Abstract

Hematological malignancies represent a heterogeneous group with numerous subtypes, each exhibiting distinct courses and prognoses. They can be broadly categorized into three main groups: lymphomas, myelomas, and leukemias. In particular, F-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT) is an indispensable imaging modality in the management of lymphomas and myelomas. However, the limitations of CT, including its low soft tissue resolution and inadequacies in bone marrow imaging, can pose challenges in the management of hematological malignancies. Magnetic resonance imaging (MRI), with its high soft tissue contrast and superior sensitivity in evaluating bone marrow, complements the limitations of F-18 FDG PET/CT, thereby playing a crucial role in the management of these malignancies. Nonetheless, MRI is not without its drawbacks, such as the presence of artifacts, challenges in imaging lung parenchyma, and a relatively delayed depiction of treatment response. Recently, the introduction of F-18 FDG PET/MRI has combined the metabolic information provided by F-18 FDG with the high tissue contrast and additional functional data offered by MRI, effectively bridging the gaps left by each modality alone. Furthermore, the absence of additional ionizing radiation in MRI, as compared to CT, is a significant advantage, particularly in the assessment of lymphomas that are commonly observed in pediatric populations. In the evaluation of myeloma, the high resolution provided by MRI in assessing bone marrow infiltrations is particularly promising. However, several significant challenges remain, including attenuation correction issues in PET/MRI systems, artifacts, limited accessibility, difficulties in evaluating lung parenchyma, and relatively high costs. There is a need for more comprehensive studies to clearly establish the concordance between standardized uptake values across both systems. Although the current lack of sufficient studies on the role of PET/MRI in hematological malignancies precludes its inclusion in clinical guidelines, it seems inevitable that it will be incorporated as more research becomes available in the future.