Dosimetry for New Radiation Therapy Approaches Using High Energy Electron Accelerators

Kokurewicz, Karolina; Schüller, A.; Brunetti, E.; Subiel, Anna; Kranzer, Rafael; Hackel, Thomas; Meier, Markus W.; Kapsch, Ralf‐Peter; Jaroszynski, D. A.

doi:10.3389/fphy.2020.568302

Cited by 10 publications

(8 citation statements)

References 53 publications

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“…52,53 For electron FLASH beams, large correction factors were reported in multiple studies to account for recombination in the sensitive volume. 52,[54][55][56][57][58] The Advanced Markus was the ionization chamber mainly studied in the context of electron beams thanks to its small sensitive volume (5 mm surface diameter and 1 mm spacing between electrodes) and large maximum dose per pulse with respect to cylindrical ionization chambers. For example, a Farmer ionization chamber is able to measure accurately doses per pulse up to 0.91 mGy without saturating whereas the Advanced Markus ionization chamber can be used for up to a dose per pulse of 5.56 mGy (99% collection).…”

Section: Ionization Chambersmentioning

confidence: 99%

Ultra‐high dose rate dosimetry: Challenges and opportunities for FLASH radiation therapy

et al. 2022

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The clinical translation of FLASH radiotherapy (RT) requires challenges related to dosimetry and beam monitoring of ultra‐high dose rate (UHDR) beams to be addressed. Detectors currently in use suffer from saturation effects under UHDR regimes, requiring the introduction of correction factors. There is significant interest from the scientific community to identify the most reliable solutions and suitable experimental approaches for UHDR dosimetry. This interest is manifested through the increasing number of national and international projects recently proposed concerning UHDR dosimetry. Attaining the desired solutions and approaches requires further optimization of already established technologies as well as the investigation of novel radiation detection and dosimetry methods. New knowledge will also emerge to fill the gap in terms of validated protocols, assessing new dosimetric procedures and standardized methods. In this paper, we discuss the main challenges coming from the peculiar beam parameters characterizing UHDR beams for FLASH RT. These challenges vary considerably depending on the accelerator type and technique used to produce the relevant UHDR radiation environment. We also introduce some general considerations on how the different time structure in the production of the radiation beams, as well as the dose and dose‐rate per pulse, can affect the detector response. Finally, we discuss the requirements that must characterize any proposed dosimeters for use in UDHR radiation environments. A detailed status of the current technology is provided, with the aim of discussing the detector features and their performance characteristics and/or limitations in UHDR regimes. We report on further developments for established detectors and novel approaches currently under investigation with a view to predict future directions in terms of dosimetry approaches, practical procedures, and protocols. Due to several on‐going detector and dosimetry developments associated with UHDR radiation environment for FLASH RT it is not possible to provide a simple list of recommendations for the most suitable detectors for FLASH RT dosimetry. However, this article does provide the reader with a detailed description of the most up‐to‐date dosimetric approaches, and describes the behavior of the detectors operated under UHDR irradiation conditions and offers expert discussion on the current challenges which we believe are important and still need to be addressed in the clinical translation of FLASH RT.

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Section: Ionization Chambersmentioning

confidence: 99%

Ultra‐high dose rate dosimetry: Challenges and opportunities for FLASH radiation therapy

et al. 2022

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“…In most studies on the FLASH effect, dedicated electron accelerators 19–23 or modified clinical linear accelerators 24–26 were used, delivering electron pulses of ultra‐high dose per pulse (UH‐DPP) in the range from 0.5 to 10 Gy/pulse. However, these somewhat extreme irradiation conditions are indeed challenging in terms of dosimetry 11,20,22,26–30 . As a matter of fact, only passive dosimetric systems (basically alanine, 31,32 Gafchromic films, 33 and thermo‐luminescent dosimeters 28 ) have been successfully used at present, provided that specific irradiation protocols are adopted.…”

Section: Introductionmentioning

confidence: 99%

“…However, these somewhat extreme irradiation conditions are indeed challenging in terms of dosimetry. 11 , 20 , 22 , 26 , 27 , 28 , 29 , 30 As a matter of fact, only passive dosimetric systems (basically alanine, 31 , 32 Gafchromic films, 33 and thermo‐luminescent dosimeters 28 ) have been successfully used at present, provided that specific irradiation protocols are adopted. A delay of hours or even days can be needed in order to get the response from the passive detector irradiation.…”

Section: Introductionmentioning

confidence: 99%

Design, realization, and characterization of a novel diamond detector prototype for FLASH radiotherapy dosimetry

Marinelli

Felici²,

Galante³

et al. 2022

Medical Physics

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Purpose FLASH radiotherapy (RT) is an emerging technique in which beams with ultra‐high dose rates (UH‐DR) and dose per pulse (UH‐DPP) are used. Commercially available active real‐time dosimeters have been shown to be unsuitable in such conditions, due to severe response nonlinearities. In the present study, a novel diamond‐based Schottky diode detector was specifically designed and realized to match the stringent requirements of FLASH‐RT. Methods A systematic investigation of the main features affecting the diamond response in UH‐DPP conditions was carried out. Several diamond Schottky diode detector prototypes with different layouts were produced at Rome Tor Vergata University in cooperation with PTW‐Freiburg. Such devices were tested under electron UH‐DPP beams. The linearity of the prototypes was investigated up to DPPs of about 26 Gy/pulse and dose rates of approximately 1 kGy/s. In addition, percentage depth dose (PDD) measurements were performed in different irradiation conditions. Radiochromic films were used for reference dosimetry. Results The response linearity of the diamond prototypes was shown to be strongly affected by the size of their active volume as well as by their series resistance. By properly tuning the design layout, the detector response was found to be linear up to at least 20 Gy/pulse, well into the UH‐DPP range conditions. PDD measurements were performed by three different linac applicators, characterized by DPP values at the point of maximum dose of 3.5, 17.2, and 20.6 Gy/pulse, respectively. The very good superimposition of three curves confirmed the diamond response linearity. It is worth mentioning that UH‐DPP irradiation conditions may lead to instantaneous detector currents as high as several mA, thus possibly exceeding the electrometer specifications. This issue was properly addressed in the case of the PTW UNIDOS electrometers. Conclusions The results of the present study clearly demonstrate the feasibility of a diamond detector for FLASH‐RT applications.

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“…In the era of rapid technological advance, there has been manifold development in strategies to increase the efficacy of radiotherapy, including but not limit to calibration [ 28 ], simulation [ 29 ], OARs contouring [ 30 ], dosimetry-based planning [ 31 ], treatment [ 32 ] and quality assurance [ 33 ]. Accurate OARs contouring is deemed a critical step in the development of effective radiotherapy plans since all subsequent radiotherapy planning and delivery process are dependent on OARs contouring.…”

Section: Discussionmentioning

confidence: 99%

Implementation of web-based open-source radiotherapy delineation software (WORDS) in organs at risk contouring training for newly qualified radiotherapists: quantitative comparison with conventional one-to-one coaching approach

Yuen¹,

Li²,

Mak³

et al. 2021

BMC Med Educ

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Background Due to the role expansion of radiotherapists in dosimetric aspect, radiotherapists have taken up organs at risk (OARs) contouring work in many clinical settings. However, training of newly qualified radiotherapists in OARs contouring can be time consuming, it may also cause extra burden to experienced radiotherapists. As web-based open-source radiotherapy delineation software (WORDS) has become more readily available, it has provided a free and interactive alternative to conventional one-to-one coaching approach during OARs contouring training. The present study aims to evaluate the effectiveness of WORDS in training OARs contouring skills of newly qualified radiotherapists, compared to those trained by conventional one-to-one coaching approach. Methods Nine newly qualified radiotherapists (licensed in 2017 – 2018) were enrolled to the conventional one-to-one coaching group (control group), while 11 newly qualified radiotherapists (licensed in 2019 – 2021) were assigned to WORDS training group (measured group). Ten OARs were selected to be contoured in this 3-phases quantitative study. Participants were required to undergo phase 1 OARs contouring in the beginning of the training session. Afterwards, conventional one-to-one training or WORDS training session was provided to participants according to their assigned group. Then the participants did phase 2 and 3 OARs contouring which were separated 1 week apart. Phase 1 – 3 OARs contouring aimed to demonstrate participants’ pre-training OARs contouring ability, post-training OARs contouring ability and knowledge retention after one-week interval respectively using either training approach. To prevent bias, the computed tomography dataset for OARs contouring in each phase were different. Variations in the contouring scores for the selected OARs were evaluated between 3 phases using Kruskal-Wallis tests with Dunn tests for pairwise comparisons. Variations in the contouring scores between control and measured group in phase 1 – 3 contouring were analyzed using Wilcoxon signed-rank test. A p-value < 0.05 was considered to be statistically significant. Results In both control group and measured group, significant improvement (p < 0.05) in phase 2 and 3 contouring scores have been observed comparing to phase 1 contouring scores. In comparison of contouring scores between control group and measured group, no significant differences (p > 0.05) were observed in all OARs between both groups. Conclusions The results in this study have demonstrated that the outcome of OARs contouring training using WORDS is comparable to the conventional training approach. In addition, WORDS can offer flexibility to newly qualified radiotherapists to practice OARs contouring at will, as well as reduce staff training burden of experienced radiotherapists.

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Dosimetry for New Radiation Therapy Approaches Using High Energy Electron Accelerators

Cited by 10 publications

References 53 publications

Ultra‐high dose rate dosimetry: Challenges and opportunities for FLASH radiation therapy

Ultra‐high dose rate dosimetry: Challenges and opportunities for FLASH radiation therapy

Design, realization, and characterization of a novel diamond detector prototype for FLASH radiotherapy dosimetry

Implementation of web-based open-source radiotherapy delineation software (WORDS) in organs at risk contouring training for newly qualified radiotherapists: quantitative comparison with conventional one-to-one coaching approach

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