White Blood Cell Scan is a Nuclear Medical Scan used to identify and localize occult inflammation or infection. It is used for patients who have a fever of unknown origin, suspected osteomyelitis, or inflammatory bowel disease. It is used to indicate whether or not an abnormal mass (e.g., a pancreatic pseudocyst) is infected.
WBC Scan is based on the fact that White Blood Cells are attracted to areas of infection or inflammation. When the patient has a suspected infection or inflammation, yet the site cannot be localized, the injection of radiolabeled WBCs may identify and localize that area of inflammation or infection. Appropriate treatment can then be performed. This is especially helpful in patients who have a fever of unknown causes, suspected occult intraabdominal infection, or suspected (yet radiographically unapparent) osteomyelitis infection. The scan can differentiate infectious from noninfectious processes. Areas of noninfectious inflammation (e.g., inflammatory bowel disease) also take up the radiolabeled WBCs.
WBC scan requires drawing about 40 to 50 mL of blood from the patient, separating out the WBCs, labeling the WBCs with technetium or indium, and reinjecting them into the patient. Four to 24 hours later, imaging of the whole body may show an area of increased radioactivity suggestive of accumulation of the radiolabeled WBCs in an area of infection or inflammation.
The imaging procedure is performed by a trained technologist in approximately 30 minutes. A physician trained in nuclear medicine interprets the results. The only discomfort associated with this procedure is the intravenous (IV) injection of the radionuclide.
The Reticuloendothelial System normally accumulates radiolabeled cells. This should be taken in consideration when signs of White Blood Cell localization are seen Liver, Spleen, or Bone Marrow.
No precaution or any other steps are required since the patient will not be exposed to high amounts of radioactivity. The patient will only have small amounts of the isotope will be taken.
Procedural Steps of WBC Scan
- Approximately 40 to 50 mL of blood is withdrawn from the patient, and the WBCs are extracted from the rest of the blood cells. This is usually done by centrifugation. With leukopenia, the WBC count is so low that separating them out from the other blood cellular components would be very difficult. In these instances, donor WBCs are used instead of autologous WBCs. Donor WBCs are also used for human immunodeficiency virus (HIV) positive patients to minimize the risk to laboratory workers.
- The WBCs are suspended in saline and tagged with technetium-99m (99mTc) or indium-111 (111In) lipid-soluble product. 99mTc is preferable to 111In because its half-life is longer. Therefore it is cheaper and more readily available for the infrequent times this scan is requested.
- The tagged WBCs are reinjected into the patient.
- In 4, 24, and 48 hours after injection, a gamma camera is placed over the body.
- The patient is placed in supine, lateral, and prone positions so that all surfaces of the body can be visualized.
- The radionuclide image is recorded on film.
Indications of finding WBC Localizations outside the Reticuloendothelial System
If WBC localizations are found outside Liver, Spleen, or Bone Marrow this can be an indication of infliction with Abscess, Osteomyelitis, or Poststernotomy since White Blood Cells localize to areas of infection and and show up as increased radionuclear uptake that can be detected in WBC Scan.
Another cause of detecting radio nuclear hotspots is Inflammation, areas of noninfectious inflammation attract the radiolabeled White Blood Cells which can be detected using WBC Scan as in the cases of Inflammatory Bowel Disease and Arthritis.