Anatomic and functional imaging in the management of lymphoma

Lymphoma has become one of the most successfully treated malignancies. The success of treatment and long-term prognosis depend on accurate staging in which imaging plays a pivotal role. In addition to staging, imaging assists in the evaluation of early and late response to therapy, detecting disease activity in a residual mass and locating sites of recurrence. The mainstay of imaging remains computed tomography (CT), which has replaced lymphangiography, and staging laparotomy. Magnetic resonance imaging (MRI) has additional value in detecting disease in bone marrow, the musculoskeletal and central nervous system. Recent technical developments in CT and MRI have improved acquisition times and resolution, but the main drawback of cross-sectional imaging techniques is their reliance on size criteria to define disease, with consequent failure to detect disease in small lymph nodes and exclude disease in large, but treated, masses. Diffuse visceral involvement is likewise difficult to detect by both modalities. Functional imaging with nuclear medicine techniques offers an answer to these problems. Imaging with the fluorinated glucose analogue, [18F]FDG positron emission tomography (PET), can detect metabolically active disease by its increased glycolysis that is proportional to mitotic activity. It can separate high from low-grade tumors and aid in prognostication. Recent publications suggest that imaging with [18F]FDG PET should be an important component in staging; assessment of response to therapy and restaging. Like other imaging modalities, it has its own drawbacks including inability to detect very small lesions (<5 mm) and reduced specificity due to increased uptake in metabolically active inflammatory and infective tissues. The new generation of hybrid PET-CT combines anatomical and functional imaging and is considered the state-of-the-art imaging technique for the assessment of lymphoma and other malignancies.