Synthetic Phase-Sensitive Inversion Recovery and Extramural Vascular Invasion Scoring Systems for Vascular Invasion Detection and Metastasis Risk in Rectal Cancer.

Purpose To develop and validate a modified extramural vascular invasion (EMVI) scoring system with synthetic phase-sensitive inversion recovery (SyPSIR) images to improve vascular invasion detection and metastasis prediction in patients with rectal cancer. Materials and Methods Participants with rectal cancer were eligible for this single-center prospective study between October 2020 and June 2024, with follow-up intervals of 3-6 months (median follow-up, 23 months; range, 3-50 months). All participants underwent EMVI evaluation using conventional T2-weighted imaging-based and modified synthetic phase-sensitive inversion recovery-incorporated scoring systems, with diagnostic performance for pathologic EMVI detection evaluated against histopathology. Receiver operating characteristic curve analysis was used to evaluate the diagnostic performance of the pathologic EMVI results. Kaplan-Meier survival analysis and multivariable Cox regression analysis were used to compare the prognostic performance of the scoring systems, and a nomogram for metastasis risk stratification was developed. Results This study included 356 participants (mean age, 65 years ± 10 [SD]; 238 males) with rectal cancer (304 with pathologically confirmed EMVI). The modified EMVI scoring system demonstrated better diagnostic performance for pathologic EMVI detection than the conventional T2-weighted imaging system (sensitivity: 59%-80% vs 33%-49%; area under the receiver operating characteristic curve: 0.72-0.80 vs 0.59-0.68; P < .05). Multivariable Cox regression analysis confirmed that a modified MRI-based EMVI (mrEMVI) was the most independent predictor of metastasis-free survival (MFS) (hazard ratio, 10.76; P < .001), with Kaplan-Meier analysis demonstrating its better prognostic stratification ability in both the training and validation cohorts. A prognostic nomogram incorporating the modified mrEMVI, mucinous component, mrN stage, mrT stage, and tumor deposit achieved excellent discrimination for 3-year MFS (area under the receiver operating characteristic curve, 0.86-0.98), with reasonable calibration, and demonstrated clinical utility across relevant decision thresholds. Conclusion The modified EMVI scoring system outperformed the conventional T2-weighted imaging system in both pathologic EMVI detection and metastasis prediction. The integrated nomogram incorporating the modified mrEMVI provides a robust tool for accurate 3-year MFS prediction. Keywords: Abdomen/GI, MR-Imaging, Diagnosis, Prognosis & Prediction Supplemental material is available for this article. © The Author(s) 2026. Published by the Radiological Society of North America under CC BY 4.0 license.