Effects of initial electron beam parameters of a linear accelerator on the properties of bremsstrahlung radiation in a radiotherapy setting

Горлачев, Г. Е.; Polozov, Sergey; Dalechina, Alexandra; Ksenofontov, A. I.; Kistenev, A. V.

doi:10.1134/s1547477116070244

Cited by 1 publication

(1 citation statement)

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“…A3(a) in the Appendix A1]. Since beam size and target thickness may affect lateral dose profiles, [33][34][35] we simulated the effect of the two parameters on the penumbra across the edge of a halfblocked beam, and found that penumbra is more sensitive to the beam size than to the target thickness [see Figs. A3(b)-A3(d) in the Appendix A1].…”

Section: A2 Transient Temperature Behaviormentioning

confidence: 99%

Thermal limits on MV x‐ray production by bremsstrahlung targets in the context of novel linear accelerators

Wang

Trovati

Borchard³

et al. 2017

Medical Physics

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Purpose To study the impact of target geometrical and linac operational parameters, such as target material and thickness, electron beam size, repetition rate, and mean current on the ability of the radiotherapy treatment head to deliver high-dose-rate x-ray irradiation in the context of novel linear accelerators capable of higher repetition rates/duty cycle than conventional clinical linacs. Methods The depth dose in a water phantom without a flattening filter and heat deposition in an x-ray target by 10 MeV pulsed electron beams were calculated using the Monte-Carlo code MCNPX, and the transient temperature behavior of the target was simulated by ANSYS. Several parameters that affect both the dose distribution and temperature behavior were investigated. The target was tungsten with a thickness ranging from 0 to 3 mm and a copper heat remover layer. An electron beam with full width at half maximum (FWHM) between 0–3 mm and mean current of 0.05–2 mA was used as the primary beam at repetition rates of 100, 200, 400, and 800 Hz. Results For a 10 MeV electron beam with FWHM of 1 mm, pulse length of 5 μs, by using a thin tungsten target with thickness of 0.2 mm instead of 1 mm, and by employing a high repetition rate of 800 Hz instead of 100 Hz, the maximum dose rate delivered can increase 2 times from 0.57 Gy/s to 1.16 Gy/s. In this simple model, the limiting factor on dose rate is the copper heat remover’s softening temperature, which was considered to be 500 °C in our study. Conclusions A high dose rate can be obtained by employing thin targets together with high repetition rate electron beams enabled by novel linac designs, whereas the benefit of thin targets is marginal at conventional repetition rates. Next generation linacs used to increase dose rate need different target designs compared to conventional linacs.

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Section: A2 Transient Temperature Behaviormentioning

confidence: 99%