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

• protons: 43 (i.e. atomic number)

• physical half-life: 6 hours

• biological half-life: ~1 day

• 4.0 < pH < 8.0 ^6,7

• radiochemical purity: >95%

• molecular geometry (pertechnetate anion): tetrahedral ^6,7

• normal distribution: stomach, thyroid, salivary glands, testes

• excretion: renal, GI

• target organs: thyroid, colon, bladder, stomach, testicular (rarely performed)

• compounding of technetium radiopharmaceuticals using technetium pertechnetate may be done under room temperature or heating ⁹

Uses, doses and timings

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

• Meckel diverticulum

  • adult dose: 370 MBq (10 mCi) IV

  • pediatric 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

  • pediatric 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 irradiated with deuterons in the cyclotron of the University of Berkeley ⁸.

See also

• Thyroid scan (Tc-99m)