The diagnostic role of nuclear medicine in haematological malignancies

Lymphomas are malignancies of the haematological system and normally originate and disseminate through the lymphatic system. Radionuclide methods have been in use for the past several decades in the management of lymphoma. Initially lymphoscintigraphy was used for identifying lymph node involvement in lymphoma. However the advent of CT and MRI saw lymphoscintigraphy relegated to the side line. Subsequently, the recognition of post therapy residual mass of fibrous tissue, looking like lymphoma on CT and MRI has lead to a resurgent interest in the functional nuclear medicine diagnostic procedures, especially imaging with Ga-67 citrate and Tc-99m MIBI. Whilst these could be used in a small number of difficult patients, often post therapy; the advent of F-18 FDG PET has lead to an overwhelming increase in the use of radionuclide techniques. Positron emission tomography (PET) is a novel functional imaging technique that can use a glucose analog (2-fluoro-2-deoxy-D-glucose [FDG]) radiolabeled with the positron emitter fluorine-18 to evaluate glycolytic activity, which is greater in malignancies, including lymphoma. Several studies have suggested a role for FDG-PET in the diagnosis and followup of patients with lymphoma, and it is rapidly becoming a standard procedure for lymphoma management. PET provides several inherent advantages over other nuclear imaging techniques. The short half-life of FDG allows patient convenience and improved imaging characteristics. With modern dedicated PET machines, a resolution of approximately 5 mm can be achieved, and the ability to co-register PET with anatomic computerized tomography (CT) imaging allows for ease of interpretation. Moreover, using a quantitative approach to interpretation with the standardized uptake value (SUV) (ratio of activity per volume unit over injected activity per body mass), PET imaging appears to be more precise than conventional scintigraphy and is rapidly becoming an essential part in the management of lymphoma. (author)