Role of attenuation correction for fluorine-18 fluorodeoxyglucose positronemission tomography in the primary staging of malignant lymphoma

Fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) has b een shown to improve the diagnostic accuracy in the staging of malignant ly mphomas, based on the metabolic signal of the lesions. This study was under taken to determine the effect of attenuation correction in the detection of nodal and extranodal lesions in the primary staging of malignant lymphomas . Fifty-one untreated patients with either non-Hodgkin lymphoma (NHL, n=29) or Hodgkin's disease (n=22) were retrospectively evaluated. Static FDG-PET imaging of the trunk was performed following administration of 250-350 MBq FDG. Attenuation correction was performed in all patients. Images were rec onstructed iteratively with or without transmission scans. Image evaluation was performed independently by two observers, who each examined one set of images (i.e. attenuation-corrected or uncorrected). The final decision as to whether results were discordant was reached by consensus of both observe rs. Out of 593 evaluated lymph node regions, 187 regions of increased FDG u ptake were identified by both techniques. Differences between the readers c oncerned mainly the anatomical assignment of lesions (n=33) or the status ( benign/malignant) of individual lesions (n=24). However, direct comparison of the two sets of images demonstrated very similar lesion contrast on atte nuation-corrected and non-attenuation-corrected images. Real differences co uld be determined only in five regions (neck, 1; mediastinum, I; upper abdo men, 3). Thirty-seven extranodal lesions (including lung, liver, spleen, bo ne marrow and soft tissue) were detected by both techniques without signifi cant differences. It is concluded that in this study, attenuation correctio n did not improve the diagnostic accuracy of FDG-PET in the detection of ly mph node or organ involvement during the primary staging of malignant lypho mas. Of more importance seemed to be the experience of the reader regarding the classification of a lesion's status the anatomical assignment, knowled ge of physiological uptake and artefacts, and systematic and skilful examin ation of all regions scanned.