WO2007072490A1

WO2007072490A1 - An operating mode for ultrasound imaging systems

Info

Publication number: WO2007072490A1
Application number: PCT/IL2006/001478
Authority: WO
Inventors: Abraham Bruck
Original assignee: Ultraview Ltd.
Priority date: 2005-12-23
Filing date: 2006-12-24
Publication date: 2007-06-28

Abstract

The present invention provides an ultrasound imaging apparatus supporting pulsed-echo ultrasound modes of operation as well as optoacoustic, (thermoacoustic) ultrasound mode of operation and displaying simultaneously the mode relevant images overlaid one on top of the other on a combined image.

Description

AN OPERATING MODE FOR ULTRASOUND IMAGING SYSTEMS

FIELD OF THE INVENTION

The present invention relates to ultrasound imaging combined with optoacoustic signal. More particularly, the present invention relates to utilization of combined 2D pulse-echo ultrasound and optoacoustic signal for medical needs.

BACKGROUND OF THE INVENTION

Ultrasound imaging of small part structures including breast, thyroid, prostate; ophthalmic structures; cardiac structures; the peripheral vascular systems; the fetus and uterus; abdominal organs such as the liver, kidneys, and gall bladder; skin structures is a known medical imaging technique. Ultrasound imaging is based on transmission of short ultrasound pulses along a definite direction and receiving the ultrasound echoes from the different tissue interfaces along the propagation direction of the ultrasound pulse. The arrival time of the echoes determine the distance of the echo source from the ultrasound transmitter/receiver. A complete image can be reconstructed by varying the direction of the ultrasound beam and recording the echo intensities as a function of direction and distance. The beam direction can be varied by mechanically moving a single transmit/receive ultrasound transducer, or by electronic means using an array of transducers. Usually the same transducer is used for transmitting and for receiving. This type of image displays tissue interfaces with intensities proportional to the reflection coefficients of these interfaces providing anatomic information.

Optoacoustic imaging of ophthalmic; brain; peripheral vascular; small parts including breast, thyroid, prostate structures is also a known method. The optoacoustic imaging is based on transmitting short pulses of electromagnetic radiation, for example light using a laser that can be a narrow beam along a definite direction, or a spread out beam illuminating a selected volume. The laser beam excites ultrasound in the tissue that now becomes an ultrasound source. The ultrasound is detected by an ultrasound receiver, or array of receivers, to produce a complete image, or a signal distribution along a single laser beam direction. This type of image represents the characteristic of the laser light absorption (function of wave-length), the elasticity, and the thermal properties of the tissue. Examples of using various forms of electro-magnetic radiation in optoacoustic imaging are disclosed in several patent disclosures such as:

1 . US patent no. 4,385,634 "Radiation induced thermoacoustic imaging" filed in 1981 by Bowen.

2. US patent no. 6,652,459 Ophthalmic uses of lasers" filed in 2001 by Payne et al. This patent teaches a method for analyzing and therapy of the eye utilizing laser-induced ultrasound.

3. US patent no. 5,840,023 Optoacoustic imaging for medical diagnosis" filed in 1996 by Oraevsky et al.

4. European patent EP 920277 (application 97904228.0) European version of 3.

5. US patent no. 6,309,352 "Real time optoacoustic monitoring of changes in tissue properties" filed in 1998 by Oraevsky et al.

6. German patent DE 4400674A1 Niesner at al. filed 1994

7. European patent 0282234A1 Dowling filed in 1988 8. Photoacoustic Ultrasound Theory - Robert A. Kruger - SPIE Vol.

2134A. 9. Laser based optoacoustic optoacoustic imaging in biological tissues -

Oraevsky at al - SPIE Vol. 2134A.

Combination of ultrasound echo intensity image with other echo properties such as tissue motion image (Color Flow Imaging), using the

Doppler effect to analyze the ultrasound echo, is a known method for imaging of blood flow and tissue motion. The excitation source for both is the same ultrasound source, and the ultrasound echo is analyzed.

In the present invention, the two methods are combined while the optoacousticaly generated ultrasound data is overlaid on the pulse echo ultrasound image, in real time. The method produces a combined image that reflects the pulse echo ultrasound properties together with the optoacoustic properties of the tissue as a function of spatial location.

In most recent years, the need for such combination was expressed by researchers in the industry and examples can be viewed at: 1. Emilianov et al. - "Combined ultrasound, optoacoustic, and elasticity imaging" Proceedings SPIE vol. 5320, (2004).

2. Niederhouser et al. - "Combined ultrasound and optoacoustic system for real time, high contrast, vascular imaging" IEEE transactions on medical imaging vol. 24 no. 4, (2005). However, to the best of the inventor's knowledge, a sole description of how to combine the two methods in order to achieve the results that are needed for real time imaging is shown in a previous PCT application of the inventor published as WO/2006/077579.

In one aspect of the present invention, integration of a new operating mode into pulse echo ultrasound systems is provided. The new mode enables real-time combination of pulse-echo imaging with thermoacoustic (optoacoustic) imaging and displays both images as one combined image.

According to a further aspect the present invention, the apparatus provides a device for the measurement of the concentration of substances in a body fluid in vivo.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an apparatus that overlays ultrasound signals generated by electro-magnetic radiation such as laser beam through the optoacoustic (thermoacoustic) effect on top of a standard 2D real time, pulse-echo ultrasound image. The overlaid optoacoustic image provides information regarding the concentration of substances in body fluids.

It is another object of the present invention to provide a mode of operation as an integral part of ultrasound imaging system enabling combination of pulse-echo ultrasound imaging with optoacoustic imaging.

In addition, it is provided in accordance with another preferred embodiment of the present invention an apparatus for guiding a laser beam focused to a predetermined position. Perform treatment and follow up treatment at the predetermined position, the apparatus comprising a pulse- echo ultrasound system adapted to receive and process the optoacousticaly generated ultrasound signals.

It is thus provided in accordance with a preferred embodiment of the present invention, an ultrasound imaging apparatus supporting pulse-echo ultrasound modes of operation as well as optoacoustic,(thermoacoustic) ultrasound mode of operation and displaying simultaneously the mode relevant images overlaid one on top of the other on a combined image; the system comprising: conventional pulse-echo ultrasound probe; pulsed electro-magnetic source generating radiation; control lines connecting said pulsed electro-magnetic source and said imaging apparatus..

Furthermore and in accordance with another preferred embodiment of the present invention, said source is selected from a group of radiation sources such as laser, microwave, or radio frequency.

Furthermore and in accordance with another preferred embodiment of the present invention, the apparatus performs measurement of the concentration of substances in body fluids and generating an optocoustic image combined with a pulse-echo ultrasound image, as a function of said concentration.

Furthermore and in accordance with another preferred embodiment of the present invention, the apparatus further comprising an attachment fixed to the conventional pulse-echo ultrasound probe that includes an optical fiber allowing a laser beam to be directed to a predetermined position relative to said ultrasound probe, wherein said laser beam generates radiation that is adapted to be directed to the predetermined position. Furthermore and in accordance with another preferred embodiment of the present invention, the laser beam is focused to the predetermined position and the optoacoustic signal is overlaid over a real-time 2D ultrasound image so as to establish a target for treatment and treatment monitoring of the tissue at the predetermined target position. Furthermore and in accordance with another preferred embodiment of the present invention, said radiation imparts power for treatment.

Furthermore and in accordance with another preferred embodiment of the present invention, said radiation is delivered to the body surface through an optical fiber that is an integral part of said pulse-echo ultrasound probe. Furthermore and in accordance with another preferred embodiment of the present invention, the operation sequence comprising: performing a first sequence of at least 1 pulse-echo along a predetermined axial direction; performing a second sequence of at least one electromagnetic excitation along said axial direction; performing said first sequence and said second sequence along multitude axial directions; constructing a final image from signals received from said multitude axial directions. Furthermore and in accordance with another preferred embodiment of the present invention, the operation sequence comprises: generating one complete pulse-echo image frame; generation a complete electromagnetically excited image frame to produce a final image; and combining final image from said pulse-echo images frame and excited image frame. BRIEF DESCRIPTION OF THE FIGURES

In order to better understand the present invention and appreciate its practical applications, the following Figures are attached and referenced herein. Like components are denoted by like reference numerals.

It should be noted that the figures are given as examples and preferred embodiments only and in no way limit the scope of the present invention as defined in the appending Description and Claims.

Figure-1 illustrates an attachment to ultrasound systems provided with new mode of operation supporting optoacoustic imaging in accordance with a preferred embodiment of the present invention, wherein the laser fiber is attached to the ultrasound probe.

Figure-2 illustrates an ultrasound apparatus provided with new mode of operation supporting optoacoustic imaging in accordance with another preferred embodiment of the present invention, wherein the laser fiber moves freely on the body.

Figure-3 illustrates an exemplary solution for an ultrasound system having a mode of operation providing for optoacoustic imaging together with 2D pulse echo ultrasound imaging in accordance with a preferred embodiment of the present invention.

Figure-4 illustrates an exemplary solution for an ultrasound system having a mode of operation providing for optoacoustic imaging together with 2D pulse echo ultrasound imaging in accordance with another preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION AND THE FIGURES

The present invention provides an ultrasound apparatus consisting of inclusion of a new operating mode into ultrasound imaging systems. The new mode will enable real-time combination of pulse echo ultrasound imaging with thermoacoustic (optoacoustic) imaging and display both images as one combined image.

According to one aspect of the present invention, attachment that can be fitted to a multitude of standard real time ultrasound imaging probes (transducers) is provided. The attachment includes a fiber that delivers the laser beam.

In a pulse echo system, an ultrasound pulse is transmitted along a predetermined direction and the ultrasound echoes are received as a function of time, using the ultrasound propagation velocity, the time is translated to distance along the predetermined direction: 2d=vt

The factor 2 accounts for the fact that the transmitted ultrasound and the reflected ultrasound propagate at the same velocity. A 2D image is obtained by repeating the procedure along a set of directions generating a 2D area and displaying the relevant echo intensity as brightness, (B mode).

For the thermoacoustic excitation, (optical, microwave, etc.), the generation of the ultrasound is by the electromagnetic radiation having a propagation velocity much higher then that of the ultrasound (actually relative to the ultrasound velocity it can be assumed as infinite). To enable the imaging of the thermoacousticaly excited ultrasound, in the new operating mode, the transmission of the ultrasound is disabled, the time dependent receiving is correlated with the timing of the external excitation pulse, the calculation of the distance along the receive direction should now be: d=vt Implementation Example-1

Receiving along each direction, at least twice; once in pulse echo method and once in thermoacoustic method as described above, generating relevant images. Both images are displayed one over the other at the correct geometrical locations. Displaying the thermoacoustic image in a different color than the ULS image will show the thermoacoustic properties on top of the pulse echo properties.

Implementation Example-2 Generate a complete 2D image with the pulse echo method,. then generate a second 2D image with the thermoacoustic method, adjust scaling and display the images one on top of the other.

It should be mentioned that all the consideration above can be applied also for synthetic aperture imaging methods; this is without limiting the scope of the present invention.

Reference is now made to Figures 1 and 2 illustrating ultrasound apparatii provided with new mode of operation supporting optoacoustic imaging in accordance with preferred embodiments of the present invention, wherein the laser fiber is attached to the ultrasound probe and moved freely on the body, respectively.

In Figure 1 , an integral assembly of an ultrasound imaging probe 22 and a laser fiber 6 that is fixed in attachment 14 is provided. Ultrasound probe 22 is used for the standard, pulse echo, ultrasound imaging and for the acquisition of the ultrasound signals generated by the optoacoustic effect. ULS probe 22 is an electronic array. The electronic array is connected to a

ULS system that includes the mode for optoacoustic imaging 21 or 31 ; the two options will be shown herein after.

ULS system including the mode for optoacoustic imaging 21 or 31 is electronically connected to ULS probe 22 as well as to laser 4. Figure 2 illustrates similar system; however, laser fiber 6 is not fixed to an attachment and in turn, is freely disposed on the body. Reference is now made to Figure 3 illustrating an exemplary solution for an ultrasound system having a mode of operation providing for optoacoustic imaging together With 2D pulse echo ultrasound imaging in accordance with a preferred embodiment of the present invention. Ultrasound system 21 comprises the following main components:

The electronic array of ULS probe 22 is connected through an acquisition unit 16 to a switch 15 switching between 2D data processing that comprises 2D beam former 17, 2D process 18, 2D scan converter 19, and the optoacoustic processing that comprises optoacoustic image former 9, optoacoustic processing 10, and optoacoustic scan converter 11. The switch is controlled by a controller 5 that controls also the laser sequence. The optoacoustic image and the 2D pulse echo ultrasound images are merged by a merger 12 and the combined image is displayed on monitor 13.

Reference is now made to Figure 4 illustrating an exemplary solution for an ultrasound system having a mode of operation providing for optoacoustic imaging together with 2D pulse echo ultrasound imaging in accordance with another preferred embodiment of the present invention. In this second example of the main components of ultrasound system 31, which is shown in Figure 2, the system comprises the new mode of operation arranged in a different manner than in the embodiment before.

The probe elements 22 are electronically connected through an acquisition unit 16 to a first switch 15 and a second switch 26 switching between 2D beam former 17 and a memory 23. Since each laser pulse generates optoacoustic signal in the whole illuminated region, the memory is required to store the optoacoustic signal received by each element of the receiver array in the attachment. Beam former 17 receives data either directly from the probe that scans the body, or from the memory component 23 by scanning it through a time matching circuit 24. The memory contains the optoacoustic data, the time matching circuit takes care of the fact that the time of flight for pulse echo is twice the time of flight for optoacoustics. The output of beam former 17 is switched by a third switch 27 between 2D processing 18 and optoacoustic processing 29. The output of the processing is directed through switch 28 to scan converter 30 combining the two image sources and displaying them on monitor 13. The laser sequence is controlled by controller 5.

It should be noticed that any other form of arrangement that implement the combined imaging can be used in the ULS system without limiting the scope of the present invention.

It should be clear that the description of the embodiments and attached Figures set forth in this specification serves only for a better understanding of the invention, without limiting its scope as covered by the following Claims. It should also be clear that a person skilled in the art, after reading the present specification can make adjustments or amendments to the attached Figures and above described embodiments that would still be covered by the following Claims.

Claims

C L A I M S

1. An ultrasound imaging apparatus supporting pulse-echo ultrasound modes of operation as well as optoacoustic,(thermoacoustic) ultrasound mode of operation and displaying simultaneously the mode relevant images overlaid one on top of the other on a combined image; the system comprising: conventional pulse-echo ultrasound probe; pulsed electro-magnetic source generating radiation; control lines connecting said pulsed electro-magnetic source and said imaging apparatus..

2. The apparatus as claimed in Claim 1 , wherein said source is selected from a group of radiation sources such as laser, microwave, or radio frequency.

3. The apparatus as claimed in Claim 1 , performing measurement of the concentration of substances in body fluids and generating an optocoustic image combined with a pulse-echo ultrasound image, as a function of said concentration.

4. The apparatus as claimed in Claim 1 , further comprising an attachment fixed to the conventional pulse-echo ultrasound probe that includes an optical fiber allowing a laser beam to be directed to a predetermined position relative to said ultrasound probe, wherein said laser beam generates radiation that is adapted to be directed to the predetermined position.

5. The apparatus as claimed in Claim 4, wherein the laser beam is focused to the predetermined position and the optoacoustic signal is overlaid over a real-time 2D ultrasound image so as to establish a target for treatment and treatment monitoring of the tissue at the predetermined target position.

6. The apparatus as claimed in Claim 1 , wherein said radiation imparts power for treatment.

7. The apparatus as claimed in Claim 1 , wherein said radiation is delivered to the body surface through an optical fiber that is an integral part of said pulse-echo ultrasound probe.

8. The apparatus as claimed in claim 1 , wherein the operation sequence comprising: performing a first sequence of at least 1 pulse-echo along a predetermined axial direction; performing a second sequence of at least one electromagnetic excitation along said axial direction; performing said first sequence and said second sequence along multitude axial directions; constructing a final image from signals received from said multitude axial directions.

9. A system as claimed in claim 1 , wherein the operation sequence comprises: generating one complete pulse-echo image frame; generation a complete electromagnetically excited image frame to produce a final image; and combining final image from said pulse-echo images frame and excited image frame.