Characterization of a diode dosimeter for UHDR FLASH radiotherapy

Rahman, M. M.; Kozelka, Jakub; Hildreth, Jeff; Schönfeld, A.A.; Sloop, Austin; Ashraf, Mudasir; Brůža, Petr; Gladstone, David J.; Pogue, Brian W.; Simon, William E.; Zhang, Rongxiao

doi:10.1002/mp.16474

Cited by 15 publications

(4 citation statements)

References 39 publications

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“…The SiC performance with accumulated radiation dose can also be compared with the shown by commercially available silicon diodes: for example, the signal of PTW's microSilicon detector decreases 0.5% per kGy when irradiated with 10 MeV electrons, according to the manufacturer (PTW 2019). Furthermore, the sensitivity decrease measured with a Sun Nuclear EDGE diode is 0.4% per kGy of 10 MeV electrons (Rahman et al 2023). Similar values can be extracted from the characterization of different silicon prototypes (Bruzzi 2016, Bueno et al 2022.…”

Section: Discussionsupporting

confidence: 69%

State-of-the-art silicon carbide diode dosimeters for ultra-high dose-per-pulse radiation at FLASH radiotherapy

Fleta,

Pellegrini,

Godignon

et al. 2024

Phys. Med. Biol.

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Objective: The successful implementation of FLASH radiotherapy in clinical settings, with typical dose rates >40Gy/s, requires accurate real-time dosimetry. Approach: Silicon carbide p-n diode dosimeters designed for the stringent requirements of FLASH radiotherapy have been fabricated and characterized in an ultra-high pulse dose rate electron beam. The circular SiC PiN diodes were fabricated at IMB-CNM (CSIC) in 3μm epitaxial 4H-SiC. Their characterization was performed in PTB’s ultra-high pulse dose rate reference electron beam. The SiC diode was operated without external bias voltage. The linearity of the diode response was investigated up to doses per pulse of 11Gy and pulse durations from 3 to 0.5μs. Percentage depth dose measurements were performed in ultra-high dose per pulse conditions. The effect of the accumulated dose of 20MeV electrons in the SiC diode sensitivity was evaluated. The temperature dependence of the response of the SiC diode was measured in the range 19–38°C. The temporal response of the diode was compared to the time-resolved beam current during each electron beam pulse. A flashDiamond prototype detector and Alanine measurements were used for reference dosimetry. Main results: The SiC diode response was independent both of DPP and of pulse dose rate up to at least 11Gy per pulse and 4MGy/s with tolerable deviation for relative dosimetry (<3 %). When measuring the percentage depth dose under UHDR conditions, the SiC diode performed comparably well to the reference flashDiamond. The sensitivity reduction after 100kGy accumulated dose was <2%. The diode was able to follow the temporal structure of the 20 MeV electron beam even for irregular pulse estructures. The measured temperature coefficient was (–0.079±0.005)%/ºC. Significance: The results of this study demonstrate for the first time the suitability of silicon carbide diodes for relative dosimetry in ultra-high dose rate pulsed electron beams up to a DPP of 11Gy per pulse.

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Section: Discussionsupporting

confidence: 69%

State-of-the-art silicon carbide diode dosimeters for ultra-high dose-per-pulse radiation at FLASH radiotherapy

Fleta,

Pellegrini,

Godignon

et al. 2024

Phys. Med. Biol.

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“…In most studies conducted to date, only three parameters (Ḋ m, DPP, IDR) have been set on all but the possible combinations remaining to be tested are countless. This has not been possible due to electron LINAC used for experiments that could not vary all the beam parameters linked to the FLASH effect ( 64 ). Furthermore, most of these studies ( 15 , 31 ) have used modified medical and industrial linacs to achieve UHDR, mostly by removing important components from the beam path such as the monitor chambers ( 65 ).…”

Section: Discussionmentioning

confidence: 99%

Electron FLASH radiotherapy in vivo studies. A systematic review

Giannini,

Gadducci,

Fuentes

et al. 2024

Front. Oncol.

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FLASH-radiotherapy delivers a radiation beam a thousand times faster compared to conventional radiotherapy, reducing radiation damage in healthy tissues with an equivalent tumor response. Although not completely understood, this radiobiological phenomenon has been proved in several animal models with a spectrum of all kinds of particles currently used in contemporary radiotherapy, especially electrons. However, all the research teams have performed FLASH preclinical studies using industrial linear accelerator or LINAC commonly employed in conventional radiotherapy and modified for the delivery of ultra-high-dose-rate (UHDRs). Unfortunately, the delivering and measuring of UHDR beams have been proved not to be completely reliable with such devices. Concerns arise regarding the accuracy of beam monitoring and dosimetry systems. Additionally, this LINAC totally lacks an integrated and dedicated Treatment Planning System (TPS) able to evaluate the internal dose distribution in the case of in vivo experiments. Finally, these devices cannot modify dose-time parameters of the beam relevant to the flash effect, such as average dose rate; dose per pulse; and instantaneous dose rate. This aspect also precludes the exploration of the quantitative relationship with biological phenomena. The dependence on these parameters need to be further investigated. A promising advancement is represented by a new generation of electron LINAC that has successfully overcome some of these technological challenges. In this review, we aim to provide a comprehensive summary of the existing literature on in vivo experiments using electron FLASH radiotherapy and explore the promising clinical perspectives associated with this technology.

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“…There are several alternative dosimetry methods being developed to resolve the challenges of ion chambers in FLASH environments, including diamond detectors, diode dosimeters, and plastic scintillators. [63][64][65][66] Preliminary cell studies using the Clinac-FLEX system have demonstrated differential dose rate effects in normal and cancer breast cells (Figure 7). While the FLASH dose rate diminished the radiation-induced morphological changes of normal breast cells, it caused similar killing of breast cancer cells than the non-FLASH dose rate.…”

Section: Machinementioning

confidence: 99%

Initial experience with an electron FLASH research extension (FLEX) for the Clinac system

Oh,

Gallagher,

Hyun

et al. 2023

J Applied Clin Med Phys

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PurposeRadiotherapy delivered at ultra‐high‐dose‐rates (≥40 Gy/s), that is, FLASH, has the potential to effectively widen the therapeutic window and considerably improve the care of cancer patients. The underlying mechanism of the FLASH effect is not well understood, and commercial systems capable of delivering such dose rates are scarce. The purpose of this study was to perform the initial acceptance and commissioning tests of an electron FLASH research product for preclinical studies.MethodsA linear accelerator (Clinac 23EX) was modified to include a non‐clinical FLASH research extension (the Clinac‐FLEX system) by Varian, a Siemens Healthineers company (Palo Alto, CA) capable of delivering a 16 MeV electron beam with FLASH and conventional dose rates. The acceptance, commissioning, and dosimetric characterization of the FLEX system was performed using radiochromic film, optically stimulated luminescent dosimeters, and a plane‐parallel ionization chamber. A radiation survey was conducted for which the shielding of the pre‐existing vault was deemed sufficient.ResultsThe Clinac‐FLEX system is capable of delivering a 16 MeV electron FLASH beam of approximately 1 Gy/pulse at isocenter and reached a maximum dose rate >3.8 Gy/pulse near the upper accessory mount on the linac gantry. The percent depth dose curves of the 16 MeV FLASH and conventional modes for the 10 × 10 cm2 applicator agreed within 0.5 mm at a range of 50% of the maximum dose. Their respective profiles agreed well in terms of flatness but deviated for field sizes >10 × 10 cm2. The output stability of the FLASH system exhibited a dose deviation of <1%. Preliminary cell studies showed that the FLASH dose rate (180 Gy/s) had much less impact on the cell morphology of 76N breast normal cells compared to the non‐FLASH dose rate (18 Gy/s), which induced large‐size cells.ConclusionOur studies characterized the non‐clinical Clinac‐FLEX system as a viable solution to conduct FLASH research that could substantially increase access to ultra‐high‐dose‐rate capabilities for scientists.

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Characterization of a diode dosimeter for UHDR FLASH radiotherapy

Cited by 15 publications

References 39 publications

State-of-the-art silicon carbide diode dosimeters for ultra-high dose-per-pulse radiation at FLASH radiotherapy

State-of-the-art silicon carbide diode dosimeters for ultra-high dose-per-pulse radiation at FLASH radiotherapy

Electron FLASH radiotherapy in vivo studies. A systematic review

Initial experience with an electron FLASH research extension (FLEX) for the Clinac system

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