Broadband Characterization of Plastic and High Intensity Therapeutic Ultrasound Phantoms using Time Delay Spectrometry–with Validation using Kramers-Kronig Relations

摘要

We extended Time Delay Spectrometry (TDS) for broadband characterization of plastics (low-density polyethylene, LDPE) and tissue-mimicking material (TMM). Our results suggest that TDS and the conventional broadband pulse method give comparable measurements for frequency-dependent attenuation coefficient and phase velocity near the center frequency, where signal-to-noise ratio is high. However, TDS measurements show enhanced bandwidth for attenuation coefficient of 30–40% (LDPE) and 89–100% (TMM) and for phase velocity of 43% (LDPE) and 36% (TMM) for a single transmitter / receiver pair. In addition, TDS provides measurements of dispersion that are consistent with predictions based on the Kramers-Kronig relations to within 5 m/s over the band from 2 – 12 MHz in low-density polyethylene (LDPE) and to within 1 m/s in TMM over the band from 0.5 – 29 MHz.