Introduction: The term radiosynoviorthesis (RSV) has been used and has been applied to relieve pain and inflammation from rheumatoid arthritis (RA) by the use of radionuclides and indicated as an effective alternative to chemical and surgical synovectomy in cases of RA and other inflammatory arthropathies such as osteoarthritis and hemophiliac arthropathy. Advances in this area have been facilitated by the availability of a wide range of beta emitting radionuclides and the easy incorporating into bio-degradable particles and colloids. Yttrium-90 is the most useful of the radionuclide that have been considered for therapeutic applications in knee joint, half-life of 64.1h and beta rays of high-energy 2.3MeV, with no gamma rays, and decays to a stable daughter 90Zr by internal pair production (positron). After an injection of a beta emitting radiopharmaceutical into the synovial cavity, some of the injected radioactivity is absorbed by phagocyte along the synovial surface, achieving significant reduction of pain and joint effusion in approximately 70% of the patients Current clinical practice determined the distribution of the particles or colloids through Bremsstrahlung imaging combined with anatomic imaging via SPECT/CT. Bremsstrahlung imaging is not quantifiable, and thus accurate dose distribution cannot be obtained.

Objetive: The rheumatologist and the nuclear medicine experts working in routine practice, presented this case report using the standard PET/CT to assess the biodistribution of 90Y–HA (hidroxiapatite), used in the treatment of arthritis rheumatoid.

Methods: A 54 year old female with zero positive rheumatoid arthritis experienced recurrent knee effusion in spite non biological and biological therapy with two anti TNF blockers and lately with Tocilizumab. The patient was submitted to radiosynovectomy by the injection into de articular cavity of 185MBq/3mL of 90Y-HA (hidroxiapatite) guided by Ultrasson. The images were performed to investigate extra articular radiotracer extravagation by PET/CT (GE-Healthcare), 1 FOV by 15minutes at 1 hour and 24 hours after injection. The fused images showed diffuse intra articular distribution and no signs of extra lacked.

Conclusion: PET/CT imaging following 90Y-HA radiation synovectomy appears to be feasible and helpful to monitor the technique and predict potential local complications. The patient remains synovial fluid free on the knee five months after the intraarticular effusion. The gain in resolution presented in the clinical case using PET/CT, should therefore contribute to increasing the accuracy of the dose distribution into the joint cavity and their surrounding healthy tissues. The improved accuracy of the dose distribution and with the resolution gain from PET/CT future patient treatment outcomes may be improved. However, the conclusion from our pilot study appears to be that 90Y-HA can be visualized with a simple 15min PET/CT scan. This technique may potentially become the standard of care for confirming the distribution of particles into de joint.