COMPARISON OF 18-FDG PET AND CT FOR PRETH ERAPEUTIC STAGING OF MALIGNANT-LYMPHOMA

Aim: Comparison of diagnostic efficiency of FDG-PET and CT regarding l ocalisation, histology, size and FDG-uptake of a lesion. Methods: CT- and FDG-PET studies of 27 patients with histologically confirmed malig nant lymphoma as primary disease or relapse were evaluated retrospecti vely. In CT lesions with a diameter (D-CT) > 15 mm were regarded as po sitive. Focal accumulations of FDG, not explained by physiological met abolism, found by visual interpretation in iterative reconstructed PET -scans, were quantified for diameter (D-PET) and corrected standardize d uptake value (SUV), corrected for partial-volume-effect. Lesions wer e classified depending on histology and lesion quality (lymph nodes, b ulks, extranodal lesions). Results: CT detected 78 lesions in 26 patie nts, all confirmed by FDG-PET. PET localized 18 additional lesions (+2 3%); in high grade NHL +25%. Both methods were equally efficient in ce vical lymph nodes and lung lesions, in all other regions of lymphatic nodules and in case of liver and spleen lesions PET localized more les ions. SUV was significantly higher in high-grade NHL (19.0) than in lo w-grade NHL and Hodgkin's disease (10.6 resp. 11.1). D-CT and D-PET co rrelated significantly (r = 0.75). Conclusion: Diagnostic efficiency o f FDG-PET is equivalent or superior to CT in staging of malignant lymp homa before therapy. Qualitative interpretation seems sufficient for s taging, quantitative analysis may add information about malignancy gra de in NHL.