Contrast-enhanced CT for attenuation correction in ultra-high sensitivity long-axial field-of-view lymphoma PET: amplified quantification problems?

PURPOSE: F]FDG PET leads to higher quantification inaccuracies when used in high-sensitivity LAFOV systems. This project aimed to assess the clinical feasibility of CE-CT for AC in LAFOV-PET for lymphoma patients. METHODS: F]FDG-PET for restaging with low dose AC-CT and diagnostic CE-CT were included in this retrospective analysis. PET images were reconstructed using ultra-high sensitivity (UHS) mode with CE-CT and AC-CT. Lesions and reference regions (liver and mediastinal blood pool (BP)) were evaluated. RESULTS: of lesions showed a similar magnitude of increase (5.97vs.5.68, p < 0.01, 5.80% median intra-lesion increase). The SUV-ratio of the lesions to reference organs decreased when CE-CT instead of AC-CT was used for AC (BP: 2.79vs.2.99, p < 0.01, median per-lesion decrease - 4.90%; liver: 1.85vs.1.97, p < 0.01, median per-lesion decrease - 2.64%). CONCLUSION: The use of CE-CT for AC of LAFOV-PET in UHS mode leads to higher SUV measurements. Also, lymphoma lesions show a consistent increase in uptake. The errors in the lesions seem higher than in conventional standard axial field-of-view PETs that use CE-CT for AC. Therefore, interpretation of borderline cases warrants attention to potential errors.