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WO2009140607A1 - Production et détection de vibration grâce à un vibromètre aux ultrasons à dispersion d'onde de cisaillement ayant de grands mouvements d'arrière-plan - Google Patents

Production et détection de vibration grâce à un vibromètre aux ultrasons à dispersion d'onde de cisaillement ayant de grands mouvements d'arrière-plan Download PDF

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Publication number
WO2009140607A1
WO2009140607A1 PCT/US2009/044163 US2009044163W WO2009140607A1 WO 2009140607 A1 WO2009140607 A1 WO 2009140607A1 US 2009044163 W US2009044163 W US 2009044163W WO 2009140607 A1 WO2009140607 A1 WO 2009140607A1
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Prior art keywords
motion
ultrasonic
subject
recited
echo signals
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PCT/US2009/044163
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Inventor
James F. Greenleaf
Shigao Chen
Yi Zheng
Aiping Yao
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Mayo Foundation for Medical Education and Research
Mayo Clinic in Florida
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Mayo Foundation for Medical Education and Research
Mayo Clinic in Florida
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Priority to US12/992,228 priority Critical patent/US8659975B2/en
Publication of WO2009140607A1 publication Critical patent/WO2009140607A1/fr
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/08—Measuring devices for evaluating the respiratory organs
    • 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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52017—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 particularly adapted to short-range imaging
    • G01S7/52019—Details of transmitters
    • G01S7/5202—Details of transmitters for pulse systems
    • G01S7/52022—Details of transmitters for pulse systems using a sequence of pulses, at least one pulse manipulating the transmissivity or reflexivity of the medium
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52017—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 particularly adapted to short-range imaging
    • G01S7/52023—Details of receivers
    • G01S7/52036—Details of receivers using analysis of echo signal for target characterisation
    • G01S7/52038—Details of receivers using analysis of echo signal for target characterisation involving non-linear properties of the propagation medium or of the reflective target
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52017—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 particularly adapted to short-range imaging
    • G01S7/52023—Details of receivers
    • G01S7/52036—Details of receivers using analysis of echo signal for target characterisation
    • G01S7/52042—Details of receivers using analysis of echo signal for target characterisation determining elastic properties of the propagation medium or of the reflective target
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7203—Signal processing specially adapted for physiological signals or for diagnostic purposes for noise prevention, reduction or removal

Definitions

  • the field of the invention is coherent imaging using vibratory energy, such as ultrasound and, in particular, systems and methods for shearwave dispersion ultrasound vibrometry ("SDUV").
  • vibratory energy such as ultrasound
  • SDUV shearwave dispersion ultrasound vibrometry
  • a linear array system includes a transducer having a large number of elements disposed in a line.
  • a small group of elements are energized to produce an ultrasonic beam that travels away from the transducer, perpendicular to its surface.
  • the group of energized elements is translated along the length of the transducer during the scan to produce a corresponding series of beams that produce echo signals from a two-dimensional region in the subject.
  • the pulsing of the inner elements in each energized group is delayed with respect to the pulsing of the outer elements.
  • the time delays determine the depth of focus which can be changed during scanning. The same delay factors are applied when receiving the echo signals to provide dynamic focusing during the receive mode.
  • Fig. 4 is a block diagram of a linear ultrasound transducer that forms a part of one configuration of the ultrasound system of Fig. 3;
  • r(t f ,t,) A(t / ,t g ) ⁇ s ⁇ f t f + ⁇ f + ⁇ siR( ⁇ f t, + ⁇ ,)) Eqn. (3); [0036] where A(t f ,t s ⁇ is the amplitude of the complex envelope of the received echo signal; t f is fast time, which is representative of depth; t s is slow time, which is representative of pulse repetition; ⁇ f is the transmission center frequency; ⁇ s is again the tissue vibration frequency; ⁇ s is again the tissue vibration phase; and ⁇ is an angle between the ultrasound beam and direction of tissue motion. The vibration becomes a phase term of the angular modulation. Furthermore, the modulation index, ⁇ , is:
  • a Kalman filter process is employed to recursively estimate the phase and amplitude of the harmonic shear wave motion.
  • a Kalman filter is a numerical method used to track a time-varying signal in the presence of noise. If the signal can be characterized by some number of parameters that vary slowly with time, then Kalman filtering can be used to tell how incoming raw measurements should be processed to best estimate those parameters as a function of time.
  • a Kalman filter extracts information about the imparted harmonic motion from random and noisy measurement data with known vibration frequency and unknown vibration amplitude and phase.
  • H k is a measurement vector having the form:
  • w 4 is a white driving sequence vector that allows some variations in the vibration amplitude and phase
  • ⁇ is a transition matrix, which has the form:
  • ⁇ s a tan- 1 feM J Eqn. (21 );
  • the above method can be applied to estimate the phase, ⁇ s , of tissue vibration propagating over a known distance, Ar.
  • the shear wave speed can be estimated using the phase change, A ⁇ s , that occurs over the distance, Ar, by:
  • the pushing pulse duration is increased while maintaining its intensity. This provides an increase in the induced shear wave magnitude while maintaining ultrasound beam intensities within safe limits.
  • a lower pulse repetition frequency PRF
  • PRF pulse repetition frequency
  • the ultrasonic vibration pulse 100 is applied during a time period of duration AT .
  • the PRF of the ultrasonic detection pulses 102 is increased, the pulse repetition period ("PRP") is correspondingly decreased.
  • PRP pulse repetition period
  • a non-uniform temporal sampling is generally defined for those situations when AT > PRP, as illustrated in Fig. 1B.
  • a non-uniform temporal sampling also exists when AT ⁇ PRP ; however, this will result in aliasing and is a generally undesirable configuration.
  • the pulse timing sequence shown in Fig. 1A where a uniform and lower PRF is employed, is very simple and may work well under certain conditions.
  • interpolation can be used on the vibration sequence demodulated from ultrasound echoes.
  • the interpolated sequence will have uniform temporal sampling and, therefore, can be processed as if there are no missing data samples. While this approach works well for in vitro tissue experiments, the results will degrade if large background motion is present. Thus, this approach is likely limited for in vivo applications, which are likely to see large background motions. Also, as stated above, if the PRF is too low, the higher harmonics of the pushing pulses will exceed the Nyquist sampling limit of the motion detection ultrasound, which will result in aliasing artifacts.
  • the non-uniform temporal sampling approach shown in Fig. 1 B provides a degree of flexibility in pulse sequence design.
  • the pushing pulse 100 can be significantly longer than in uniform approaches, such as the one in Fig. 1A.
  • a higher overall PRF can also be maintained, which provides some compensation when the signal-to-noise ratio ("SNR") is low for the detected signal indicative of the harmonic shear wave motion.
  • SNR signal-to-noise ratio
  • the non-uniform temporal sampling shown in Fig. 1B presents a processing challenge that is addresses during the Kalman filtering process.
  • Kalman filtering can be applied directly to non-uniform sampled data, if the measurement equation properly accommodates the differences between the pushing pulse period and the pulse repetition period ("PRP") of the detection pulses. Therefore, the state equation given by Eqn. (18) is applicable if modified, even when tissue motion is sampled non-uniformly in time.
  • the measurement vector, H 4 is modified to properly account for the exact timing of each iteration, thereby providing a means by which the Kalman filter can accommodate nonuniform sampled sequence.
  • the measurement vector, H A for the k' h echo located between the n ⁇ and
  • H k ⁇ sin( ⁇ s (kT+n(AT-T))) cos( ⁇ t (kT + n( ⁇ T-T)))] Eqn. (23).
  • Kalman filtering process is carried out using Eqns. (15), (17), (18), and (23). In this manner, uniform sampling is not required when the Kalman filter is appropriately modified to identify the next time step before each iteration.
  • the binary pushing pulses when performing SDUV the binary pushing pulses generate harmonics in addition to the fundamental pushing frequency, and these harmonics can introduce errors during the Kalman filtering process if they are not included in the vibration model utilized by the Kalman filter. This is because the Kalman filter assumes that the signal indicative of the harmonic motion contains only one frequency and that all other out-of-band motions are white noise. While this assumption is correct under certain circumstances, such as where one transducer is dedicated to maintain continuous monochromatic vibration within the studied tissue, it is not true when the binary pushing pulses contain a fundamental frequency (e.g., 100 Hz) and higher harmonics (e.g., 200 Hz, 300 Hz, and 400 Hz).
  • a fundamental frequency e.g. 100 Hz
  • harmonics e.g. 200 Hz, 300 Hz, and 400 Hz
  • s m sin(m ⁇ s (kT + n(AT -T)fj Eqn. (25);
  • the Kalman filter gain vector all have 2N elements.
  • the transition matrix, ⁇ , covariance matrix of the estimation errors, and the covariance matrix of the driving sequences all have a dimension of 2N ⁇ 2N, which are extensions of the 2 ⁇ 2 matrices described above. While only the first few harmonics are generally useful when estimating the harmonic shear wave motion, all of the harmonics are included in the Kalman filtering process for more accurate estimations.
  • a vibroacoustography system which employs the present invention employs an ultrasonic transducer 311 that is operable to produce focused ultrasound beams.
  • the transducer 311 such as a phased array transducer, intermittently transmits a beam of ultrasonic vibration pulses 100 to a vibration origin 200 in the tissue of interest 202 to vibrate, or oscillate, the tissue 202 at a prescribed frequency.
  • the focus of the transducer is electronically steered to a motion detection point 206 at a distance, ⁇ r , from the vibration origin 200 and harmonic motion 204 at that point is detected.
  • a vibration mode is multiplexed with a detection mode. This enables the detection of the harmonic motion 206 by the same transducer 311 as that transmitting the vibration pulses 100 and both vibration and detection can be achieved without mechanically moving the transducer 311.
  • a transducer array 311 includes a plurality of separately driven elements 312 which each produce a burst of ultrasonic energy when energized by a pulse produced by a transmitter 313.
  • the ultrasonic energy reflected back to the transducer array 311 from the subject under study is converted to an electrical signal by each transducer element 312 and applied separately to a receiver 314 through a set of switches 315.
  • the transmitter 313, receiver 314, and the switches 315 are operated under the control of a digital controller 316 responsive to the commands input by the human operator.
  • a complete scan is performed by acquiring a series of echoes in which the switches 315 are set to their transmit position, the transmitter 313 is gated on momentarily to energize each transducer element 312, the switches 315 are then set to their receive position, and the subsequent echo signals produced by each transducer element 312 are applied to the receiver 314.
  • the separate echo signals from each transducer element 312 are combined in the receiver 314 to produce a single echo signal which is employed to produce a line in an image on a display system 317.
  • the transmitter 313 drives the transducer array 311 such that the ultrasonic energy produced is directed, or steered, in a beam.
  • a sector scan is performed by progressively changing the time delays T 1 in successive excitations.
  • the angle ⁇ is thus changed in increments to steer the transmitted beam in a succession of directions.
  • the timing of the pulses 320 is reversed.
  • a linear transducer array may also be employed in the ultrasonic imaging system of Fig. 3.
  • the transmitter 313 drives the transducer array 311 such that an ultrasonic beam is produced which is directed substantially perpendicular to its front surface.
  • a subgroup of the elements 312 are energized to produce the beam and the pulsing of the inner elements 312 in this subgroup are delayed relative to the outer elements 312 as shown at 320.
  • a beam focused at point P results from the interference of the small separate wavelets produced by the subgroup elements.
  • the time delays determine the depth of focus, or range R , and this is typically changed during a scan when a two-dimensional image is to be produced. The same time delay pattern is used when receiving the echo signals resulting in dynamic focusing of the echo signals received by the subgroup of elements 312. In this manner a single scan line in the image is formed.
  • the subgroup of elements to be energized are shifted one element position along the transducer length and another scan line is required.
  • the focal point, P of the ultrasonic beam is thus shifted along the length of the transducer 311 by repeatedly shifting the location of the energized subgroup of elements 312.
  • the echo signals produced by each burst of ultrasonic energy emanate from reflecting objects located at successive positions, R , along the ultrasonic beam. These are sensed separately by each segment 312 of the transducer array 311 and a sample of the magnitude of the echo signal at a particular point in time represents the amount of reflection occurring at a specific range, R .
  • the function of the receiver 314 is to amplify and demodulate these separate echo signals, impart the proper time delay to each and sum them together to provide a single echo signal which accurately indicates the total ultrasonic energy reflected from each focal point, P , located at range, R , along the ultrasonic beam oriented at the angle, ⁇ .
  • each transducer element channel of the receiver 314 To simultaneously sum the electrical signals produced by the echoes from each transducer element 312, time delays are introduced into each separate transducer element channel of the receiver 314.
  • the delay introduced in each channel may be divided into two components, one component is referred to as a beam steering time delay, and the other component is referred to as a beam focusing time delay.
  • the beam steering and beam focusing time delays for reception are precisely the same delays, T 1 , as the transmission delays described above.
  • the focusing time delay component introduced into each receiver channel is continuously changing during reception of the echo to provide dynamic focusing of the received beam at the range, R , from which the echo signal emanates.
  • the receiver 314 Under the direction of the digital controller 316, the receiver 314 provides delays during the scan such that the steering of the receiver 314 tracks with the direction of the beam steered by the transmitter 311 and it samples the echo signals at a succession of ranges and provides the proper delays to dynamically focus at points, P, along the beam.
  • each emission of an ultrasonic pulse results in the acquisition of a series of data points which represent the amount of reflected sound from a corresponding series of points, P , located along the ultrasonic beam.
  • echoes from multiple focused locations can be received to measure vibration information from several points of the tissue.
  • the limitation of the lateral resolution of the transducer for two closely located points can be improved by assigning different transmitting codes for different locations.
  • the display system 317 receives the series of data points produced by the receiver 314 and converts the data to a form producing the desired image. For example, if an A-scan is desired, the magnitude of the series of data points is merely graphed as a function of time. If a B-scan is desired, each data point in the series is used to control the brightness of a pixel in the image, and a scan comprised of a series of measurements at successive locations along the length of the transducer 311 (linear array mode) or steering angles (PASS mode) is performed to provide the data necessary for display of an image.
  • linear array mode linear array mode
  • PASS mode steering angles
  • the transmitter 313 includes a set of channel pulse code memories which are indicated collectively at 550.
  • Each pulse code memory 550 stores a bit pattern 551 that determines the frequency of the ultrasonic pulse 552 that is to be produced. This bit pattern is read out of each pulse code memory 550 by a master clock and applied to a driver 553 which amplifies the signal to a power level suitable for driving the transducer 311.
  • the bit pattern is a sequence of four "1" bits alternated with four "0" bits to produce a 5 megahertz ("MHz") ultrasonic pulse 552.
  • the transducer elements 311 to which these ultrasonic pulses 552 are applied respond by producing ultrasonic energy.
  • the pulses 552 for each of the N channels must be produced and delayed by the proper amount. These delays are provided by a transmit control 554 which receives control signals from the digital controller 316. When the control signal is received, the transmit control 554 gates a clock signal through to the first transmit channel 550. At each successive delay time interval thereafter, the clock signal is gated through to the next channel pulse code memory 550 until all the channels to be energized are producing their ultrasonic pulses 552. Each transmit channel 550 is reset after its entire bit pattern 551 has been transmitted and the transmitter 313 then waits for the next control signal from the digital controller 316.
  • the receiver 314 is comprised of three sections: a time-gain control ("TGC") section 600, a beam forming section 601 , and a mid processor 602.
  • the time-gain control section 600 includes an amplifier 605 for each of the N receiver channels and a time-gain control circuit 606.
  • the input of each amplifier 605 is connected to a respective one of the transducer elements 312 to receive and amplify the echo signal which it receives.
  • the amount of amplification provided by the amplifiers 605 is controlled through a control line 607 that is driven by the time-gain control circuit 606.
  • As is well known in the art as the range of the echo signal increases, its amplitude is diminished.
  • the brightness of the image diminishes rapidly as a function of range, R .
  • This amplification is controlled by the operator who manually sets TGC linear potentiometers 608 to values which provide a relatively uniform brightness over the entire range of the scan.
  • the time interval over which the echo signal is acquired determines the range from which it emanates, and this time interval is divided into segments by the TGC control circuit 606.
  • the settings of the potentiometers are employed to set the gain of the amplifiers 605 during each of the respective time intervals so that the echo signal is amplified in ever increasing amounts over the acquisition time interval.
  • the beam forming section 601 of the receiver 314 includes N separate receiver channels 610.
  • Each receiver channel 610 receives the analog echo signal from one of the TGC amplifiers 605 at an input 611 , and it produces a stream of digitized output values on an / bus 612 and a Q bus 613.
  • Each of these / and Q values represents a sample of the echo signal envelope at a specific range, R .
  • These samples have been delayed in the manner described above such that when they are summed at summing points 614 and 615 with the / and Q samples from each of the other receiver channels 610, they indicate the magnitude and phase of the echo signal reflected from a point, P , located at range, R , on the ultrasonic beam.
  • the mid processor section 602 receives the beam samples from the summing points 614 and 615.
  • the / and Q values of each beam sample is a digital number which represents the in-phase and quadrature components of the magnitude of the reflected sound from a point, P .
  • the mid processor 602 can perform a variety of calculations on these beam samples, where choice is determined by the type of image to be reconstructed. For example, if a conventional magnitude image is to be produced, a detection process indicated at 620 is implemented in which a digital magnitude, M , is calculated from each beam sample according to:
  • the resulting magnitude values output at 621 to the display system 317 result in an image in which the magnitude of the reflected echo at each image pixel is indicated by pixel brightness.
  • the present invention is implemented by a mechanical property processor 622 which forms part of the mid-processor 602. As will be explained in detail below, this processor 602 receives the / and Q beam samples acquired during a sequence of measurements of the subject tissue 202 and calculates a mechanical property of the tissue 202.
  • a method for measuring mechanical properties, such as shear elasticity and shear viscosity, of a tissue of interest using a shear wave speed dispersion technique is performed with an ultrasound system 300, such as the one described above.
  • the mechanical property processor 622 controls the measurements made by the ultrasound system 300, the vibration pulse output of the transducer elements 312, processes the resulting echo signals I and Q to satisfy the above-described Eqns. (5) and (6), and calculates a mechanical property of the target tissues.
  • target tissues may be, for example, an artery or myocardial tissue, and the mechanical property may be stiffness.
  • the ultrasound system 300 is operated first using B-mode scanning to acquire an anatomical ultrasound image of a region of interest, such as the heart or liver, as indicated at step 700.
  • a target of interest is determined such as by selected in the ultrasound image a plurality of motion detection points at which it is desired to obtain mechanical properties, as indicated at step 702.
  • a vibration origin is selected.
  • the vibration origin and the plurality of motion detection points are, for example, selected to be co-linear and spaced as discussed below.
  • the shear wave speed dispersion technique makes use of an estimation of wave speed using equation (22), which includes a phase difference, such that the phase ⁇ s , of the echo signals is determined at a plurality of points. This is achieved, for example, using a single vibration origin and two different motion detection points each located a different distance from the vibration origin; however, it is also possible to use a single detection point and change the vibration origin.
  • the determination of a desired distance, R , between a vibration origin and a motion detection point and the determination of a desired spacing, Ar, between the motion detection points can be based on a consideration of the type of tissue that is under examination. For example, an appropriate distance, R , in the liver may be on the order of one centimeter, while an appropriate distance, R , for a breast lesion may be on the order of five millimeters.
  • the outgoing shear wave generated at the vibration origin using amplitude modulated pulses can be approximated as a cylindrical shear wave. Its amplitude decreases as the wave propagates outwards from the excitation center due to both geometry effects and attenuation resulting from the medium in which the wave propagates.
  • the gating frequency and the modulation frequency of the ultrasonic pulses are determined, as indicated at step 706.
  • the gating frequency is 2.5 kHz and a prescribed modulation frequency for a first shear wave speed is 100 Hz.
  • the transmission of intermittent ultrasonic vibration pulses to a vibration origin, and the transmission of ultrasonic detection pulses and the receipt of echo signals from the motion detection point occurs under the control of the digital controller 316 of the ultrasound system 300, as indicated at step 708.
  • the ultrasonic vibration pulses are amplitude modulated ("AM") and are applied to the subject in an on-off time sequence with a detection mode occurring during the off intervals of the vibration pulses.
  • AM amplitude modulated
  • the non-uniform temporal pulse sequencing illustrated in Fig. 1B is employed, wherein the duration of the "on" period when the pushing pulse 100 is applied, AT, is larger than the pulse repetition period ("PRP") of the ultrasonic detection pulses 102.
  • the "on" phase of this sequence essentially comprises an intermittent or gated AM signal composed of ultrasonic vibration pulses that are modulated at a modulation frequency.
  • the application of a continuous wave AM signal to a subject in this manner generates a radiation force having a frequency equal to the modulation frequency of the beam.
  • the radiation force imparts a harmonic shear wave 204 to the tissue if interest 202.
  • the application of a gated rather than a continuous AM signal generates a radiation force including various frequency components and a shear wave 204 including these frequency components is imparted to the subject tissue 202.
  • two focused ultrasound beams having a beat frequency can also be employed for vibrating the tissue 202.
  • the two beams can be achieved by dividing the elements 312 of the transducer array 311 into two groups and using the first group to transmit ultrasonic pulses at a first frequency, ⁇ ⁇ , and the second group to transmit ultrasonic pulses at a second frequency, ⁇ 2 .
  • the first frequency may be IMHz +10OHz and the second frequency may be IMHz-IOOHz .
  • the ultrasound system 300 is operated to acquire echo signals from the subject tissues at a series of motion detection points.
  • 100 echoes sampled at a 40 MHz sample rate are acquired at each of 11 motion detection points that are spread evenly along 10 to 20 mm of the length of the artery are measured.
  • Eight echo samples at the desired location are used to obtain average / and Q values.
  • the ultrasonic detection pulses can be applied to the motion detection points in a number of ways. For example, each motion detection point can be fully sampled before the detection pulses are steered to the next point. However, in the alternative the plurality of motion detection points can be sampled substantially contemporaneously.
  • parallel beamforming is employed it both the transmission of the detection pulses and the reception of the resulting echo signals.
  • a substantially plane wave is produced in the region of the tissue of interest undergoing harmonic shear wave motion by properly phasing the transducer elements 312. This results in a rather broad beam instead of a focused ultrasound beam.
  • the backscattered ultrasound is then formed into focused beams in a beamformer after being received by the transducer 311.
  • the transducer elements 312 are energized in subgroups such that a plurality of focused ultrasound beams are directed to the plurality of motion detection points.
  • the motion detection points can be sampled in a so-called interleaved manner.
  • an ultrasonic detection pulse is applied to the f h motion detection point either before or after an echo is received from the (j-l) lh motion detection point.
  • the time difference between the transmission of an ultrasonic detection pulse to the (y -l)' and /* detection point is thereby defined as T d .
  • the received echo signals By acquiring the received echo signals in this manner, they are samples of the harmonic shear wave motion at different times; thus, a phase estimate (for example, as estimated by Kalman filtering) of the harmonic shear wave motion needs to be corrected accordingly.
  • the phase estimated by the Kalman filter for the f motion detection point Given the received echo signals, the phase estimated by the Kalman filter for the f motion detection point is:
  • the amplitude and phase of the tissue motion at each point is then estimated from the acquired / and Q echo samples.
  • the arctangent of the ratio of the Q and / beam samples are calculated and the mean value is removed to obtain the harmonic motion in slow time, as indicated above in Equations (7) and (8).
  • the harmonic motion is modeled by a second order differential equation with random amplitude and phase and the known beat frequency.
  • the amplitude and phase is then estimated in a recursive, Kalman filter process that minimizes the mean square error between the model and the measured tissue harmonic motion given by:
  • x k is an estimate for the state variable vector, x k .
  • the Kalman filtering is performed using Eqns. (15), (20), and (21).
  • the state variable vector, x k is given by the state equation of Eqn. (28):
  • the change in tissue oscillation phase as a function of distance is then calculated for this beat frequency using the calculated phase values at the 11 points along the artery.
  • the digital controller determines whether the last frequency has been measured. If not, at process block 718, another frequency is selected and process blocks 708-714 are repeated at each desired prescribed frequency. For example, shear wave speeds are calculated using a set of modulation frequencies including 100 Hz, 200 Hz, 300 Hz, 400 Hz and 500 Hz.
  • the next step is to calculate the shear wave speeds in the subject tissue 202 at the different beat frequencies.
  • Linear regression is applied to the 11 phase changed measurements to yield a phase change over 10 mm distance along the artery. From this phase change over distance information, the shear wave speed at each beat frequency is estimated as described with reference to equation (22).
  • the final step is to calculate a mechanical property of the tissue 202 from the shear wave speed information.
  • the shear elasticity and viscosity of the tissue 202 is estimated from the set of shear wave speeds. These mechanical properties indicate the stiffness of the artery, which is a valuable clinical measurement, but also, for example, the stiffness of myocardial and liver tissue. This calculation is based on shear wave speed dispersion as described, for example, by S. Chen, et al., in "Complex Stiffness Quantification Using Ultrasound Stimulated Vibrometry," IEEE Ultrasonics Symposium, 2003; 941-944.
  • the shear wave speeds at multiple frequencies are fit with appropriate theoretical models to solve for the shear elasticity and viscosity. For example, one appropriate equation is the so-called Voigt model:
  • c s is the shear wave speed, //, is the shear modulus
  • /Z 2 is the shear viscosity
  • ⁇ is frequency
  • p is the density of the tissue, which can be assumed to be 1000 kilograms per cubic meter
  • harmonic motion is detected at a motion detection point by transmitting detection pulses to the motion detection point and receiving echo pulses therefrom. These signals are then analyzed as described above in the mid-processor 602 of the receiver 314. A signal indicative of the induced harmonic shear wave motion is detected at the prescribed frequency in the received ultrasonic echo signals and a characteristic of the detected signal, such as amplitude and/or phase, is determined. The mechanical property is then calculated using the measured characteristic. Depending on the model used to relate a measured characteristic to a mechanical property, it may be necessary to determine a measured characteristic at more than one point and/or at more than one frequency. For example, using the Voigt model requires shear wave speed to be calculated at a plurality of prescribed frequencies. Using equation (22) to calculate the shear wave speed, c s , requires phase measurements at two or more motion detection points.
  • an amplitude could be measured and the change in amplitude over distance could be determined and used in conjunction with an appropriate model to determine one or more other mechanical properties of the subject target tissue.
  • tone bursts of ultrasonic pulses are not modulated but have a specific amplitude, duration and period such that they impart a force having desired frequency components.
  • tone bursts of ultrasonic pulses having a duration of 1 ms and repeated every 10 ms will generate a radiation force that includes frequency components at a fundamental frequency and multiples thereof, for example at 100 Hz, 200 Hz 1 300 Hz, 400 Hz and 500 Hz.
  • Using such a waveform for vibration provides advantages in faster data acquisition as described below as well as in lower tissue and transducer heating.
  • the measurements need not be repeated over different frequencies, since the tone bursts include frequency components at multiple frequencies. These tone bursts are also easier to implement using a conventional ultrasound system and the average intensity and power would be lower as compared to for example a similar gated AM modulation method. Further, because the off interval is generally longer when utilizing tone bursts, the detection pulses can be steered to more than one motion detection point during the off intervals.
  • an ultrasound system can be used for excitation in a manner such as described herein, and other known means, such as MRI or optical methods, can be used to detect the ultrasound motion.

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Abstract

L'invention concerne un procédé, pour mesurer une propriété mécanique d'un sujet, qui comprend l'utilisation d'un transducteur ultrasonore pour appliquer des impulsions de vibration ultrasonore à une origine de vibration chez le sujet dans une séquence temporelle marche-arrêt afin de communiquer au sujet un mouvement harmonique à une fréquence prescrite et, lorsque les impulsions de vibration sont coupées, en utilisant de préférence le même transducteur, pour appliquer des impulsions de détection ultrasonore à un point de détection de mouvement et pour recevoir des signaux d'écho à partir de celui-ci afin de détecter le mouvement harmonique sur le sujet au niveau du point de détection de mouvement. Les impulsions de détection ultrasonore sont parsemées d’impulsions de vibration et peuvent être appliquées de manière non uniforme. À partir des signaux d'écho ultrasonore reçus, un signal harmonique est détecté et une caractéristique telle que l'amplitude ou la phase du signal harmonique détecté est calculée en utilisant un filtre de Kalman ou une interpolation.
PCT/US2009/044163 1997-07-21 2009-05-15 Production et détection de vibration grâce à un vibromètre aux ultrasons à dispersion d'onde de cisaillement ayant de grands mouvements d'arrière-plan Ceased WO2009140607A1 (fr)

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WO2012080913A1 (fr) * 2010-12-13 2012-06-21 Koninklijke Philips Electronics N.V. Réglage de mesures de force de rayonnement acoustique pour compenser des effets de mouvement d'arrière-plan
CN106840362A (zh) * 2017-03-20 2017-06-13 西安交通大学 基于声辐射力脉冲响应的激光测振监测hifu损伤粘弹性的方法
CN107106120A (zh) * 2014-10-29 2017-08-29 梅约医学教育与研究基金会 用于通过超声换能器的持续振动进行超声弹性成像的方法
WO2018060820A1 (fr) * 2016-09-29 2018-04-05 Koninklijke Philips N.V. Imagerie par onde de cisaillement ultrasonore avec compensation de mouvement d'arrière-plan
US10448924B2 (en) 2010-12-13 2019-10-22 Koninklijke Philips N.V. Ultrasonic acoustic radiation force excitation for ultrasonic material property measurement and imaging
CN110471096A (zh) * 2019-09-11 2019-11-19 哈尔滨工程大学 一种分布式海底飞行节点群体定位方法
WO2020002445A1 (fr) * 2018-06-27 2020-01-02 Koninklijke Philips N.V. Détection par onde de cisaillement de viscosité anatomique et dispositifs, systèmes et procédés associés
CN115211869A (zh) * 2022-08-23 2022-10-21 浙江大学 一种基于经验模态分解和卡尔曼滤波的脑电信号去噪方法、装置及系统
US11644440B2 (en) 2017-08-10 2023-05-09 Mayo Foundation For Medical Education And Research Shear wave elastography with ultrasound probe oscillation
US12023199B2 (en) 2015-10-08 2024-07-02 Mayo Foundation For Medical Education And Research Systems and methods for ultrasound elastography with continuous transducer vibration

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WO2000010638A2 (fr) * 1998-08-24 2000-03-02 Baskent University Formeur de faisceaux, de surechantillonnage asynchrone
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WO2012080913A1 (fr) * 2010-12-13 2012-06-21 Koninklijke Philips Electronics N.V. Réglage de mesures de force de rayonnement acoustique pour compenser des effets de mouvement d'arrière-plan
CN103260525A (zh) * 2010-12-13 2013-08-21 皇家飞利浦电子股份有限公司 针对背景运动影响调节声辐射力效应的测量结果
JP2013544615A (ja) * 2010-12-13 2013-12-19 コーニンクレッカ フィリップス エヌ ヴェ バックグランド動き効果に関する音響放射力効果の測定の調整
US11446006B2 (en) 2010-12-13 2022-09-20 Koninklijke Philips N.V. Adjusting measurements of the effects of acoustic radiation force for background motion effects
US10485514B2 (en) 2010-12-13 2019-11-26 Koninklijke Philips N.V. Adjusting measurements of the effects of acoustic radiation force for background motion effects
US10448924B2 (en) 2010-12-13 2019-10-22 Koninklijke Philips N.V. Ultrasonic acoustic radiation force excitation for ultrasonic material property measurement and imaging
EP3215018A4 (fr) * 2014-10-29 2018-09-12 Mayo Foundation for Medical Education and Research Procédé d'élastographie aux ultrasons par vibration continue d'un transducteur ultrasonore
CN107106120B (zh) * 2014-10-29 2021-11-16 梅约医学教育与研究基金会 用于通过超声换能器的持续振动进行超声弹性成像的方法
CN107106120A (zh) * 2014-10-29 2017-08-29 梅约医学教育与研究基金会 用于通过超声换能器的持续振动进行超声弹性成像的方法
US10779799B2 (en) 2014-10-29 2020-09-22 Mayo Foundation For Medical Education And Research Method for ultrasound elastography through continuous vibration of an ultrasound transducer
US12023199B2 (en) 2015-10-08 2024-07-02 Mayo Foundation For Medical Education And Research Systems and methods for ultrasound elastography with continuous transducer vibration
WO2018060820A1 (fr) * 2016-09-29 2018-04-05 Koninklijke Philips N.V. Imagerie par onde de cisaillement ultrasonore avec compensation de mouvement d'arrière-plan
US11364015B2 (en) 2016-09-29 2022-06-21 Koninklijke Philips N.V. Ultrasonic shear wave imaging with background motion compensation
CN106840362A (zh) * 2017-03-20 2017-06-13 西安交通大学 基于声辐射力脉冲响应的激光测振监测hifu损伤粘弹性的方法
CN106840362B (zh) * 2017-03-20 2019-08-23 西安交通大学 基于声辐射力脉冲响应的激光测振监测hifu损伤粘弹性方法
US11644440B2 (en) 2017-08-10 2023-05-09 Mayo Foundation For Medical Education And Research Shear wave elastography with ultrasound probe oscillation
JP2021528157A (ja) * 2018-06-27 2021-10-21 コーニンクレッカ フィリップス エヌ ヴェＫｏｎｉｎｋｌｉｊｋｅ Ｐｈｉｌｉｐｓ Ｎ．Ｖ． 解剖学的粘度の剪断波検出 、関連するデバイス、システム、及び方法
US20210251607A1 (en) * 2018-06-27 2021-08-19 Koninklijke Philips N.V. Shear wave detection of anatomical viscosity and associated devices, systems, and methods
CN112638275A (zh) * 2018-06-27 2021-04-09 皇家飞利浦有限公司 解剖结构粘度的剪切波检测以及相关联的设备、系统和方法
WO2020002445A1 (fr) * 2018-06-27 2020-01-02 Koninklijke Philips N.V. Détection par onde de cisaillement de viscosité anatomique et dispositifs, systèmes et procédés associés
JP7284769B2 (ja) 2018-06-27 2023-05-31 コーニンクレッカ フィリップス エヌ ヴェ 解剖学的粘度の剪断波検出 、関連するデバイス、システム、及び方法
US12023200B2 (en) 2018-06-27 2024-07-02 Koninklijke Philips N.V. Shear wave detection of anatomical viscosity and associated devices, systems, and methods
CN110471096A (zh) * 2019-09-11 2019-11-19 哈尔滨工程大学 一种分布式海底飞行节点群体定位方法
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