Radiolabeling brachytherapy sources with re-188 through chelating microfilms: Stents

Abstract

Rhenium-188 (Re-188, T(1/2) = 17 h) emits beta particles (E(max) = 2. 12 MeV) having an ideal range for intravascular brachytherapy and certain cancer brachytherapies. Re-188 was attached to metal wafers and stents via a chelating microfilm, and these brachytherapy sources characterized in vitro and in vivo. To prepare the sources, a siloxane film containing reactive amines was plasma deposited on the metal, a chelating microfilm conjugated to the amines, and the chelating microfilm used to attach Re-188. Re-188 was selectively bound to materials coated with the chelating microfilm. Binding correlated with the amount of radionuclide used. Wafers (1 cm(2)) bound up to 62.9 MBq (1.7 mCi) of Re-188 with yields generally near 30%. Stents bound up to 26.6 MBq (720 microCi). Typically, stents were labeled to bind 4-12 MBq and deposit 10-30 Gy at 2 mm in the arterial wall. In phantom studies, the longer nitinol stents deposited doses of 2.3 Gy/MBq (0.085 Gy/microCi), while shorter stainless steel stents deposited 4.62 Gy/MBq (0.171 Gy/microCi). After placement in arteries of pigs, only the Re-188-stents were detected by scintigraphy at times up to 24 h. Scintigraphy did not detect activity in other organs. Blood sampling (0.1-24 h) detected maximum radioactivity (up to 388 cpm/mL/100micro Ci) at 6 h. We conclude that on-demand radiolabeling of stents and other brachytherapy sources with Re-188 can be performed routinely.

Deposition of 90YPO4 and 144CePO4 radioisotopes on polymer surfaces for radiation delivery devices

“…A number of gamma-and beta-emitting radionuclides including 188 Re, 90 Y, 32 P, 90 Sr, and 192 Ir have been used in brachytherapy sources. The radioisotope is encapsulated; contained within catheters 7 or balloons (as 188 Re solutions); 9 chelated by microfilms; 13 or impregnated with radioactive ions by particle bombardment in a cyclotron or accelerator, as in the case of 32 P stents. 14 These approaches contrast with the technique presented in this article, which uses a chitosan hydrogel to coat the balloons or wires, followed by phosphoric acid absorption, and then deposition of 90 Y and 144 Ce onto the surface as YPO 4 or CePO 4 .…”