Registration of 3D U/S and CT images of the prostate

Radiotherapy is a rapidly growing cancer treatment technique. In brachytherapy - one radiotherapy treatment technique - pre- and post-planning is usually carried out using CT imaging. As CT scanners cannot easily be moved from one operation room to an other and as CT does not have real-time imaging capability, alternative imaging modalities are needed to realize the vision of image guided surgery. Ultrasound (U/S) is such an alternative imaging modality. For the comparison of U/S and CT image fusion is very useful. After volume segmentation (see ref. 1) the volumes have to be registered, and afterwards the fused volume can be displayed. In this paper we investigate the registration part. We present two different approaches for the 3D registration of CT and U/S volumes. They are compared regarding accuracy and speed of calculation. The resulting fused volumes are visualized using the "InViVo" software where the registration routines have been integrated into.