RadiolGAN: Multicenter Feasibility Study of Synthetic CT From 3D Ultra-Short Echo Time MRI for Enhanced Pulmonary Radiologic Sign Visualization.
BACKGROUND Chest CT requires breath-holding and ionizing radiation. 3D ultrashort echo time (UTE) MRI allows radiation-free imaging, but the image quality is suboptimal. PURPOSE To develop RadiolGAN and evaluate synthetic CT (sCT) from 3D UTE MRI for enhanced pulmonary visualization. STUDY TYPE Prospective multicenter study. POPULATION Three hundred and fifty-nine subjects (167 women, 192 men; 52 ± 19 years) from four centers: 244 training, 61 internal test, and 54 external test. FIELD STRENGTH/SEQUENCE 3 T, 3D UTE gradient-echo sequence. ASSESSMENT Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), noise, peak signal-to-noise ratio (PSNR), mean structural similarity index (MS-SSIM), universal quality index (UQI), and learned perceptual image patch similarity (LPIPS). Three radiologists rated pulmonary structures (bronchi, vessels, fissures, artifacts, diagnostic confidence) and radiologic signs (nodules/masses, ground-glass opacities, patchy shadows/consolidation, emphysema/bullae, bronchiectasis) on a 5-point Likert scale. STATISTICAL TESTING Repeated-measures ANOVA, paired t-tests, and Friedman tests; p < 0.05 significant. RESULTS In the external test set, RadiolGAN-CT showed higher SNR (32.63 ± 1.21 vs. 26.07 ± 1.53) and CNR (25.36 ± 1.06 vs. 21.64 ± 1.32), and lower noise (15.74 ± 0.85 vs. 19.66 ± 1.01) than 3D UTE. Versus CycleGAN-CT, RadiolGAN-CT achieved higher PSNR (65.32 ± 0.19 vs. 64.68 ± 0.21), MS-SSIM (0.912 ± 0.004 vs. 0.892 ± 0.004), FSIM (0.808 ± 0.007 vs. 0.783 ± 0.006), and UQI (0.854 ± 0.007 vs. 0.843 ± 0.007), and lower LPIPS (0.221 ± 0.010 vs. 0.236 ± 0.009). No differences were found between RadiolGAN-CT and CycleGAN-CT in SNR (p = 0.612), CNR (p = 0.547), or noise (p = 0.595). Diagnostic confidence was higher for RadiolGAN-CT (3.98 ± 1.09) than CycleGAN-CT (3.59 ± 1.06) and 3D UTE (2.84 ± 1.30). Ground-glass opacity depiction did not differ between RadiolGAN-CT and CycleGAN-CT (p = 0.903). DATA CONCLUSION RadiolGAN enables high-fidelity sCT from 3D UTE, improving structural depiction and perceptual similarity. EVIDENCE LEVEL 1. TECHNICAL EFFICACY 2.