Evaluation of 90Y phosphate particles as a possible radiation synoviorthesis agent.

Background: 90Y is one of the radioisotopes used extensively for therapy due to its favourable nuclear characteristics. Particles and colloids incorporating 90Y are being used for radiation synovectomy, especially in European countries.

Methods: In our present work, 90Y phosphate particles were prepared and evaluated for use in radiation synovectomy. The radioactive particles were prepared by reacting carrier added 90YCl3 with phosphoric acid.

Results: The radiolabelling yield obtained was >95%. The particles were found to be stable in saline for up to 7 days of study at 37 degrees C. Particle size analysis of inactive yttrium phosphate showed that most of the particles were in the size range of 2-20 microm. Biodistribution studies carried out by intra-articular injection of the particles into the knee joints of rats showed that approximately 99% of the particles were retained in the joints with negligible radioactivity in the major organs even at 48 h post-injection. Scintigraphic studies in rabbit showed that >99% of the radioactive particles were retained in the knee joint even at 96 h post-injection. No significant radioactivity above background was detected in the blood.

Conclusion: The promising results warrant further studies on 90Y phosphate particles for use in radiation synovectomy.