Endorectal MRI using a 0.5 T mid-field system in the staging of localized prostate cancer

The accuracy of high field, endorectal MRI in the staging of localized prostate cancer has been the focus of many previous reports. We present our findings with a mid-field magnet. Twenty-two patients with clinically localized prostate cancer were prospectively staged with endorectal MRI using a 0.5 T magnet. All patients subsequently underwent radical prostatectomy and the results of pre-operative MRI staging were compared with the histological findings. The overall staging accuracy for mid-field, endorectal MRI was 77% (17/22). The sensitivity and specificity were 50% (7/14) and 100% (8/8), for diagnosing capsular penetration and 100% (4/4) and 94% (17/18), for seminal vesicle invasion. This study demonstrates that as a result of recent developments in mid-field MRI design it is now possible to use these MR systems in conjunction with an endorectal probe to stage localized prostate cancer and that the accuracy is comparable to previous reports using high-field magnets.