New preparation method for 99mTc-phytate.

A new method is described in which Pt-Sn or Sn-Sn electrodes are used to activate 99mTcO4-. The 99mTc is incorporated into phytic acid by stannous ion released from a tin anode by the corrosive reaction. The most suitable pH for labeling phytic acid by this method was below 5 and the 99mTc-phytate formed could be precipitatedd with Ca+2 at a pH above 3.5. Though 99mTc-phytate is soluble in aqueous solution, it forms an insoluble species with Ca+2 in vivo and is trapped in the reticuloendothelial system. More than 93% of the 99mTc-phytate localized in the liver of mice; here its biologic half-time is about 112 hr. The 99mTc-phytate prepared by this method promises to be useful as a liver-scanning agent. Since our method does not require an applied electric potential, it appears to be one of the most convenient methods for labeling compounds with 99mTc.