Broadband characterization of plastic and high intensity therapeutic ultrasound phantoms using time delay spectrometry-With validation using Kramers-Kronig relations.

Time delay spectrometry (TDS) is extended for broadband characterization of plastics (low-density polyethylene, LDPE) and tissue-mimicking material (TMM). The 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 to 12 MHz in LDPE and to within 1 m/s in TMM over the band from 0.5 to 29 MHz.