Dosimetric Evaluation in Radiation Synovectomy

Rheumatoid arthritis can manifest itself through synovitis, of which the knee is the common locale. The treatment using an intra-articular radioisotope injection has been applied in various countries. In this work, the dose of radioactive material absorbed in the joint is evaluated, taking into consideration the dose received in the articular cartilage and adjacencies using a three-dimensional voxel model representing the knee. The radioisotopes studied were Samarium-153 and Dysprosium-165. The results show that the synovial membrane receives 85 to 98% of the normalized dose taken from all voxels representative of the synovium. The following features of Sm and of Dy its short physical half-life, the gamma emissions with low energy which allow monitoring the injection trough scintigraphy images, the possibility of binding themselves to macroaggregates that are retained in the joint, the high percentage of the effective dose spread in the synovial membrane make these suitable radioisotopes for radiation synovectomy.