Study on Predicting Microsatellite Instability in Rectal Cancer Using T2 Mapping Combined with ADC Value

Objective: To explore the feasibility and diagnostic efficacy of T₂ mapping technique combined with apparent diffusion coefficient (ADC) value in preoperatively predicting the microsatellite instability (MSI) status of rectal cancer. Methods: A retrospective analysis was performed on MRI data of 152 patients with pathologically confirmed rectal cancer from January 2022 to June 2025, including 40 cases in the MSI group and 112 cases in the microsatellite stability (MSS) group. All patients underwent T₂ mapping and diffusion-weighted imaging (DWI) scans, and the tumor T₂ values and ADC values were measured. Independent samples t-test was used to compare differences between groups, receiver operating characteristic (ROC) curve analysis was applied to evaluate diagnostic efficacy, multivariate logistic regression was used to construct a combined prediction model, and 10-fold cross-validation and Bootstrap resampling were conducted to assess model stability. Results: The T₂ value in the MSI group was significantly lower than that in the MSS group (92.18 ± 7.21 ms vs. 99.47 ± 7.85 ms, p 0.001), and the ADC value in the MSI group was significantly higher than that in the MSS group (1.06 ± 0.18 vs. 0.91 ± 0.19 × 10⁻³ mm²/s, p 0.001). The area under the curve (AUC) of T₂ value for predicting MSI was 0.865, and that of ADC value was 0.741; the AUC of the combined model increased to 0.915 (sensitivity: 82.5%, specificity: 89.3%). The model showed good stability (Bootstrap AUC = 0.913). Conclusion: T₂ mapping combined with ADC value can non-invasively and accurately predict the MSI status of rectal cancer. The diagnostic efficacy of the combined model is significantly superior to that of a single parameter, indicating high potential for clinical translation.