Hydroxyapatite labelled with yttrium-90 or lutetium 177 for radiation synovectomy

Radiation Synovectomy (radiosynovectomy, radiosynoviorthesis or RSV) is a method of treatment by intra-articular application of beta-emitting radioisotopes. There are several radionuclides available for this treatment and some radiopharmaceuticals have been shown to be effective and safe for this procedure. Hydroxyapatite (HA) particles are regarded as one of the most suitable carriers for applications in RSV, and labelling with 177Lu or 90Y has been investigated. Owing to their favourable decay characteristics, 177Lu Lu has been used in RSV of small-sized joints and 90Y has been the most useful radionuclide for applications in knee joints. The present work describes the preparation, labelling and quality control of HA using both radionuclides. The labelling yield is higher than 87.0%. The final product presents a radiochemical purity >98.9%, with the particle range >12 μm and a stability of 5 days at room temperature. A scintigraphic investigation by gamma camera was performed in rats to evaluate the extra-articular leakage from the knee. Both preparations appeared suitable for RSV with no extra-articular leakage and no acute complication in the clinical study using 90Y-HA.