Dynamic contrast specific ultrasound tomography

Cumulative phase delay imaging (CPDI) is a modality recently introduced for contrast-specific ultrasound tomography. CPDI has already shown capable of imaging ultrasound contrast agents (UCAs) when working at pressures (0.05≤MI≤0.2) and frequencies (2.5-3 MHz) of interest for clinical applications. However, its ability of capturing UCA-kinetics was never shown. To this end, we imaged the passage of UCA-boluses through a dedicated gelatin flow-phantom. Each bolus resulted from a 5-mL injection with a 240-μL/L SonoVue® dilution. For imaging, the ULA-OP ultrasound research platform and an Esaote LA332 linear-array probe were employed. A frequency of 2.5 MHz and mechanical index (MI) equal to 0.07 were used. CPDI and Harmonic Imaging (HI) were simultaneously applied to each bolus-passage (in tomographic and echo-mode, respectively) to compare the two methods. Features commonly used to quantify UCA-kinetics were evaluated and used for the comparison: full-width-half-maximum (FWHM), wash-in-time (WIT), arrival-time (AR), and peak-time (PT). The obtained median absolute differences were equal to 0.625s, 0.25s, 0.1875s, and 0.06s for FWHM, AT, WIT, and PT, respectively. These results are encouraging, and open the way for the development of dynamic contrast-specific ultrasound tomography, possibly adding important features to multi-parametric ultrasound tomography of the breast, and improving breast cancer localization.