A Closer Look At Nuclear Medical Imaging

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The combination of the two studies (with the Indium-WBC study on the left and the 99m Tc-MDP study on the right) delineates the region of an infectious process within the cuboid bone while simultaneously ruling out the existence of infection elsewhere wit
This photo demonstrates an area of ulceration with localized erythema, warmth and edema three years after an acute Charcot breakdown.
This lateral radiograph shows the end result of a neuropathic breakdown: a rocker bottom foot with a plantarflexed cuboid bone creating a pressure point and ulceration.
As one can see, the 99mTc-MDP study reveals the extent of degenerative bone in a “burned out” Charcot foot while the indium 24-hour image fails to reveal a focus of infection in that same patient with Charcot neuroarthropathy.
One can employ serial NMLI studies initially to identify the extent of an infectious process and subsequently to confirm therapeutic success. The initial 99mTc-MDP study reveals a focus of uptake that seems to include the head of the first metatarsophalan
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Author(s): 
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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