Abstract: Lymphoma is a malignant tumor of the blood system.Bone marrow infiltration(BMI) advances the disease to stage IV and is a marker of disease progression and poor prognosis.Conventional bone marrow biopsy is a traumatic detection, and the rate is low.The emergence of PET/CT and whole-body MRI supplements the means of BMI detection.PET/CT and whole-body MRI both exhibit a high detection rate for lymphoma BMI, particularly for aggressive lymphoma BMI.However, both approaches to determine high and low is inconclusive, For red bone marrow, benign bone marrow lesions(inflammation and others), lymphoma BMI lesions, as well as bone marrow changes after tumor therapy and bone marrow residual or recurrent lesions, whole body MRI is difficult to distinguish.PET/CT can excellently identify these lesions.However, PET/CT uses ionizing radiation:false negative results can be present for inert lymphoma BMI lesions and lesions beyond the PET/CT resolution.Certain circumstances may limit the use of PET/CT, including normal tissue, whose ¹⁸F-FDG physiological uptake may change; inflammation, which is related to ¹⁸F-FDG uptake, changes in the distribution of ¹⁸F-FDG caused by high blood glucose or high blood insulin, bone marrow activation in tumor patients after treatment, and so on.In these cases, we can use whole-body MRI.Therefore, the two approaches are complementary.Neither PET/CT nor whole body MRI can replace BMB.BMB under the guidance of PET/CT or whole-body MRI considerably improves the detection rate of BMI for patients with negative BMB findings, but imaging findings are positive.In addition, whole-body MRI-positive patients may present poorer prognosis than whole-body MRI-negative patients.