# US 2014/0150556 A1 · Measurement and Imaging of Scatterers with Memory of Scatterer Parameters Using at Least Two-Frequency Elastic Wave Pulse Complexes

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- Number: US 2014/0150556 A1
- Document ID: US20140150556A1
- Status: Published application
- Kind: A1
- Application number: 14/044,334
- Filed: 2013-10-02
- Published: 2014-06-05
- Earliest claimed: 2008-01-09
- Assignees: SURF Technology AS
- Inventors: Bjørn A.J. ANGELSEN; Rune Hansen; Tonni F. Johansen; Svein-Erik Måsøy; Sven Peter Nasholm; Thor Andreas Tangen
- Web page: https://patentgrep.com/patent/US20140150556A1

## CPC

- G01N 29/343: {pulse waves, e.g. particular sequence of pulses, bursts}
- A61B 8/08: Clinical applications (A61B8/02, A61B8/04, A61B8/06 take precedence)
- A61B 8/485: {involving measuring strain or elastic properties}
- G01S 7/52022: {using a sequence of pulses, at least one pulse manipulating the transmissivity or reflexivity of the medium}
- G01S 7/52038: {involving non-linear properties of the propagation medium or of the reflective target}
- G01S 7/52077: {with means for elimination of unwanted signals, e.g. noise or interference}
- G01S 7/52095: {using multiline receive beamforming}
- G01S 15/8952: {using discrete, multiple frequencies}
- G01S 7/52049: {using correction of medium-induced phase aberration}
- G01S 15/8929: {using a three-dimensional transducer configuration}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- 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

## Abstract

Measurement or imaging of elastic wave nonlinear scatterers with a memory of scattering parameters comprises selecting LF pulses having characteristics to change the scattering parameters of nonlinear scatterers. A transmit time relation is selected so that the incident HF pulse propagates sufficiently close to the LF pulse that the effect of the incident LF pulse on its scatterer parameters is observed by the HF pulse. At least two elastic wave pulse complexes comprising a high frequency (HF) pulse and a selected low frequency (LF) pulse are transmitted towards the region. Received HF signals are combined to form nonlinear HF signals representing the scatterers with memory, with suppression of received HF signals from other scatterers. At least one of the received HF signals may be corrected by time delay correction and/or speckle correction with a speckle correction filter, determined by movement of the scattering object. Systems are also disclosed.

## Claims

### Claim 1

A method for measurement or imaging of elastic wave nonlinear scatterers with a memory of scattering parameters in a region of a scattering object, comprising:
a) selecting LF pulses having characteristics to change the scattering parameters of at least certain of the nonlinear scatterers with a memory that lasts for at least a time interval after the incident LF pulse has passed the nonlinear scatterer;
b) selecting a transmit time relation between the LF pulses and HF pulses so that at least in the measurement or imaging depth range the incident HF pulse propagates spatially behind the incident LF pulse of the same pulse complex, but sufficiently close to the LF pulse that the HF pulse hits the nonlinear scatterers while the effect of the incident LF pulse on its scatterer parameters is observed by the HF pulse;
c) transmitting at least two elastic wave pulse complexes towards the region, the pulse complexes comprising a high frequency (HF) pulse in an HF band and a selected low frequency (LF) pulse in an LF band, wherein at least the LF pulse varies for at least two transmitted pulse complexes, the LF pulse of a pulse complex can be zero, the LF pulse for at least one pulse complex is nonzero, and in the pulse complexes comprising an HF pulse and a non-zero LF pulse, the transmit time have the selected transmit time relation;
d) picking up received HF signals from at least one of scattered and transmitted HF components from the at least two transmitted pulse complexes; and
e) combining the received HF signals from the at least two pulse complexes to form nonlinear measurement HF signals representing the nonlinear scatterers with memory of scattering parameters, with suppression of received HF signals from other scatterers.

### Claim 2 (depends on 1)

The method of claim 1, wherein the depth range is divided into depth intervals and the scattering object is moving, the method further comprising:
between steps d) and e), correcting at least one of the received HF signals in at least one depth interval by at least one of:
i) time delay correction with a correction delay determined by movement of the scattering object; and
ii) speckle correction with a speckle correction filter determined by movement of the scattering object,
to form, together with potentially uncorrected received HF signals, a group of at least two intermediate HF signals from the at least two transmitted pulse complexes in the at least one depth interval; and
step e) comprises combining the at least two intermediate HF signals to suppress linear scattering components from the moving object to form nonlinear measurement HF signals representing the local nonlinear scatterers in the at least one depth interval with memory of scattering parameters.

### Claim 3 (depends on 2)

The method of claim 2, comprising estimating at least one of said correction delay and speckle correction filter from a combination of the received HF signals from at least two pulse complexes.

### Claim 4 (depends on 3)

The method of claim 3, wherein the at least two pulse complexes include LF pulses having at least one common characteristic.

### Claim 5 (depends on 4)

The method of claim 4, wherein the at least one common characteristic is chosen from the group consisting of center frequency, amplitude, polarity, and pulse length.

### Claim 6 (depends on 4)

The method of claim 4, wherein the at least two pulse complexes include a pulse complex having a nonzero LF pulse and a pulse complex having a zero LF pulse.

### Claim 7 (depends on 6)

The method of claim 6, wherein the at least two pulse complexes comprise at least three pulse complexes, wherein at least two of the at least three pulse complexes have equal LF pulses and at least one of the at least three pulse complexes have a different LF pulse.

### Claim 8 (depends on 2)

The method of claim 2, wherein the nonlinear scatterers have a resonance frequency, the method comprising:
selecting the center frequency of the LF pulse close enough to the scatterer resonance frequency, so that a variation in scattering parameters with memory are produced by the resonating oscillations of the nonlinear scatterers excited by the LF pulse.

### Claim 9 (depends on 2)

The method of claim 2, wherein the nonlinear scatterers are at least one of micro-bubbles and micro-calcifications.

### Claim 10 (depends on 2)

The method of claim 2, comprising, for imaging of resonant nonlinear scatterers with at least one unknown resonance frequency:
transmitting multiple groups of pulse complexes;
wherein:
the center frequency of the LF pulse is the same within each group and varies between at least some of the groups; and
if the center frequency of the LF pulse for at least one of the groups is close enough to the nonlinear scatterer resonance frequencies of the nonlinear scatterers, so that a variation in scattering parameters with memory are produced by the resonating oscillations of nonlinear scatterers excited by the LF pulse for the at least one of the groups,
detecting from the received HF signals the presence of nonlinear scatterers with resonance frequencies close to the LF pulse center frequency for said at least one of the groups.

### Claim 11 (depends on 2)

The method of claim 2, further comprising processing the nonlinear measurements or imaging signals to form an image display of said nonlinear scatterers with memory of scattering parameters, with suppression of image components from other scatterers.

### Claim 12 (depends on 1)

The method of claim 1, further comprising processing the nonlinear measurements or imaging signals to form an image display of said nonlinear scatterers with memory of scattering parameters, with suppression of image components from other scatterers.

### Claim 13

An instrument for measurement or imaging of elastic wave nonlinear scatterers with a memory of scattering parameters in a region of a scattering object, the instrument comprising:
a) at least one controller configured to:
i) select LF pulses having characteristics to change the scattering parameters of the nonlinear scatterers with a memory that lasts for at least a time interval after the incident LF pulse has passed the nonlinear scatterer; and
ii) determine transmit time relation between the LF and HF pulses so that at least in the measurement or imaging range the incident HF pulse propagates spatially behind the incident LF pulse and close enough to the incident LF pulse that the HF pulse hits the nonlinear scatterers while the effect of the incident LF pulse on its scatterer parameters is observed by the HF pulse;
b) a transmitter configured to:
transmit at least two elastic wave pulse complexes towards the region, each of the at least two elastic wave pulse complexes comprising a high frequency (HF) pulse in an HF band and a selected low frequency (LF) pulse in an LF band, wherein at least the LF pulse varies for at least two transmitted pulse complexes, the LF pulse of a pulse complex can be zero, the LF pulse for at least one pulse complex is nonzero, and in the pulse complexes comprising an HF pulse and a nonzero LF pulse, the transmit time relations have the selected transmit time; and
c) a receiver configured to pick received HF signals from at least one of scattered and transmitted HF components from the at least two transmitted pulse complexes;
wherein the at least one controller is further configured to combine the received HF signals from the at least two pulse complexes with different LF pulses to form nonlinear measurement or imaging HF signals that represent the local resonant scatterers, with suppression of received HF signals from other scatterers.

### Claim 14 (depends on 13)

The instrument of claim 13, wherein the depth range is divided into depth intervals, the scattering object is moving, and the at least one controller is further configured to:
correct at least one of the received HF signals in at least one depth interval by at least one of:
i) time delay correction with a correction delay determined by movement of the moving object, and
ii) speckle correction with a speckle correction filter determined by movement of the moving object,
to form, together with potentially uncorrected received HF signals, a group of at least two intermediate HF signals from the at least two transmitted pulse complexes; and
combine the at least two intermediate HF signals to suppress linear scattering components from the moving object to form nonlinear measurement or imaging HF signals representing the local nonlinear scatterers with memory of scattering parameters.

### Claim 15 (depends on 14)

The instrument of claim 14, wherein the at least one controller is further configured to estimate at least one of the correction delay and the speckle correction filter through a combination of the received HF signals from at least two pulse complexes.

### Claim 16 (depends on 15)

The instrument of claim 15, wherein the at least one controller is configured to select LF pulses having at least one common characteristic in the at least two pulse complexes.

### Claim 17 (depends on 16)

The instrument of claim 16, wherein the at least one common characteristic is chosen from the group consisting of center frequency, amplitude, polarity, and pulse length.

### Claim 18 (depends on 15)

The instrument of claim 15, wherein the at least one controller is configured to select a nonzero LF pulse for at least one of the at least two pulse complexes and a zero LF pulse for at least one of the at least two pulse complexes.

### Claim 19 (depends on 16)

The instrument of claim 16, wherein:
the at least one controller is configured to define at least three pulse complexes;
at least two of the at least three pulse complexes have equal LF pulses; and
at least one of the at least three pulse complexes have a different LF pulse.

### Claim 20 (depends on 14)

The instrument of claim 14, wherein the nonlinear scatterers have a resonance frequency, and the at least one controller is further configured to:
select the LF frequency close enough to the scatterer resonance frequency, so that a variation in scattering parameters with memory are produced by the resonating oscillations of the nonlinear scatterers excited by the LF pulse

### Claim 21 (depends on 14)

The instrument of claim 14, wherein, to image resonant nonlinear scatterers with unknown resonance frequencies, the at least one controller is configured to transmit multiple groups of pulse complexes, wherein:
the center frequency of the LF pulse is the same within each group and varies between at least some of the groups; and
the center frequency of the LF pulse for at least one of the groups is close enough to at least one group of scatterer resonance frequencies that variations in scattering parameters with memory are produced by the resonating oscillations of the nonlinear scatterers excited by the LF pulse for the at least one of the groups.

### Claim 22 (depends on 14)

The instrument of claim 14, further comprising:
a display unit to display an image;
wherein the at least one controller is further configured to process the nonlinear measurement signals to form image signals of the nonlinear scatterers with memory of scattering parameters, with suppression of image components from other scatterers.

### Claim 23 (depends on 13)

The instrument of claim 13, further comprising:
a display unit to display an image;
wherein the at least one controller is further configured to process the nonlinear measurement signals to form image signals of the nonlinear scatterers with memory of scattering parameters, with suppression of image components from other scatterers.

### Claim 24 (depends on 13)

The instrument of claim 13, further comprising:
an HF receiver beam former configured to record the received HF signals from multiple HF receive beams, parallel in time; and
the at least one controller has sufficient processing capacity to process the received HF signals from the multiple HF receive beams, so that the image frame rate for 2D and 3D imaging is substantially increased as compared to a rate at which collected HF signals from single HF receive beam directions are received serially in time.

### Claim 25 (depends on 13)

The instrument of claim 13, wherein the at least one controller is further configured to select a processing method for best performance of the measurements or imaging under constraints that are preset or set by an operator.

### Claim 26 (depends on 13)

The instrument of claim 13, wherein the at least one controller is further configured to:
estimate wave front aberration corrections; and
correct the wave front aberrations.