Staging of urinary bladder tumors by MRI:: Utility of intravesical administration of an iron oxide-containing contrast medium in combination with high-resolution, T2-weighted imaging.

Aim: To investigate superparamagnetic iron oxide (SPIO) particles as intravesically applied contrast material in combination with high-resolution T-2-weighted MR imaging for the diagnostic assessment of urinary bladder tumors. Methods: A prospective study was performed in 40 patients with suspected urinary bladder tumors who underwent MR imaging with a body phased-array coil at 1.5 T. Prior to imaging, a SPIO-containing solution (179.2 mg Fell) was instilled into the bladder. All patients were examined with T-2-weighted, half-fourier acquired single shot turbo spin echo sequences and T-1-weighted fast low angle shot sequences in 3 planes as well as a T-2-weighted turbo spin echo sequence (TSE) using a 512 matrix. An additional gadolinium-enhanced dynamic study was performed in 33 patients. All patients underwent transurethral resection of the bladder or cystectomy. Results: The combination of intravesically applied SPIO particles and a high-resolution T2-weighted TSE sequence depicted intravesical tumors as small as 4 mm. A reliable identification of the different layers of the bladder wall was possible in 5 cases only. The T-2-weighted TSE sequence allowed the correct determination of the depth of infiltration in 29 of 36 patients with urothelial cancer by assessing the inner and outer boundary of the urinary bladder wall. This sequence had a diagnostic accuracy of 81% compared to 84% for the dynamic study (26/31). Conclusion: Even small tumors could be identified with the T-2-weighted TSE sequence after intravesical administration of SPIO particles but it was not possible to reliably differentiate the layers of the bladder wall. The results suggest that a dynamic MR imaging study cannot be dispensed with in patients with urinary bladder cancer.