VI-RADS (Bladder Cancer Muscle Invasion, mpMRI)

VI-RADS (Panebianco et al., European Urology Oncology 2018) standardizes multiparametric MRI reporting of bladder tumors before transurethral resection. T2W images supply the structural category (SC) from the integrity of the low-signal muscularis propria line; DWI/ADC and DCE supply the diffusion (DW) and contrast-enhancement (CE) categories. Categories 1–2 show an intact muscle line (lesions under or over 1 cm, respectively); category 3 lacks the reassuring category-2 features without clear muscle disruption; category 4 shows focal extension into the muscularis propria; category 5 shows extension through the wall into extravesical fat. The overall score is 1 when all three sequences are category 1, and 2 when all are 2 (or SC 3 with both functional categories 2); it is 3 when categories are concordantly 3 (or SC 3 with one functional category 3 and the other 2); it is 4 when at least one sequence is category 4 with the remainder 3–4, when SC 3 pairs with a functional category 4, or when SC 5 pairs with functional category 4; it is 5 when SC plus DW and/or CE are category 5 with the remaining category 4–5. DWI is the dominant sequence, with DCE taking over when DWI is suboptimal; T2W serves as the first-pass guide for categories 1–3. Pooled performance across validation studies shows high sensitivity and specificity for muscle invasion (cut-offs of ≥3 or ≥4, AUC ≈0.94) with good to excellent interobserver agreement.