Multiparametric Magnetic Resonance Imaging for Bladder Cancer: Development of VI-RADS (Vesical Imaging-Reporting And Data System)

Abstract

Context: Management of bladder cancer (BC) is primarily driven by stage, grade, and biological potential. Knowledge of each is derived using clinical, histopathological, and radiological investigations. This multimodal approach reduces the risk of error from one particular test, but may present a staging dilemma when results conflict. Multiparametric magnetic resonance imaging (mpMRI) may improve patient care through imaging of the bladder with better resolution of the tissue planes than computed tomography and without radiation exposure.

Objective: To define a standardized approach to imaging and reporting mpMRI for BC, by developing a VI-RADS score.

Evidence acquisition: We created VI-RADS (Vesical Imaging-Reporting And Data System) through consensus using existing literature.

Evidence synthesis: We describe standard imaging protocols and reporting criteria (including size, location, multiplicity, and morphology) for bladder mpMRI. We propose a five-point VI-RADS score, derived using T2-weighted MRI, diffusion-weighted imaging, and dynamic contrast enhancement, which suggests the risks of muscle invasion. We include sample images used to understand VI-RADS.

Conclusions: We hope that VI-RADS will standardize reporting, facilitate comparisons between patients, and in future years, will be tested and refined if necessary. While we do not advocate mpMRI for all patients with BC, this imaging may compliment pathology or reduce radiation-based imaging. Bladder mpMRI may be most useful in patients with non-muscle-invasive cancers, in expediting radical treatment or for determining response to bladder-sparing approaches.

Patient summary: Magnetic resonance imaging (MRI) scans for bladder cancer are becoming more common and may provide accurate information that helps improve patient care. Here, we describe a standardized reporting criterion for bladder MRI. This should improve communication between doctors and allow better comparisons between patients.

Keywords: Bladder cancer; Multiparametric magnetic resonance imaging; RADS; Scoring; Staging.

Fig. 1 –

Schematic appearance of bladder wall anatomy and respective MRI appearances at T2W imaging, DWI, ADC, and DCE MRI. T2W images show low SI of muscular layer, and cannot visualize/discriminate the urothelium and the lamina propria. At DWI, the muscular layer appears as an intermediate SI line, while inner layer is not visualized; ADC maps shows intermediate signal of muscular layer compared with high signal of urine. The bladder wall components change appearance during the phases of DCE imaging. ADC = apparent diffusion coefficient; DCE = dynamic contrast enhancement; DWI = diffusion-weighted imaging; MRI = magnetic resonance imaging; SI = signal intensity; T2W = T2 weighted.

Fig. 2 –

Schematic map of the bladder modified from the Japanese Urological Association, the Japanese Society of Pathology, Japan Radiological Society schema (published in General rule for clinical and pathological studies on renal pelvic, ureteral and bladder cancer, Kanehara Publisher Inc., 2011, p. 16).

Fig. 3 –

Schematic illustration of mpMRI appearances of VI-RADS scores 1–5 using T2, DCE MRI, DWI, and ADC weighted images. ADC = apparent diffusion coefficient; DCE = dynamic contrast enhancement; DWI = diffusion-weighted imaging; MRI = magnetic resonance imaging; mpMRI = multiparametric MRI; SI = signal intensity.

Fig. 4 –

Summary schematic representation of VI-RADS scoring. Scoring interpretation: for categories 1–3, the “first pass scoring” T2 sequence should be considered. For categories 4 and 5, the dominant sequences are DWI (first, when image quality is optimal) and DCE (second). CE = contrast-enhanced category; DCE = dynamic contrast enhancement; DW = diffusion-weighted category; DWI = diffusion-weighted imaging; SC = structural category; SI = signal intensity.