Real-time in-vivo imaging of human liver vasculature using coherent flow power Doppler: a pilot clinical study.

Power Doppler (PD) is a commonly used technique for flow detection and vessel visualization in radiology clinics. Despite its broad set of applications, PD suffers from multiple noise sources and artifacts, such as thermal noise, clutter, and flash artifacts. In addition, a trade-off exists between acquisition time and Doppler image quality. These limit the ability of clinical PD imaging in deep-lying and small-vessel detection and visualization, particularly among patients with high body-mass-indices (BMI). To improve Doppler vessel detection, we have previously proposed coherent flow power Doppler (CFPD) imaging and demonstrated its performance on porcine vasculature. Here, we report on a pilot clinical study of CFPD imaging on healthy human volunteers and patients with high BMI to assess the clinical feasibility of the technique in liver imaging. In this study, we built a real-time CFPD imaging system using a GPU-based software beamformer and CFPD processing module. Using the real-time CFPD imaging system, the liver vasculature of 15 healthy volunteers with normal BMI below 25 and 15 patients with BMI greater than 25 were imaged. Both PD and CFPD image streams were produced simultaneously. The generalized contrast-to-noise ratio (gCNR) of the PD and CFPD images were measured to provide quantitative evaluation of image quality and vessel detectability. Comparison of PD and CFPD image shows that gCNR is improved by 35% in healthy volunteers and 28% in high BMI patients with CFPD compared to PD. Example images are provided to show that the improvement in Doppler image gCNR leads to greater detection of small vessels in the liver. In addition, we show that CFPD can suppress in-vivo reverberation clutter in clinical imaging.