A qualitative and quantitative interaction technique for freehand 3D ultrasound imaging

Conventional freehand 3D ultrasound imaging techniques separate the scanning and reconstruction steps from the visualization step. Several approaches that enable real-time volume reconstruction and visualization during acquisition have been described in the literature in recent years. However, these approaches are not fully interactive, since they do not provide sufficient feedbacks on volume reconstruction. In this paper, we present a qualitative and quantitative interaction technique (QAQIT) which can provide accurate feedbacks on volume reconstruction in real time during acquisition. Two threads are designed for data acquisition: one is to acquire B-scan images from the ultrasound scanner sequentially, and the other is to obtain positions and orientations from the position sensor continuously. A matching thread matches the latest acquired image with its relative position and orientation (PAO), and then reconstructs the image into a predefined volume. After the 3D reconstruction of each image, we calculate the reconstructed ratio (RR) and increased ratio (IR) of the reconstruction volume (RV), then update the display of the RR, and drive the volume rendering of the RV according to the IR. A freehand system based on the QAQIT has been developed on a personal computer (PC). We demonstrate our system on an embryo phantom.