Diagnostic Accuracy of High Resolution MR Imaging in Local Staging of Bladder Tumors

Objective: To determine the diagnostic accuracy of high-resolution MR imaging done at 1.5T in distinguishing bladder-restricted tumor from non-bladder-restricted tumor and compare the mean short axis dimension of metastatic pelvic lymph nodes with benign pelvic lymph nodes. Study Design: Analytical study. Place and Duration of Study: Shaukat Khanum Memorial Cancer Hospital, Lahore, Pakistan, from March 2008 to July 2011 Methodology: Patients with bladder cancer were enrolled. Based on pathologic T-staging following radical cystectomy, patients were assigned to one of two groups. Patients with stage Ti and T2 disease were assigned to the bladderrestricted tumor (BRT) group and those with stage T3 and T4 disease to the non-bladder-restricted tumor (NBRT). High-resolution unenhanced MR imaging done prior to cystectomy was reviewed retrospectively (1.5 T MRI unit; GE Healthcare). Results from MR imaging-based categorization were compared with pathology reports to fulfill the objective. Mean short-axis diameter of largest visible lymph nodes in patients with nodal metastasis was compared with mean short-axis diameter of largest visible lymph nodes in patients with benign lymph nodes. Results: The accuracy of MRI in differentiating distinguishing bladder-restricted tumor from non-bladder-restricted tumor was 67.72%. The mean short axis diameter of metastatic lymph nodes was greater than that of non-metastatic lymph nodes, i.e., 7.4 mm and 5.4 mm respectively. Conclusion: Conventional high resolution 1.5T MRI does not appear to offer advantage over imaging done at low field strength scanners.