Value of PET/CT versus PET and CT performed as separate investigations in patients with Hodgkin's disease and non-Hodgkin's lymphoma

Purpose: The aim of this study was to assess the clinical benefit of combined [F-18] FDG PET/CT in patients with malignant lymphoma as compared to separately performed PET and CT. Methods: Overall, 100 patients with Hodgkin's disease (HD) or non-Hodgkin's lymphoma (NHL) were included in this study. Co-registered PET/ CT with [F-18] FDG and contrast medium was performed in 50 consecutive patients with NHL (n= 38) or HD ( n= 12) for initial staging ( IS) ( n= 12) or re-treatment staging (RS) ( n= 38). Another 50 patients with NHL ( n= 32) or HD ( n= 18) underwent separate PET and CT investigations within a time frame of 10 days for IS ( n= 22) or RS ( n= 28). Lymphoma involvement was separately evaluated for seven different regions in each patient. Each patient had clinical follow-up evaluation for > 6 months. PET and CT data were analysed separately as well as side-by-side or in fused mode. Results: In the PET/ CT group, region-based evaluation for lymphoma involvement suggested a sensitivity/specificity of 85%/ 91% for CT, 98%/ 99% for PET and 98%/ 99% for PET/ CT. In the PET and CT group, region-based evaluation showed a sensitivity/ specificity of 87%/80% for CT, 98%/ 99% for PET and 98%/ 100% for PET and CT read side by side. Conclusion: PET was superior to CT alone and was improved further by side-by-side reading of both examinations. However, no significant difference was observed between PET/ CT and separate PET and CT imaging in patients with lymphoma.