Holmium-166-DTPA as a liquid source for endovascular brachytherapy.

Liquid radiation sources with beta emitters have advantages of accurate positioning and uniform dose distribution to the vessel walls to prevent the restenosis of coronary artery. As a liquid radiation source, 166Ho-DTPA was prepared and evaluated its in-vivo pharmacokinetic behavior through animal studies.166Ho-DTPA was prepared by simple mixing the Holmium with DTPA at room temperature. The radiolabelling yield was 100% when the DTPA/Holmium molar ratio was >2. Radiolabelling of 166Ho-DTPA was not dependent on the pH range of 1.7-7.5. High radiochemical stability (>98%) was maintained over a period of 6 hours even with a radioactivity ( approximately 11.1 GBq/12 mg of DTPA) stored at room temperature. Biodistribution of 166Ho-DTPA in rats and gamma camera images in rabbits showed that 166Ho-DTPA was quickly excreted via the urinary system. The average of T(max) and T(1/2) of 166Ho-DTPA in the kidneys of rabbits were 3.71 +/- 1.18 min and 9.15 +/- 3.15 min. 166Ho-DTPA is a potential liquid radiation source for radiation brachytherapy to prevent the restenosis of the coronary artery using a liquid-filled balloon.