Whole-body MRI including diffusion-weighted imaging and FDG-PET/CT for the assessment of bone marrow infiltration in lymphoma

Abstract Background Lymphomas, comprising Hodgkin and non-Hodgkin types, are malignant neoplasms that can affect various organs, with bone marrow (BM) being the most frequent site of extranodal involvement. Accurate detection of BM infiltration is essential for staging and management. Imaging modalities like FDG-PET CT and whole-body MRI (WB-MRI), including diffusion-weighted imaging (DWI), are increasingly used as non-invasive alternatives to BM biopsy. Objectives To evaluate the diagnostic performance of FDG-PET CT and whole-body MRI including diffusion weighted imaging in the detection of lymphoma bone marrow involvement. Methods This retrospective cross-sectional study included 30 patients with histologically confirmed Hodgkin or non-Hodgkin lymphoma. Each patient underwent both 18F-FDG PET/CT and whole-body MRI (WB-MRI), which included T1-weighted imaging, short tau inversion recovery (STIR), and diffusion-weighted imaging (DWI) sequences. Bone marrow involvement was assessed in PET/CT based on focal FDG uptake with standardized uptake values (SUV) higher than liver background activity. In WB-MRI, bone marrow lesions were characterized using signal changes across T1-weighted images (T1WIs), STIR sequences, and DWI sequences. Bone marrow biopsy (when available) was used as the reference standard. The primary outcomes were the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall accuracy of each imaging modality in detecting bone marrow infiltration. A secondary outcome included the level of agreement between the two imaging modalities. Results FDG-PET CT detected malignant BMI in 86.7% of cases, with benign features noted in 13.3%. WB-MRI identified malignant involvement in 66.7%, benign in 20%, and was negative in 13.3%. Compared to biopsy, FDG-PET CT showed 100% sensitivity, 33.3% specificity, 66.7% PPV, 100% NPV, and 71.4% accuracy. WB-MRI also had 100% sensitivity, but higher specificity (66.7%), 80% PPV, 100% NPV, and 85.7% accuracy. Strong agreement was observed between both modalities, with WB-MRI showing 76.9% sensitivity, 100% specificity, 100% PPV, 40% NPV, and 80% accuracy when FDG-PET CT was used as reference. Conclusions Both FDG-PET CT and WB-MRI are highly sensitive modalities for detecting BMI in lymphoma. WB-MRI offers a radiation-free, reliable alternative to FDG-PET CT, particularly beneficial for young and pregnant patients.