期刊
MEDICAL PHYSICS
卷 43, 期 1, 页码 436-442出版社
AMER ASSOC PHYSICISTS MEDICINE AMER INST PHYSICS
DOI: 10.1118/1.4938410
关键词
radiation therapy; nanoparticle; dose enhancement; vascular disruption
资金
- Varian Medical Systems, Inc.
- National Cancer Institute of the National Institutes of Health [R03CA164645, R21CA188833]
- NATIONAL CANCER INSTITUTE [R03CA164645, R21CA188833] Funding Source: NIH RePORTER
Purpose: Previous studies have introduced gold nanoparticles as vascular-disrupting agents during radiation therapy. Crucial to this concept is the low energy photon content of the therapy radiation beam. The authors introduce a new mode of delivery including a linear accelerator target that can toggle between low Z and high Z targets during beam delivery. In this study, the authors examine the potential increase in tumor blood vessel endothelial cell radiation dose enhancement with the low Z target. Methods: The authors use Monte Carlo methods to simulate delivery of three different clinical photon beams: (1) a 6 MV standard (Cu/W) beam, (2) a 6 MV flattening filter free (Cu/W), and (3) a 6 MV (carbon) beam. The photon energy spectra for each scenario are generated for depths in tissue-equivalent material: 2, 10, and 20 cm. The endothelial dose enhancement for each target and depth is calculated using a previously published analytic method. Results: It is found that the carbon target increases the proportion of low energy (<150 keV) photons at 10 cm depth to 28% from 8% for the 6 MV standard (Cu/W) beam. This nearly quadrupling of the low energy photon content incident on a gold nanoparticle results in 7.7 times the endothelial dose enhancement as a 6 MV standard (Cu/W) beam at this depth. Increased surface dose from the low Z target can be mitigated by well-spaced beam arrangements. Conclusions: By using the fast-switching target, one can modulate the photon beam during delivery, producing a customized photon energy spectrum for each specific situation. (C) 2016 American Association of Physicists in Medicine.
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