Application of T1-mapping combined with high-spatial-resolution T2-weighted imaging in discriminating mucinous from nonmucinous adenocarcinoma in rectal cancer.

Purpose: The aim of this study was to evaluate the utility of T1-mapping, high-spatial-resolution T2-weighted imaging (HR-T2WI), and their combined model in distinguishing between adenocarcinoma not otherwise specified (AC) and mucinous adenocarcinoma (MC) in rectal cancer.

Methods: A total of 55 patients with pathologically confirmed AC and 37 patients with MC were included in the study. Two radiologists independently reviewed the HR-T2WI and provided assessments of histopathological type. Additionally, T1 relaxation times were quantified using whole-tumor volume methods both pre-contrast (T1p) and post-contrast administration (T1e). The absolute reduction in T1 value (T1d) and the percentage reduction (T1d%) were calculated. Receiver operating characteristic curve analysis was performed to evaluate diagnostic efficacy.

Results: HR-T2WI demonstrated a sensitivity, specificity, and accuracy of 81.08%, 94.55%, and 89.13%, respectively, in distinguishing rectal MC. T1p, T1e, and T1d values were significantly higher in the MC group compared to the AC group (P < 0.001, = 0.019, and < 0.001, respectively), while there was no statistically significant difference in T1d% between the two groups. Among these quantitative parameters, T1p showed the highest diagnostic efficiency for identifying MC, with a sensitivity of 59.46%, specificity of 92.73%, and moderate diagnostic accuracy (AUC = 0.819). Combining HR-T2WI with T1p (sensitivity = 86.49%, specificity = 92.73, AUC = 0.927) yielded superior performance over single parameters in distinguishing histopathological subtypes.

Conclusion: T1p is effective in discriminating between AC and MC in rectal cancer. Importantly, the combined model incorporating HR-T2WI and T1p demonstrated enhanced capability in distinguishing histopathological subtypes of rectal cancer, which benefits individualized treatment.