New multi-volume rendering technique for three-dimensional power Doppler imaging

In this paper, we present a new multi-volume rendering technique (i.e., progressive fusion) to combine 3D anatomical structures from B-mode imaging and flow information from power Doppler imaging. A post-fusion technique, in which B-mode and power Doppler volumes are independently rendered and then fused based on alpha blending, is typically used in 3D power Doppler imaging. However, it has limitations in preserving the spatial relationship (i.e., depth order) between tissue structure and vasculature since they are rendered independently and then merged. With the proposed progressive fusion, B-mode and power Doppler volumes are composited together while rendering by sharing the opacity values. After compositing, two rendered frames are blended by utilizing a 2D color lookup table designed to fuse two properties (i.e., tissues and blood flows). We have evaluated the progressive-fusion multi-volume rendering method with the phantom and in vivo data acquired using a commercial ultrasound machine (EUB-8500, Hitachi Medical Corporation, Japan) with a 3.5 MHz mechanical probe. From the preliminary study, we have found that the new progressive-fusion method can better retain and display the spatial relationship between tissue structure, vasculature and their corresponding depth order.