Cyclotron-produced. The two photopeak energies (171 and 245 keV) allow simultaneous dual-isotope imaging with Tc-99m (140 keV), which is essential for the labeled WBC + sulfur colloid technique.
In-111 oxine-labeled WBCs (predominantly labeled neutrophils):
- Patient’s WBCs are harvested, labeled with In-111 oxine ex vivo, and reinjected
- Labeled leukocytes migrate to sites of acute infection/inflammation
- Imaging at 24 hours
- Prosthetic joint infection: combine with Tc-99m sulfur colloid marrow scan — concordant photopenia on both = normal marrow displacement by prosthesis; discordant increased WBC uptake without marrow activity = infection (high sensitivity and specificity)
- Not useful for chronic infection (neutropenic patients, vertebral osteomyelitis — better with Ga-67 or FDG-PET)
DTPA cisternography: injected intrathecally to evaluate CSF leak. Normal flow: basal cisterns by 1 hour, convexities by 24 hours. CSF leak shows early activity in nasal/ear regions.
OctreoScan (pentetreotide): targets somatostatin receptors (SSTR2/5) on neuroendocrine tumors. Now largely replaced by Ga-68 DOTATATE PET (superior sensitivity and spatial resolution, shorter imaging time).