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Emerging evidence indicates that the therapeutic window of radiotherapy can be significantly increased using ultra-high dose rate dose delivery (FLASH), by which the normal tissue injury is reduced without compromising tumor cell killing. The dose rate required for FLASH is 40 Gy/s or higher, 2-3 orders of magnitude greater than conventional radiot...
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... best configurations of the bunchers and corresponding beam parameters are summarized in Fig. 4. The same plot demonstrates the simulated energy spectrum of the accelerated beam, the quality of which is very good (narrow beam head and thin low-energy tail). The parameters of the optimized linac simulated in Parmela are presented in Table 1. These numbers demonstrate that we were able to increase the beam current by ~50% thanks to the deep redesign of the buncher, application of solenoid, and due to the decision to operate with longer sections (almost 2.4 m). ...Context 2
... best configurations of the bunchers and corresponding beam parameters are summarized in Fig. 4. The same plot demonstrates the simulated energy spectrum of the accelerated beam, the quality of which is very good (narrow beam head and thin low-energy tail). The parameters of the optimized linac simulated in Parmela are presented in Table 1. These numbers demonstrate that we were able to increase the beam current by ~50% thanks to the deep redesign of the buncher, application of solenoid, and due to the decision to operate with longer sections (almost 2.4 m). ...Similar publications
Background
Beam scanning is a useful technique for the treatment of large tumors when the primary beam size is limited, which is the case with radiation beams used in FLASH radiotherapy.
Purpose
To optimize beam scanning as a dose delivery method for FLASH radiotherapy, it is necessary to first understand the effects of beam scanning on the FLASH...
Objective:The objective of this study was to investigate the impact of mean and instantaneous dose rates on the production of reactive oxygen species (ROS) during ultra-high dose rate (UHDR) radiotherapy. The study aimed to determine whether either dose rate type plays a role in driving the FLASH effect, a phenomenon where UHDR radiotherapy reduces...
Objective. Beam current transformers (BCT) are promising detectors for real-time beam monitoring in ultra-high dose rate (UHDR) electron radiotherapy. However, previous studies have reported a significant sensitivity of the BCT signal to changes in source-to-surface distance (SSD), field size, and phantom material which have until now been attribut...
The FLASH effect is a radiobiological phenomenon that has garnered considerable interest in the clinical field. Pre-clinical experimental studies have highlighted its potential to reduce side effects on healthy tissues while maintaining isoeffectiveness on tumor tissues, thus widening the therapeutic window and enhancing the effectiveness of radiot...
Introduction
We have previously adapted a clinical linear accelerator (Elekta Precise, Elekta AB) for ultra-high dose rate (UHDR) electron delivery. To enhance reliability in future clinical FLASH radiotherapy trials, the aim of this study was to introduce and evaluate an upgraded beam control system and beam tuning process for safe and precise UHD...
Citations
... Another factor that allows for improvement in dose rate is increasing the beam energy. The conversion efficiency from electron beam power to X-ray power scales approximately with E 3 , so a small increase in energy can make a big difference in X-ray intensity (Kutsaev et al., 2022). The increased X-ray energy also allows greater penetration. ...
... The structure parameters used for the estimation were considered as follows. The SW structure is a scaled to L-band version of an S-band linac that we are currently building for the demonstration version of FLASH (Kutsaev et al., 2022). The TW structure has a geometry similar to a 40 MeV L-band linac for neutron production that is being built by RadiaBeam for Rensselaer Polytechnic Institute (Adolphsen et al., 2014), optimized for the highest shunt impedance (R sh ). ...
... Two criteria were used for the optimization quality: beam transmission-should be maximized, and beam spectrum width-should be minimized. The approach for the buncher optimization is described in the works (Kutsaev, 2010;2021a;Kutsaev et al., 2022) The best configurations of the bunchers and corresponding beam parameters are summarized in Table 2 and Figure 9. Next, we designed the second acceleration section to accelerate the beam from 9 MeV to 18 MeV. Again, the bore diameter was made as large as possible, and the total length was designed to be less than 2.0 m so that the electric acceleration field would be uniform. ...
Introduction: This study examines how a practical source of X-ray radiation, capable of delivering unprecedented X-ray of 100 Gy/s at 1 m for X-ray FLASH radiotherapy can be designed. Methods: We proposed the design of a linac, capable of accelerating 18 MeV 8 mA electron beam with further conversion to bremsstrahlung X-rays. The design is based on L-band traveling wave accelerating structures with high power efficiency, operating in a short-burst/long-pulse regime that allows operating power supply in a regime, beyond its specifications. Results: This study demonstrates the feasibility of a high-power linac for a clinical X-ray FLASH therapy system, using detailed analysis and simulations. Despitẽ 500x higher output than a standard clinical linac, the design utilizes available accelerator components for maximal practicality. Discussion: Recent studies have demonstrated that the FLASH effect that allows to effectively kill tumor cells while sparing normal tissue occurs when large dose rates (≥40 Gy/s) are delivered in less than 1 s. Photons are very attractive since modest energies of several MeV are needed, which can be achieved with compact and cost-efficient accelerators. However, since the efficiency of electron-to-photon conversion is only a few percent, the required beam intensity must be an order of magnitude higher than that state-of-the-art accelerators can provide. The proposed ROAD-FLASH accelerator layout allows achieving both the FLASH dose rate and superior dose conformity, comparing to the similar projects. The current paper focuses on providing a technical roadmap for building an economical and practical linear accelerator for ROAD X-ray FLASH delivery. KEYWORDS X-ray radiotherapy, FLASH effect, electron linac, ultra-high dose rate, ROAD
... Figure 13 shows a model of the proposed ROAD-FLASH system [137]. The linac (see Table 4 for a summary of parameters) consists of a 1.3 A, 140 kV electron gun, prebuncher [139], and two traveling wave linac sections powered by a commercially available 20 MW L-band klystron with 167 µs pulses at 150 Hz, to bring an 8.14 mA average current electron beam to 18 MeV. Assuming a dose conversion factor of 2000 Gy/min/mA at 18 MeV, such a linac will be able to provide an uncollimated dose rate of 271 Gy/s at 1 m (8.14 mA × 2•10 3 /60 Gy/s/mA), which is equivalent to a ~100 Gy/s collimated dose at 80 cm, assuming a ~25% dose delivery efficiency [140]. ...
... The linac (see Table 4 for a summary of parameters) consists of a 1.3 A, 140 kV electron gun, prebuncher [138], and two traveling wave linac sections powered by a commercially available 20 MW L-band klystron with 167 µs pulses at 150 Hz, to bring an 8.14 mA average current electron beam to 18 MeV. Assuming a dose conversion factor of 2000 Gy/min/mA at 18 MeV, such a linac will be able to provide an uncollimated dose rate of 271 Gy/s at 1 m (8.14 mA × 2·10 3 /60 Gy/s/mA), which is equivalent to a~100 Gy/s collimated dose at 80 cm, assuming a~25% dose delivery efficiency [139]. The beam is transported through a rotary vacuum joint into a rotating magnetic gantry that brings the beam to a rotating X-ray target directed at the patient. ...
he general concept of radiation therapy used in conventional cancer treatment is to increase the therapeutic index by creating a physical dose differential between tumors and normal tissues through precision dose targeting, image guidance, and radiation beams that deliver a radiation dose with high conformality, e.g., protons and ions. However, the treatment and cure are still limited by normal tissue radiation toxicity, with the corresponding side effects. A fundamentally different paradigm for increasing the therapeutic index of radiation therapy has emerged recently, supported by preclinical research, and based on the FLASH radiation effect. FLASH radiation therapy (FLASH-RT) is an ultra-high-dose-rate delivery of a therapeutic radiation dose within a fraction of a second. Experimental studies have shown that normal tissues seem to be universally spared at these high dose rates, whereas tumors are not. While dose delivery conditions to achieve a FLASH effect are not yet fully characterized, it is currently estimated that doses delivered in less than 200 ms produce normal-tissue-sparing effects, yet effectively kill tumor cells. Despite a great opportunity, there are many technical challenges for the accelerator community to create the required dose rates with novel compact accelerators to ensure the safe delivery of FLASH radiation beams.
