The design, construction and performance of a variable collimator for epithermal neutron capture therapy beams
| Autor: | Otto K. Harling, Kent J. Riley, S. J. Ali, Peter J. Binns |
|---|---|
| Rok vydání: | 2004 |
| Předmět: |
Neutrons
Materials science Radiological and Ultrasound Technology Aperture business.industry Equivalent dose Boron Neutron Capture Therapy Collimator Boron carbide law.invention chemistry.chemical_compound Neutron capture Optics chemistry Beamline law Humans Radiology Nuclear Medicine and imaging Neutron Particle Accelerators business Monte Carlo Method Software Beam (structure) |
| Zdroj: | Physics in Medicine and Biology. 49:2015-2028 |
| ISSN: | 1361-6560 0031-9155 |
| DOI: | 10.1088/0031-9155/49/10/012 |
| Popis: | A patient collimator for the fission converter based epithermal neutron beam (FCB) at the Massachusetts Institute of Technology Research Reactor (MITR-II) was built for clinical trials of boron neutron capture therapy (BNCT). A design was optimized by Monte Carlo simulations of the entire beam line and incorporates a modular construction for easy modifications in the future. The device was formed in-house by casting a mixture of lead spheres (7.6 mm diameter) in epoxy resin loaded with either 140 mg cm(-3) of boron carbide or 210 mg cm(-3) of lithium fluoride (95% enriched in 6Li). The cone shaped collimator allows easy field placement anywhere on the patient and is equipped with a laser indicator of central axis, beam's eye view optics and circular apertures of 80, 100, 120 and 160 mm diameter. Beam profiles and the collateral dose in a half-body phantom were measured for the 160 mm field using fission counters, activation foils as well as tissue equivalent (A-150) and graphite walled ionization chambers. Leakage radiation through the collimator contributes less than 10% to the total collateral dose up to 0.15 m beyond the edge of the aperture and becomes relatively more prominent with lateral displacement. The measured whole body dose equivalent of 24 +/- 2 mSv per Gy of therapeutic dose is comparable to doses received during conventional therapy and is due principally (60-80%) to thermal neutron capture reactions with boron. These findings, together with the dose distributions for the primary beam, demonstrate the suitability of this patient collimator for BNCT. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|