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Radiologic imaging plays a critical role in the staging and follow-up of patients with lymphoma. The initial stage of disease helps to define appropriate therapeutic interventions, and the extent and location of disease have traditionally been established through the use of anatomic imaging, in addition to physical examination and bone marrow biopsy. Furthermore, as different patients show varying degrees of responsiveness to standard chemotherapy, imaging studies can help determine whether an individual patient is responding appropriately to therapy, and therefore whether continuation of that therapy is warranted. Finally, after completion of treatment, patients are followed for evidence of relapse or progression of disease through a combination of imaging and clinical follow-up. These studies help to establish the status of disease and therefore the appropriate intervention or observation.

Anatomic imaging, such as computed tomography (CT) and magnetic resonance imaging (MRI) have been used extensively in patients with lymphoma. However, these modalities are limited by their dependence on size abnormalities in defining areas of tumor involvement. This limitation renders anatomic imaging suboptimal for detecting small foci of disease or for differentiation of viable tumor from fibrosis in a residual mass following treatment.

Functional imaging modalities, in contrast to anatomic imaging, take advantage of cellular processes to identify tissues of interest. Two such functional imaging modalities, Gallium-67 (Ga-67) scintigraphy and positron emission tomography using 18-fluoro-2-deoxyglucose (FDG-PET), utilize tracers that are taken up via metabolic pathways, therefore resulting in enhancement of highly metabolic tissues, such as tumor foci. This characteristic allows identification of tumor sites based on cellular metabolic activity rather than anatomic abnormalities, permitting detection of small foci of disease or differentiation of tumor from fibrosis. Both Ga-67 scintigraphy and FDG-PET have shown advantages in defining active lymphoma over classical imaging alone. However, the greater technical ease and apparent improved accuracy of FDG-PET imaging are contributing to its increasing acceptance as the functional imaging modality of choice in the care of lymphoma patients.

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