## A Method for Direct Localized Sound Speed Estimates Using Registered Virtual Detectors

Publication: Research - peer-review › Journal article – Annual report year: 2012

### Standard

**A Method for Direct Localized Sound Speed Estimates Using Registered Virtual Detectors.** / Byram, Brett C. ; Trahey, Gregg E.; Jensen, Jørgen Arendt.

Publication: Research - peer-review › Journal article – Annual report year: 2012

### Harvard

*Ultrasonic Imaging*, vol 34, no. 3, pp. 159–180. DOI: 10.1177/0161734612455576

### APA

*Ultrasonic Imaging*,

*34*(3), 159–180. DOI: 10.1177/0161734612455576

### CBE

### MLA

*Ultrasonic Imaging*. 2012, 34(3). 159–180. Available: 10.1177/0161734612455576

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### Author

### Bibtex

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### RIS

TY - JOUR

T1 - A Method for Direct Localized Sound Speed Estimates Using Registered Virtual Detectors

AU - Byram,Brett C.

AU - Trahey,Gregg E.

AU - Jensen,Jørgen Arendt

PY - 2012

Y1 - 2012

N2 - Accurate sound speed estimates are desirable in a number of fields. In an effort to increase the spatial resolution of sound speed estimates, a new method is proposed for direct measurement of sound speed between arbitrary spatial locations. The method uses the sound speed estimator developed by Anderson and Trahey. Their least squares fit of the received waveform’s curvature provides an estimate of the wave’s point of origin. The point of origin and the delay profile calculated from the fit are used to arrive at a spatially registered virtual detector. Between a pair of registered virtual detectors, a spherical wave is propagated. By beamforming the data, the time-offlight between the two virtual sources can be calculated. From this information, the local sound speed can be estimated. Validation of the estimator is made using phantom and simulation data. The set of test phantoms consisted of both homogeneous and inhomogeneous media. Several different inhomogeneous phantom configurations were used for the physical validation. The simulation validation focused on the limits of target depth and signal-to-noise ratio on virtual detector registration. The simulations also compare the impact of two- and three-layer inhomogeneous media. The phantom results varied based on signal-to-noise ratio and geometry. The results for all cases were generally less than 1% mean error and standard deviation. The simulation results varied somewhat with depth and F/#, but primarily, they varied with signal-tonoise ratio and geometry. With two-layer geometries, the algorithm has a worst-case spatial registration bias of 0.02%. With three-layer geometries, the axial registration error gets worse with a bias magnitude up to 2.1% but is otherwise relatively stable over depth. The stability over depth of the bias in a given medium still allows for accurate sound speed estimates with a mean relative error less than 0.2%.

AB - Accurate sound speed estimates are desirable in a number of fields. In an effort to increase the spatial resolution of sound speed estimates, a new method is proposed for direct measurement of sound speed between arbitrary spatial locations. The method uses the sound speed estimator developed by Anderson and Trahey. Their least squares fit of the received waveform’s curvature provides an estimate of the wave’s point of origin. The point of origin and the delay profile calculated from the fit are used to arrive at a spatially registered virtual detector. Between a pair of registered virtual detectors, a spherical wave is propagated. By beamforming the data, the time-offlight between the two virtual sources can be calculated. From this information, the local sound speed can be estimated. Validation of the estimator is made using phantom and simulation data. The set of test phantoms consisted of both homogeneous and inhomogeneous media. Several different inhomogeneous phantom configurations were used for the physical validation. The simulation validation focused on the limits of target depth and signal-to-noise ratio on virtual detector registration. The simulations also compare the impact of two- and three-layer inhomogeneous media. The phantom results varied based on signal-to-noise ratio and geometry. The results for all cases were generally less than 1% mean error and standard deviation. The simulation results varied somewhat with depth and F/#, but primarily, they varied with signal-tonoise ratio and geometry. With two-layer geometries, the algorithm has a worst-case spatial registration bias of 0.02%. With three-layer geometries, the axial registration error gets worse with a bias magnitude up to 2.1% but is otherwise relatively stable over depth. The stability over depth of the bias in a given medium still allows for accurate sound speed estimates with a mean relative error less than 0.2%.

KW - Ultrasound

KW - Sound speed

KW - Beamforming

KW - Channel data

U2 - 10.1177/0161734612455576

DO - 10.1177/0161734612455576

M3 - Journal article

VL - 34

SP - 159

EP - 180

JO - Ultrasonic Imaging

T2 - Ultrasonic Imaging

JF - Ultrasonic Imaging

SN - 0161-7346

IS - 3

ER -