Tagged WBC Scan

General

• 3 major radiotracers used

  • Ga-67-WBC

  • In-111-WBC

  • Tc-99m WBC

• In-111 —> better for active infection, hardware infection, minimal uptake in bowel

• Ga-67 —> better for chronic infection, high uptake in bowel

• Tc-99 —>

In-111 WBC

• Tracks neutrophil migration

• Used for active and some chronic infection

• Images at 24-48 hours

• Minimal bowel activity (unless issue)

• Medium energy collimator used

• When to use:

  • For most active infections

  • Chronic osteomyelitis

  • Hardware infection + sulfur colloid bone scan

General for In-111 WBC scans

• Indium-111 oxide labeled WBC

• Images actual neutrophil migration/accumulation

• T1/2 = 2.8 days

• Energy = 174, 247 keV

• Take patient’s WBC, add a radiotracer, inject them back into the body

• Normal in spleen, liver and bone

• Excreted by spleen (clears WBC)

• If you find a positive lesion on WBC scan that is in the marrow then you need to do a Tc-99 sulfur colloid bone scan to confirm the lesion (should be photopenic on the sulfur colloid scan)

• Critical organ = spleen

• Great test to evaluate for hardware infection

Key Points

• Neutropenic patients

  • Fewer WBC

    • High risk of a false negative test

• False positive associated with

  • Splenule

  • Acute bleed

  • Neoplasm

Normal Study

Inflammatory bowel disease

• In-WBC can be used in diagnosis of IBD

• Need to scan early (1-2 hours) when doing this because the labeled cells will get sloughed off from the focal site of active inflammation and mimic pan-colitis or multifocal sites of inflammation

Ga-67-WBC

• Binds acute phase reactants - lactoferrin, transferrin, etc.

  • Therefore uptake can be seen with infectious, inflammatory and some neoplastic processes

• Images at 24-72 hours

• Better for chronic infections, or chronic inflammatory processes

Pyelonephritis