Multisequence MRI Enables High‐Fidelity FDG ‐ PET Synthesis for Epilepsy Using GANs

BACKGROUND: FDG-PET aids presurgical epilepsy evaluation but is limited by access and radiation exposure. PURPOSE: To evaluate synthetic FDG-PET generated from T1-weighted imaging and resting-state fMRI metrics. STUDY TYPE: Retrospective. POPULATION: 481 participants underwent simultaneous FDG PET/MR. Internal cohort: 311 epilepsy patients split into training/validation/internal test sets (n = 249/31/31; age 18.79 ± 16.33/22.20 ± 11.21/21.65 ± 17.62 years; male/female 145/104, 13/18, 22/9). External cohort: 115 temporal lobe epilepsy patients (age 25.36 ± 10.95 years; male/female 68/47) and 55 healthy controls (age 27.62 ± 5.82 years; male/female 24/31); 92 had surgery with 1-year outcome. FIELD STRENGTH: Hybrid PET/MR at 3.0 T; gradient-echo T1WI, echo-planar imaging and resting-state BOLD gradient-echo EPI. ASSESSMENT: Performance was assessed using SSIM, PSNR, MSE, NRMSE, SUVR correlation, and Bland-Altman analysis. Three blinded readers performed visual quality grading and detection of temporal lobe hypometabolism. Hippocampal radiomics was used for classification of hippocampal sclerosis and Engel outcome. STATISTICAL TESTS: t-tests, chi-square tests, Pearson correlation, Kolmogorov-Smirnov tests, DeLong tests, and false discovery rate correction. RESULTS: Excellent/Good visual ratings occurred in 82.8% (166/201), with Fleiss' κ = 0.42. SSIM was 0.98 ± 0.01 (internal) and 0.97 ± 0.01 (external); PSNR was 66.66 ± 1.25 and 64.16 ± 1.83, respectively. SUVR correlation with ground-truth PET was r = 0.94 (internal) and r = 0.89 (external); Bland-Altman bias was -0.02 (95% limits of agreement: -0.22 to 0.18) internally and -0.00002 (95% limits: -0.35 to 0.35) externally. Detection accuracy for temporal hypometabolism was 90.3% (internal; κ = 0.735) and 87.1% (external; κ = 0.758). Radiomics AUCs using synthetic PET were 0.72 (95% CI: 0.62-0.83) for hippocampal sclerosis versus healthy controls and 0.77 (95% CI: 0.67-0.87) for Engel IA versus IB-IV; DeLong tests versus ground-truth PET were non-significant (p = 0.56 and p = 0.48). CONCLUSION: Multisequence MRI-based synthetic PET showed high agreement with ground-truth PET across image-quality and quantitative SUVR metrics, providing a PET-like metabolic surrogate when FDG-PET is unavailable or impractical. LEVEL OF EVIDENCE: Evidence Level 3. STAGES OF TECHNICAL EFFICACY: Stage 3.