FLASH Radiotherapy With Electrons: Issues Related to the Production, Monitoring, and Dosimetric Characterization of the Beam

Martino, Fabio; Barca, Patrizio; Barone, Salvatore; Bortoli, Eleonora; Borgheresi, Rita; Stefano, Silvia De; Francesco, Massimo Di; Faillace, L.; Giuliano, Lucia; Grasso, Luigi; Linsalata, S.; Marfisi, Daniela; Migliorati, M.; Pacitti, M.; Palumbo, L.; Felici, G.

doi:10.3389/fphy.2020.570697

Cited by 55 publications

(57 citation statements)

References 32 publications

(62 reference statements)

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“…[3][4][5][6][7][8][9][10][11][12][13][14] In addition, recent preclinical studies increasingly support the clinical translation of FLASH radiotherapy (RT). [15][16][17][18] In most studies on the FLASH effect, dedicated electron accelerators [19][20][21][22][23] or modified clinical linear accelerators [24][25][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.…”

Section: Introductionmentioning

confidence: 99%

“…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%

“…The PTW 60019 diamond detector, developed by some of the authors at Rome Tor Vergata University in cooperation with PTW‐Freiburg, is well assessed in conventional RT dosimetry, due to its near tissue equivalence, radiation hardness, and good spatial resolution 40–45 . Nevertheless, Di Martino et al 22 . reported a signal nonlinearity from such detector at DPP values greater than about 0.1 Gy/pulse as well.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Marinelli

Felici²,

Galante³

et al. 2022

Medical Physics

Self Cite

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“…Working with pulsed X-ray beam, another way of considering the dose rate sensitivity is to consider the dose rate normalized to the pulse duration, also called absolute dose rate [57], as found in FLASH therapy context, for example. With the highest dose rate reached at ORIATRON facility using an X-ray beam with a production rate of 195 Hz, a pulse duration of 4.8 µs and at 1 m from the electron conversion target, the dose rate reported was 130 mGy(SiO 2 )/s.…”

Section: Correlation Between Rie Plateau and Dose Ratesmentioning

confidence: 99%

Optical Fiber-Based Monitoring of X-ray Pulse Series from a Linear Accelerator

et al. 2021

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We investigated in this work the radioluminescence properties of a Ce-doped multimode silica-based optical fiber (core diameter of 50 µm) manufactured by the sol–gel technique when exposed to the high-energy X-rays (~600 keV) of the ORIATRON facility of CEA. We demonstrated its potential to monitor in real-time the beam characteristics of this facility that can either operate in a pulsed regime (pulse duration of 4.8 µs, maximum repetition rate of 250 Hz) or in a quasi-continuous mode. The radiation-induced emission (radioluminescence and a minor Cerenkov contribution) linearly grew with the dose rate in the 15–130 mGy(SiO2)/s range, and the afterglow measured after each pulse was sufficiently limited to allow a clear measurement of pulse trains. A sensor with ~11 cm of sensitive Ce-doped fiber spliced to rad-hard fluorine-doped optical fiber, for the emitted light transport to the photomultiplier tube, exhibited interesting beam monitoring performance, even if the Cerenkov emission in the transport fiber was also considered (~5% of the signal). The beam monitoring potential of this class of optical fiber was demonstrated for such facilities and the possibilities of extending the dose rate range are discussed based on possible architecture choices such as fiber type, length or size.

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“…While semiconductors showed uncorrectable saturation for UHDR dose rates. 10 Active work is currently ongoing to identify suitable online dosimeters for UHDR dosimetry. For a clinical dosimeter to be implemented in UHDR-RT for in-depth treatment delivery monitoring, it is desirable to use advanced dosimetry techniques that are able to also provide real-time (in vivo) readouts per linac pulse beyond superficial depths for internal dose monitoring and beam localization.…”

Section: Introductionmentioning

confidence: 99%

A simulation study of ionizing radiation acoustic imaging (iRAI) as a real‐time dosimetric technique for ultra‐high dose rate radiotherapy (UHDR‐RT)

et al. 2021

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Electron-based ultra-high dose rate radiation therapy (UHDR-RT), also known as Flash-RT, has shown the ability to improve the therapeutic index in comparison to conventional radiotherapy (CONV-RT) through increased sparing of normal tissue. However, the extremely high dose rates in UHDR-RT have raised the need for accurate real-time dosimetry tools. This work aims to demonstrate the potential of the emerging technology of Ionized Radiation Acoustic Imaging (iRAI) through simulation studies and investigate its characteristics as a promising relative in vivo dosimetric tool for UHDR-RT. Methods: The detection of induced acoustic waves following a single UHDR pulse of a modified 6 MeV 21EX Varian Clinac in a uniform porcine gelatin phantom that is brain-tissue equivalent was simulated for an ideal ultrasound transducer. The full 3D dose distributions in the phantom for a 1 × 1 cm 2 field were simulated using EGSnrc (BEAMnrc∖DOSXYZnrc) Monte Carlo (MC) codes. The relative dosimetry simulations were verified with dose experimental measurements using Gafchromic films. The spatial dose distribution was converted into an initial pressure source spatial distribution using the medium-dependent dose-pressure relation. The MATLAB-based toolbox k-Wave was then used to model the propagation of acoustic waves through the phantom and perform time-reversal (TR)-based imaging reconstruction. The effect of the various linear accelerator (linac) operating parameters, including linac pulse duration and pulse repetition rate (frequency), were investigated as well. Results:The MC dose simulation results agreed with the film measurement results, specifically at the central beam region up to 80% dose within approximately 5% relative error for the central profile region and a local relative error of <6% for percentage dose depth. IRAI-based FWHM of the radiation beam was within approximately 3 mm relative to the MC-simulated beam FWHM at the beam entrance. The real-time pressure signal change agreed with the dose changes proving the capability of the iRAI for predicting the beam position. IRAI was tested through 3D simulations of its response to be based on the temporal changes in the linac operating parameters on a dose per pulse basis as expected theoretically from the pressure-dose proportionality.The pressure signal amplitude obtained through 2D simulations was proportional to the dose per pulse. The instantaneous pressure signal amplitude decreases as the linac pulse duration increases, as predicted from the pressure wave generation

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FLASH Radiotherapy With Electrons: Issues Related to the Production, Monitoring, and Dosimetric Characterization of the Beam

Cited by 55 publications

References 32 publications

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

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

Optical Fiber-Based Monitoring of X-ray Pulse Series from a Linear Accelerator

A simulation study of ionizing radiation acoustic imaging (iRAI) as a real‐time dosimetric technique for ultra‐high dose rate radiotherapy (UHDR‐RT)

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