MRI-ultrasound registration for targeted prostate biopsy

T2-weighted magnetic resonance images (MRI) imaging using an endorectal coil combined with a pelvic phased-array coil has been shown to provide high resolution images of the prostate. To integrate MRI analysis in standard prostate biopsy procedures, preoperative MRI must be accurately registered to 3-D transrectal ultrasound (TRUS) images. Shape changes due to patient motion, or drugs can induce further differences in glandular shape variation between preoperative MRI and 3-D TRUS during biopsy. In the proposed work, we model the deformation relating MRI and TRUS so as to enable analysis of MRI in conjunction with ultrasound (color blended or side-by-side) for planning of biopsy targets. Registration of MRI at various resolutions and endorectal balloon volumes and ultrasound volumes yielded average fiducial registration error of 3.06 mm using 6 and 12 bead phantoms.