Tc-99m HMPAO labeled WBC

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Tc-99m HMPAO (hexamethylpropyleneamine oxime) labeled WBC is one of the technetium radiopharmaceuticals used in WBC imaging.

There are three potential radiochemical impurities in the Tc-HMPAO: a hydrophilic secondary complex, the free pertechnetate and the reduced Tc-hydrolyzate. The minimum expected radiochemical purity is approximately 80%.

Characteristics

  • photon energy: 140 KeV
  • physical half life: 6 hours
  • biological half life: 4 hours
  • molecular geometry: square pyramidal
  • normal distribution: spleen, liver, kidney, bone marrow
  • pharmacokinetics: radiolabel in vitro
  • excretion: hepatobiliary, renal
  • target organ: colon, bladder, spleen
  • miscellaneous facts:
    • lipophilic: crosses cell membranes and the blood brain barrier; bound to mitochondria and the nucleus within cells
    • better image quality and lower radiation dose than In-111 WBC
    • high false positive rate for spine infection (Ga-67 may be preferable)

Uses, doses and timings

  • infection
    • adult dose: 370 MBq (10 mCi) IV
    • timing: 2 hours for abdominal
    • timing: 4 hours for skeletal (30 min whole body acquisition, 10 min spots)