Low Z target switching to increase tumor endothelial cell dose enhancement during gold nanoparticle‐aided radiation therapy. Issue 1 (31st December 2015)

• Record Type: Journal Article
• Authors: Berbeco, Ross I.; Detappe, Alexandre; Tsiamas, Panogiotis; Parsons, David; Yewondwossen, Mammo; Robar, James
• Is Part Of: Medical physics. Volume 43:Issue 1(2016)
• Page Start: 436
• Page End: 442
• Publication Date: 2015-12-31
• Subjects: blood vessels -- cellular biophysics -- dosimetry -- gold -- Monte Carlo methods -- nanomedicine -- nanoparticles -- radiation therapy -- tumours; Dose‐volume analysis -- Applications -- Nanotechnologies‐applications -- Monte Carlo simulations -- Cell processes -- Dosimetry/exposure assessment; Radiation therapy -- Nano‐structures -- Nano‐biotechnology or nano‐medicine, e.g. protein engineering or drug delivery -- Scintigraphy; radiation therapy -- nanoparticle -- dose enhancement -- vascular disruption; Photons -- Dosimetry -- Carbon -- Cancer -- Nanoparticles -- Gold -- Linear accelerators -- Medical imaging -- Tissues; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1118/1.4938410
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : 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.