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An investigation of the feasibility of gadolinium for neutron capture synovectomy
Author(s) -
Gierga D. P.,
Yanch J. C.,
Shefer R. E.
Publication year - 2000
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.599037
Subject(s) - neutron capture , neutron , gadolinium , synovectomy , nuclear medicine , neutron source , neutron temperature , radiochemistry , nuclear physics , materials science , physics , chemistry , medicine , rheumatoid arthritis , metallurgy
Neutron capture synovectomy (NCS) has been proposed as a possible treatment modality for rheumatoid arthritis. Neutron capture synovectomy is a two‐part modality, in which a compound containing an isotope with an appreciable thermal neutron capture cross section is injected directly into the joint, followed by irradiation with a neutron beam. Investigations to date for NCS have focused on boron neutron capture synovectomy (BNCS), which utilizes the10 B ( n , α ) 7 Li nuclear reaction to deliver a highly localized dose to the synovium. This paper examines the feasibility of gadolinium, specifically157 Gd , as an alternative to boron as a neutron capture agent for NCS. This alternative modality is termed Gadolinium Neutron Capture Synovectomy, or GNCS. Monte Carlo simulations have been used to compare10 B and157 Gd as isotopes for accelerator‐based NCS. The neutron source used in these calculations was a moderated spectrum from the9 Be ( p , n ) reaction at a proton energy of 4 MeV. The therapy time to deliver the NCS therapeutic dose of 10 000 RBE‐cGy, is 27 times longer when157 Gd is used instead of10 B . The skin dose to the treated joint is 33 times larger when157 Gd is used instead of10 B . Furthermore, the impact of using157 Gd instead of10 B was examined in terms of shielded whole‐body dose to the patient. The effective dose is 202 mSv for GNCS, compared to 7.6 mSv for BNCS. This is shown to be a result of the longer treatment times required for GNCS; the contribution of the high‐energy photons emitted from neutron capture in gadolinium is minimal. Possible explanations as to the relative performance of157 Gd and10 B are discussed, including differences in the RBE and range of boron and gadolinium neutron capture reaction products, and the relative values of the10 B and157 Gd thermal neutron capture cross section as a function of neutron energy.