Deep learning-based simulated contrast-enhanced MRI for rectal cancer evaluation: a multicenter study

To assess the feasibility and accuracy of using deep learning to generate simulated contrast-enhanced T1-weighted rectal MRI scans from pre-contrast MRI sequences in rectal cancer patients.

This study included 514 patients with pathologically confirmed rectal carcinoma who underwent contrast-enhanced MRI at three academic institutions. A two-dimensional generator adversarial network was used to simulate contrast-enhanced MRI scans from pre-contrast T1-weighted images. Quantitative assessments of image similarity, error metrics, and Dice coefficient for tumor overlap were performed. Three radiologists, blinded to the contrast method, evaluated image quality, tumor enhancement, and extramural vascular invasion (EMVI) in 104 paired real and simulated scans. Tumor size correlation was analyzed with intraclass correlation coefficients (ICCs), and modified Bland-Altman plots were used to assess agreement. ROC curves evaluated diagnostic performance of EMVI detection, and quality scores were compared using the McNemar test.

Simulated scans demonstrated high similarity to real scans (structural similarity index: 0.82, Dice coefficient: 0.86 ± 0.14 for tumor overlap). Tumor size measurements correlated strongly (ICC: 0.76-0.88), with minimal differences in length (0.11 mm) and depth (0.10 mm). ROC analysis revealed slightly higher AUC values for real scans (0.702, 0.772, 0.713) compared to simulated scans (0.685, 0.694, 0.661) for three radiologists, respectively. Nearly all synthetic scans (98%) were rated diagnostically suitable.

Deep learning-generated simulated contrast-enhanced MRI scans demonstrated comparability to real scans in terms of tumor size, enhancement area, and image quality, suggesting their potential as a supportive tool for diagnosis and treatment evaluation.