Tc-99m pertechnetate

Tc-99m pertechnetate (Na^{+ 99m}Tc O₄^-) is one of the technetium radiopharmaceuticals used in imaging of thyroid, colon, bladder and stomach.

Technetium (^99mTc) has eight oxidation states ⁶, from -1 to +7; specifically, the oxidation state of technetium in the pertechnetate anion (^99mTcO₄^-) is +7. The pertechnetate anion is, among the chemical species of technetium, the most stable in aqueous solution. ^6,7

Characteristics

• photon energy: 140 keV
• physical half-life: 6 hours
• biological half-life: ~ 1 day
• 4.0 < pH < 8.0 ^6,7
• molecular geometry (pertechnetate anion): tetrahedral ^6,7
• normal distribution: stomach, thyroid, salivary glands, (testicles)
• excretion: renal, GI
• target organs: thyroid, colon, bladder, stomach, testicular (rarely performed)

Uses, doses and timings

Paediatric doses have been derived from various sources, a true international consensus remains work in progress.

• Meckel diverticulum
  • adult dose: 370 MBq (10 mCi) IV
  • paediatric dose: 1.85 MBq/kg (0.05 mCi/kg) ⁵
    • minimum 9.25 MBq (0.25 mCi) ⁵
  • time of imaging: immediate (1 frame/s x 60 s then q 5-10 min x 1 hr)
• parathyroid subtraction
  • adult dose:  37-74 MBq (1-2 mCi) IV
  • time of imaging: image for 15 minutes after Tl-201 injection and imaging
• testicular
  • adult dose: 370 MBq (10 mCi) IV
  • paediatric dose: pending mCi/kg
    • minimum 185 MBq (5 mCi) ³
  • time of imaging: 60-second flow study with delayed static images
• thyroid
  • adult dose: 37-370 MBq (1-10 mCi) IV
    • usually 111-185 MBq (3-5 mCi)
  • time of imaging: 20 minutes

History and etymology

Technetium was discovered in 1937 by C. Perrier and Emilio Segre at Palermo University. They managed to isolate technetium-97 from a sample of molybdenum irratiated with deuterons in the cyclotron of the University of Berkeley ⁸.

See also

• Tc-99m pertechnetate
• Thyroid scan (Tc-99m)