MRI-Guided Robotic Prostate Biopsy: A Clinical Accuracy Validation

Abstract. Prostate cancer is a major health threat for men. For over five years, the U.S. National Cancer Institute has performed prostate biopsies with a magnetic resonance imaging (MRI)-guided robotic sys-tem. Purpose: A retrospective evaluation methodology and analysis of the clinical accuracy of this system is reported. Methods: Using the pre and post-needle insertion image volumes, a registration algorithm that contains a two-step rigid registration followed by a deformable refinement was developed to capture prostate dislocation during the procedure. The method was validated by using three-dimensional contour overlays of the segmented prostates and the registrations were accurate up to 2 mm. Re-sults: It was found that tissue deformation was less of a factor than organ displacement. Out of the 82 biopsies from 21 patients, the mean target displacement, needle placement error, and clinical biopsy error was 5.9 mm, 2.3 mm, and 4 mm, respectively. Conclusion: The results suggest that motion compensation for organ displacement should be used to im-prove targeting accuracy.