Perspectives in linear accelerator for FLASH VHEE: Study of a compact C-band system

Faillace, L.; Alesini, D.; Bisogni, G.; Bosco, Fabio; Carillo, Martina; Cirrone, P.; Cuttone, G.; Arcangelis, D. De; Gregorio, Angelica De; Martino, Fabio; Favaudon, Vincent; Ficcadenti, L.; Francescone, D.; Franciosini, G.; Gallo, A.; Heinrich, Sophie; Migliorati, M.; Mostacci, A.; Palumbo, L.; Patera, V.; Patriarca, Annalisa; Pensavalle, J.H.; Perondi, Francesca; Remetti, Romolo; Sarti, A.; Spataro, B.; Torrisi, G.; Vannozzi, Alessandro; Giuliano, Lucia

doi:10.1016/j.ejmp.2022.10.018

Cited by 20 publications

(11 citation statements)

References 18 publications

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“…Multiple initiatives set out to explore the clinical application of broad beam VHEE using UHDR 21,27,31 and novel VHEE RT devices using a limited number of fixed beam portals are designed to deliver a whole treatment fraction on time scales compatible with those of preclinical irradiations that resulted in a substantial FLASH effect. 27 The achievable dosimetric plan quality is of concern when using only a few 3D-conformed broad VHEE beams and may therefore decisively influence patient selection for such a treatment modality.…”

Section: Discussionmentioning

confidence: 99%

“…20,21,[25][26][27] More particularly, there are several initiatives that aim at the clinical implementation of VHEE-based FLASH-RT by applying or exploring the use of multi-directional collimated broad VHEE beams to administer UHDR treatments. 21,27,31 For this VHEE-based 3D-CRT delivery approach, the achievable dosimetric conformity is of concern and will depend on the patient cohort and individual target characteristics.…”

Section: Introductionmentioning

confidence: 99%

“…Hence, a relatively simple treatment technique that may achieve conformal dose delivery on such time scales to optimize its FLASH potential is the use of a limited number of fixed beam lines (FBL) that deliver collimated broad VHEE beams quasi‐simultaneously using 3D‐conformal RT (3D‐CRT) 20,21,25–27 . More particularly, there are several initiatives that aim at the clinical implementation of VHEE‐based FLASH‐RT by applying or exploring the use of multi‐directional collimated broad VHEE beams to administer UHDR treatments 21,27,31 . For this VHEE‐based 3D‐CRT delivery approach, the achievable dosimetric conformity is of concern and will depend on the patient cohort and individual target characteristics.…”

Section: Introductionmentioning

confidence: 99%

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3D‐conformal very‐high energy electron therapy as candidate modality for FLASH‐RT: A treatment planning study for glioblastoma and lung cancer

et al. 2023

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BackgroundPre‐clinical ultra‐high dose rate (UHDR) electron irradiations on time scales of 100 ms have demonstrated a remarkable sparing of brain and lung tissues while retaining tumor efficacy when compared to conventional dose rate irradiations. While clinically‐used gantries and intensity modulation techniques are too slow to match such time scales, novel very‐high energy electron (VHEE, 50–250 MeV) radiotherapy (RT) devices using 3D‐conformed broad VHEE beams are designed to deliver UHDR treatments that fulfill these timing requirements.PurposeTo assess the dosimetric plan quality obtained using VHEE‐based 3D‐conformal RT (3D‐CRT) for treatments of glioblastoma and lung cancer patients and compare the resulting treatment plans to those delivered by standard‐of‐care intensity modulated photon RT (IMRT) techniques.MethodsSeven glioblastoma patients and seven lung cancer patients were planned with VHEE‐based 3D‐CRT using 3 to 16 coplanar beams with equidistant angular spacing and energies of 100 and 200 MeV using a forward planning approach. Dose distributions, dose‐volume histograms, coverage (V95%) and homogeneity (HI98%) for the planning target volume (PTV), as well as near‐maximum doses (D2%) and mean doses (Dmean) for organs‐at‐risk (OAR) were evaluated and compared to clinical IMRT plans.ResultsMean differences of V95% and HI98% of all VHEE plans were within 2% or better of the IMRT reference plans. Glioblastoma plan dose metrics obtained with VHEE configurations of 200 MeV and 3–16 beams were either not significantly different or were significantly improved compared to the clinical IMRT reference plans. All OAR plan dose metrics evaluated for VHEE plans created using 5 beams of 100 MeV were either not significantly different or within 3% on average, except for Dmean for the body, Dmean for the brain, D2% for the brain stem, and D2% for the chiasm, which were significantly increased by 1, 2, 6, and 8 Gy, respectively (however below clinical constraints). Similarly, the dose metrics for lung cancer patients were also either not significantly different or were significantly improved compared to the reference plans for VHEE configurations with 200 MeV and 5 to 16 beams with the exception of D2% and Dmean to the spinal canal (however below clinical constraints). For the lung cancer cases, the VHEE configurations using 100 MeV or only 3 beams resulted in significantly worse dose metrics for some OAR. Differences in dose metrics were, however, strongly patient‐specific and similar for some patient cases.ConclusionsVHEE‐based 3D‐CRT may deliver conformal treatments to simple, mostly convex target shapes in the brain and the thorax with a limited number of critical adjacent OAR using a limited number of beams (as low as 3 to 7). Using such treatment techniques, a dosimetric plan quality comparable to that of standard‐of‐care IMRT can be achieved. Hence, from a treatment planning perspective, 3D‐conformal UHDR VHEE treatments delivered on time scales of 100 ms represent a promising candidate technique for the clinical transfer of the FLASH effect.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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3D‐conformal very‐high energy electron therapy as candidate modality for FLASH‐RT: A treatment planning study for glioblastoma and lung cancer

et al. 2023

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“…Indeed, they combine the advantages of being able to reach deep‐seated tumors, being relatively insensitive to tissue heterogeneities, with the ability to be delivered at UHDRs therefore allowing possible healthy tissue preservation related to the FLASH effect 2,3 . While VHEE generation is still in its early stages (only a few research facilities are currently available), recent advances in linac radiofrequency technology and beam dynamics, or modified linacs as a lower cost alternative could rapidly lead to new generations of accelerators that are both compact and allow the production of electrons up to 200 MeV 4,5 . Several studies have already compared possible VHEE treatment plans to currently used techniques (IMRT, VMAT, or protons), leading to the conclusion that they may offer clinical advantages in terms of healthy tissue sparing for many cancer locations 6–8 .…”

Section: Introductionmentioning

confidence: 99%

“…2,3 While VHEE generation is still in its early stages (only a few research facilities are currently available), recent advances in linac radiofrequency technology and beam dynamics, or modified linacs as a lower cost alternative could rapidly lead to new generations of accelerators that are both compact and allow the production of electrons up to 200 MeV. 4,5 Several studies have already compared possible VHEE treatment plans to currently used techniques (IMRT, VMAT, or protons), leading to the conclusion that they may offer clinical advantages in terms of healthy tissue sparing for many cancer locations. [6][7][8] Lately, the feasibility of producing a clinically acceptable pediatric whole brain RT plan using a FLASH 40 MeV electron beam has also been demonstrated using an alternative configuration of a linear accelerator design currently being built for FLASH radiobiology research.…”

Section: Introductionmentioning

confidence: 99%

Secondary radiation dose modeling in passive scattering and pencil beam scanning very high energy electron (VHEE) radiation therapy

Deut,

Ronga,

Bonfrate

et al. 2023

Medical Physics

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Background Electrons with kinetic energy up to a few hundred MeV, also called very high energy electrons (VHEE), are currently considered a promising technique for the future of radiation therapy (RT) and in particular ultra‐high dose rate (UHDR) therapy. However, the feasibility of a clinical application is still being debated and VHEE therapy remains an active area of research for which the optimal conformal technique is also yet to be determined. Purpose In this work, we will apply two existing formalisms based on analytical Gaussian multiple‐Coulomb scattering theory and Monte Carlo (MC) simulations to study and compare the electron and bremsstrahlung photon dose distributions arising from two beam delivery systems (passive scattering with or without a collimator or active scanning). Methods We therefore tested the application of analytical and MC models to VHEE beams and assessed their performance and parameterization in the energy range of 6–200 MeV. The optimized electron beam fluence, the bremsstrahlung, an estimation of central‐axis and off‐axis x‐ray dose at the practical range and neutron contributions to the total dose, along with an extended parameterization for the photon dose model were developed, together with a comparison between double scattering (DS) and pencil beam scanning (PBS) techniques. MC simulations were performed with the TOPAS/Geant4 toolkit to verify the dose distributions predicted by the analytical calculations. Results The results for the clinical energy range (between 6 and 20 MeV) as well as for higher energies (VHEE range between 20 and 200 MeV) and for two treatment field sizes (5 × 5 and 10 × 10 cm2) are reported, showing a reasonable agreement with MC simulations with mean differences below 2.1%. The relative contributions of photons generated in the medium or by the scattering system along the central‐axis (up to 50% of the total dose) are also illustrated, along with their relative variations with electron energy. Conclusions The fast analytical models parametrized in this study allow an estimation of the amount of photons produced behind the practical range by a DS system with an accuracy lower than 3%, providing important information for the eventual design of a VHEE system. The results of this work could support future research on VHEE radiotherapy.

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A prototype scintillator real‐time beam monitor for ultra‐high dose rate radiotherapy

Levin,

Friedman,

Ferretti

et al. 2024

Medical Physics

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BackgroundFLASH Radiotherapy (RT) is an emergent cancer RT modality where an entire therapeutic dose is delivered at more than 1000 times higher dose rate than conventional RT. For clinical trials to be conducted safely, a precise and fast beam monitor that can generate out‐of‐tolerance beam interrupts is required. This paper describes the overall concept and provides results from a prototype ultra‐fast, scintillator‐based beam monitor for both proton and electron beam FLASH applications.PurposeA FLASH Beam Scintillator Monitor (FBSM) is being developed that employs a novel proprietary scintillator material. The FBSM has capabilities that conventional RT detector technologies are unable to simultaneously provide: (1) large area coverage; (2) a low mass profile; (3) a linear response over a broad dynamic range; (4) radiation hardness; (5) real‐time analysis to provide an IEC‐compliant fast beam‐interrupt signal based on true two‐dimensional beam imaging, radiation dosimetry and excellent spatial resolution.MethodsThe FBSM uses a proprietary low mass, less than 0.5 mm water equivalent, non‐hygroscopic, radiation tolerant scintillator material (designated HM: hybrid material) that is viewed by high frame rate CMOS cameras. Folded optics using mirrors enable a thin monitor profile of ∼10 cm. A field programmable gate array (FPGA) data acquisition system generates real‐time analysis on a time scale appropriate to the FLASH RT beam modality: 100–1000 Hz for pulsed electrons and 10–20 kHz for quasi‐continuous scanning proton pencil beams. An ion beam monitor served as the initial development platform for this work and was tested in low energy heavy‐ion beams (86Kr+26 and protons). A prototype FBSM was fabricated and then tested in various radiation beams that included FLASH level dose per pulse electron beams, and a hospital RT clinic with electron beams.ResultsResults presented in this report include image quality, response linearity, radiation hardness, spatial resolution, and real‐time data processing. The HM scintillator was found to be highly radiation damage resistant. It exhibited a small 0.025%/kGy signal decrease from a 216 kGy cumulative dose resulting from continuous exposure for 15 min at a FLASH compatible dose rate of 237 Gy/s. Measurements of the signal amplitude versus beam fluence demonstrate linear response of the FBSM at FLASH compatible dose rates of >40 Gy/s. Comparison with commercial Gafchromic film indicates that the FBSM produces a high resolution 2D beam image and can reproduce a nearly identical beam profile, including primary beam tails. The spatial resolution was measured at 35–40 µm. Tests of the firmware beta version show successful operation at 20 000 Hz frame rate or 50 µs/frame, where the real‐time analysis of the beam parameters is achieved in less than 1 µs.ConclusionsThe FBSM is designed to provide real‐time beam profile monitoring over a large active area without significantly degrading the beam quality. A prototype device has been staged in particle beams at currents of single particles up to FLASH level dose rates, using both continuous ion beams and pulsed electron beams. Using a novel scintillator, beam profiling has been demonstrated for currents extending from single particles to 10 nA currents. Radiation damage is minimal and even under FLASH conditions would require ≥50 kGy of accumulated exposure in a single spot to result in a 1% decrease in signal output. Beam imaging is comparable to radiochromic films, and provides immediate images without hours of processing. Real‐time data processing, taking less than 50 µs (combined data transfer and analysis times), has been implemented in firmware for 20 kHz frame rates for continuous proton beams.

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Perspectives in linear accelerator for FLASH VHEE: Study of a compact C-band system

Cited by 20 publications

References 18 publications

3D‐conformal very‐high energy electron therapy as candidate modality for FLASH‐RT: A treatment planning study for glioblastoma and lung cancer

3D‐conformal very‐high energy electron therapy as candidate modality for FLASH‐RT: A treatment planning study for glioblastoma and lung cancer

Secondary radiation dose modeling in passive scattering and pencil beam scanning very high energy electron (VHEE) radiation therapy

A prototype scintillator real‐time beam monitor for ultra‐high dose rate radiotherapy

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