Median filters used for volume reconstruction in freehand 3-d ultrasound

Freehand 3-D ultrasound imaging has been playing an important role in obtaining entire 3-D impression of tissues and organs. Reconstructing a sequence of irregularly located B-scan images into a volume data set with regular voxel arrays is one of key procedures for visualization and data analysis. In this study, we investigated the feasibility of median filters for volume reconstruction in freehand systems. Three median filters were proposed to filter noises and obtain voxel intensities. Qualitative and quantitative comparison results were presented to demonstrate the performance of median filters for volume reconstruction. Compared with conventional distance weighted (DW) interpolation, the three median filters were able to preserve more image details and reconstruct volume data with better quality.