Room: Karl Dean Ballroom A1
Purpose: To study the dose deposited during radiosynoviorthesis by radionuclides carried by stochastically migrating macrophages in arthritic joints and to estimate both the activity that would deposit 100 Gy at the prescription point in the tissue and the resulting dose-volume histograms. Currently, Re-186 and Er-169 are used for medium and small joints respectively while Sn-117m is under investigation.
Methods: The GATE Monte Carlo software was used to simulate the dose from 6 Î¼m diameter radioactive particles moving randomly with uniform, Lorentzian or LÃ©vy distributions of the velocity. Twenty half-lives of Sn-117m, Er-169 and Re-186 were simulated in a synovial joint model adopted from the dissertation of LS Johnson. A dose profile as a function of depth, administered activity relative to 1 MBq/cmÂ² of Sn-117m, activity as a function of depth to deposit 100 Gy at the prescription depth, and dose-volume histograms were studied.
Results: The administered activity relative to 1 MBq/cmÂ² of Sn-117m was calculated to be 1.60, 1.60, and 2.077 MBq/cmÂ² of Er-169; and; 2.10, 2.10, and 8.51 MBq/cmÂ² of Re-186; for the uniform, Lorentzian, and LÃ©vy distributions respectively. The activity required to deposit 100 Gy at a depth of 0.5 mm from the synovial surface was estimated to be 0.413, 0.413, and 40.2 MBq/cmÂ² of Sn-117m; 0.917, 0.917, and 28.7 MBq/cmÂ² of Er-169; and 1.28, 1.28, and 1.78 MBq/cmÂ² of Re-186 for the three velocity distributions.
Conclusion: Sn-117m could replace Er-169 and Re-186 in the radiosynoviorthesis of medium and small-sized joints respectively.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by an unrestricted grant from Serene, LLC
Monte Carlo, Dose Volume Histograms
Not Applicable / None Entered.