Indium-111 oxine labeled white blood cell scan

Indium-111 oxine labeled white blood cell (WBC) scan (or In-111 oxine labeled white blood cell scan) is a nuclear medicine test which attempts to localize infection and/or inflammation by injecting the patient's previously extracted and radioactively-labeled white blood cells. 

Procedure

The patient's blood is withdrawn and white blood cells extracted. These are then labeled with indium-111 oxine and injected back into the patient. It is, obviously, imperative that the patient receives his or her own white blood cells back and careful systems must be in place to ensure that this occurs. 

The patient is then imaged 24 hours later giving the white blood cells the opportunity to migrate to the site of inflammation/infection. 

After detecting a focus of increased uptake within the bone marrow on a WBC scan, a technetium-99m (Tc-99m) sulfur colloid bone scan must be performed to confirm a marrow replacing process in the setting of clinical suspicion for osseous infection (photopenia on Tc-99m sulfur colloid) because reactive marrow (uptake on Tc-99m sulfur colloid) can also demonstrate increased osseous uptake on WBC scans ².

Characteristics

• photon energy: 174 KeV, 247 KeV ¹

• physical half-life: 2.8 days

• normal distribution: spleen, liver, bone (first 4 hours pulmonary activity seen)

• excretion: spleen

• critical organ: spleen

• pharmacokinetics: 

  • labeled leukocytes localize at sites of infection through diapedesis, chemotaxis, and enhanced vascular permeability

  • cleared by reticuloendothelial system

Limitations

As is the case with many nuclear medicine tests, it suffers from intrinsically poor spatial resolution. SPECT and SPECT/CT acquisition can help to overcome limitations of poor spatial resolution and improve accuracy in localization.

Alternative studies

Alternative nuclear medicine studies include FDG-PET, gallium-67, Tc-99m-HMPAO-WBC scan.