Leukocyte scan

Leukocyte scan is a diagnostic imaging procedure used in the field of nuclear medicine to identify sites of infection or inflammation within the body. This technique involves the use of leukocytes (white blood cells) that are labeled with a radioactive substance, typically technetium-99m (99mTc) or indium-111 (111In), and then reintroduced into the patient's bloodstream. The labeled leukocytes migrate to areas of infection or inflammation, allowing these sites to be visualized using a gamma camera.

Procedure

The leukocyte scan procedure involves several steps. Initially, a sample of the patient's blood is drawn, from which leukocytes are isolated. These cells are then labeled with a radioactive isotope, either 99mTc or 111In. After labeling, the radiolabeled leukocytes are reinjected into the patient. Imaging is usually performed after allowing sufficient time for the leukocytes to accumulate in areas of infection or inflammation, typically 2 to 24 hours post-injection, depending on the isotope used and the clinical scenario.

Clinical Applications

Leukocyte scans are primarily used to detect and localize sites of infection or inflammation. They are particularly useful in identifying:

• Osteomyelitis (infection of the bone)
• Inflammatory bowel disease (IBD)
• Fever of unknown origin (FUO)
• Infected prosthetic joints
• Abdominal abscesses

Advantages and Limitations

One of the main advantages of leukocyte scans is their ability to specifically target areas of infection or inflammation, providing a functional image that is often more informative than structural imaging techniques such as X-ray or MRI. However, the procedure is time-consuming and technically demanding, requiring the handling of radioactive materials and patient's blood. The resolution of the images is also lower compared to some other imaging modalities, which can limit the ability to precisely localize small sites of infection.

Comparison with Other Imaging Modalities

Leukocyte scans are often used in conjunction with other imaging techniques to provide a comprehensive evaluation of suspected infection or inflammation. For example, while an MRI may provide detailed anatomical information, a leukocyte scan can offer additional functional insights by highlighting active sites of infection or inflammation.

Safety

The use of radiolabeled leukocytes involves exposure to a small amount of radiation. However, the procedure is generally considered safe, and the benefits in diagnosing and managing infections or inflammatory conditions typically outweigh the risks associated with radiation exposure.