Purpose: Here, we tested whether combined contrast-enhanced magnetic resonance imaging (CCE-MRI), using a mixture Gadolinium and iron-oxide based contrast agents, can segment the bladder wall from the bladder lumen. CCE-MRI relies on the differences in particle size and contrast mechanisms of two agents for improved image contrast. Methods: Under isoflurane anesthesia, T1-weighted imaging of adult female Sprague-Dawley rat bladder was performed using standard turbo spin echo sequences at 7 Tesla, before and after transurethral instillation of 0.3 mL of single contrast (CE-MRI) or combined contrast mixture (CCE-MRI) composed of 0.4-64 mM of gadolinium chelate (Gd-DTPA/Gadavist) and 5 mM ferumoxytol. Bladder wall contrast was assessed in control group exposed to saline and in bladder injury group exposed to 0.5 mL of protamine sulfate (10 mg/mL) for 30min. Results: CCE-MRI following instillation of 0.4-4 mM Gd-DTPA and 5 mM ferumoxytol mixture achieved segmentation between the bladder lumen and bladder wall. Hyperintensity in the bladder wall combined with hypointensity in the lumen is consistent with the increased diffusion of the dissolved Gd-DTPA and localization of the larger nanoparticles of ferumoxytol in the lumen. The normalized hyperintense signal in the bladder wall increased from 0.46 ± 0.07 in control group to 0.73 ± 0.14 in protamine sulfate exposed group (p < 0.0001). Conclusions: CCE-MRI following instillation of contrast mixture identifies bladder wall changes likely associated with bladder injury with improved image contrast.
- Copyright © 2016, American Journal of Physiology-Renal Physiology