To assess whether quantitative T1 relaxometry can measure permeability, assess chronic inflammation and mural thickening of mouse bladder wall. Adult female C57BL6 mice unexposed to radiation (controls) or 40 weeks post-irradiation10Gy were scanned at 9.4T before and after instillation (0.1mL) of aqueous, novel contrast mixture containing 4mM Gadobutrol and 5mM Ferumoxytol. Rapid Acquisition with Refocused Echo (RARE) sequence with variable Repetition Times (TR) generated pixel wise map of T1 relaxation times for segmented bladder wall layers from voxel-wise, nonlinear least square data fitting of TR dependent signal intensity acquired with TR array of 0.4-10s followed by the histology of harvested bladder. Significant differences between pre-contrast and post contrast T1 (DT1) noted in urothelium and lamina propria of both groups but only in detrusor of irradiated group (p<0.001; Two-way ANOVA). Nearly two-fold higher Gadobutrol permeability (550 ± 73μM vs 294 ± 160μM; p<0.01) derived as per 1/DT1 = r1. [C] in urothelium of irradiated group (0.75± 0.04mm vs 0.44± 0.08mm; p<0.001). Inflammation and bladder wall thickening predicted by MRI was subsequently confirmed by histology and altered expression of CD45 and zonula occludens-1 (ZO-1) relative to controls. Novel contrast mixture enhanced MRI relies on the retention of large molecular weight Ferumoxytol in lumen for negative contrast, while permeation of the non-ionic, small molecular weight Gadobutrol through ZO-1 generates positive contrast in bladder wall for virtual measurement of paracellular permeability and assessment of chronic inflammation in thin and distensible bladder wall, which is also defined by its variable shape and location within pelvis.