Standardized uptake value based evaluation of lymphoma by FDG and FLT PET/CT

Although (18) F-FDG PET/CT imaging is the conventional method for evaluating lymphoma, PET/CT imaging with radiopharmaceuticals other than FDG is being investigated. We evaluated the utility of different standardized uptake value (SUV) measurements in (18) F-FLT PET/CT scans compared with PET/CT scans performed with FDG. Two scans, each using one of the radiopharmaceuticals, were performed on each of 114 patients with histologically proven lymphoma. Maximum and mean SUV (SUV(max)) and (SUV(mean)) of all visualized lesions, with backgrounds of mediastinal blood pool, liver, spleen and vertebra were calculated. The ratios of the SUVs of the lesions to those of each reference region were statistically analyzed. Using receiver operating characteristic curves, we analyzed the differences in uptake of the two agents in aggressive and indolent B-cell non-Hodgkin lymphoma. We found that the SUV(max) measurements of FDG were significantly different between aggressive and indolent B-cell non-Hodgkin lymphoma. The receiver operating characteristic curve of SUV(max) of tumour/liver for FDG studies resulted in the most area under the curve. The SUV(max) of the tumour/mediastinum ratio for FLT studies resulted in the most area under the curve (0.781). There was no significant correlation between FDG and FLT uptake in most types of lymphoma we studied. Further studies of the characteristics of (18) F-FLT should employ the tumour/mediastinum SUV(max) ratio for accurate uptake measurement.