Comparison of Virtual MR Elastography Based on Intravoxel Incoherent Motion With MR Elastography in the Assessment of Intratumoral Fibrosis in Rectal Cancer

Background Intratumoral fibrosis influences treatment efficacy and prognosis of rectal cancer (RC). The roles of MR elastography (MRE) and Virtual MRE (VMRE) remain unclear in assessing it in RC. Purpose To evaluate MRE for assessing intratumoral fibrosis in RC, identify optimal b ‐values for VMRE, and compare their diagnostic performance. Study Type Prospective cohort. Population A total of 71 participants with pathologically confirmed RC (47 men; mean age, 62 ± 10 years). Field Strength/Sequences 3T, T2‐weighted turbo‐spin echo, contrast‐enhanced T1‐weighted gradient‐recalled echo, Intravoxel incoherent motion (IVIM) ( b = 0, 100, 200, 1000, 1500 s/mm 2 ), and spin‐echo MRE. Assessment All participants were divided at a 7:3 ratio: subgroup 1 ( N = 49) determined the optimal b ‐value combination and established the empirical relationship between shifted apparent diffusion coefficient (sADC) and VMRE (V c , V φ ) based on IVIM, with MRE ( c , φ ) as reference; subgroup 2 ( N = 22) validated this relationship. MRE and VMRE evaluated intratumoral fibrosis in 43 surgically diagnosed participants. Statistical Tests Receiver operating characteristic (ROC), Pearson correlation, DeLong test. Bonferroni‐adjusted p < 0.05 indicated statistical significance. Results The optimal combination of b ‐values was 0 and 1500 s/mm 2 ( r c = −0.808, r φ = −0.644) for VMRE in subgroup 1. In 43 surgically diagnosed participants, area under curves (AUCs) of c and φ for assessing intratumoral fibrosis were 0.779 and 0.684, respectively (Adjusted p = 0.828). AUCs of V c and V φ converted from sADC 0–1500 values were 0.792 and 0.784, respectively (Adjusted p > 0.999). No significant differences in AUCs were observed among all parameters (Adjusted p : 0.384 to > 0.999). Sensitivity and specificity ranges of MRE and VMRE were 85.7%–90.5% and 54.5%–68.2%, respectively. Data Conclusions MRE was used to evaluate intratumoral fibrosis in RC. The optimal b ‐values combination for VMRE in RC was 0 s/mm 2 and 1500 s/mm 2 . No significant difference was observed for assessing intratumoral fibrosis between MRE and VMRE. Evidence Level 2. Technical Efficacy Stage 2.