PET/ MRI VERSUS PET/ CT IN STAGING OF LYMPHOMAS

Abstract

Lymphomas are a heterogeneous group of diseases that arise from the constituent cells of the immune system or from their precursors; they are known to arise from virtually any organ or tissue in the body. Lymphomas are broadly classified into two main groups: Non-Hodgkin's lymphoma (NHL) and Hodgkin's lymphoma (HL). NHL is more common and represents nearly 85% of lymphomas. In both Hodgkin’s disease and non-Hodgkin lymphoma, imaging plays an important role for primary diagnosis and staging, with an impact on therapy. Current guidelines encourage the use of 18F-FDG PET/CT for primary staging of 18F-FDG–avid and potentially curable lymphomas (e.g., diffuse large B-cell lymphoma (NHL), Hodgkin’s disease). Several studies have shown the value of FDG PET/CTfor staging, restaging, and therapy monitoringof lymphomas. The addition of CT for anatomic correlation in the newer PET/CT systems has improved staging sensitivity and specificity. In a recent systematic review, the overall sensitivity and specificity of FDG PET/CT for initial staging of NHL and Hodgkin’s disease were 97% and 100%, respectively. The advantages of FDG PET/CT for the staging and restaging of both NHL and Hodgkin’s disease are mostly attributed to the detection of FDG-avid, normal-sized lymph nodes (usually <1 cm), and of extranodal sites that were previously missed at CT (most commonly the liver, spleen, cortical bone, bone marrow, and skin). In a few cases, Para spinal and pulmonary lesions that were interpreted as benign at CT are seen to be malignant at FDG PET/CT.18F-FDG PET/CT might even eliminate the need for bone marrow biopsy in the primary staging of Hodgkin’s disease because 18F-FDG PET/CT is highly sensitive and specific for bone marrow involvement in this disease, at 92% and 90%, respectively, except for cerebral lymphoma.