Non-Invasive Assessment of the Lower Urinary Tract – MRI Urodynamics*

Lower urinary track symptoms (LUTS) affect many older adults. Multi-channel urodynamics provides information about bladder pressure and urinary flow but offer little insight into changes in bladder anatomy and detrusor muscle function. Use of non-invasive methods for the study of lower urinary tract anatomy and function has been limited. Image based patient specific computational models have been extensively used for cardiovascular evaluation and personalized treatment planning. The objective of this study was to implement a magnetic resonance imaging (MRI) urodynamics method, as well as a patient specific MRI-based computational fluid dynamics (CFD) simulation of bladder voiding.

Three men with known LUTS (ages 73, 71, and 54) and three control subjects (ages 66, 42, and 44) were recruited under an IRB approved protocol. MRI was performed on a clinical 3T scanner using a high-density flexible surface coil array. A dynamic acquisition was performed using 3D Differential Subsampling with Cartesian Ordering (DISCO) with a temporal resolution of 3.7 seconds. 15 minutes prior to the MRI scans, 1/3 of a single weight-based dose (0.1 mmol/kg) of gadolinium-based contrast was hand injected intravenously allowing the visualization of bladder and urethral deformation and general LUT biomechanics. Images were imported into MIMICS (Materialise, Leuven, Belgium), where bladder facia and mucosa, and urethral mucosa are segmented to obtain 3D renderings. Three critical points during the voiding event were determined from the 3D segmentations, pre-void, maximum flow rate, and post-void phases.

A methodology to evaluate and characterize biomechanics of the bladder and uretrha during voiding in human subjects was successfully implemented. This MRI based techinique is an invaluable imaging modality that can be used to characterize anatomical and functional information of the LUT throughout the voiding cycle in a safe, accurate, and reproducible way