Contrast-enhanced CT for attenuation correction in ultra-high sensitivity long-axial field-of-view lymphoma PET:...

It is unclear whether the use of contrast enhanced (CE) CT for attenuation correction (AC) of [¹⁸F]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.

Lymphoma patients who underwent LAFOV-[¹⁸F]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.

SUV_max of BP and the liver increased when CE-CT was used instead of AC-CT for AC (BP: median 2.41vs.2.21, p < 0.01, 8.78% intra-patient increase; liver: 3.07vs.2.87, p < 0.01, 7.86% medina intra-patient increase). Similarly, SUV_mean was higher in CE-CT reconstructions (BP: 1.96vs.1.77, p < 0.01, 10.14% median intra-patient increase; liver: 2.50vs.2.32, p < 0.01, 7.54% median intra-patient increase). SUV_max 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%).

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.