Optimal timing of post-biopsy MR imaging of the prostate

Purpose: To assess the quantity and frequency of hemorrhage after prostatic biopsy. As post-biopsy blood products may interfere with interpretation of MR images, we also investigated the optimal timing for MR examination afte r biopsy. Material and Methods: Fifteen patients scheduled for prostatic biopsies wer e imaged with endorectal MR before and after the procedure. In addition, MR studies of 42 patients with prostate cancer were retrospectively analyzed. The amount of post-biopsy blood product and the degree of its interference with image interpretation were assessed. Results: Of a total of 57 patients, 44 (77%) had visible post-biopsy hemorr hage. However, the presence of blood products were considered to interfere with interpretation of the images in only 12 (21%) cases. This disturbing e ffect seems to diminish after 21 days from biopsy. The total amount of bloo d clearly decreased after 28 days. Conclusion: Deferring MR imaging for at least 3 weeks after prostatic biops y is advisable. T1-weighted images are necessary to rule out false-positive findings caused by post-biopsy hemorrhage.