Studies on the production and quality assurance of miniature (125)I radioactive sources suitable for treatment of ocular and prostate cancers.

(125)I sources were prepared by adsorption of (125)I on palladium-coated silver wires. The effect of reducing agent on percentage adsorption of (125)I was studied and the amount of adsorbed activity on source core was studied by repeated adsorption cycles. The activity per source in the sources produced from the same batch varied with coefficient of variation (i.e. the ratio of standard deviation to mean multiplied by 100) less than 10%. The unencapsulated source exhibited low leachability (< 0.01%). The laser parameters were optimized to obtain quality welds with negligible leak rate. The sources were laser-encapsulated in titanium capsules of 0.8 mm (OD) x 4.5mm (l). The release of radioactivity from encapsulated sources in an immersion test at 50 degrees C for 5 h was <5 nCi (185 Bq). The surface contamination on the sealed capsules was found to be<0.05 nCi or 1.85 Bq per source. The sources were used in the treatment of a child having retinoblastoma.

Comparison of methods for preparation of 125I brachytherapy source cores for the treatment of eye cancer.

Two procedures for fixing the 125I activity on different matrices were explored. In the first method, anodic deposition of 125I on silver wire was used. In the second, 125I was adsorbed as iodate (IO3-) on alumina microspheres by using a solid-solution interface technique. While the 125I uptake was approximately 84% on the silver wires by electrodeposition method, the microspheres showed approximately 97% by the solid-solution interface technique. The low leachable (0.05%) wires, and comparatively high leachable (approximately 4%) spheres were trial encapsulated and laser welded. The encapsulated sources were measured for source strength and were found to be suitable for the treatment of eye cancer.

A novel approach for the adsorption of iodine-125 on silver wire as matrix for brachytherapy source for the treatment of eye and prostate cancer.

The adsorption of iodine-125 on silver wire bits coated with palladium to be sealed in titanium capsules as brachytherapy sources was studied. A method was optimized to obtain quantitative adsorption of 125I on the palladium treated silver wires. A comparative evaluation of palladium coated and uncoated (bare) silver wires on the adsorption of 125I was made. While, the adsorption of bare silver wires showed low, inconsistent uptake (approximately 60%) of 125I with high leachability (approximately 4%), the Pd coated silver wires showed quantitative and consistent uptake of 125I (approximately 90%) and exhibited low leachability (0.01%). 125I adsorbed on Pd coated silver wires could be used as a matrix for the preparation of interstitial sources in eye and prostate cancer therapy.

Potential 166Ho radiopharmaceuticals for endovascular radionuclide therapy. II. Preparation and evaluation of 166Ho-DTPA.

166Ho, with its favourable radiation characteristics of t(1/2) 26.8 h and Ebeta 1.85 and 1.75 MeV, is proposed as a suitable choice for the endovascular radionuclide therapy (EVRT) technique of liquid filled, low pressure balloon angioplasty. 166Ho was produced by the (n,gamma) reaction on a natural Ho2O3 target. The specific activity obtained was approximately 100 mCi x mg(-1) when irradiated at a flux of 2 x 10(13) n x cm(-2) s(-1) for approximately 7 days, and the possible contaminant 166Ho(m) was not detected. 166Ho was easily complexed with diethylenetriaminepentaacetic acid (DTPA) at a ligand to metal molar ratio ([L]:[M]) of 1:1 at room temperature (22-23 degrees C) and a reaction time of a few minutes. The radiochemical purity was >99%, as determined by paper chromatography using a mixture of pyridine, ethanol and water (1:2:4) as solvent. The complex had good stability up to 72 h at 37 degrees C in a serum environment. In a study using Swiss mice > 85% of the injected dose was cleared into the urine within 30 min post-injection, with insignificant retention in any major tissues. The studies show that the 166Ho-DTPA complex could be an alternative to the more expensive and difficult to access 188Re based products for EVRT, and provide adequate uniform radiation dose for the arterial vessel wall under treatment.

Studies on the preparation and stability of samarium-153 propylene diamine tetramethylene phosphonate (PDTMP) complex as a bone seeker.

Propylene diamine tetra methylene phosphonate (PDTMP) was synthesised by modifying a method reported for the synthesis of EDTMP. Complexation of the synthesised phosphonate ligand with 153Sm was carried out by varying the experimental parameters and the complex was radiochemically characterized. Biodistribution studies showed that the uptake by bone in rats was 2% per g of bone, which was retained upto 48 h. The uptake by other organs was insignificant, except by the liver which showed a slightly higher absorption.