Abstract
PURPOSE: This study evaluated the comparative performance of standardized uptake value (SUV) measurements derived from positron emission tomography/magnetic resonance imaging (PET/MRI) and digital positron emission tomography/computed tomography (PET/CT) in lymphoma patients. A retrospective analysis was conducted to compare semi-quantitative measures and assess the correlation and concordance between the two imaging modalities. METHODS: A total of 106 lymphoma patients underwent both PET/CT and PET/MRI, either in the order of PET/CT followed by PET/MRI (PET/CT(first) group, n = 51) or PET/MRI followed by PET/CT (PET/MRI(first) group, n = 55). SUV measurements in lesions, liver, and mediastinal blood pool were compared between modalities. RESULTS: SUV(max) and SUV(mean) were significantly lower in PET/MRI than PET/CT (P < 0.001), except SUV(mean) for mediastinal blood pool in the PET/MRI(first) group (P = 0.090). Correlation between modalities was very high for the lesions (ρ = 0.90-0.96). The Deauville five-point scale (D5PS) scores had good agreement between modalities (κ = 0.6566 for PET/CT(first) and κ = 0.4846 for PET/MRI(first); P < 0.001), but the response categorization would have been different in 22/262 PET/CT(first) group and 21/155 PET/MR(first) group. CONCLUSION: SUV measurements from PET/MRI demonstrated strong correlation and good agreement in D5PS classification compared to digital PET/CT. Nonetheless, variations in PET subsystem technologies across modalities may influence quantitative values, and such differences should be carefully considered when interpreting results.