Hypothesis / aims of study
There remains an unmet need for an imaging technique which will differentiate ulcerative Painful Bladder Syndrome/Interstitial Cystitis (PBS/IC) from non-ulcerative PBS/IC. MRI is a radiation-free imaging technique that demonstrates excellent contrast of pelvic tissues in 3D-anatomy. Past attempts at unenhanced  and contrast enhanced  T1 weighted MRI of human bladder wall were unable to improve the contrast-noise ratio (CNR) and the spatial resolution per image pixel. Intravesical novel contrast mixture (NCM) has been recently shown to improve the CNR of rat bladder wall injured with protamine sulfate . In this clinical study, the safety and feasibility of MRI enhanced with intravesical NCM in evaluating patients with PBS/IC was tested.
Study design, materials and methods
After giving informed consent, 6 women (25-78y) submitted to 3T MRI before and after intravesical NCM. The 6 women consisted of 2 controls, 2 with non-ulcerative PBS/IC, and 2 with ulcerative PBS/IC. NCM 50 ml was freshly prepared by diluting Gadobutrol (Gadovist, Bayer) 1:250 and Ferumoxytol (Feraheme, AMAG Pharmaceuticals) 1:104 in sterile water for injection (Figure 1). Respiratory monitoring belt was placed around patient and under receiver coil for checking breath-hold during fast image acquisition with repetition time/echo time of 5.5/2ms. Single slice of 5mm thickness was acquired during single breath-hold of 17 seconds for each flip angle to minimize the motion and chemical shift artifacts. Quantitative measurement of T1 made from the differences in signal intensity of 20 pixels representing bladder wall in pre-contrast and post-contrast images taken at different flip angles.
Interpretation of results
MRI enhanced with intravesical NCM allowed differentiation of the bladder wall into different tissue layers with an increased depth of gadolinium diffusion in the ulcerative-type PBS/IC patients. This pilot study was limited by the small size and was not powered to demonstrate the group-wise differences in bladder wall thickness. The significantly reduced bladder wall T1 relaxation times in the ulcerative PBS/IC patients are promising and warrant further evaluation in an independent trial with a larger sample size.