Update on multiparametric MRI of urinary bladder cancer
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While many institutions perform MRI during the work-up of urinary bladder cancer, others use MRI rarely if at all, possibly due to a variation in the reported staging accuracy and unfamiliarity with the potential benefits of performing MRI. Through increased application of functional imaging techniques including diffusion-weighted imaging (DWI) and dynamic contrast-enhanced (DCE) imaging, there has been a resurgence of interest regarding evaluation of bladder cancer with MRI. Several recent meta-analyses have shown that MRI is accurate at differentiating between ≤T1 and T2 disease (with pooled sensitivity/specificity of ∼90/80%) and differentiating between T2 and ≥T3 disease. DWI and DCE, in combination with high-resolution T2 -weighted images, improves detection and possibly local staging accuracy of bladder cancer. High b value echo-planar DWI is particularly valuable for tumor detection. Zoomed field of view and segmented readout DWI techniques improve image quality by reducing susceptibility artifact, while methods to extract calculated high b value images save time and improve the contrast-to-noise ratio. DCE traditionally required imaging of the pelvis with high temporal but lower spatial resolution; however, advances in parallel and keyhole imaging techniques can preserve spatial resolution. The use of compressed sensing reconstruction may improve utilization of DCE of the bladder, especially when imaging the abdomen simultaneously, as in MR urography. Quantitative imaging analysis of bladder cancer using pharmacokinetic modeling of DCE, apparent diffusion coefficient values, and texture analysis may enable radiomic assessment of bladder cancer grade and stage. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;48:882-896.
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