Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/08—Clinical applications
  • A61B8/0883—Clinical applications for diagnosis of the heart
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/48—Diagnostic techniques
  • A61B8/485—Diagnostic techniques involving measuring strain or elastic properties
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/52—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/5215—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves involving processing of medical diagnostic data
  • A61B8/5238—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves involving processing of medical diagnostic data for combining image data of patient, e.g. merging several images from different acquisition modes into one image
  • A61B8/5246—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves involving processing of medical diagnostic data for combining image data of patient, e.g. merging several images from different acquisition modes into one image combining images from the same or different imaging techniques, e.g. color Doppler and B-mode
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/54—Control of the diagnostic device
  • A61B8/543—Control of the diagnostic device involving acquisition triggered by a physiological signal
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/46—Ultrasonic, sonic or infrasonic diagnostic devices with special arrangements for interfacing with the operator or the patient
  • A61B8/461—Displaying means of special interest

Definitions

• This invention relates to ultrasonic diagnostic imaging systems and, in particular, to the use of ultrasonic strain imaging to evaluate ischemic areas of the heart which have suffered an infarct.
• cardiology ultrasound One of the uses of cardiology ultrasound is to evaluate the heart of a patient who has suffered an infarct. It would be desirable, for instance, to be able to image the coronary arteries to look for blockages that may have caused an ischemic event.
• Ultrasound is generally not capable of directly visualizing the coronary arteries due their motion, location outside the heart, proximity to the lungs, and other characteristics.
• arterial functions are indirectly diagnosed with ultrasound by assessing myocardial wall motion.
• An abnormal or asynchronous wall motion suggests reduced arterial flow, probably due an occlusion of a coronary artery by an arterial plaque or blood clot.
• Abnormal functioning of the myocardium due to an occlusion can be diagnosed by visualizing the contractility of the myocardium. Contractility can be assessed by
• strain is determined by tracking myocardial motion over the full heart cycle or at least its contraction phase, only one strain image can be produced for a heart cycle.
• the present invention includes ultrasound systems, such as an ultrasonic diagnostic imaging system for real time strain imaging that includes an ultrasound imaging probe having an array transducer which acquires ultrasound echo signals, an image processor, coupled to the imaging probe, which produces a first sequence of image frames in real time, a strain calculator coupled to the image processor which processes image frame data to
• a color mapper which produces a color map from strain values
• a color map warper that is responsive to the color map and a new sequence of image frames and configured to warp the color map to an image frame of the new sequence to generate a warped color map
• a display which displays an image frame in
• the present invention can include an ultrasound imaging system having
• the present invention includes methods of ultrasound imaging, such as a method of producing real time ultrasonic strain images, which includes acquiring frames of echo image data, estimating tissue displacements between acquired frames from the echo image data, calculating strain values from the displacements, forming a color map of the strain values, acquiring additional frames of echo image data, warping the color map to the
• FIGURE 1 is a block diagram of an ultrasound system constructed in accordance with the principles of the present invention.
• FIGURES 2a - 2d illustrate the motion of points in the myocardium during the contraction of the heart .
• FIGURE 3 illustrates motion of points in the myocardium when observed in a short axis view of the heart .
• FIGURE 4 is a flowchart of strain imaging of the heart in accordance with the principles of the present invention.
• FIGURE 5 illustrates cross-correlation functions of the echo data of consecutive images of the heart.
• FIGURE 6 graphically illustrates a typical cross-correlation distribution of speckle from a moving heart in an embodiment of the present
• an ultrasonic diagnostic imaging system which is able to image the heart at a high frame rate and calculate strain over localized areas of the myocardium. For each pixel on the image, a strain parameter is determined which is
• strain map is then fitted to the first image of the next heart cycle and displayed as a parametric color overlay over the image frames of the next cycle of heart images.
• the color overlay is warped to
• the present invention provides ultrasonic diagnostic imaging systems for real time strain imaging.
• the ultrasound systems can include a variety of components, such as an ultrasound imaging probe.
• the probe can include an array transducer which acquires ultrasound echo signals.
• the systems can include an image processor.
• the image processor can be coupled to the imaging probe and configured to produce a first sequence of image frames in real time.
• the systems can include a strain calculator coupled to the image processor. The strain
• the calculator can be configured to process image frame data to estimate strain during the image frame sequence.
• the systems can include a color mapper.
• the systems can be configured to include processors, memory, and other structures that can be programmed to serve as a color mapper.
• the color mapper can be configured to produce a color map based on the strain values.
• the systems can include a color map warper.
• the systems can include a color mapper.
• the systems can be configured to include processors, memory, and other structures that can programmed to serve as a color map warper.
• the color map warper can be responsive to the color map and a new sequence of image frames and configured to warp the color map to an image frame of the new sequence, thereby
• the systems can also include a display which displays an image frame in combination with the warped color map.
• the image frames can include cardiac image frames.
• the first sequence of image frames can be acquired during a first heart cycle, and a new sequence of image frames can be acquired during a subsequent heart cycle.
• the systems can include a frame memory, coupled to the image processor, which stores sequences of image frames .
• the systems can include a displacement estimator.
• the systems can include a color mapper.
• the systems can be configured to include processors, memory, and other structures that can be programmed to serve as a displacement
• the displacement estimator can be responsive to a sequence of image frames can configured to estimate tissue
• the displacement estimator can include a displacement cross-correlator which estimates displacements by cross-correlating echo data, and a displacement integrator which performs Lagrangian integrated displacement values.
• the systems can include a speckle tracker which identifies tissue
• the systems can include a color mapper.
• the systems can be configured to include processors, memory, and other structures that can be programmed to operate as the speckle tracker and the color mapper.
• the systems can be coupled to an ECG sensor, which senses a patient ECG waveform.
• the systems can further include a beamformer, coupled to the array
• transducer which operates to acquire image frame sequences in relation to the ECG waveform.
• a probe 10 has a transducer array of elements 12 which scans the region of the body in front of the array.
• the array may be a one-dimensional or a two- dimensional array for 2D or 3D scanning.
• the array transducer is operated as a phased array.
• the probe is operated by a beamformer 20 which controls the timing of transmit pulses and processes received echo signals.
• the probe 10 is coupled to the mainframe ultrasound system by a probe cable 14 and a transmit/receive switch 16 which protects sensitive electronics of the beamformer during high voltage transmission.
• the beamformer delays and combines signals received from the
• transducer elements to form coherent echo signals from points in the image field.
• the echo signals are coupled to a signal processor 22 which enhances the signals as by filtering and produces detected echo signals.
• the processed echo signals are then formed into a spatial image of the desired format by an image processor 24. Successively produced image frames are stored in a frame memory 30.
• the effect of such force is estimated by measuring strain, the deformation of the heart resulting from contractile stress.
• the strain measurement process begins by tracking the motion of the myocardium as it contracts. Since ultrasound produces coherent signals, it exhibits a phenomenon known as speckle. So long as the probe remains stationary, the speckle pattern will persist from one image frame to the next. The detailed speckle pattern is tracked by a speckle tracker 32, which thereby follows small regions of myocardial tissue by following the change in position of their speckle pattern from one image frame to the next. Since the echo signal intensity variation resulting from speckle is at a very low level and thus
• FIGURE 1 illustrates displacements of the speckle pattern from one image to the next by cross- correlation.
• the echoes of consecutive image frames are cross-correlated by a displacement cross- correlator 34 to locate the peak of the cross- correlation function.
• a typical cross-correlation function is shown in FIGURE 6.
• FIGURE 7 illustrates one cross-correlation function 52 from the cross- correlation of first and second consecutive image frames, and a second cross-correlation function 54 from the cross-correlation of the second and the next consecutive image frames.
• This lag d is the displacement of the tissue in the image sequence from one frame to the next. Because this lag signal is susceptible to noise, the displacements over a plurality of consecutive frames are integrated by a displacement integrator 36.
• a displacement integrator 36 Preferably
• Lagrangian integration is used to produce a single value for each point in the myocardium which is representative of the displacements over the
• the integrated displacements are then used by a strain calculator 38 to produce spatial derivatives which are spatial strain values for each pixel location.
• a weighted combination of nominal and shear strain values is used to create a parametric image.
• One example of such combination is: ( 0.5E yy +0.25E xy +0.25E XX ), where E xx is the strain perpendicular to an A-line, E yy is strain along the A-line and E xy is the shear strain extracted from axial displacements. This is a measure of rotation.
• These strain values are then mapped as color values in a two-dimensional or three- dimensional color map by strain color mapping 40.
• the color map spatially corresponds to the myocardium as it appears in the image frames over which the strain values were calculated.
• the color map could be displayed as a static color map of strain for the heart cycle over which the strain values were
• the strain color map is stored in the strain color mapping processor 40 and frames are acquired over a subsequent heart cycle.
• frames of each heart cycle are acquired at known phases of the heart cycle in relation to the R-wave of the heart's ECG signal.
• physiological electrodes 26 are attached to the patient's body during scanning for the production of an ECG waveform and image frame acquisition timing can thereby be based upon the timing of the R-wave of the ECG signal.
• the strain color mapping processor 40 When the R-wave of the subsequent heart signal is produced, it triggers the strain color mapping processor 40 to couple the color map to a color map warper 42.
• the color map warper receives an image frame produced during the new heart cycle and may optionally also receive spatial information on the tracked speckle in the new image from the speckle tracker 32. The color map warper then warps or fits the color map from the previous heart cycle to the cardiac image of the new heart cycle. With the color map thus spatially aligned to the
• the warped color map and the new image frame are coupled to the display processor, where the color map is applied as a color overlay over the image frame.
• the new image frame and its color overlay of the warped color map are then displayed on a display 50.
• the color map of the myocardial strain is thereby fit within the boundary of the myocardium in each image of the new heart cycle.
• Each warped color map is then displayed as a color overlay superimposed over each successive cardiac image frame of the new heart cycle.
• the real time display of the image frames of the new heart cycle thus includes the fitted strain color overlay which thereby displays a dynamic real time image sequence of the strain characteristics of the
• the tracked speckle values of each new image frame of the new heart cycle can be used by the color map warper 42 to fit the strain values of the color map to corresponding speckle locations in each new image frame. Rather than warping the color map as a whole, the strain values of the color map are continually repositioned to match with their changing corresponding speckle locations in each new image frame.
• elements 32-40 of the ultrasound system are calculating strain values over the new heart cycle so that a new color map is produced for the new heart cycle.
• the new color map is then used as a new warped color overlay for the following cardiac cycle.
• FIGURE 2 illustrates how individual points of the myocardium can move during a contraction of the heart and how this movement manifests itself in ultrasound images.
• FIGURE 2a shows three points in the myocardium, My A , My B , and My c , which move during heart contraction along respective paths A, B and C. After an initial period of time, the time between successive image frames in this example, the points in the myocardium have contracted to the positions along paths A, B, and C as shown in FIGURE 2b) .
• FIGURE 2d captured by ultrasound imaging is a succession of straight-line displacements 60 as shown in FIGURE 2d) .
• This displacement when depicted in the larger context of myocardial contraction, would appear as shown in FIGURE 3.
• This drawing shows a short axis view of the myocardium in which the myocardial slice through the heart appears like a donut .
• these points are arrayed as shown at the left side of FIGURE 3.
• the points After the heart has contracted, the points have moved inward and are closer together as shown on the right side of FIGURE 3.
• points of myocardial muscle can be expected to move 20% closer together over the contractile phase of the heart.
• This displacement of each myocardial point is represented by a single value after
• the present invention includes methods of producing real time ultrasonic strain images.
• the methods can include acquiring frames of echo image data, estimating tissue
• acquiring frames of echo image data can include acquiring image frames of a heart.
• Estimating tissue displacements can include
• the speckle tracking can include estimating displacements by cross- correlation, and performing Lagrangian integration of displacements.
• the methods can include acquiring a patient ECG waveform, and acquiring the frames of echo image data in relating to the timing of the ECG waveform.
• Warping the color map can include fitting the color map to the boundaries of the myocardium in each of the additional frames.
• Warping the color map can include fitting the color map to the speckle pattern in each of the additional frames.
• the method of the present invention is depicted in the flowchart of FIGURE 4.
• the first step 102 is to acquire high frame rate echo data. The higher the frame rate of the image frames, the smaller the displacement increments of the points in the
• myocardium (see FIGURE 2d)) .
• image frames are acquired at a rate of 100 Hz or greater.
• a higher frame rate will provide improved performance when 2D images are used which are subject to movement of myocardial points out of the image plane.
• the higher frame rate will help assure that a myocardial point is sampled at least two times before it leaves the image plane, enabling a strain estimation to be made for the point.
• speckle tracking is begun by estimating displacements of features in the image frame such as speckle by cross-correlation at 104.
• strain is calculated as the spatial derivatives of the
• strain values are then used to form a color map in step 108.
• step 110 image frames of the next heartbeat are acquired.
• the color map is then warped to fit the myocardium in the image frames of the next heartbeat, and displayed as a color overlay over the myocardium in the new image.
• the warping and overlay process is continued throughout the next heartbeat while, as the same time, image frames of the next heartbeat are processed to form a color map to be used as a warped overlay with the image frames of the following heart cycle.
• processor create means for implementing the actions specified in the block diagram block or blocks or described for the systems and methods disclosed herein.
• the computer program instructions may be executed by a processor to cause a series of
• the computer program instructions may also cause at least some of the operational steps to be performed in parallel. Moreover, some of the steps may also be performed across more than one processor, such as might arise in a multi-processor computer system. In addition, one or more processes may also be performed
• the computer program instructions can be stored on any suitable computer-readable hardware medium including, but not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by a computing device.
• processors can include hardware such as microprocessors, field programmable gate arrays (FPGAs), integrated circuits, or the like.

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• 2016
  • 2016-01-22 WO PCT/IB2016/050308 patent/WO2016120763A1/en not_active Ceased
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