# US 10,863,968 B2 · Ultrasonic imaging system with angularly compounded acoustic radiation force excitation

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- Number: US 10,863,968 B2
- Document ID: US10863968B2
- Status: Granted
- Kind: B2
- Application number: 14/501,207
- Filed: 2014-09-30
- Published: 2016-03-31
- Granted: 2020-12-15
- Earliest claimed: 2014-09-30
- Assignees: Wisconsin Alumni Research Foundation
- Applicants: Wisconsin Alumni Research Foundation
- Inventors: Ivan Miguel Rosado-Mendez; Timothy Jon Hall
- Web page: https://patentgrep.com/patent/US10863968B2

## CPC

- A61B 8/4494: {characterised by the arrangement of the transducer elements}
- A61B 8/485: {involving measuring strain or elastic properties}
- A61B 8/5207: {involving processing of raw data to produce diagnostic data, e.g. for generating an image}
- B06B 1/0215: {for generating pulses, e.g. bursts of oscillations, envelopes}
- G01S 7/52022: {using a sequence of pulses, at least one pulse manipulating the transmissivity or reflexivity of the medium}
- G01S 7/52042: {determining elastic properties of the propagation medium or of the reflective target (diagnostic techniques involving the measurement of strain A61B8/485)}
- G01S 7/52047: {for elimination of side lobes or of grating lobes; for increasing resolving power}
- G01S 7/52071: {Multicolour displays; using colour coding; Optimising colour or information content in displays, e.g. parametric imaging}
- G01S 15/8915: {using a transducer array}
- G01S 15/8927: {using simultaneously or sequentially two or more subarrays or subapertures}
- G10K 11/346: {using phase variation}
- G10K 11/348: {using amplitude variation}
- B06B 2201/20: Application to multi-element transducer
- B06B 2201/40: with testing, calibrating, safety devices, built-in protection, construction details
- B06B 2201/55: Piezoelectric transducer
- B06B 2201/76: Medical, dental
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- B06B: METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, {e.g.} FOR PERFORMING MECHANICAL WORK IN GENERAL (for particular applications, see the relevant subclasses, e.g. B07B1/40, B23Q17/12, B24B31/06; measurement of mechanical vibrations G01H; in direction finding, locating, distance or velocity measuring G01S; {generating seismic energy G01V1/02}; control of mechanical vibrations in general G05D; sound-producing devices, e.g. bells, sirens, whistles G10K, {e.g. methods or devices for transmitting, conducting, or directing sound in general G10K11/00}; generation of electrical oscillations H03B; electromechanical resonators in general H03H; electromechanical transducers {for communication techniques, e.g. microphones, speakers} H04R)
- 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
- G10K: SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR

## Abstract

An ultrasound machine for generating push-pulses to excite shear wave stimulation employs separated angled beams that converge at the target region to generate the push-pulses. In one embodiment, the beams are modulated by a set of apodization functions to reduce side lobes caused by the narrowing of the apertures of the beam as well as transducer heating by reducing the average energy deposited in each transducer element.

## Claims

### Claim 1

An ultrasonic imaging system comprising:
an ultrasound transducer array providing for independently controllable array elements providing ultrasonic excitation to adjacent tissue; and an acoustic radiation force impulse (ARFI) transducer controller communicating with the transducer to:
(a) provide a signal to the transducer array to generate an axial push excitation from a first subset of the array elements applying an axial acoustic radiation force along an axis extending away from the transducer in a direction of ultrasound propagation during a push time depositing the axial acoustic radiation force in a target region in tissue receiving ultrasonic energy from the transducer array, the axial acoustic radiation force adapted to push the tissue into shear wave motion; and
(b) receive signals from the transducer array to monitor a lateral propagation of the shear wave motion perpendicular to the axis following the push time; and
(c) selecting a second subset of the array elements separating the first subset of array elements to be inactive during the entire generation of the axial push excitation wherein at least two ultrasound beams are provided by the axial push excitation and having propagation axes that are angled to intersect at the target region at a depth of the target region within the tissue;
wherein the at least two ultrasound beams first converge at the target region;
wherein the ultrasound beams provide a region without transmitted ultrasonic energy between a center of the ultrasound transducer and the target region;
wherein the ultrasound of each ultrasound beam is unfocused;
wherein the signal excites the array elements producing at least two beams with different amplitudes of ultrasonic signal as a function of the array element number according to at least one non-constant apodization function.

### Claim 2 (depends on 1)

The ultrasonic imaging system of claim 1 wherein the ultrasound transducer is a linear transducer array and array elements at either end of the array are excited by the signal, and array elements between the ends are not excited by the signal.

### Claim 3 (depends on 1)

The ultrasonic imaging system of claim 1 wherein the ultrasound energy of each beam is phased to provide a planar wavefront at an angle to a front face of the array.

### Claim 4 (depends on 1)

The ultrasonic imaging system of claim 1 wherein the apodization function is varied during the push time.

### Claim 5 (depends on 4)

The ultrasonic imaging system of claim 4 wherein the apodization functions alternate between even and odd functions.

### Claim 6 (depends on 4)

The ultrasonic imaging system of claim 4 wherein the apodization functions provide a Slepian sequence.

### Claim 7 (depends on 1)

The ultrasonic imaging system of claim 1 wherein a number of different apodization functions applied during the push time is greater than five.

### Claim 8 (depends on 1)

The ultrasonic imaging system of claim 1 further including a display displaying information related to the propagation of the shear waves selected from the group consisting of propagation speed and information derived from propagation speed.

### Claim 9 (depends on 1)

The ultrasonic imaging system of claim 1 wherein the total push time is in excess of 10 microseconds.

### Claim 10

A method of ultrasound imaging employing an ultrasonic imaging system having: an ultrasound transducer array providing for independently controllable array elements providing ultrasonic excitation to adjacent tissue; an acoustic radiation force impulse (ARFI) transducer controller communicating with the transducer to:
(a) provide a signal to the transducer array to generate an axial push excitation from a first subset of array elements applying an axial acoustic radiation force along an axis extending away from the transducer in a direction of ultrasound propagation during a push time depositing the axial acoustic radiation force in a target region in tissue receiving ultrasonic energy from the transducer array, the axial acoustic radiation force adapted to push the tissue into shear wave motion; and
(b) receive signals from the transducer array to monitor a lateral propagation of a the shear wave motion perpendicular to the axis following the push time; and
(c) select a second subset of the array elements separating the first subset of array elements to be inactive during the entire generation of the axial push excitation; wherein at least two ultrasound beams are provided by the axial push excitation intersecting at the target region at a depth of the target region within the tissue;
wherein the at least two ultrasound beams first converge at the target region;
wherein the ultrasound beams provide a region without transmitted ultrasonic energy between a center of the ultrasound transducer and the target region;
wherein the ultrasound of each ultrasound beam is unfocused;
wherein the signal excites the array elements producing at least two beams with different amplitudes of ultrasonic signal as a function of the array element number according to at least one non-constant apodization function
the method comprising the steps of:
(a) providing the signal to the transducer array to generate the at least two ultrasound beams from the first subset of array elements in the active state emitting ultrasound laterally separated by a region of the second subset of the array elements selected to be inactive during generation of the axial push excitation;
(b) exciting target tissue with axial acoustic radiation force to push the tissue into shear wave motion, the at least two ultrasound beams intersecting at the target region at the depth of the target region within the tissue; and
(c) measuring the lateral propagation of the shear wave motion perpendicular to the axis of the ultrasound propagation following the push time.

### Claim 11 (depends on 10)

The method of claim 10 wherein the ultrasound energy of each ultrasound beam is phased to provide a planar wavefront at an angle to a front face of the array.

### Claim 12 (depends on 10)

The method of claim 10 including the step of varying the apodization function during the push time.

### Claim 13 (depends on 12)

The method of claim 12 wherein the apodization functions alternate between even and odd functions during the push time.

### Claim 14 (depends on 12)

The method of claim 12 wherein the apodization functions are varied to provide a Slepian sequence.