A Closer Look At Nuclear Medical Imaging

By Molly S. Judge, DPM, CNMT, and Nellie L. Kelty, MAS, CNMT

When a patient with Charcot neuroarthropathy presents with an acutely symptomatic limb, joint or a non-healing wound, the differential diagnosis always includes infection. Bone and joint infections are naturally associated with a high degree of potential morbidity. This potential morbidity is significantly increased when there is a delay in diagnosis or when the diagnosis is missed altogether. Therefore, validating a definitive diagnosis of infection and clarifying when it involves bone is essential to providing appropriate and timely treatment.
Nuclear medicine leukocyte imaging (NMLI) allows prompt confirmation of the presence of infection and identifies the location of a focus of infection when it exists.1 In addition, these studies have a predictable appearance in the face of an active Charcot arthropathy without infection. Given the limb threatening consequences of an infected Charcot joint, using NMLI allows one to differentiate between Charcot and osteomyelitis.2
Clinicians can repeat NMLI after the completion of antibiotic therapy in order to rule out the complication of indolent infection. In the absence of infection, these imaging studies provide supplemental data to support the pursuit of an alternative diagnosis in the differential list.

A Brief Overview Of The History Of Nuclear Imaging
Nuclear medicine imaging techniques for identifying and isolating infection have been used since the 1950s. Gallium was one of the first isotopes used to localize infections and other pathologic processes. This agent binds with transferrin, an iron bound protein found within the cytoplasm of white blood cells (WBCs). An intravenous injection of gallium citrate provides an in vivo labeling of leukocytes and bacterial organisms, which allows one to identify inflammatory processes.1 Since the introduction of gallium imaging for infection, research has brought about the development of alternate, radiolabeled WBC studies to enhance the specificity and imaging quality of these exams.

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