Clinical usefulness of camera-based whole trunk FDG pet in the initial staging of patients with malignant lymphomas

This study was performed to evluate the clinical usefulness of whole trunk F-18-FDG coincidence PET (CoDe-PET) imaging in the staging of mlignant lymphomas. Thirty-five patients with histologically proven malignant lymphomas underwent F-18 FDG CoDe-PET using a dual-head gamma camera equipped with coincidence detection circuitry for initial stating before treatment. Histological subgroups included low (4), intermediate (15), high (4), undetermined (7) grades non-Hodgkins lymphoma and Hodgkins disease (5). The entire trunk from the cervical to the inguinal regions were scanned. Attenuation correction was not made and image reconstruction was done using filtered back-projection CoDe-PET images were compared with corresponding CT or MRI and the lymphomatous involvements identified by both CoDe-PET and CT/MRI were regarded as actual locations of disease. Discordant results were verified with biopsy or clinical follow-up. A total of 73 lymphomatous involvements were noted on both CoDe-PEt and CT. CoDe-PET detected 19 additional lymphomatous lesions not identified by CT or MRI. Of them, three were true-positive (extra-nodal involcements), and one was false-positive. CT or MRI demonstrated 9 more lymphomatous lesions not shown on CoDe-PET and only one was confirmed positive. Four of 9 were small intra-abdominal nodal lesions less than 1.5 cm. Staging was changed from III to IV in three patients by CoDe-PET by depieting extra-nodal involvements and from I to II in one by detecting nodal involvement. Camera-based whole trunk FDG PET without attenuation correction is clinically acceptable for staging malignant lymphomas and useful especially in the assessment of extra-nodal involvement. However, in the detection of nodal involvement, it should be used in conjunction with CT or MRI since small nodal lesions can be missed