Fast spectral approach for delay correction in heterogeneous media
Journal of the Acoustical Society of America(2023)
摘要
Ultrasound imaging makes fundamental assumptions about the interrogated medium, including the propagation speed of the waves. For many clinical applications, assuming a constant speed of sound (SoS, typically 1540 m/s) is sufficiently accurate to yield diagnostically useful images. However, when the medium is appreciably heterogeneous (e.g., trans-skull, or through deep layers of subcutaneous fat), this approximation fails and the distortion of the wavefronts yields a degraded image (i.e., there is aberration). Correcting these distortions for a known SoS distribution is typically intensive computationally. Here, we demonstrate the utility of the heterogeneous angular spectrum method (HASM), a spectral method developed for passive cavitation imaging, to recover efficiently the appropriate apodization and delays in transmit and receive toward corrected images. Compared with a straight ray computation (i.e., no refraction) with mean 5% SoS variation, HASM was roughly tenfold faster, and computed delays matched to within (−84 ± 89) ns [compared with (−660 ± 312) ns error for 1540 m/s assumption]. Furthermore, transmit corrections for focused or plane-wave sequences may be obtained similarly with the method for a specified depth. HASM, thus, has promise toward real-time image enhancement and improved diagnostic utility. [Work Supported by the ASA FV Hunt Postdoctoral Fellowship.]
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关键词
fast spectral approach,delay correction,heterogeneous media
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