Feasibility and limitation of parametric perfusion imaging based on dynamic contrast-enhanced plane wave imaging

Parametric perfusion imaging (PPI) obtained from dynamic CEUS images can depict the microvascular hemodynamic distribution. CEUS with plane wave imaging (PWI) is a choice for accurate PPI. However, the limitation of disruption rate of microbubbles (DRM) can't be overcome in PWI completely because peak negative pressure (PNP) in PWI attenuates linearly with imaging depth. The objective of this study was to illustrate the feasibility and limitation of PWI-based PPI through comparing perfusion features of conventional focused wave imaging (FWI) and PWI after clarifying the DRM of PWI. To compare perfusion features of FWI and PWI, transducer was first excited under the same acoustic parameters, especially a similar PNP in 'focal' region; and five separate in vivo same injections were performed on a rabbit kidney. Raw data of PWI and FWI were recorded by Sonix-DAQ and Touch. Three pairs of time-intensity curves (TICs) were then extracted from dynamic PWI and FWI in 'pre-focal', 'focal', and 'post-focal' regions, respectively. Perfusion parameters were estimated from the denoised and fitted TICs, including peak value (PV), area under curve (AUC), half transit time (HTT), and wash in ratio (WIR). Available infusion time and DRM were finally quantified by changes in HTT and AUC, respectively. Due to the differences in the scanning modes and PNP distributions, the perfusion features in PWI differed from those in FWI. Because PNPs of PWI were higher than these of FWI in the 'pre- and post-focal' regions, PV and AUC in PWI were lower and DRM in PWI was higher than these parameters in FWI. Compared with FWI in the 'focal' region under the same PNP, all parameters in PWI were larger due to the few insonation times for microbubbles in PWI, and DRM in PWI was lower. Although the low DRM in PWI was limited by the relative location between the imaging object and PNP distribution, the average WIR, HTT, and AUC in PWI were 66.67%, 20.51%, and 4.96% higher than those in FWI, respectively. So PWI-based PPI with the long infusion time and limited low DRM is feasible, which can provide sufficient perfusion details and information for PPI.