Estimation of tissue strain using a 4D ultrasound catheter

Abstract

To provide a medical system.SOLUTION: The medical system includes an ultrasound probe configured for insertion into an organ of a body, and a processor. The probe includes a two-dimensional (2D) ultrasound transducer array, and a sensor configured to output signals indicative of a position, direction and orientation of the 2D ultrasound transducer array inside the organ. The processor is configured to (a) use the signals output by the sensor to register multiple ultrasound images of a tissue region, acquired over a given time duration by the 2D ultrasound transducer array, with one another, (b) estimate, based on the ultrasound images acquired over the given time duration, three-dimensional displacements as a function of time for one or more locations in the tissue region, (c) estimate respective mechanical strains of the one or more locations in the tissue region, based on the three-dimensional displacements, and (d) present a time-dependent rendering of the mechanical strains to a user.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention generally relates to invasive medical devices and methods, specifically, intravascular medical probes and methods using ultrasound.

Background Art

[0002] Invasive ultrasound techniques for evaluating the dynamic characteristics of the wall tissue of organs within the body have been previously proposed. For example, Bunting et al. describe a strain-based method called Myocardial Elastography (ME) for characterizing the size and location of ablation lesions within the myocardium in a paper titled "Cardiac lesion mapping in vivo using intracardiac myocardial elastography" (IEEE transactions on ultrasonics, ferroelectrics, and frequency control, 65.1 (2017), pages 14-20).

[0003] As another example, U.S. Patent No. 6,527,717 describes an accurate tissue motion system and method. The motion of an ultrasonic transducer is taken into account in the estimation of tissue motion. In one embodiment, the motion sensor includes a position sensor for determining the location of the transducer relative to a target or other reference point. The motion sensor may include a magnetic position sensor or an electromagnetic position sensor. By correcting for the transducer motion, localized tissue contraction or expansion, such as myocardial or fibrous motion, is better isolated. Accurate motion estimation is also provided by determining the angle of motion from ultrasonic data. The angle of motion is used to adjust the velocity estimate and provide a two-dimensional velocity vector (i.e., a motion estimate that includes motion in at least two dimensions). Tissue motion is determined by correlating speckles or features represented by two different sets of ultrasonic data acquired at different times. Additional embodiments include tracking the location of the tissue under consideration. Strain characteristics, such as strain velocity or strain, are calculated for the tracked tissue under consideration. Ultrasonic data associated with different locations relative to the transducer are selected as a function of tracking and used to determine the strain characteristics. Motion estimates corrected for transducer movement can also be used to determine strain or strain velocity. In yet another embodiment, motion estimates are generated using data from an intracardiac transducer array. Strain characteristics are determined from the motion estimates. The other embodiments described above can be used in conjunction with an intracardiac transducer array to provide accurate motion analysis based on imaging from within the heart.

[0004] In a paper titled "4D cardiac electromechanical activation imaging" (Computers in biology and medicine, 113(2019):103382), Grondin et al. suggest that electromechanical imaging techniques could enable scientists to link the electrical and mechanical functions of the heart. Since cardiac diseases typically manifest in both electrical and mechanical ways, such linking would have high clinical value, but currently lacks such mapping techniques in vivo.

[0005] U.S. Patent Application Publication No. 2020 / 0214662 describes a system and method for generating an electromechanical map. The method includes acquiring ultrasound data comprising a series of sequential image frames and radio frequency (RF) signals corresponding to locations within the heart; measuring displacement and strain based on the ultrasound data to determine electromechanical activation at those locations; converting the ultrasound data into a series of isochrone plots; and combining the series of isochrone plots to generate an electromechanical map. The electromechanical map shows the electromechanical activation and endovascular structure of the heart.

[0006] U.S. Patent No. 7,542,544 describes an ultrasound imaging system that acquires echo signals from an object being imaged, such as a moving coronary artery, where the cross-correlation between echo signals is used as an objective measure of relative object positioning. This method is used in a pre-scan procedure to determine the optimal gate window for acquiring image data during a cardiac gated scan and is used as a real-time gate signal during the scan. The present invention enables a highly flexible gate scheme. Since the acquired correlation data shows the instantaneous correlation between any phase of the cardiac cycle and any other phase, it is possible to gate during any phase of the cycle if desired. This only requires more heartbeats to acquire data. Since heartbeat-by-heartbeat mapping can be achieved for any spatial correspondence, including correspondences that change between heartbeats, it is also possible to acquire image data if the patient has an arrhythmia. Finally, the correlation can also accommodate multiple breath holds, as it detects any changes due to respiration.

[0007] International Publication No. 2020 / 044117 describes a catheter-based ultrasound imaging system configured to provide a 360-degree circumferential view around an intravascular / intracardiac imaging catheter head by generating a three-dimensional view of the tissue surrounding the imaging head over time. The ultrasound imaging system can also provide tissue state mapping capabilities. Assessment of vascular and tissue characteristics includes the pathway and depth of lesions during cardiac interventions such as ablation. The ultrasound imaging system comprises a catheter having a static or rotational sensor array tip supporting continuous circumferential rotation around its axis, connected to an ultrasound module and a separate processing machine that enables ultrafast imaging, and a rotational motor that rotates the sensor array tip by converting radial motion around the longitudinal catheter axis via a rotational torque transmission portion. This enables the capture and reconstruction of vascular information, including tissue structure around the catheter tip, for the generation of a three-dimensional view over time. [Overview of the project] [Problems that the invention aims to solve]

[0008] However, known approaches to measuring tissue strain in vivo are often noisy or do not provide the desired visibility for the purpose of clinical use. Therefore, improvement is desired. [Means for solving the problem]

[0009] One embodiment of the present invention, described below, provides a medical system comprising an ultrasound probe and a processor. The ultrasound probe is configured to be inserted into an organ of the body and comprises (i) a two-dimensional (2D) ultrasound transducer array and (ii) a sensor configured to output signals indicating the position, direction, and orientation of the 2D ultrasound transducer array within the organ. The processor is configured to (a) use the signals output by the sensor to align a plurality of ultrasound images of a tissue region acquired by the 2D ultrasound transducer array over a given duration with respect to each other; (b) estimate a three-dimensional displacement as a function of time for one or more locations within the tissue region based on the ultrasound images acquired over a given duration; (c) estimate the mechanical strain of each of the one or more locations within the tissue region based on the three-dimensional displacement; and (d) present a time-dependent rendering of the mechanical strain to the user.

[0010] In some embodiments, the processor is configured to present a time-dependent rendering of mechanical strain in conjunction with an electrophysiological (EP) signal layer.

[0011] In some embodiments, the EP signal layer includes local activation times (LAT). In other embodiments, the EP signal layer includes one of a bipolar tissue voltage level and a unipolar tissue voltage level.

[0012] In one embodiment, the processor is configured to use the signals output by the sensor to generate a composite rendering that includes a layer of heart rate timing and a layer of local activation time (LAT).

[0013] In another embodiment, the processor is further configured to use the estimated strain to identify scar tissue within a tissue region.

[0014] According to another embodiment of the present invention, a medical system comprising an ultrasound probe and a processor is additionally provided. The ultrasound probe is configured to be inserted into an organ of the body and comprises (i) a two-dimensional (2D) ultrasound transducer array and (ii) a sensor configured to output signals indicating the position, direction, and orientation of the 2D ultrasound transducer array within the organ. The processor is configured to (a) use the signals output by the sensor to align a plurality of ultrasound images of a tissue region acquired by the 2D ultrasound transducer array over a given duration with respect to each other; (b) estimate three-dimensional displacement as a function of time for one or more locations within the tissue region based on the ultrasound images acquired over a given duration; (c) estimate the mechanical strain of each of one or more locations within the tissue region based on the three-dimensional displacement; and (d) estimate the parameters of the cardiac cycle within the region based on the strain.

[0015] In some embodiments, the processor is configured to visualize cardiac cycle parameters to the user.

[0016] In some embodiments, the processor is configured to use the signals output by the sensor to generate a composite rendering that includes estimated cardiac cycle parameters and an electrophysiological (EP) signal layer.

[0017] In one embodiment, the parameters of the cardiac cycle include the period length. In another embodiment, the parameters of the cardiac cycle include the timing of the cardiac cycle.

[0018] In some embodiments, the processor is configured to use detected timing to trigger another device in sync with the cardiac cycle.

[0019] According to another embodiment of the present invention, a method is further provided which includes inserting an ultrasound probe into an organ of the body, the ultrasound probe comprising (i) a two-dimensional (2D) ultrasound transducer array, and (ii) a sensor configured to output signals indicating the position, direction, and orientation of the 2D ultrasound transducer array within the organ. Multiple ultrasound images of a tissue region acquired by the 2D ultrasound transducer array over a given duration are aligned with each other using signals output by the sensor. Based on the ultrasound images acquired over a given duration, three-dimensional displacement as a function of time is estimated for one or more locations within the tissue region. The mechanical strain for each of the one or more locations within the tissue region is estimated based on the three-dimensional displacement. A time-dependent rendering of the mechanical strain is presented to the user.

[0020] According to another embodiment of the present invention, a method is further provided which includes inserting an ultrasound probe into an organ of the body, the ultrasound probe comprising (i) a two-dimensional (2D) ultrasound transducer array, and (ii) a sensor configured to output signals indicating the position, direction, and orientation of the 2D ultrasound transducer array within the organ. Multiple ultrasound images of a tissue region acquired by the 2D ultrasound transducer array over a given duration are aligned with each other using signals output by the sensor. Based on the ultrasound images acquired over a given duration, three-dimensional displacement as a function of time is estimated for one or more locations within the tissue region. The mechanical strain of each of the one or more locations within the tissue region is estimated based on the three-dimensional displacement. Based on the strain, parameters of the cardiac cycle are estimated within the region.

[0021] The present invention will be more fully understood by considering the following "Modes for Carrying Out the Invention" in conjunction with the drawings.

Brief Description of the Drawings

[0022] [Figure 1] It is a schematic depiction of a catheter-based ultrasonic imaging system using a catheter having a distal end assembly comprising a 2D ultrasonic probe and a location sensor according to an embodiment of the present invention. [Figure 2] It is a schematic depiction of ultrasonic intracardiac acquisition using the system of FIG. 1, followed by derivation of tissue motion maps, composite tissue motion, EP propagation maps, and EP parameters according to an embodiment of the present invention. [Figure 3] It is a flowchart schematically showing a method for deriving and displaying the results of FIG. 2 according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[0023] Overview Embodiments of the present invention described herein provide methods and systems for using a probe, such as a catheter, having a 2D array of ultrasonic transducers for generating three-dimensional (3D) or four-dimensional (4D) ultrasonic images. In this context, the term "3D ultrasonic image" refers to an ultrasonic image representing a specific volume in three dimensions. The term "4D ultrasonic catheter" refers to a catheter incorporating a 2D array of ultrasonic transducers. The term "4D ultrasonic image" refers to a time series of 3D ultrasonic images of a specific volume acquired by the 2D array. A 4D image can be regarded as a 3D video, and the fourth dimension is time. Another way to describe a 4D image (or rendering) is as a time-dependent 3D image (or rendering). When used in the heart, a 4D ultrasonic catheter may be referred to as an "Intracardiac Echocardiography (ICE)" catheter.

[0024] In the disclosed embodiments, the catheter also includes an integrated location sensor, such as a magnetic location sensor, that is pre - aligned with the 2D array based on a known relative position and orientation on the catheter shaft between the location sensor and the 2D array. The 2D array generates an ultrasonic beam in the shape of a 3D sector that occupies a defined solid angle (such a beam is referred to herein as a "wedge" in contrast to the "fan" of a 1D array). Thus, the 2D array can image a 2D section of the inner wall of an organ, such as a ventricle. Due to the integrated location sensor and its pre - alignment with the 2D array, the spatial coordinates of all voxels within the imaged section are known.

[0025] In one embodiment, the processor uses location data from the location sensor to align real - time acquisitions (e.g., images of a given cardiac region acquired over a given duration) within the space with each other. In this way, the processor can subtract the movement of the catheter and thus can show the movement of the tissue region with very high accuracy. This method can be applied at the acquired data level or the image level, and the images can be aligned to remove the movement of the catheter.

[0026] Specifically, some embodiments of the present invention use a 4D ultrasonic catheter to measure the movement of selected tissue regions with high spatio - temporal resolution. The movement analysis can be performed by an algorithm that tracks the location of tissue within a series of images, such as a series of MPEG images. The operator of the 4D catheter can select, for example, the location, (ξ,η,ζ), of a particular tissue within the wall of the left ventricle. Then, the processor tracks the location of the tissue over time in three dimensions. The tracking provides the 3D values of the tissue location displacement (Δξ,Δη,Δζ) over time, and different values correspond to the mechanical strain of the internal tissue.

[0027] As described above, the accuracy of the displacement values ​​(Δξ, Δη, Δζ) is significantly greater than that of catheters without an integrated location sensor. This is because catheters without an integrated location sensor have no way of subtracting their own movement. Furthermore, since strain is measured in three orthogonal directions, embodiments of the present invention can calculate a strain tensor as described below. The result provides accurate three-dimensional cardiac motion, which the processor can present to the user as a map or video.

[0028] Typically, electrophysiological (EP) renderings of cardiac chamber images presented to electrophysiologists are tissue surface maps superimposed with color values ​​of derived electrical parameters, such as local activation time (LAT). The flow of cardiac EP wavefronts over the ventricles, such as the ventricles, as a heartbeat, provides useful information to electrophysiologists. LAT typically corresponds to myocardial movement, and it would be useful to be able to visualize this movement without needing to acquire the electrical signals used to derive LAT. Correlating the flow of EP parameters with myocardial movement along the cardiac cycle would also be useful.

[0029] Several embodiments of the present invention use a 4D ultrasound catheter to acquire images of the cardiac chamber walls during a given heartbeat. The images are analyzed to show how the muscles move in the waves passing through the heart during the heartbeat. In one embodiment, a processor converts momentum into a color scale and then overlays the motion-representing colors onto the ultrasound image. The resulting image effectively functions as a replacement for a "standard" LAT map but has the advantage of not requiring the acquisition of electrical signals from the heart.

[0030] Alternatively, wave motion can be incorporated into the EP parameter map, allowing both EP propagation ("electrical motion") and physical motion to be observed simultaneously on the same map. Visualizing the two motions on the same map allows observation of correlations between them (or lack thereof, which can indicate the organizing source of rhythmic disturbances).

[0031] When the heart is beating irregularly, i.e., not in sinus rhythm, measuring the heart rate, i.e., the period length, can be difficult. Therefore, some embodiments of the present invention use a 4D ultrasound catheter to acquire images of the cardiac chamber walls as heartbeats. In one embodiment, images are acquired over a number of heartbeats, and the images are analyzed to show the movement of the cardiac muscle. These movements are then used to estimate parameters of the cardiac cycle, such as the period length and the timing of the period relative to some reference time.

[0032] The analysis can also reveal details of any irregularities that may occur, such as atrial fibrillation (AF) or premature ventricular contractions (PVCs). Period length and timing can be correlated with measured electrical activity, such as electrocardiograph (ECG) signals, and as a result, acquired ultrasound images can be used as triggers for some external device instead of using ECG signals.

[0033] During intracardiac procedures involving ultrasound imaging, it can be difficult to identify areas of the ventricle containing scar tissue. Several embodiments of the present invention image cardiac walls, such as the left ventricular wall, and measure the motion of the wall surface. Scar tissue in the wall moves differently from the surrounding areas and is typically stationary. In some embodiments, a processor analyzes the acquired images in real time to identify stationary areas or areas that move differently from their surroundings. The identified areas are marked as scar tissue on the displayed video image, also in real time.

[0034] System Description Figure 1 is a schematic diagram of a catheter-based ultrasound imaging system 20 according to one embodiment of the present invention, which uses a catheter 21 having a distal end assembly 40 comprising a 2D ultrasound array 50 and a location sensor 52. The integrated location sensor 52 is pre-aligned with the 2D array 50 of the catheter 21.

[0035] Specifically, the sensor 52 is configured to output a signal indicating the position and orientation of the 2D ultrasound transducer array 52 within the organ. The system's processor is configured to use the signal output by the sensor to align multiple ultrasound image sections acquired by the 2D ultrasound transducer array 50 with each other.

[0036] As shown, the distal end assembly 40 is attached to the distal end of the catheter shaft 22. The catheter 21 is inserted through the sheath 23 into the heart 26 of a patient 28 lying on an operating table 29. The proximal end of the catheter 21 is connected to a control console 24. In the embodiments described herein, the catheter 21 is used for ultrasound-based diagnostic purposes, but the catheter may be further used, for example, with a tip electrode 56, to perform treatments such as electrical sensing and / or ablation of tissue within the heart 26.

[0037] The physician 30 navigates the distal end assembly 40 of the catheter 21 to a target location within the heart 26 by manipulating the shaft 22 using a manipulator 32 near the proximal end of the catheter.

[0038] In one embodiment, the 2D ultrasound array 50, shown in detail in inset 25, is configured to image the left atrium of the heart 26.

[0039] As shown in inset 45, the ultrasound array 50 includes a 2D array 50 of multiple ultrasound transducers 53. Inset 45 shows the ultrasound array 50 navigated to the hilum 54 of the pulmonary veins in the left atrium. In this embodiment, the 2D array 50 is an array of 32 × 64 ultrasound transducers. The 2D array can image a section of the inner wall of the hilum. For the integrated location sensor and its pre-alignment with the 2D array, the spatial coordinates of all pixels in the imaged section are known. A suitable example of a 2D array is described in "4-D ICE: A 2-D Array Transducer With Integrated ASIC in a 10-Fr Catheter for Real-Time 3-D Intracardiac Echocardiography" by D. Wildes et al. in IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 63, no. 12, pp. 2159-2173, Dec. 2016, doi: 10.1109 / TUFFC.2016.2615602, which is incorporated herein by reference in its entirety.

[0040] The control console 24 includes a processor 39, typically a general-purpose computer, with a suitable front-end and interface circuit 38 for receiving signals from the catheter 21, and optionally for performing procedures via the catheter 21 within the heart 26, and for controlling other components of the system 20. The console 24 also includes a driver circuit 34 configured to drive a magnetic field generator 36.

[0041] During the navigation of the distal end 22 in the heart 26, the console 24 receives position and orientation signals from the location sensor 52 in response to the magnetic field from the external magnetic field generator 36. The magnetic field generator 36 is located at a known location outside the patient 28, for example, under the table 29 on which the patient is lying. These position and orientation signals indicate the position and orientation of the 2D ultrasound array 50 in the coordinate system of the position tracking system.

[0042] Methods for sensing position and orientation using an external magnetic field are implemented in various medical applications, for example, in the CARTO® system manufactured by Biosense Webster, and are described in detail in U.S. Patent Nos. 6,618,612 and 6,332,089, International Publication No. 96 / 05768, and U.S. Patent Application Publications 2002 / 0065455, 2003 / 0120150, and 2004 / 0068178, all of which are incorporated herein by reference.

[0043] Exemplary catheters and imaging assemblies that allow deflection and rotation to facilitate imaging by a physician are described in detail in U.S. Patent No. 9,980,786, No. 10,537,306, and U.S. Patent Application Publication No. 2020-0061340(A1), all of which are incorporated herein by reference.

[0044] In some embodiments, the processor 39 can be configured to operate the array 50 in “time mode” to image the movement of cardiac regions over time, with gated acquisitions occurring over multiple heartbeats. Additionally or alternatively, imaging can be performed over a single heartbeat. In one embodiment, the imaged cardiac regions are presented to the physician 30 by the processor 39 on the monitor 27, for example, as a real-time volumetric rendering 55 video.

[0045] The processor 39 typically comprises a general-purpose computer, which is programmed with software that performs the functions described herein. The software can be downloaded to the computer in electronic form, for example, over a network, or, alternatively or additionally, can be provided and / or stored on a non-temporary physical medium such as magnetic memory, optical memory, or electronic memory.

[0046] The exemplary configuration shown in Figure 1 is selected solely for the purpose of clarifying the concept. The techniques of this disclosure can be similarly applied using other system components and settings. For example, system 20 may include additional components to perform non-cardiac catheterization procedures.

[0047] Estimation and presentation of organizational distortions As described above, a 4D catheter operator can select a specific tissue location (ξ,η,ζ) within the wall of the left ventricle, for example, and the tissue location is tracked in three dimensions over time. The tracking provides 3D values ​​(Δξ,Δη,Δζ) of the change in the tissue location over time, with different values ​​corresponding to the distortion of the internal tissue.

[0048] The 3D distortion tensor, which can then be visualized across organ renderings, can be calculated as follows:

[0049]

number

[0050]

number

[0051] Figure 2 is a schematic diagram illustrating the intracardiac ultrasound acquisition using the system 20 of Figure 1 according to an embodiment of the present invention, followed by the derivation of a tissue motion map 350, composite tissue motion, local activation time (LAT) map 355, and EP parameters 377.

[0052] As can be seen, system 20 uses catheter 21 to perform ultrasound 2D beam 250 acquisition of an imaged section 260 of the inner wall 54 of organ 254. During ultrasound acquisition, location sensor 52 tracks the position, orientation, and direction of the ultrasound array 50 in the coordinate system 333 of the magnetic tracking system in Figure 1.

[0053] Figure 2 shows the location of specific tissue within wall 54 {(ξ j ,η j ,ζ j )}222 is tracked in 3D over time, {(ξ j (t), η j (t), ζ j This further illustrates how graph 344 of (t)} is obtained.

[0054] Using the 3D tracked location and equations 1 and 2 above, the processor 39 generates a rendering 350 of tissue distortion. The rendering 350 may be a color-coded rendering, where different colors 352 indicate different levels of distortion. In the rendering 350, scar tissue areas 354 can be identified by their intrinsic color, such that they exhibit very low distortion (e.g., distortion below a given threshold).

[0055] As seen in Figure 2, using the alignment enabled by the location readings of the array 50 by the sensor 52, the processor 39 can further combine the rendering 350 with the rendering of EP characteristics (such as rendering of LAT values) to obtain a composite rendering 355. As can be seen, both the color-coded physical motion of the EP wavefront 360 and the rendering 350 are observed simultaneously on the same map 355.

[0056] Finally, the processor 39 can analyze the map 350 to derive and display cardiac pulse parameters 377, such as period length and heartbeat timing.

[0057] The exemplary configuration shown in Figure 2 is selected solely for the purpose of clarifying the concept. For example, the composite map 355 may include other EP maps, such as a bipolar tissue voltage level map or a unipolar tissue voltage level map.

[0058] Figure 3 is a schematic flowchart illustrating a method for deriving and displaying the results of Figure 2 according to one embodiment of the present invention. This procedure begins in step 380, 4D ultrasound acquisition, by performing intraventricular 2D ultrasound acquisition, as shown in Figure 1.

[0059] Next, in the tissue motion map derivation step 382, ​​the processor 39 derives a tissue motion map, such as the rendering 350 shown in Figure 2.

[0060] In the 3D distortion rendering presentation step 384, the processor 39 displays to the user the cardiac tissue motion rendering from step 382, ​​such as the rendering 55 on the monitor 27 in Figure 1.

[0061] To generate a composite map such as map 360, the processor 39, in a coordinate alignment step 388, uses readings from the sensor 52 to align the coordinates of the tissue motion map with the coordinates of an EP map such as a LAT map.

[0062] Subsequently, in the composite rendering presentation step 390, the processor 39 can display the composite rendering from step 388 to the user on the monitor 27 in Figure 1.

[0063] Using the strain map derived in step 382, ​​the processor 39 extracts cardiac function parameters, such as the heartbeat parameters 377 in Figure 2, in the cardiac parameter extraction step 392. Finally, in the cardiac parameter presentation step 394, the processor 39 can display the cardiac parameters extracted from the exercise map in step 382 to the user on the monitor 27 in Figure 1. In one embodiment, cardiac parameters (e.g., period time) are displayed as a graphically coded 3D rendering. Additionally or alternatively, cardiac period timing can be used as a trigger signal to synchronize some external device.

[0064] In various embodiments, the process shown in Figure 3 above can be applied to 4D and / or 3D images as needed.

[0065] While the embodiments described herein primarily address cardiac applications, the methods and systems described herein can be used for other body organs with necessary modifications. For example, strain information from ultrasound can be correlated with intramuscular calcium levels estimated using another imaging modality. As another example, ultrasound can be used to measure diaphragmatic strain in correlation with nerve excitation when evaluating diaphragmatic function.

[0066] Accordingly, the embodiments described above are cited as examples, and it will be understood that the present invention is not limited to those specifically shown and described above. Rather, the scope of the present invention includes both combinations and partial combinations of the various features described in the above specification, as well as variations and modifications thereof not disclosed in the prior art, which would be conceivable to those skilled in the art by reading the foregoing description. Documents incorporated into this patent application by reference shall be considered integral parts of this application, except that to the extent that any term is defined in such incorporated documents in a manner that contradicts the definitions made expressly or implicitly herein, only the definitions herein shall be considered.

[0067] [Implementation Method] (1) A medical system, An ultrasound probe for insertion into the body's organs, A two-dimensional (2D) ultrasonic transducer array, An ultrasonic probe comprising: a sensor configured to output signals indicating the position, direction, and orientation of the 2D ultrasonic transducer array within the organ; It is a processor, Using the signal output by the sensor, multiple ultrasound images of tissue regions acquired over a given duration by the 2D ultrasound transducer array are aligned relative to each other. Based on the ultrasound images acquired over the given duration, the three-dimensional displacement is estimated as a function of time for one or more locations within the tissue region. Based on the three-dimensional displacement, estimate the mechanical strain at one or more locations within the tissue region, A processor configured to present the user with a time-dependent rendering of the aforementioned mechanical distortion, A medical system equipped with these features. (2) The medical system according to Embodiment 1, wherein the processor is configured to present the time-dependent rendering of the mechanical strain together with an electrophysiological (EP) signal layer. (3) The medical system according to Embodiment 2, wherein the EP signal layer includes a local activation time (LAT). (4) The medical system according to Embodiment 2, wherein the EP signal layer includes one of a bipolar tissue voltage level and a unipolar tissue voltage level. (5) The medical system according to Embodiment 1, wherein the processor is configured to use the signal output by the sensor to generate a composite rendering including a layer of heart rate timing and a layer of local activation time (LAT).

[0068] (6) The medical system according to Embodiment 1, wherein the processor is further configured to use the estimated strain to identify scar tissue within the tissue region. (7) A medical system, An ultrasound probe for insertion into the body's organs, A two-dimensional (2D) ultrasonic transducer array, An ultrasonic probe comprising: a sensor configured to output signals indicating the position, direction, and orientation of the 2D ultrasonic transducer array within the organ; It is a processor, Using the signal output by the sensor, multiple ultrasound images of tissue regions acquired over a given duration by the 2D ultrasound transducer array are aligned relative to each other. Based on the ultrasound images acquired over the given duration, the three-dimensional displacement is estimated as a function of time for one or more locations within the tissue region. Based on the three-dimensional displacement, estimate the mechanical strain at one or more locations within the tissue region, A processor configured to estimate the parameters of the cardiac cycle within the region based on the aforementioned strain, A medical system equipped with these features. (8) The medical system according to Embodiment 7, wherein the processor is configured to visualize the parameters of the cardiac cycle to the user. (9) The medical system according to Embodiment 7, wherein the processor is configured to use the signals output by the sensor to generate a composite rendering including the estimated parameters of the cardiac cycle and an electrophysiological (EP) signal layer. (10) The medical system according to Embodiment 7, wherein the parameters of the cardiac cycle include the period length.

[0069] (11) The medical system according to Embodiment 7, wherein the parameters of the cardiac cycle include the timing of the cardiac cycle. (12) The medical system according to Embodiment 10, wherein the processor is configured to use the detected timing to trigger another device in synchronization with the cardiac cycle. (13) A method, The procedure involves inserting an ultrasound probe into an organ of the body, wherein the ultrasound probe is A two-dimensional (2D) ultrasonic transducer array, The system includes a sensor configured to output signals indicating the position, direction, and orientation of the 2D ultrasound transducer array within the organ, and is intended for insertion. Using the signal output by the sensor, multiple ultrasound images of tissue regions acquired over a given duration by the 2D ultrasound transducer array are aligned relative to each other. Based on the ultrasound images acquired over the given duration, the three-dimensional displacement is estimated as a function of time for one or more locations within the tissue region. Based on the three-dimensional displacement, estimate the mechanical strain at one or more locations within the tissue region, Presenting the user with a time-dependent rendering of the aforementioned mechanical distortion, Methods that include... (14) The method according to Embodiment 1, wherein presenting the time-dependent rendering includes presenting the time-dependent rendering of the mechanical strain together with an electrophysiological (EP) signal layer. (15) The method according to embodiment 14, wherein the EP signal layer includes a local activation time (LAT).

[0070] (16) The method according to embodiment 14, wherein the EP signal layer includes one of a bipolar structure voltage level and a unipolar structure voltage level. (17) The method according to Embodiment 13, comprising using the signal output by the sensor to generate a composite rendering including a layer of heart rate timing and a layer of local activation time (LAT). (18) The method of Embodiment 13, comprising using the estimated strain to identify scar tissue within the tissue region. (19) A method, The procedure involves inserting an ultrasound probe into an organ of the body, wherein the ultrasound probe is A two-dimensional (2D) ultrasonic transducer array, The system includes a sensor configured to output signals indicating the position, direction, and orientation of the 2D ultrasound transducer array within the organ, and is intended for insertion. Using the signal output by the sensor, multiple ultrasound images of tissue regions acquired over a given duration by the 2D ultrasound transducer array are aligned relative to each other. Based on the ultrasound images acquired over the given duration, the three-dimensional displacement is estimated as a function of time for one or more locations within the tissue region. Based on the three-dimensional displacement, estimate the mechanical strain at one or more locations within the tissue region, Based on the aforementioned strain, the parameters of the cardiac cycle within the region are estimated, Methods that include... (20) The method according to embodiment 19, wherein the parameters of the cardiac cycle are visualized to the user.

[0071] (21) The method according to Embodiment 19, comprising using the signal output by the sensor to generate a composite rendering including the estimated parameters of the cardiac cycle and an electrophysiological (EP) signal layer. (22) The method according to embodiment 19, wherein the parameters of the cardiac cycle include the period length. (23) The method according to embodiment 19, wherein the parameters of the cardiac cycle include the timing of the cardiac cycle. (24) The method of Embodiment 23, which includes using the detected timing to trigger another device in synchronization with the cardiac cycle.

Claims

1. It is a medical system, An ultrasound probe for insertion into the body's organs, A two-dimensional (2D) ultrasonic transducer array, An ultrasonic probe comprising: a sensor configured to output signals indicating the position, direction, and orientation of the 2D ultrasonic transducer array within the organ; It is a processor, Using the signal output by the sensor, multiple ultrasound images of tissue regions acquired over a given duration by the 2D ultrasound transducer array are aligned relative to each other, and the movement of the ultrasound probe is eliminated. Based on the ultrasound images acquired over the given duration, the three-dimensional displacement is estimated as a function of time for one or more locations within the tissue region. Based on the three-dimensional displacement, estimate the mechanical strain at one or more locations within the tissue region, A processor configured to present to the user a time-dependent 3D image showing the level of mechanical strain in different colors, A medical system equipped with these features.

2. The medical system according to claim 1, wherein the processor is configured to display the time-dependent 3D image showing the mechanical strain overlaid with a map showing electrophysiological (EP) signals.

3. The medical system according to claim 2, wherein the map showing the EP signal includes local activation time (LAT).

4. The medical system according to claim 2, wherein the map showing the EP signal includes at least one of bipolar tissue voltage levels and unipolar tissue voltage levels.

5. The medical system according to claim 1, wherein the processor is configured to use the signal output by the sensor to align the coordinates of a map showing mechanical strain with the coordinates of a map showing local activation time (LAT), and to generate a composite map including information indicating the timing of heartbeats.

6. The medical system according to claim 1, wherein the processor is further configured to identify as scar tissue a region exhibiting strain below a given threshold, or a region moving differently from the surrounding region.

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