVDF film, a pad is placed to provide an area of contact between the skin surface 111 and the strip of PVDF film. An example of one such sensor from the array of sensors 1 16 is illustrated by a strip of PVDF film 130, having a first end 132 and a second end 134 ( which are attached to the chassis 122) and a pad 136 that makes contact with the skin surface l l ! . In one embodiment, the diameter of the pads is 0.1 875 inches and the thickness of the pads is 0.0625 inches. The sensitivity of the PVDF film along its major axis is 22176 V/uait strain for a PVDF film thickness of 0,028 millimeters. The PVDF film generates a voltage in response to strain imparted from the motion of the skin surface 1 1 1. in one embodiment, the chassis 1 2 is made out of metal such as aluminum, in other embodiments the chassis 122 is made out of plastic or another material sufficient to provide the necessary anchor points for the strips of PVDF film.

[0044] Each sensing transducer is in electrical contact: with at least one preamplifier 120 using connection 1 18, It is advantageous to place a preamplifier proximate to its sensing transduce!" in order to minimize the addition of electronic noise. Additional amplification stages can be used and in one embodiment the outputs from the preamplifiers 120 are passed to a bank of ampli fiers (not shown), such as those available from ithaco Corporation Model 451. In one embodiment, the outputs of the sensing transducers (army 1 16) are carried in a cable bundle 124 and are processed in a data acquisition system .126 that can contain a graphical user interface (GUI).

[00451 Those of skill in the art will appreciate that adjustments to the array geometry can be made, i.e., sensor dimensions and sensor spacing. Vibrational energy 1 10 includes shear wave energy propagation with shear wavelengths on the order of several tens of millimeters, e.g. approximately 40 millimeters at 200 cycles per second and approximately 20 millimeters at 500 cycles per second.

[0046J Figure IB illustrates, generally at 150, a block diagram of a computer system (data acquisition system) in which embodiments of the invention may be used. The block diagram is a high-level conceptual representation and may be implemented in a variety of ways and by various architectures. With reference to Figure IB, bus system 1 2 interconnects a Central Processing Unit (CPU) 164, Read Only Memory (ROM) 166, Random Access Memory (RAM) 168, storage 160, display 161 , audio 162, . keyboard 164, pointer 166, data acquisition unit (D.AU) 126, and

communications 170. The bus system 1 2 may be for example, one or more of such buses as a system bus, Peripheral Component interconnect (PCI), Advanced Graphics Port (AGP), Small Computer System Interface (SCSI), Institute of Electrical and Electronics Engineers (IEEE) standard number 1394 (FireVVire), Universal Serial Bus (USB), or a dedicated bus designed for a custom application, etc. The CPU 164 may be a single, multiple, or even a distributed computing resource. Storage 160 may be Compact Disc (CD), Digital Versatile Disk (DVD), hard disks (HD), optical disks, tape, flash, memory sticks, video recorders, etc. The computer system ISO can be used to recei ve vibrational cardiac data via 124 from the array 1 16 of vibration sensors (Figure 1A). Note that depending upon the actual implementation of a computer system, the computer system may include some, ail, more, or a

rearrangement of components in the block diagram,

[00471 Thus, in various embodiments, vibrational cardiac data is received at

124 for processing by the computer system 150, Such data can be transmitted via communications interface 170 for further processing and diagnosis in a remote location, as illustrated in Figure IB at 172, Connection with a network, such as an intranet or the Internet is obtained via 1 2, as is recognized by those of skill in the art, which enables the data processing device 150 to communicate with other data processing de vices in remote locations.

[0048] For example, embodiments of the invention can be implemented on a computer system 150 configured as a desktop computer or work station, on for example a WINDOWS* compatible computer running operating systems such as WINDOWS* XP Home or WINDOWS* XP Professional, Linux, etc. as well as computers from APPLE COMPUTER, Inc. running operating systems such as OS X, etc. Alternatively, or in conjunction with such an implementation, embodiments of the invention can be configured with devices such as speakers, earphones, video monitors, etc. configured for use with a Bluetooth communication channel.

J0049] Figure 2 illustrates, generally at 200, a plot of vibrational cardiac data as a function of time for two heart cycles, according to one embodiment of the invention. With reference to Figure 2, a representati ve output from, one of the vibration sensors, from array 116 (Figure 1 A) is illustrated, where a magnitude of the sensor^'s output is plotted on a vertical axis 204 as a function of time 202. A first heart cycle 206 contains a first peak 208 corresponding to the closure of the mitral and tricuspid valves. This first peak is described in the literature as a "lub" sound when heard through a stethoscope. The first heart cycle 206 contains a second peak at 210, which corresponds to the closure of the two semi-lunar, aortic and pulmonary vai ves at the beginning of diastolic period 212. This second peak is described in the literature as a "dub" sound when heard through a stethoscope. The diastolic period 212 follows the second peak 210.

(0050J The heart continues to beat, and a second heart cycle 226 is produced thereby with the same major features found in the first heart, cycle; a first peak at 228, followed by a second peak at 230, and a diastolic interval (Dl) 232. Successive heart cycles (not shown) will continue to occur as the heart continues to beat. During the diastolic intervals, 2 2, 232, etc., blood flow is at a maximum in the coronary arteries and unwanted coronary events, such as the first peaks 208, 228 and the second peaks 210, 230 are separated in time and their effect on the diastolic interval is at a minimum.

[0051 i in one embodiment, it is desirable to process vibrational cardiac data accumulated over approximately one hundred and twenty ( 120) heart cycles in order to provide a sufficiently long averaging time record length for an array of 14 channels. In practice, with human test subjects, it has been observed that the hitman test subjects can comfortably breath-hold for approximately twenty (20) heart cycles, in this case, a human test subject will alternate between breath-hold and normal breathing, for breath recovery, while the heart waveform is measured, Jn one embodiment, a nominal duration of the entire heart waveform is .from one h undred and twenty (120) to one hundred and eighty ( 1 0) seconds and is made up of six (6) twenty (20) to thirt (30) second segments. In another embodiment, a number of heart cycles is approximately equal to ten (10) to fifteen (35) tunes the number of sensor channels in array N. Such a number of heart cycles is needed to adequately resolve the numerically higher eigenvalues as described below in sections of the following discussion. A shorter duration heart waveform (fewer heart cycles) can be collected if the eigen value range is limited accordingly . Those of skill in the art will appreciate that the entire heart waveform can vary in length and that the examples provided herein are given for illustration only and do not limit embodiments of the invention.

1_,00521 The number of heart cycles over which a human test subject can comfortably breath-hold will vary between human test subjects and will depend on many factors such as age, physical condition, etc. When vibrational cardiac data is collected during breath-hold, the effects of breathing on the measured vibrational cardiac data are minimized. The number of segments can be adjusted to suite the particular test conditions, given the length of time that the human test subject can breath-hold for and the number of sensor channels in the array N. In one embodiment, a human starts and stops the acquisition of the vibrational cardiac data to coincide with acquisition during breath-hold periods.

1_,00531 The M sensor array, described in Figure IA, is used to measure and process vibrational cardiac energy, which is measured at the surface 1 .1 1 during the diastolic intervals, in one embodiment, such measurement and processing of the vibrational cardiac energy is used to determine whether a plaque deposits) (coronary artery lesion(s)) 108 exists in the human due to coronary arter-' disease. In other embodiments, such processing can be used to detect vibrational energy generated within the human in genera! and not necessarily caused by coronary artery disease. (0054) Figure 3 illustrates, generally a 300, a method for processing vibrational cardiac data, according to embodiments of the in vention. The method is applied to vibrational cardiac data that is measured with art array of N sensing transducers, which are mounted on the surface of a human^'s body as described above in conjunction, with the previous figures. With reference to Figure 3, a method starts at a block 302.

[0055] For the purpose of extr cting diastolic intervals from their respective heart cycles, at a biock 304 a technician seiects a singie high quaiity channel from the arra of N sensing transducers. A high quaiity channel has a high signal ~to-noise ratio, wherein the sigaal-to-noise ratio i expressed as the ratio between the height of a first peak of a heart cycle and the background level during the diastolic interval and the height of a second peak of the heart cycle and background level of the vibrational cardiac data. The selection of a high quaiity channel can be performed by a technician or it can be automated in a selection algorithm that would be performed by a data processing system such as the computer system (data acquisition system) described above hi conjunction with Figure IB. Figure 4 illustrates, generally at 400, several channels 402, 404, 406, and 408 of vibrational cardiac data according to an embodiment of the invention. In this example, Channel 6 indicated at 404 is selected as the high quaiity channel, with signal -to-noise ratio metric indicated at 410, 10056 j Optionally, at a block 308, the vibrational cardiac data from the high quality channel is band pass filtered to suppress energy at frequencies that are above and below the frequency content of the first and second peaks of the heart cycle. The band pass filter operation typically passes energy in the band from approximately 5 cycles per second (Hz) to several tens of Hz,

[0057] Optionally, at a block 310, envelope detection can be applied to the vibrational cardiac data from the high quality channel. Envelope detection operation is given by:

eft) - abs(x.(t)). and can be performed before the band-pass filter operation of block 3 0. x(^'t) is the high quality channel vibrational cardiac data time series, ahs is the absolute value operator, and eft) is the envelope amplitude.

10058 j Optionally, one or more segments of heart cycle data can be collected to provide the entire heart waveform as described above. When multiple segments are collected, a master replica is selected from each segment,

|0059| With reference to Figure 3, at a block 314, a master replica is selected from the high quality channel, which was specified at the block 304. The master replica is selected by selecting a heart cycle that is highly representative of a majority of heart cycles within the segment of the heart waveform represented by the high quality channel. The master replica is either a portion of or the entire heart cycle so identified. To illustrate the process, Figure 4 displays vibrational cardiac data, generally at 400, collected front four (4) different transducer channels, i.e., a channel five (5) at 402„ a channel six (6) at 404, a channel seven (7) at 406 and a channel eight (8) at 408. The vibrational cardiac data collected from channel six (6) at 404 (Figure 4) will be used for master replica selection and correlation due to favorable signal-to- noise characteristics as indicated at 410.

(0060) Optionally; the data from 404 can be band-pass filtered, a described at the block 306 (Figure 3) and is displayed as 502 in Figure 5. Figure 5 illustrates, generall at 500, master replica selection according to an embodiment of the invention. A noise burst due to breathing is marked at 504 and the same band-pass filtered data is displayed again at 506 where the master replica (MR) window is indicated at 508.

{0061 j At a block 316 the master replica is correlated wi th the high quality channel vibrational cardiac data from which it was selected. This cross-correlation procedure produces a correlation waveform that is a function of the time lag between the master replica and the segment waveform extending over the entire length of the segment minus the time length of the master replica. The correlation waveform ^'has local maxima when the master replica is temporally well aligned as a function of time lag with a corresponding high signai-to-noise ra tio portion of the segment waveform. These local maxima establish time reference points that are used to identify the diastolic window and to align successive heart cycles in time, i.e., synchronize, for signal analysis.

| 62 j At a block 318, the local maxima identified in the block 316 are used to separate heart cycles from a segment as a function of time. Figure 6 illustrates, in one embodiment, a correlation scan, generally at 600, that resulted from the vibrational cardiac data shown at 506 in Figure 5. With reference to Figure 6, in one embodiment, the process begins by analyzing the correlation data 602 to locate local maxima for all values of time (t) for which the correlation coefficient c(t) is:

c(t) > max jc(t-l) c{H-l >).

[0063 | Next, all values for which c(t) talis below a threshold are discarded.

With, reference to Figure 6, correlation coefficient c(t) is plotted at 602 as a function of time 604. A. threshold is indicated at 60S. The threshold 608 can be defined by an operator with graphical user interface (GUI) or it can be defined by the system.

[00641 Next, a time difference is obtained between a correlation peak and the peak that came before it in time. If the time difference is less than a threshold, then the maximum peak value is discarded as a possible heart beat cycle starting time. This process discards all candidate heart cycle starting times for heart cycles with a heart rate greater than a specified threshold. For example, a 0.5 second time difference threshold would disallow heart rates above 120 beats per minute (bptn). The local m xima thai are left are used to identify the heart cycles from which the vibrationai cardiac data will be extracted and processed. Generally lower vahres of correlation coefficient can be observed in interval 606 which correspond with the effects of breathing noise.

(0065) Corresponding with a block 320 (Figure 3), Figure 7 illustrates, in one embodiment, assembling multiple heart cycles. With reference to Figure 7, the local maxima that are identified by the analysis described above in conjunction with the block 3 8 are used to define windows in time as the window starting times. The vibrational cardiac data corresponding to these windows in time are over plotted as illustrated; where amplitude is indicated on an axis 702 and time along an axis 704. Envelope amplitude maxima 712 and 7.14 are followed by a diastolic interval 710. Envelope amplitude maxima 71 and 718 are used to help the identification of the diastolic interval; however it is not mandatory to use all four Envelope amplitude ma ima to locate the diastolic interval 710. A single envelope amplitude maxima and knowledge of the human's heart beat rate are sufficient to identify the diastolic interval 710. A start time 706 and a stop time 70S are placed at the ends of the diastolic interval either by a technician or these indicator can be located

automatically by an algorithm in an automated process,

[0 $6| Optionally, for each of the diastolic intervals indicated at 7.10, a power parameter, such as average squared amplitude over the duration of the heart cycle is computed for each heart cycle. Then ail of the average squared amplitude levels are averaged to produce a mean squared amplitude level averaged over all heart cycles over plotted. Each heart cycle's average squared amplitude level is compared to a multiple of the mean squared le vel and is discarded if its value exceeds the multiple of the mean squared level. In one embodiment the multiple is equal to 2.0. This heart cycle waveform pruning operation is used to discard those heart cycles that are contaminated by noise which is likely due to breathing and/or intestinal activity.

[00671 Corresponding with a block 322 (Figure 3), Figure 8 illustrates, in one embodiment; generally at 800, diastolic intervals selected for further processing. With reference to Figure 8, using the heart cycle starting times,, estimated above in conjunction with the previous figures, e.g., Figure 7„ a subsequence of adjacent time samples are extracted from the vibrational cardiac data S I 0. In Figure 8, vibrational cardiac data from a high quality transducer channel are plotted with amplitude on an axis 802 and time on an axis 804. Vibrational cardiac data are accepted from 21 diastolic intervals. The intervals marked at 806 are contaminated with excessive noise and are rejected.

[0068] Corresponding with a block 324 (Figure 3), the vibrational cardiac data that are extracted during the identical time window for all N sensors channels, from the diastolic windows, can be processed as a continuous ensemble of data or the diastolic window can be further partitioned into subintervals or slots as described above. Referring back to Figure 2, the diastolic window 2 Ϊ 2 is divided into four 4 slots 214 and the next diastolic window 232 i partitioned into four (4) slots 234. Adjacent time slots with the slots 214 or 234 can overlap in time. The slots have fixed starting times relative to the respective diastolic interval and are typically separated by less than one tenth of an average heart cycle (for example, 0, 1 seconds for a 60 beat per minute heart cycle). In one embodiment, the length of the slot interval, in number of time samples, is taken to be the number of points in a discrete Fast Fourier Transform. (FFT) operation which is performed independently within each slot. This procedure effectively strobes the same time slot number (e.g. 1 , 2, 3, 4, etc.) from each heart cycle for FFT spectrum analysis. In various embodiments, the temporal length of an FFT window slot is in the range ofO.1.5+0.1 seconds. Thus, for each sensor channel, a complex Fourier spectrum of the vibrational cardiac data is computed from the time series data.

10069 j Corresponding with a block 326 (Figure 3), Figure 9 illustrates a two- dimensional space-time frequency power spectrum (cross-channel power spectral density matrix "CSDM") of vibrational cardiac data, generally at 900, according to one embodiment of the invention. With reference to Figure 9, spatial frequency number is plotted on an axis 902 and temporal frequency is plotted on an axis 904. Normalized amplitude is indicated by a grey scale color and a reference key is illustrated at 906.

|0070| The CSDM is either computed for the entire heart cycle, based on averaging ail heart cycles in the entire heart waveform or it can optionally be computed for the a specific slot number in the heart cycle, hi either ease, the CSDM is computed by placing the complex Fourier spectrum (FFT outputs), obtained by processing the transducer channel outputs, into a four-dimensional matrix indexed as x(n, b, k, m): x{ I , h, k, m)

x(2, b, K ifi)

\ { b, k, m ) ^: x(N, b, k, m) where n is the vibration transducer number, k is the FFT discrete frequency bin number, b is the retained heart beat count, and m is the slot number, in eases where a heart waveform contains multiple segments, heart beat count, b will span multiple time segments, where each segment corresponds to a breath holding period as described above.

[00711 With N as the number of vibration transducer channels, the CSDM is then, an N-by- complex Hcrmitian R(k, ra) matrix, R(k, m) is calculated as a time average over the heart beat count index b, separately for each frequency bin k, and slot number tn. according to;

I »

R(k, ra) ^:::— xib, k, m)*s(b, k, ra)'

Where B is the number of heart beat cycles in the averaging ensemble which can span multiple segments of acquired vibrational transducer data in some embodiments. The value of B will depend on the number of separate transducer channels processed for a gi ven measurement. Generally, a lower bound for the value of B is approximately four (4) times the number of transducers, N. A preferred value for B is eight (8) to ten (10) times N. Those of skill in the art will recognize that the goal in selecting the value for B is to reduce the variance in the estimation of the CSDM matrix, therefore the value of B can be set at various numbers and the val ues of eight (8) to ten ( 1 ) are illustrative and not limiting.

[00721 Corresponding with a block 328 (Figure 3), the processes from a block

306 to the block 326 are repeated as needed for each segment in the heart waveform. Thus, if the heart waveform contains more than one segment, control transfers from 330 to the block 306 and the intervening process blocks are repeated. Note, that for each segment in the heart waveform, a new master replica is chosen and a correlation step is performed on a segment-by-segmen basis. This process accommodates variations in heart rate within a segment and the time averaging in the CSDM process (block 326) spans the time epoch for ail segments acquired and processed within a heart waveform. |0 73 J Corresponding with a block 332 (Figure 3), Figure 10 illustrates a two-dimensional space-time frequency power spectrum (Temporal-Spatial Spectrum (TSS)) processed for Equivalent Rectangular Bandwidth (ERB)„ generally at 1 00, according to one embodiment of the invention. With reference to Figure 10, temporal frequency is plotted on an axis 1004 and eigenvalue number/index (Spatial frequency number (sv» is plotted on an axis 1002. Relative amplitude .1006 of the data is displayed as a modulation of gray scale. Foll owing compl etion of the CSDM calculation (block 330), an eigenvalue-eigenvector decomposition (EBD) of the CSDM in each slot and for each FFT frequency bin in the range k < k < k^ is computed. This decomposition of the CSDM provides estimates of the b!ood flow turbulence induced noise spectrum level and bandwidth.

[0074 J With N transducer ch annels, the distribution of energy i n the CSDM eigenvalues at each freq uency also quantifi es the degree of angular concentration of spatial radiation points. The metric of spatial distribution of energy sources is referred to herein as spatial bandwidth and is non-parametric since it docs not require a propagation model parameterization, including wave speed, of the non- homogeneous body medium 112 (Figure 1 A) through which the wave energy propagates from the turbulent induced noise location within the artery (Figure 1A). |0075J The EED is calculated according to:

:[ (k_f m), L(k m), M(k, m){ = svd(R(k, m)> where Mil, m) is the -by-N matrix of orthonormal eigenvectors of ( (k, m) as columns and L(k, m) is the diagonal matrix of corresponding eigenvalues arranged in monotomcally decreasing order from the upper left to lower right.

| 76| In one embodiment, to establish a noise floor for the analysis, the smallest f eigenvalues are averaged over all FFT frequency values and then these frequency averages are in turn, averaged over the smallest N_f values. This produces a two dimensional space-time average. The number Nf is typically ten to thirty percent of the total number of transducer channels, N, and the frequency bins over which frequency averaging is performed are within the range above 100. This two dimensional averaged eigenvalue, λο« is termed the TSS noise floor. The TSS noise floor sets a threshold, over whic an accumulation (summation) of eigenvalues is performed. This accumulation of eigenvalues contains an estimate of the blood flow turbulence induced noise energy.

|^'0β77| For the largest p^::: 1 , 2, 3 N- Nf eigenvalues, ail of the eigenvalues as a function of frequency for a fixed value of p that exceed a threshold given by λ₀ are counted by integer counter C_¾>) and averaged as λ*ο_>) and those that do not exceed the threshold are counted by C_B,;_!)(aiso averaged as λ_Βί!,,.

|0078J Referring back to Figure 9, the CSDM eigenvalues are plotted along the vertical axis as a functio of frequency (horizontal axis) .for the sample case described herein. The estimation of the CSDM presented in Figure 9 has been obtained by time averaging the "slot Γ interval processed data over five segments with a total of ninety (90) heart cycles. The 3^ia. 5^tf\ and 7^ih harmonies of the 60 cycle power line artifact are evident in the data. Subsequently, these artifacts are nulled, blocked, and extrapolated through, which effectively notches out the FFT frequency bins as illustrated in the image at 950. Similar processing can be performed on the other slots within the diastolic interval.

(0079J Corresponding with a block 334 (Figure 3), referring back to Figure

10, The counter C_si,,} when multiplied by the FFT f equency bin width ( equal to the numerical inverse of the FFT interval in seconds) is termed the E uivalent

Rectangular spectral Bandwidth, ERB, for spatial eigenvalue p. The estimated number set C = [Cup λ*&>, C_S(_P). λ^, , α„ λ<, for p - 1 , 2, ... , ~Nf can provide a diagnostic tooi for the detection of arterial blood flow turbulence and thereby the causative pathology. A simulation of such detection was performed on a phantom and is described below in conjunction with Figure II through Figure 14.

[^'0080] Referring back to Figure 10, presentation of the set C in relative terms, shows that the magnitudes of the temporal frequency bandwidth counter and the Signal-to-Noise Ratio (SNR) metric (L,_(r!y%) are in proportion to and therefore a positively correlated marker for blood flow turbulence. In addition, the extent to which the threshold is crossed for larger values of p is in proportion to the extent of spatial distribution, i.e. spatial bandwidth, of the arterial occlusions that result in blood flow turbulence.

[0081] In other embodiments, different algorithms can be used to express

Equivalent Rectangular Bandwidth (ERB), Ail such expressions maintain both longtime averaged and spauai-teraporal spectrum analysis of the signals from an array of vibration sensors. Irt one such alternative embodiment, the temporal eigenvalue spectrum for each, spatial frequency index, L(k, p), kj_ow < k < k^, for each spatial frequency index, p, is searched over the temporal frequency index k for the point at which the level has decreased to a re-specified value ( e.g. -3 db, -6 db, ... ) relative to the maximum val ue. This embodiment is appropriate where the shape of the eigenvalue spectrum lias a monotonieally decreasing trend with increasing k.

[0082] The process begins by pre-sraoothing the estimated frequency

spectrum as a least squares fit of iogl0(L(k, p)) to a two parameter linear f traction over the range of k. Such smoothing permits a specific value of k ^::= &,_ίΡ) at the specified reduced value threshold point relative to the maximum value, logHKLCkfow, p)j, to be identified. Given the estimated value of k - (¾_>> at the specified reduced value level threshold, for each of p ~ 1, 2, .... N, the eigenvalues as a function of frequency, k, that exceed the threshold are given b the averaged value above tie threshold as ^-^a d those that do not exceed the threshold are counted by C^and expressed by the averaged value below the threshold as λ_κ{ρ).

(0083) In this alternative erabodhneirt, the estimated number set C ^:::: fQ¾,„

½·ρ), Cap), Xjypi, for ^::: 1 , 2 , j or its functional equivalent, can be used with appropriate human data to provide a diagnostic tool for the detection of arterial blood flow turbulence and the causative pathology. An example of such use is illustrated below in conjunction with Figure I I through Figure 14.

[0084] ^'Examination of the set C\ shows that the magnitudes of the temporal frequency bandwidth counter and the Signal-to- oise Ratio (SNR) metric

(?>-sf ; n(p ,) are in proportion to and are therefore a positi vely correlated marker for the presence of blood flow turbulence. This alternative embodiment can be generalized b performing higher order approximations to the estimated eigenvalue spectrum and thereby increasing iiie number of parameters subjected to a diagnosti c process. On this issue, the example presented above embodies the lowest possible complexity. }008SJ Figure 11 illustrates a phantom, generally at 1 100, constructed to simulate blood flow through art area of stenosis, according to one embodiment of the invention. With reference to Figure 11, a phantom simulator of the human thorax 1 102 in the vicinity of the chest wail was formed from silicone gel 1 106 with a predcterrained stiffness comparable to human tissue. The phantom contained high- stiffness human rib surrogates 1 10$ made of shaped plastic. Blood flow was simulated within latex tube 1 104 having cross-sectional characteristics typical of the left anterior descending (LAD) human coronary artery with a 3.0 millimeters (mm) inner diameter. Fluid flow occluders of different topologies were inserted into the latex tubing and the blood was simulated in viscosity with mixtures of 25 to 50 % glycol and distilled water. All dimensions were known and the latex tube was embedded at a depth of 40 mm from the contiguous surface of the phantom.

10086 j ^"The long axis of the vibration sensor linear array (not shown) was placed parallel to the rib surrogates 1108 and directly over the linear space between a pair of the rib surrogates 1 108. Such placement simulates placement on a human and established a direct vibration wave path from the induced turbulent flow site to the v ibration sensors located on the contiguou s surface of the phantom.

1_,00871 Figure 12 illustrates detection of stenosis occlusion i a phan tom, generally at 1 200, according to embodiments of the invention. With reference to Figure 12, the measured power spectrum level of vibration transducers is plotted on a vertical axis 1204. Spectrum le vel represents an integration in frequency of the energy in a given eigenvalue. Flow speed is plotted on an axis 1202. A series of experiments were conducted with different flow speeds with and without an occluder present in the latex tube 1 1 4 (Figure 1 1 ) to simulate an area of stenosis in a human. 10088 j One experiment consisted of comparing the case of a high flow rate, 72 em/sec, without occluder (to induce turbulence) to a realistic human diastolic LAD flow rate, 35 cm/see, with occluder induced flow turbulence (to simulate stenosis in a human). The higher flow rate had more than four times the laminar flow kinetic energy than the lower flow rate wherein turbulence was induced by the occluder. The objective of this experiment was to quantify the vibrational energy levels from both flow regimes and to evaluate the sensitivity of the methods described herein as a procedure for discriminating phantom: simulated pathological flow from normal unoecluded flow (healthy no stenosis) at a ver high level in order to produce a worst case detection scenario. (0089J Figure 12 shows the Measured Power Spectrum level (relative decibels, db) versus fluid flow rate (cm/sec) for flow "with occluder" at 1216 and "without occluder" at 1218. Plotted in Figure 12 aie the maximum and minimum eigenvalues, svOl and svl4, respectively, of the 1 sensor array estimated Cross- Spectral Density matrix (CSDM). Eigenvalue svl4 is shown at .1206 with occluder and at 1 208 without occluder. Eigenvalue sv0.1 is plotted at 1216, as a function of flow speed, with occluder in to simulate an area of stenosis. Eigen value svOl. is plotted at 12.18 without occluder to simulate the healthy state, free of stenosis.

|ββ90| Figure 12 illustrates that the vibrational energy detected at the surface of the phantom is larger in all cases, with the occluder present and low Row rate, than even the vers' high 100 cm/see flow rate with no occluder present. Of particular in terest for detecting stenosis in humans is the condition of occluded flow ( 1216) for velocities above 40 cm/sec, the detected levels remain above that for unoecluded flow (12.18) even at a flow velocity of 100 cm sec. Such results demonstrate a capability for discrimination between even very high flow rates without occluder induced noise (121.8) and nominally low flow rates with occluder produced turbulence ( 1216). (^'0091| Figure 13 illustrates an Equivalent Rectangular ^'bandwidth (ER^'B) display of vibrational energy resulting from fluid flow with occluder present (area of stenosis), generally at 300, according to one embodiment of the invention. With reference to Figure 13, temporal frequency is plotted on an axis 1302 and eigenvalue number/inde is piotted on an axis 1304. Relative amplitude 1308 of the data 1306 is displayed as a modulation of gray scale. Data 1306 represents an Equi valent Rectangular Bandwidth (ER^'B) estimate for the 35 cm/see flow rate with an occluder present. [00921 Figure 14 illustrates an Equivalent Rectangular bandwidth (ERB) estimate of vibrational energy resulting from fluid flow without occluder (healthy condition without stenosis), generally at 1400, according to one embodiment of die invention. With reference to Figure 14, the same format is used to present the data from the 14 channel array, temporal frequency is plotted on an axis 1402 and eigenvalue number/index is plotted on an axis 1404. Relative amplitude 1408 of the data 1406 is displayed as a modulation of gray scale. The flow rate of the simulated blood flow was 72 era/see. Such a rate is higher than what typically exists during normal Mood flow in a healthy human. This high rate (72 cm/sec) was selected for purposes of comparison in order to present a worst case detection scenario for the methods described herein.

[0093 J Figure 13 shows that three spatial frequency eigenvalue modes 1310 are excited with sufficient energy to exceed the 3 db E B threshold for the 35 era see flow velocity. In contrast, Figure 14 indicates that only two spatial modes 1410 exceed the ERB threshold level at notably small value of the estimated ERB. The discrimination provided by these two extreme cases illustrates the presence of detected turbulent flow induced noise,

[0094J Figure 15 illustrates, generally at 1500, an apparatus according to embodiments of the invention. With reference to Figure 15 and as is simi larly shown in Figure IA, a cross-sectional view of a human is presented, in Figure 15, the cross section contains a coronary artery 1502. A direction of blood flow is indicated at 1504. An occlusion irt the artery 1506 participates in causing downstream blood flow turbulence 1508. As described above in conjunction with Figure 1A, blood flow turbulence produces a state of vibration 1510 in the human's body which propagate energy in the form of elastic waves 1510. The eiasiic waves produce vibration of the surface of the human and are measured ncm-invasively by one or more sensors 15.16.

[00951 As the elastic wave energy 1510 propagates through the human's body it interacts with internal structures such as lung 1514 and ribs 1512. in various embodiments, it can be desirable to measure the vibration of the surface of the human in-between such ribs 1512, by placing a vibration transducers) in the intercostal space (between ribs) as shown by the placement of sensor 1 6.

[00961 Depending on the geometry of the surface of the human, the surface may provide a curved surface, such as is indicated by 1522. The sensor or array of sensors is placed in such manner as to conform to the geometry of the surface 1522, [00971 A variety of types of transducers can be used to measure vibration of a surface of a human. For example, a film sensor such as described above in conjunction with Figure 1 A can be used as well as other sensors, such as for example a laser based sensor. Sensors that respond to displacement, velocity, and acceleration can be used to measure the vibrational energy that manifests on the surface of the human. In various embodiments, proximity sensors can be used. Sensors as of now yet unknown can be used to measure the vibration of the surface of the human.

Embodiments of the invention ate not limited by the choice of sensor used to non- invasively measure the vibrational energy manifest on the surface of the human. Those of skill in the art will note that if a laser based sensor is used, physical contact between the sensor and the surface of the human is not necessary as a laser can be used to measure the surface without making phy ical contact apart from the laser beam interacting with the surface.

[00981 The output of the sensor(s) is input at 15.18 into a spectrum, analyzer

1 20. Spectrum analyzer 1520 is in various embodiments a single or muhi-ehanneS spectrum analyzer that performs a transformation f om: time to frequency. The resulting transformation has been referred to above in conjunction with Figure 3 as a complex Fourier spectrum of the vibrational cardiac data and the ensemble average of the amplitude squared spectrum is referred to below as a vibrational frequency power spectrum estimate or simply "spectral estimate" or spectral estimates" when plural spectra are referred to. As used herein, in this description of embodiments aod in the figures, it is understood by those of skill in the art that the terms power spectra! density estimate (PSD), absolute (PSD) level spectrum level, level, etc. refer to the amplitude of a power spectrum estimate. Furthermore, it is common in the art to express the level of a power spectrum as a decibel representation where the units are abbreviated as "dB." In various embodiments, the vibrational frequency power spectrum estimate is presented on a display 1524 for view by a doctor or technician or the vibrational frequency power spectrum estimate can be analyzed by an automated system to extract features related to a condition of health of a coronary artery. Such an automated system is configured in various embodiments as described above in conjunction with Figure IB.

[^'0099| As described below in the figures that follow, the vibrational frequency power spectrum estimate is used to quantify features and their characteristics which are used to support a diagnosis of a state of health of a human. A list of fea tures and their characteristics includes, but is not limited to blood flow turbulence energy from: (a) ventricular refilling turbulence characterized by a low frequency (LF) plateau with feature characteristics of level, width, and roll-off rate (slope) from the LF plateau; f b) arterial blood flow turbulence induced by diffuse occlusions characterized by a characteristic that captures the broadband spectrum level increase in the high frequency (HF) band above a 200 to 400 Hz roll-off band relative to the LF plateau level; (e) relatively localized occlusions described as having a band of surface curvature radials that induce spectral energy swaths characterized to first order by the characteristics of spectrum level, center frequency, and bandwidth; (d) localized occlusions with a dominant surface curvature that induces spectrally narrow whistles characterized by the characteristics of level (amplitude) and center frequency; (e) a roll-off over a band of frequency thai can occur anywhere in a frequency spectrum; and (f) a user defined feature. One or more features or multiples of a single type of feature can be evident in the vibrational frequency power spectrum estimates obtained from humans. As used in this description of embodiments, when reference is made to a feature, the characteristics (shape) of the feature are also implied thereby,

[06160] Figure 16 illustrates, generally at 1600, a method to assess a condition of health of a coronary artery using vibrational cardiac data, according; to

embodiments of the invention. With reference to Figure K», a method starts at a block 1602, At a block 1604 vibrational cardiac data is acquired non-invas.fve.ly from a surface of a human. At a block 1 06 unwanted coronary events are separated from the vibrational cardiac data. Separating unwanted coronary events such as heart valve vibrations are described above in conjunction with Figure 3. At a block 1608 a transient event is extracted from the vibrational cardiac data. The transient event is associated with blood flow turbulence and is used to assess a condition of health of a coronary artery. At a block .1610 the transient event is evaluated for an indication of energy due to coronary artery blood flow turbulence and the corresponding state of health of the coronary artery. At a block 1 12 a feature is identified in the vibrational frequency power spectrum estimate that is associated wit blood flow turbulence. Relating the ieature(s), or characteristic^ ) thereof in the vibratioiiai frequency power spectrum estimate to state of health in the coronary arteries of a human is described below in conjunction with the figures that .follow. At a block .1614 the method stops.

[OOlOlj Figure 17 illustrates, generally at 1700, time series plots of synchronized vibrational cardiac data, according to embodiments of the invention. With reference to Figure 17, time is plotted on a horizontal axis 1702 and amplitude is plotted on a vertical axis 1704. As described above in conjunction with Figure 3, vibrational cardiac data was collected non-mvastvely from a surface of human with a transducer. Displayed in Figure 17 is a stack of 67 synchronized heart-cycle time series waveforms. The stack of 67 heart-cycle time series waveforms is from one channel of a 14 channel array, hi order to maximize signal-to-noise ratio (SNR) in a given measurement, heart cycles can be pruned, thereby discarding outliers that arc contaminated with various sources of noise. As described above, various extraneous stimuli m the environment can manifest themselves as noise in vibrational cardiac data. These stimuli include, but are not limited to, stomach gurgling, etc. The inter- waveform correlation coefficient with a master replica exceeds 0.87 for all of the 67 waveform pairs in Figure 17.

100102] Similar to the representation ofSieart-cycie waveforms shown above in Figure 2 or Figure 7, two diastolic intervals are shown in Figure 17. A first diastolic interval is observed at 1706. The first diastolic interval 1706 is followed by a systolic interval 1708 and then a second diastolic interval 1710. A first heart sound is indicated at 1732 and a second heart sound ts indicated at 1714. Heart sounds 1712 and 1 14 are some of the unwanted coronary events that are separated from the vibrational cardiac data. During diastole, blood flow in the coronary arteries is at a maximum and the unwanted heart sound vibrations are at a minimum. Therefore, the vibrational cardiac data that occurs during a diastolic interval are processed to assess a condition of health of the coronary arteries. Blood flow through the coronary arteries is at a maximum at the onset of diastole and then decreases as a function of time through diastole. Thus, information about blood flow turbulence and a

corresponding state of health of a human's coronary artery can be obtained from an analysis of the blood flow turbulence energy that occurs during diastole.

[00103] In one or more embodiments, a diastolic interval (window), such as 1706, is divided into a plurality of time slots, such as the example of four time slots shown in Figur 1? as indicated by Ϊ 716, 1.718„ 1720, and 1722. Transforming the time series waveforms that occur in these time siots to the frequency domain produces vibrational frequency power spectra estimates which are compared in order to obtain information about both the transient and stationary behavior of the blood flow turbulence,

(0010 ^'i As described abo ve in conjunction with Figures 3 through Figure 7, a time siot is an interval of time with a known start time and duration time reiative to an established time mark. A time slot is also referred to herein as a sub-interval or a portion of a diastolic interval Note also that a time slot can be configured to be equivalent in duration to a diastolic interval. The time mark can be selected either manualiy or automatically by the system, in one embodiment, a preierred location for a start time is very early diastole durin the rapid early ventricular filling phase, when coronary blood flow is at a maximum rate. In one embodiment, a typical time slot length can be in the range 0,125 to 0.1825 seconds in duration when four (4) rime slots are used to process the diastolic window with 50% overlap between time slots. Other amounts of time slot overlap can be used and in some embodiments time slots can be configured without overlap. The example of four (4) time siots with a 50% overlap is provided merely for illustration and does not present any limitation to embodiments of the invention. Throughout diastole,, the cross-sectional shape of the coronary artery is changing and the frequency content of the blood flow turbulence induced energy is changing. These changes are observed in the vibrational frequency power spectra estimates discussed in conjunction with the figures below.

(00105] Figure 18 illustrates, generally at 1800, another set of time series plots of vibrational cardiac data collected from a human whose coronary arteries are in a healthy condition, according to embodiments of the invention. With reference to Figure 18, a stack of 1 9 synchronized heart-cycle waveforms are displayed in the figure with time plotted on an axis 1 02 and amplitude plotted on an axis 1804. The correlation coefficient computed between a master replica and all other heart cycles exceeded 0.89 for pairs of heart cycles in the stack of Figure 18. The human corresponding to the data shown in Figure 18 is a forty three (43) year old male who is symptom free with respect to cardiovascular disease. The individual exercises regularly and has a total cholesterol value of 170. The vibrational cardiac data from this individual is used below to provide information on blood flow turbulence from a healthy state of coronary artery health.

1.00106] The first heart sound interval is indicated at 1806, The first heart sound interval 180 includes a closure snap 1812 of a mitral valve and a closure snap of a tricuspid valve at 1814. The second heart sound interval 1808 includes an aortic valve closure 1818 and i 820. 1 820 is either a pulmonary valve closure and/or an early ventricular refilling turbulence transient. As described above, the diastolic interval is the region of interest. The aforementioned heart sounds constitute unwanted coronary events and are eliminated from the processing by placement of the time slots. The time intervals that are used for estimation of the vibrational frequency- power spectra are pre first heart sound time slot 1 816, diastolic interval time slot 1 (1822), diastolic interval time slot 2 ( 1824), diastolic interval time slot 3 (1826), diastolic interval time slot 4 (1828). A heart sound referred to as the fourth heart sound is indicated at 1830, which is caused by diastole refilling turbulence transicut. fOO 107J ^' he stack of one hundred and nine ( 109) vibrational cardiac data measurements from Figure 18 are transformed to the frequency domain using techniques such as the Fast Fourier Transform (FFT). Other techniques can be used to transform to the frequency domain, Ac FFT is used for example and does not. limit embodiments of the invention.

(00108) Figure 19 illustrates, generally at 1 00, vibrational^■frequency power spectra estimates corresponding to a time slot 1816 shown in Figure 18, according to embodiments of the invention. With reference to Figure 19, the one hundred and nine ( 109) time slot 1 sub-intervals in the synchronized heart cycles are Fourier transformed and then the amplitude squared of the complex Fourier transform are ensemble averaged for a given channel, in one embodiment, the procedure is repeated for each channel when an array of transducers is used to obtain the vibrational cardiac data. The averaged vibrational frequency power spectrum estimate for each channel is indicated for a channel number at 1 02 and is plotted as a function of frequency on an axis 1904. The corresponding normalized amplitude is indicated by gre scale with amplitude reference given at 1906 in decibels.

1_,00109) The lower plot in Figure 19 displays the vibrational fre uency power spectrum estimate obtained by a veraging a subset of channels from .1 02. In this case, channels one ( 1 } through thirteen (13) from the fourteen (14) channel array are averaged together. Frequency is indicated on a horizontal axis at 1908. Spectrum level is indicated on a vertical axis at 1910. [0 110] The dominant feature of the spectral estima tes is a low frequency plateau 1920. The low frequency plateau 1920 includes a relatively flat low frequency region of the spectrum between, approximately eighty (80) and. two hundred (200) cycles per second (Hz). Above 200 Hz the spectrum rolls-ofF decreasing at a rate of 27 to 29 decibels/octave in the 200 to 400 Hz octave. A decrease of 27 to 29 decibels is indicated at 1912 and the 200 to 400 Hz octave is indicated at 1 16. This plateau, in the 80 to 200 Hz band coincides with atrioventricular valve blood flow turbulence during ventricular refilling. The level and width of this plateau is proportional to a valve flow .rate and therefore to flow velocity. Mechanisms for the generation of this low frequency flow energy is a combination of valve vi bration induced by blood Sow shedding from the valve flaps and valve jet. Sow induced pressure waves in the ventricles propagating to and exiting the ventricle heart, wall. The valve vibrational energy propagates by means of elastic waves in the walls of the heart chamber, if (here is other energy that is time coincident with the third and fourth heart sounds, e.g., 1820 and 1.830 (Figure 18), then the corresponding spectrum is masked fay 1 820 and 1 30 (Figure 18). Power line artifacts of 60 Hz are indicated at 1918.

[OOll lj Figure 20 illustrates, generally at 2000, a method for averaging vibrational frequency cardiac data, according to embodiments of the invention. With reference to Figure 20, a method starts at a block 2002. At a block 2004, in one embodiment as described above in conjunction with Figure 19, an ensemble of vibrational frequency power spectra estimates, corresponding to time slots in tie synchronized heart cycles are averaged. Optionally at a block 2006, for each channel of an array, the resulting plurality of time a eraged vibrational frequency power spectra estimates ate averaged together, la one embodiment, an example of such averaging in rime and transducer channel position space is shown in Figure 19 at 19.10. The process stops at a block 200 . Note that averaging vibrational frequency power spectra estimates can be performed on all or a subset of channels.

(00112] Figure 21 illustrates, generally at 21 0, an overlay of space-time averaged vibrational frequency power spectra estimates corresponding to data from: Figure 18, according to embodiments of the invention. With reference to Figure 21, the space-time averaged vibrational frequency power spectrum estimates 2118 are plotted with frequency on an axis 21 2 and spectrum level on an axis 2104. A twenty five (25) dB roll-off indicated at 2106, occurs in the 200-400 Hz band indicated at 21 1.0 for the averaged power spectrum estimate for time slot 2, indicated at 2124. A 28 dB roll-off indicated at 2108, occurs in the 200-400 Hz band 21 10 for the averaged power spectrum estimate for time slot .1 , indicated at 2122, Reference point 2112 is the 3 dB down point from the low frequency plateau. Reference point 21 12 is used to measure the roll-offs described directl above. Artifacts of 60 Hz power iine harmonics are evident at 21 16. Those of skill in the art will recognize that such narrow band 60 cycle artifacts are tolerable as Song as they do not bias the estimated power spectral density (PSD) level outside of their narrow band.

[00113] Note that the spectrum roll-off of time slot 1 122 in a band of frequency above 400 Hz is different between Figure 19 (pre mitral valve closure time slot.) and the roll -off shown in Figure 21. The spectrum rolls-off more slowly in the band of frequency above 400 Hz in Figure 21 because in Figure 18 the time slot 4 interval captures the leading edge of the next mitral val ve closure snap, which contributed to a very broad band of energy at higher frequencies. The spectrum le vel increase above 400 Hz continues in frequency and is completely dominated by broad band energy at 2120. Valve closure snaps result in significant energy and elevated levels as can be seen by 2120 which corresponds to capturing only a port ion of the energy in the mitral valve closure snap by time slot 4 ( 1 828 in Figure 18). Thus, by eliminating unwanted cardiac events such as heart valve open or close motions the energy that is due to blood flow turbulence can be detected by the procedure.

[^'00114} With reference to Figure 21, the spectrum for time slot 1 2122 could contain, energy from the pulmonary valve closure .1 20 (Figure 18) and the earl ventricle refilling 1830 (Figure 18). The pulmonary valve snap will generate broadband energy above 200 Hz which appears to be at a very low level because this band has the lowest spectrum level for all four time slots 21 18. The ventricle refilling will produce energ below 200 Hz because it results from the flow over the surface of the atrioventricular valves which have relatively large surfaces of order centimeters with low curvatures relative to the inner dimensions of a coronary artery, which has dimensions of order millimeters with proportional curvatures,

[00115] The averaged spectrum le vel for time slot 2 is indicated at 2124. Time slot 2 captures the trailing edge of ventricle refilling (S3), the leading edge of S4 and a uiet area which permits measurement of energy due to blood flow turbulence in the left coronary artery. A moderate strength spread spectrum energy swath is indicated at 21 14. This swath has a center frequency of 350 Hz, a bandwidth of approximately 60 Hz, and a signal-to-noise ratio (SN ) of approximately 8-10 dB. This

measurement indicates that energy generated from blood flow turbulence is present in symptom free humans with respect to coronary artery disease,

[00116] Time slot 2, shown at 2124„ also indicates a low level of spectrum ripple. The ripple has a period of approximately 30 to 40 Hz and a peak-to- alley amplitude differential of 2 to 3 dB as indicated at 2126. Tin^'s effect is consistent with an interference pattern produced by energy propagating from a vibration source to a vi bration transducer (measurement location) along more than a single path. Phase coherent energy arrivals on different paths can periodically suppress or support each other and a frequency spectrum ripple period of 30 to 40 Hz is consistent with elastic wave propagation speeds in tissue with multiple path length differences on the order of centimeters.

1_,00117) Figure 22 illustrates, generally at 2200, a set of time series plots of vibrational cardiac data collected from a clinically diagnosed individual with a history of coronary artery disease, according to embodiments of the invention. With re ference to Figure 22, the sub ject of the measurements presented in Figure 22 is a male in his late sixties. Six months prior to the measurement, this man was diagnosed with total blockage of Left Anterior Descending (LA D) coronary artery and underwent a stent procedure that restored full L AD flow. Presented in Figure 22 are one hundred and four (104) synchronized heart cycle waveforms of vibrational cardiac data. These data have been collected as previously described and, in this embodiment, an array of fourteen (14) transducers was used to collect die vibrational cardiac data. The synchronized heart cycle waveforms exhibit a master replica pair wise correlation coefficient greater than 0.91.

[00118) In Figure 22 time is plotted on an axis 2202 and amplitude is plotted on an axis 2204. A systolic interval is indicated at 2206 and a diastolic interval is indicated at 2208. in this embodiment, the diastolic interval 2208 has been partitioned into four (4) overlapping time slots 2210, 2212, 214, and 2216.

Transformations from time to frequency are^•performed on each heart cycle waveform within each time slot. This process is repeated for each channel of the array of fourteen transducers. [0 119] In one embodiment, for each channel, an ensemble of power spectrum estimates are then averaged for the same time slot in each heart cycle. The results of the averaged rime slot power spectrum estimates (rime to frequency transformations) are shown ia Figure 23 on a channcl-by-cha«nel basis with the time ensemble average at the top and as a channel average across the array at the bottom:,

[00l20j Figure 23 illustrates, generally at 2300,, a set of vibrational frequency power spectra estimates correspondin to the time series from Figure 22, according to embodiments of the in vention. With reference to Figure 23, each of the averaged spectral estimates for each channel are displayed at 2300 with frequency on an axis at 2302, channel number on an axis 2304 and normalized spectrum level is indicated at 2305 as gray scale. Thirteen of the fourteen time averaged channel spectrum

estimates from 2300 are averaged together and plotted in 2350 with frequency on an axis at 2352 and spectrum level on an axis 2354, Averaging as was done in both time (ensemble of heart cycles) and space (across channels) improves a signal-to-noise ratio of the measurement. Such a veraging is not always required and in some embodiments with sufficient stgnai-to-noise ration (SNR), -meaningful information is obtained from a single time to frequency transformation of a single heart cycle from one transducer.

(00121] The processed vibrational frequency power spectrum estimate plotted in Figure 23 at 2350, corresponds to the first time slot 2210 (Figure 22) in the diastolic interval 2208 (Figure 22). Features are present in 2350 that are used to identity coronary artery blood flow turbulence . One feature is a low frequency plateau, which exists between approximately 80 and 150 Hz and is indicated at 2356, This low frequency plateau is associated with valve flow as previously discussed. Another feature i a low frequency roil -off from the plateau which occurs between 80 and 150 Hz. The ro!i-off of the amplitude is 18 dB as indicated at 2358 over the 200 to 400 Hz frequency octave. Another feature is a strong spread spectrum energy swath which occurs at 2360. This strong swath is characterized by a center frequency of 230 Hz, a bandwidth of 80 Hz, and a signal-to-noise ratio of 18 dB. Yet another feature is a weak spread spectrum energy swath which occurs at 2362. This weak swath, is characterized by a center frequency of 365 Hz, a bandwidth of 55 Hz, and a signal-to-noise ratio of 7 dB. Another feature is a medium spread spectrum energy swath which occurs at 2364. This medium swath is characterized by a center frequency of 570 Hz, a bandwidth of 1 0 Hz, and a signal-to-aoisc ratio of 8 dB. Another feature is a frequency band-limited whistle at 2366, Whistle 2366 is characterized by a center frequency of 805 H arid amplitude of 8 dB. Another feature is a difference in amplitude between the low frequency plateau 2356 and a high frequency broad band level. This difference is approximately 30 dB as indicated at 2368. Several power line artifacts of 60 Hz are evident at 2370. These power line artifacts are not considered to be features.

[00122} Figure 24 illustrates, generally at 2400, an overlay of vibrational frequency power spectra estimates from -multiple slots corresponding to the human's data shown in Figure 22, according to embodiments of the invention. With reference to Figure 24, time and channel averaged vibrational frequency power spectrum estimates for each time slot (22.1 , 2212, 2214, and 2216 from Figure 22) are plotted o a graph with frequency on an axis 2402 and spectrum level on an axis 2404, Time slot I , time slot 2, and time slot 3 contain features, the types of which were described above, which are associated with coronary artery blood flow turbulence and a state of health of a coronary artery. Time slot 4 (22.16 in Figure 22) contains valve snap energ and has been placed to capture part of the valve snap to illustrate die fact that the first three time slots (2210, 2212, and 2214 from Figure 22) are measuring blood flow turbulence.

[00123} Notably, the characteristics of some of the features exhibit transient behavior and have changed between time slot 1 and time slot 2, Similarly, characteristics of features have also changed between time slot 1 and tirrte slot 3 and between slot 2 and slot 3. For example, a feature in time slot 1 is a strong spread spectrum swath 2406. This strong spread spectrum swath 2406 has a center frequency of approximately 230 Hz and a bandwidth of approx imately 90 Hz 2407. In time slot 2 (2212) the strong spread spectrum swath 2406 (from time slot I 2210) has transformed into a frequency band limited whistle at 2408 with a center frequency of 200 Hz at 2424. Another example of a feature changing between time slots is medium spread spectrum energy swath 2412 in time slot 2 (2212) transforming into a frequency band limited whistle 2414 in time slot 3 (2214). The estimated center frequency of the swath 2412 and the whistle 2414 is 390 Hz as indicated at 2422.

[00124} Extraction of features, from such an individual and comparison of the characteristics of the features between time slots permits identification of state of health of tie individual's coronary artery or arteries. Changes in characteristics of feature(s) from one time slot to another within a given human's vibrational cardiac data permits identification of a state of hea lth of coronary arteries. Here, note that in Figure 22 the clinically diagnosed individual, who underwent the stent procedure, has turbulence inducing occluded arteries and a features which exhibit transient behavior between at least two time slots. By comparing the features that exist in each time slot a transient event can be identified and extracted and a determination can be made with respect to a state of health of the associated coronary artery(s) regarding the presence of arterial blockage. [00125] Figure 25 illustrates, generally at 2500, a method for identifying a feature related to coronary artery blood flow turbulence using a single human, according to embodiments of the .invention. With reference to Figure 25. a process starts at a block 2502, At a block 2504, a di astolic interval of a heart cycle is partitioned into at least two time slots. At a block 2506 a time to frequency transformation i performed on vibrational cardiac data collected from the time slots created in the block 2504. At a block 2508 one or more features and/or characteristics of the features that are associated with a transient event from blood flow turbulence in a coronary artery are identified. These transient events are then analyzed to determine a state of health of the human. A process stops at a block 2510. in one or more embodiments, monitoring paradigm for heart disease includes periodic

measurements made on an individual. Comparison of the individual's measurements over time will indicate an increase in blood flow turbulence energy if the individuals state of coronary artery health declines. Such comparison can be performed wi th the individual's own data, as described above in conjunction with Figure 5, or in other embodiments; compari on can be made with blood flow turbulence measurements made from known clinically diagnosed states, as described below.

IA0126S Figure 26 illustrates, generally at 2600, a comparison of vibrational cardiac data from multiple humans, according to embodiments of the in vention. With reference to Figure 26, frequency is plotted on an axis at 2602 and spectrum level is plotted on an axis at 2604. The vibrational cardiac data plotted in Figure 26 are the time and channel averaged vibrational frequenc power spectrum estimates for time slot 1 (for the symptom free person at 2630) data previously shown in Figure 21 and the person whose coronary arteries indicate coronary artery turbulence at 2620, which are data previously shown in Figure 23 and Figure 24 (2210) for the clinically diagnosed individual.

[001271 The low frequency plateau was previously described for 2630 in Figure 19 as extending from 90 to 180 Hz, The location of the strong spread spectrum energy swath 2606 slightly obscures the high frequency end of the low- frequency plateau; however the low frequenc plateau for both 2620 and 2630 are substantially equivalent in amplitude.

[00128] The roll-off of the low frequency plateau differs between the symptom free person's measurement 2620 and the clinically diagnosed person's measurement 2630. For 2630 the roll-off is 24 dB indicated at 2612. For 2620 the roil-off is 1 ? dB indicated at 2614.

[00129] The spread spectrum energy swath bandwidths are 90 Hz for 2606, 1 10 Hz for 2608, and 110 Hz for 2610. Spread spectrum energy swath 2606 has a center frequency of 230 Hz at 2 16; spread spectrum energy swath 2 1 has a center frequency of 570 Hz at 2 18. The signal-to-noise ratio for spread, spectrum swath 2606 is 1 dB and the. spread spectrum swath 2610 has a signal-to-noise ratio of 9 dB.

[00130] Figure 27 illustrates, generally at 2700, a method for identifying a feature related to coronary artery blood, flow turbulence using multiple humans, according to embodiments of the invention. With reference to Figure 27, a process starts at a block 2702. At a block 2704 a time to frequency transformation is performed on vibrational cardiac data collected during a diastohc interval of a heart cycle, thereby resulting in a vibrational frequency power spectrum estimate. At a block 2706 a feature(s) is extracted from the vibrational frequency power spectrum estimate with the aid of previously identified and clinically verified features that are related to blood flow turbulence in a coronary artery and the related condition of health of the coronary artery.

[00131] Following the teaching presented in the figures above, in various embodiments, process block 2706 includes a plurality of measurements, which can be referred to as a library of measurements. The library of measurements thus created contains different features (with their associated characteristics) of blood flow turbulence in the frequency domain that are associated with different conditions of health of coronary arteries in clinically verified cases. These features are also referred to as "signatures^" of blood flow turbulence and the associated pathology. Note that blood flow turbulence is not always associated with a diseased condition. At times, a measure of blood flow turbulence indicates a healthy condition (refer to Figure 19 and Figure 21), Note that in different embodiments, databases of library

measurements can be assembled in different ways according to the teachings presented herein. For example, a database can be based on transients that occur during diastole. A database(s) can be assembled based on symptom free individuals, thereby establishing a plurality of measurements of healthy conditions. A database(s) can be assembled that is based on features and their characteristics that are associated with clinically verified known pathologies, i.e., degree of blockage of an artery's cross -section, presence of a stent or Sack thereof, etc. Databases can be combined to form databases that combine self-evaluation changes in spectral content from one time slot to another time slot within a diastolic interval along with comparison measurements from data collected on a population of humans. Thus, apparatuses and methods have been described which permit a condition of health of a human's coronary artery(s) to be evaluated non-invasively. f 00132] For purposes of discussi ng and understanding the embodiments of the invention, it is to be understood that various terras are used by those knowledgeable in the art to describe techniques and approaches. Furthermore, in the description, for purposes of explanation, numerous specific details are set forth in order to pro vide a thorough understanding of the present invention. It will be evident, howe ver, to one of ordinary skill in the art that the present invention may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the present invention. These embodiments are described in sufficient detail to enable those of ordinar-' skill in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical, and other changes may be made without departing from the scope of the present invention.

[00133] Some portions of the description may be presented in terms of algorithms and symbolic representations of operations on, for example, data hits within a computer memory. These algorithmic descriptions and representations are the means used by those of ordinary skill in the data processing arts to most

effectively convey the substance of their work to others of ordinary skill in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of acts leading to a desired result. The acts are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, waveforms, data, time series or the like. [00134] It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely

convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the discussion, it is appreciated that throughout the description, discussions utilizing terms such as "processing" or "computing" or "calculating" or "determining" or "displaying" or the like, can -refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system^'s registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission, or display devices.

[00135] An apparatus for performing the operations herein can implement the present invention. This apparatus may be specially constructed for the required purposes, or it may comprise a general-purpose computer, selectively activated or reconfigured by a computet" program stored in the computer. Such a computer program may be stored in a computer readable storage medium, such as, but not limited to, any type of disk including floppy disks, hard disks, optical disks, compact disk read-only memories (CD-ROMs), and magnetic-optical disks, read-only memories (ROMs), random access memories CRAMs), electrically programmable read-only memories (EPROM)s, electrically erasable programmable read-only memories (EEPROMs), FLASH memories, magnetic or optical cards, etc., or any type of media suitable for storing electronic instructions either local to the computer or remote to the computer,

[00136] The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform the required method. For example, any of the methods according to the present invention can be implemented in hard-wired circuitry, by programming a general-purpose processor, or by any combination of hardware and software. One of ordinary skill in the art will immediately appreciate that the invention can be practiced with computer system configurations other than those described, including hand-held devices,

multiprocessor systems, microprocessor-based or programmable consumer electronics, digital signal processing (DSP) devices, network PCs, minicomputers, mainframe computers, and the like. The invention can also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network,

(00137) The methods of the invention may be implemented using computer software. If written in a programming language conforming to a recognized standard, sequences of instructions designed to implement the methods can be compiled for execution on a variety of hardware platforms and for interface to a variety of operating systems, in addition, the present invention is not described with reference to any particular programming language. It will be appreciated that a variety of program ming languages may be used to implement the teachings of the inventi on as described herein. Furthermore, i t is common in the art to speak of software, in one form or another (e.g., program, procedure, application, driver,...), as taking an action or causing a result. Such expressions are merely a shorthand way of saying that execution of the software by a computer causes the processor of the computer to perform an action or produce a result. [00138] It is to be understood that various terms and techniques are used by those knowledgeable in the art to describe communications,, protocols, applications, implementations, mechanisms, etc. One such technique is the description of an implementation of a technique in terms of an algorithm or mathematical expression. That is, while the technique may be, for example, implemented as executing code on a computer, the expression of that technique may be more aptly and succinctly conveyed and communicated as a formula, algorithm, mathematical expression, flow diagram or flow chart. Thus, one of ordinary skill in the art would recognize a block denoting A+B= as an additive function whose implementation in hardware and/or software would take two inputs (A and B) and produce a summation output (C). Thus, the use of formula, algorithm, or mathematical expression as descriptions is to be understood as ^'having a physical embodiment in at least hardware and/or software (such as a computer system in which the techniques of the present invention may be practiced as well as implemented as an embodiment).

1_,00139] A machine-readable medium is understood to include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computer). For example, a machine-readable medium includes read only memory (ROM); random, access memory (RAM^'); magnetic disk storage media; optical storage media; flash memo ' devices; electrical, optical, acoustical or other form of

propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.); etc.

[001 0] As used in this description, "one e bodiment." or "an embodiment" or similar phrases means that the feature^) being described are included in at least one embodiment of the invention. References to "one embodiment" in this description do not necessarily relet to the same embodiment; however, neither arc such embodiments mutually exclusive. Nor does ^'"'one embodiment" imply that there is but a single embodiment of the invention. For example, a feaiitre, structure, act, etc. described in ""one embodiment" may also be included in other embodiments. Thus, the invention may include a variety of combinations and/or integrations of the embodiments described herein.

(00141] While the invention has been described in terms of several embodiments, those of skill in the art will recognize that the invention is not limited to the embodiments described, but can be practiced with modification and alteration within the spirit and scope of the appended claims. The description is thus to be regarded as illustrative instead of limiting.

Claims

What is claimed is:

Claim 1. A method of obtaining cardiac data, comprising:

acquiring vibrational cardiac data from a transducer wherein the transducer measures vibration of a surface of a huniaifs body;

separating an unwanted coronary event from, vibrational cardiac data, wherein the effects of the unwanted coronary event on vibrational cardiac data are reduced by the separating;

performing a time-to-frequcncy transformation on at least a portion of a diastolic interval within a heart cycle of the vibrational cardiac data obtained during the separating to obtain a vibrational frequency power spectrum estimate; and

evaluating the vibrational frequency power spectrum estimate for a condition of coronary artery blood flow turbulence.

Claim 2, The method of claim ί , wherein the performing is restricted to at least a first, time slot of the diastolic interval.

Claim: 3 , The method of claim 2, further comprising:

averaging vibrational frequenc power spectra estimates from an ensemble of heart cycles, whereby a signal-to-noise ratio is increased.

Claim 4. The method of claim 3, further comprising:

performing a time-to-frequency transformation on a second time slot of the diastolic interval to obtain a second vibrational frequency power spectrum estimate and the evaluating utilizes the vibrational frequency power spectrum estimate and the second vibrational frequency power spectrum estimate.

Claim 5. The method of claim 3, wherein vibrational frequency power spectra estimates corresponding to a given time slot from a plurality of sensors, are a veraged together.

Claim 6. The method of claim 4, wherein the evaluating determines whether a. shape of a f eature changed between the vibrational frequency po wer spectrum estimate and the second vibrational -frequency power spectrum estimate.

Claim 7. The method of claim 6, wherein the feature is selected from the group consisting of a knv frequency plateau, a roll-off of a low frequency plateau, a spread spectrum energy swath, a frequency band limited whistle, and a high frequency plateau, a roll-off over a band of frequency, and a user defined feature.

Claim 8. The method of claim 7, wherein the feature provides information, about a physical characteristic of a blockage within a coronary artery.

Claim 9, The method of claim 1„ wherein the evaluating identifies a feature in the vibrational frequency power spectrum estimate and the feature is selected from the group consisting of a low frequency plateau, a roll-off of a low frequency plateau, a spread spectrum energy swath, a frequency band limited whistle, a high frequency plateau, a roll-off over a band of frequency,, and a user defined feature. Claim 10. The method of claim 9, wherein the feature provides information about a physical characteristic of a blockage within a coronary artery.

Claim 1 1 . The method of claim 4, wherein the at least a portion of the diastolic interval and the second time slot of the diastolic interval do not overlap in time.

Claim 1 2. The method of claim 4, wherein the at !cast a portion of the diastolic interval and the second time slot of the diastolic interval partially overlap in time.

Claim 1 3. The method of claim 5, further comprising;

dividing the diastolic interval into a plurality of time slots, wherein the performing is performed on each time slot within the plurality of time slots to produce a vibrational frequency power spectrum estimate for each time slot.

Claim 14. A method of obtaining cardiac data, comprising:

acquiring vibrational cardiac data from a transducer wherein the transducer measures vibration of a surface of a human's body;

separating an unwanted coronary event from the vibrational cardiac data, wherein the effects of the unwanted coronary event on the vibrational cardiac data arc reduced by the separating;

performing a tirae-to-frequency transformation on at least a portion of a diastolic interval within a heart cycle of the vibrational cardiac data obtained during the separating, the performing results in a vibrational frequency power spectrum estimate; and identifying a feature in the vibrational frequency power spectrum estimate that is associated with an occlusion in a coronary artery, wherein the identifying is accomplished with at least one comparison measurement, the at least one comparison ineasureinent is a separate measurement made from a different human of a vibrational frequency power spectrum estimate from at least a portion of a diastolic interval.

Claim 1 5. The method of claim 14, wherein the feature is associated with a state of health of a coronary artery and the feature is selected from the group consisting of a low frequency plateau, a roll-off of a low frequency plateau, a swath, a whistle, a high frequency plateau, a ro!I-off over a band of frequency, and a user defined feature.

Claim 16. The method of claim 15 wherein the state of health includes a partial blockage of a coronary artery.

Claim 17. The method of claim 15, wherein the state of health does not include a partial blockage of a coronary artery.

Claim: IS, The method of claim 14, wherein the acquiring utilizes art array of transducers, and the performing creates a vibrational frequency power spectrum estimate for each channel of the array, further comprising:

averaging the vibrational frequency power spectrum estimate for at least two channels of the array, for an ensemble of heart cycles to produce a time averaged vibrational frequency power spectrum estimate for each of the at least two channels; and averaging together the time averaged vibrational frequency power spectrum estimates for the at ieast two channels, whereby the signal-to-noise ratio is improved.

Claim ί 9. The method of claim 14, wherein the transducer is selected from the group consisting of a film sensor, a laser, a detector of surface motion.

Claim 20. The method of claim 14, wherein the identifying identifies multiple features.

Claim 21 . The method of claim 1.4, wherein the second measurement is part of a data base of measurements that have been previously identified with a variet of states of health of coronary arteries.

Claim 22. A method of obtaining cardiac data, comprising:

acquiring vibrational cardiac data from a surface of a human's body with a transducer non-invasi vely, the vibrational cardiac data occurs during at Ieast a portion of a diastolic interval within a heart cycle;

partitioning the least the portion of the diastolic interval within the heart cycle into at least two time slots;

performing a time-to-frequency transfomiation on the vibrational cardiac data within each of the at least two time slots, the performing results in at least two vibrational frequency power spectra estimates; and

evaluating the at ieast two vibrational frequency power spectra estimates to determine if a difference exists over at least one region of the at least two vibrational frequency power spectra estimates .

Claim 23. The method of claim 22, wherein the difference is used to assess whether coronary artery blood ilow torbiiieacc is indicated by the vibrational cardiac data.

Claim 24. The method of claim 23, wherein the difference is used to identity a feature in at least one of the at least two diastolic interval vibrational frequency power spectra that is associated with a state of health of a coronary artery.

Claim 25. The method of claim 24, wherein the feature is selec ted from the group consisting of a low frequency plateau, a roll-off of a low frequency plateau, a spread spectrum swath, a frequency ^'band limited whistle, a high frequency plateau, a roll-off over a band of frequency, and a user defined feature.

Claim 26. The method of claim 25 wherein the state of health includes a partial blockage of a coronary artery.

Claim 27. The method of claim 25, wherein the state of health does not include a partial blockage of a coronary artery.

Claim 28. The method of claim 22, wherein the evaluating further comprises; using a comparison measurement of vibrational cardiac data obtained from a different human during the evaluating.

Claim 29. The method of claim 28, wherein the comparison measurement is used to identify a .feature is at least one of the at least two diastolic interval vibrational frequency power spectrum estimates and the feature is selected from the group consisting of a low frequency plateau, a roll-off of a low frequency plateau, a spread spectrum swath, a frequency band limited whistle, a high frequency plateau, a roll-off over a band of frequency, and a user defined feature.

Claim 30. An apparatus to obtain cardiac data, comprising;

a data processing system, the data processing system is configured to process vibrational cardiac data;

a computer readable medium containing executable computer program instructions, which when executed by the data processing system, cause the data processing system to perform: a method comprising:

receiving vibrational cardiac data from a transducer wherein the transducer measures vibration of a surface of a human's body;

separating an unwanted coronary event from the vibrational cardiac data; performing a time-to-frequency transformation on the vibrational cardiac data from at least a portion of a diastolic interval within a heart cycle to obtain a vibrational frequency power spectrum estimate; and

identifying a feature in the vibrational frequency power spectrum estimate that is associated with a condition of coronary artery blood flow turbulence and a state of health of a coronary artery.

Claim 31. The apparatus of claim 30, further comprising: a transducer,, the transducer is configured to measure vibration of a surface of die human's body iio.n-irivasively.

Claim 32. The apparatus of claim 30, wherein the transducer is selected from the group consisting of a film sensor, a laser, a detector of surface motion, and a user specified sensor.

Claim 33. The apparatus of claim 32, wherein the receiving utilizes an array of transducers, and the performing creates a vibrational frequency power spectrum estimate for each channel of the array and then averages the vibrational frequency power spectra estimates together tor the heart cycle.

Claim 34. The apparatus of claim 30_? wherein vibrational frequency power spectra from art ensembie of heart cyc les are averaged.

Claim 35. The apparatus of claim 30, wherein the method performed by the data processing system further comprising:

performing a time-to-frequency transformation on a second time slot of the diastolic interval to obtain a second vibrational frequency power spectrum estimate and the identifying is done by comparing the vibrational frequency power spectrum estimate and the second vibrational frequency power spectrum estimate.

Claim 36. The apparatus of claim 30, wherein the feature is selected from the group consisti ng of a. low frequency plateau, a roil-off of a low frequency plateau, a spread spectrum swath, a frequency band limited whistle, a high frequency plateau, a roll-off over a baud of frequency, and a user defined feature.

Claim 37. The apparatus of claim 36 wherein the state of health includes a partial blockage of a coronary artery.

Claim 38. The apparatus of claim 36, wherein the state of health does not include a partial blockage of a coronary artery.

Claim 39. The apparatus of claim 30, wherein the unwanted coronar even t is selected from the group consisting of closure within a heart valve, and blood flow through an open heart valve.

Claim 40. The apparatus of claim 30, the method performed by the data processing system further comprising;

Claim 4.1. The apparaiits of claim 40, wherein the receiving utilizes an arra of transducers, and the performing creates a vibrational frequency power spectrum estimate for each channel of the array, the method performed by the data processing system further comprising: averaging the vibrational frequency power spectrum estimate for a particular time slot for an ensemble of heart cycles to produce a time a veraged vibrational fre uency power spectrum estimate for at least two channels of the array; and

averaging together the time averaged vibrational frequency power spectrum estimates for the at least two channels, whereby a signai-to-noise ratio is improved.

Claim 42. A method of obtaining cardiac data, comprising:

acquiring vibrational cardiac data from a transducer wherein the transducer measures vibration of a surface of a hitman's body;

separating an unwanted coronary event from vibrational cardiac data;

extracting a transient event from the vibrational cardiac data, the transient event occurs during a diastolic interval within a heart cycle; and

evaluating the transient event for a condition of coronary artery blood flow turbulence.

Claim 43. The method of claim 42, the extracting further comprising;

dividing the diastolic interval into at least two time slots; and

performing a time to frequency transformation on the vibrational cardiac data acquired within the at least two time slots to produce at least two vibrational frequency power spectra estimates.

Claim 44. The method of claim 43, further comprising;

evaluating the at least vibrational frequency power spectra estimates for a feature that is associated with a condition of health of a coronary artery.