A Test Phantom for Estimating Changes in the Effective Frequency of an Ultrasonic Scanner

Wilson, Thaddeus; Zagzebski, James A.; Li, Yadong

doi:10.7863/jum.2002.21.9.937

Cited by 13 publications

(13 citation statements)

References 23 publications

(21 reference statements)

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“…The large, homogeneous part of a previously described “effective frequency phantom” [28] was scanned using a Siemens SONOLINE Antares scanner (Issaquah, WA, USA) equipped with a 9.5 MHz VFX13-5 linear array operated at 10 MHz (screen setting), or a 6 MHz VFX9-4 linear array transducer driven at 6.15 MHz (screen setting). Inspection of spectral data showed that these frequency settings yield the broadest useable bandwidth (−15 dB) RF signals for the two probes.…”

Section: Methodsmentioning

confidence: 99%

“…The speed of sound in the homogeneous medium of the tissue mimicking phantom is 1,540 m/s, the density is 1.04 g/cm 3 , and the attenuation is 0.5 dB/cm/MHz, with a linear frequency-dependence around 5 MHz, as designed [28]. Glass-bead scatterers are placed spatially at random in the background medium.…”

Section: Methodsmentioning

confidence: 99%

“…The speed of sound and density of the beads are 5,572 m/s and 2.54 g/cm 3 ; and the Poisson’s ratio is 0.21. The bead diameter distribution measured by Wilson et al [28] fits a normal distribution where the mean is 48.1 μm and the standard deviation is 6.8 μm. The Gaussian model scatterer size estimated in this paper is an “effective” size and is not the physical scatterer size of the glass beads.…”

Section: Methodsmentioning

confidence: 99%

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Trade-offs in data acquisition and processing parameters for backscatter and scatterer size estimations

Liu

Zagzebski

2010

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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By analyzing backscattered echo signal power spectra and thereby obtaining backscatter coefficient vs. frequency data, the size of sub-resolution scatterers contributing to echo signals can be estimated.Here we investigate tradeoffs in data acquisition and processing parameters for reference phantom based backscatter and scatterer size estimations. RF echo data from a tissue-mimicking test phantom were acquired using a clinical scanner equipped with linear array transducers. One array has a nominal frequency bandwidth of 5-13 MHz and the other 4-9 MHz. Comparison of spectral estimation methods showed that the Welch method provided spectra yielding more accurate and precise backscatter coefficient and scatterer size estimations than spectra computed by applying rectangular, Hanning, or Hamming windows and much reduced computational load than if using the multitaper method. For small echo signal data block sizes, moderate improvements in scatterer size estimations were obtained using a multitaper method but this significantly increases the computational burden.It is critical to average power spectra from lateral A-lines for the improvement of scatterer size estimation. Averaging approximately 10 independent A-lines laterally, with an axial window length 10 times the center frequency wavelength optimized tradeoffs between spatial resolution and the variance of scatterer size estimates. Applying the concept of a time-bandwidth product this suggests using analysis blocks that contain at least 30 independent samples of the echo signal.The estimation accuracy and precision depend on the ka range where k is the wave number and a is the effective scatterer size. This introduces an ROI depth dependency to the accuracy and precision because of preferential attenuation of higher frequency sound waves in tissue-like media. With the 5-13 MHz transducer ka ranged from 0.5 -1.6 for scatterers in the test phantom, which is a favorable range, and the accuracy and precision of scatterer size estimations were both within ~5% using optimal analysis block dimensions. When the 4-9 MHz transducer was used, the ka value ranged from 0.3 to 0.8 -1.1 for the experimental conditions, and the accuracy and precision were found to be ~10% and 10% -25%, respectively. Although the experiments were done with two specific models of transducers on the test phantom, the results can be generalized to similar clinical arrays available from a variety of manufacturers and/or for different size of scatterers with similar ka range.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Trade-offs in data acquisition and processing parameters for backscatter and scatterer size estimations

Liu

Zagzebski

2010

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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“…For the Siemens and Zonare systems, a phantom with 7- to 20-µm glass beads imbedded in a homogenous background of microscopic oil droplets in gelatin with an attenuation slope of 0.7 dB/cm- MHz was imaged. 2 For the laboratory system, a reference scan was acquired from a flat acrylic surface.…”

Section: Methodsmentioning

confidence: 99%

Cross-Imaging Platform Comparison of Ultrasonic Backscatter Coefficient Measurements of Live Rat Tumors

Wirtzfeld

Ghoshal

Hafez

et al. 2010

Journal of Ultrasound in Medicine

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Objective To translate quantitative ultrasound (QUS) from the laboratory into the clinic, it is necessary to demonstrate that the measurements are platform independent. Because the backscatter coefficient (BSC) is the fundamental estimate from which additional QUS estimates are calculated, agreement between BSC results using different systems must be demonstrated. This study was an intercomparison of BSCs from in vivo spontaneous rat mammary tumors acquired by different groups using 3 clinical array systems and a single-element laboratory scanner system. Methods Radio frequency data spanning the 1- to 14-MHz frequency range were acquired in 3 dimensions from all animals using each system. Each group processed their radio frequency data independently, and the resulting BSCs were compared. The rat tumors were diagnosed as either carcinoma or fibroadenoma. Results Carcinoma BSC results exhibited small variations between the multiple slices acquired with each transducer, with similar slopes of BSC versus frequency for all systems. Somewhat larger variations were observed in fibroadenomas, although BSC variations between slices of the same tumor were of comparable magnitude to variations between transducers and systems. The root mean squared (RMS) errors between different transducers and imaging platforms were highly variable. The lowest RMS errors were observed for the fibroadenomas between 4 and 5 MHz, with an average RMS error of 4 × 10−5 cm−1Sr−1 and an average BSC value of 7.1 × 10−4 cm−1Sr−1, or approximately 5% error. The highest errors were observed for the carcinoma between 7 and 8 MHz, with an RMS error of 1.1 × 10−1 cm−1Sr−1 and an average BSC value of 3.5 × 10−2 cm−1Sr−1, or approximately 300% error. Conclusions This technical advance shows the potential for QUS technology to function with different imaging platforms.

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“…While the reference phantom was uniform and consisted of 45-53 lm glass beads in a gelatin for which the attenuation slope was 0.5 dB/cm/MHz [39], the sample phantom consisted of 20 lm glass beads, and its attenuation slope was 0.8 dB/cm/MHz.…”

Section: Experimental Rf Data Acquisitionmentioning

confidence: 99%

A novel power spectrum calculation method using phase-compensation and weighted averaging for the estimation of ultrasound attenuation

Heo

Kim

2010

Ultrasonics

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A Test Phantom for Estimating Changes in the Effective Frequency of an Ultrasonic Scanner

Cited by 13 publications

References 23 publications

Trade-offs in data acquisition and processing parameters for backscatter and scatterer size estimations

Trade-offs in data acquisition and processing parameters for backscatter and scatterer size estimations

Cross-Imaging Platform Comparison of Ultrasonic Backscatter Coefficient Measurements of Live Rat Tumors

A novel power spectrum calculation method using phase-compensation and weighted averaging for the estimation of ultrasound attenuation

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