Hybrid PET/MRI for Evaluation of Nodal Disease in Lymphoma

Introduction: Non Hodgkin Lymphoma (NHL) is a common hematologic malignancy accounting for 4% all cancers in United States. It is estimated that nearly 70,000 patients will be diagnosed with NHL in 2013, and 19,000 will die from this disease. 18-F FDG PET combined with anatomic CT imaging has been shown to be superior to contrast enhanced CT examination in staging of lymphoma. Thus PET/CT is routinely performed for initial staging of lymphoma. MR imaging with inclusion of diffusion weighted imaging has also shown considerable promise in evaluation of patients with lymphoma. On morphologic MR imaging, abnormal nodes are identified on the basis of size alone whereas PET identifies abnormal nodes on the basis of FDG uptake. With introduction of integrated PET/MR system simultaneous PET and MR imaging can be performed thus providing a unique opportunity to compare diffusion and PET independently and together for assessment of disease burden. Therefore the purpose of this study was to compare accuracy of morphologic MR imaging including diffusion weighted imaging (DWI-MR) to simultaneously acquired PET and radial T1-weighted free-breathing acquisition (PET/MR) for detection of nodal disease in lymphoma patients with PET/CT as a reference.