Performance characterization of a 3D liquid scintillation detector for discrete spot scanning proton beam systems

Darne, Chinmay; Alsanea, Fahed; Robertson, Daniel; Beddar, Sam

doi:10.1088/1361-6560/aa780b

Cited by 27 publications

(27 citation statements)

References 24 publications

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“…Reusability is the foundation of accurate, robust, and practical measurements in clinical dosimetry; however, such a device is currently not commercially available for proton dosimetry. [14][15][16][17][18] Among research directions, Darne et al are investigating the feasibility of using a 3D liquid scintillator surrounded by mutually orthogonal cameras as a promising solution. 17 Alternative pseudo-3D approaches utilize stacked two-dimensional (2D) dosimeters, such as radiographic and radiochromic films or ion chamber (IC) arrays.…”

Section: Introductionmentioning

confidence: 99%

“…[14][15][16][17][18] Among research directions, Darne et al are investigating the feasibility of using a 3D liquid scintillator surrounded by mutually orthogonal cameras as a promising solution. 17 Alternative pseudo-3D approaches utilize stacked two-dimensional (2D) dosimeters, such as radiographic and radiochromic films or ion chamber (IC) arrays. Film enables simultaneous high-resolution measurements at multiple depths with a single beam delivery; however, film is not reusable and so quantitative dosimetry is challenging.…”

Section: Introductionmentioning

confidence: 99%

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Quantitative proton radiation therapy dosimetry using the storage phosphor europium‐doped potassium chloride

et al. 2020

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Purpose: To (a) characterize the fundamental optical and dosimetric properties of the storage phosphor europium-doped potassium chloride for quantitative proton dosimetry, and (b) investigate if its dose radiation response can be described by an analytic radiation transport model. Methods: Cylindrical KCl:Eu 2+ dosimeters with dimensions of 6 mm diameter and 1 mm thickness were fabricated in-house. The dosimeters were irradiated using both a Mevion S250 passive scattering proton therapy system and a Varian Clinac iX linear accelerator. Photostimulated luminescence (PSL) emission spectra, excitation spectra, and luminescence lifetimes were measured for both proton and photon irradiations. Dosimetric properties including radiation hardness, dose linearity, signal stabilization, dose rate sensitivity, and energy dependence were studied using a laboratory optical reader after irradiations. The dosimeters were modeled using physical quantities including mass stopping powers in the storage phosphor and water for a given proton beam, and mass energy absorption coefficients and massing stopping powers in detector and water for a given photon beam. Results: KCl:Eu 2+ exhibited optical emission and stimulation peaks at 421 and 560 nm, respectively, for both proton and photon irradiations, enabling postirradiation readouts using a visible light source while detecting the PSL using a photomultiplier tube. KCl:Eu 2+ showed a linear response from 0 to 8 Gy absorbed dose-to-water, a large dynamic range up to 60 Gy, dose-rate independence measured from 83 to 500 MU/min, and a PSL lifetime of <5 ms that is sufficiently short for supporting rapid scanning in a two-dimensional geometry. KCl:Eu 2+ was highly reusable with only a slight signal decrease of~3% at accumulated doses over 100 Gy, which could be managed by a periodic recalibration. The detected PSL signal strength of the dosimeter in the proton field had been calculated accurately to a maximum discrepancy of 2% using known physical quantities along with its prior signal strength as measured in a photon field at the same dose-to-water. This discrepancy might be attributed to an under-response due to linear energy transfer (LET) effect. However, comparisons of depth-dose measurements in a spread-out Bragg peak (SOBP) field with a parallel-plate ionization chamber showed no clear evidence of LET effects. Furthermore, range measurements agreed with ionization chamber measurements to within 1 mm. Conclusions: KCl:Eu 2+ showed linear response over a large dynamic range for proton irradiations and reliably reproduced SOBP measurements as measured by ionization chambers. Its relatively low atomic number of 18 and near LET independence make it suited for quantitative proton dosimetry. In addition, its high radiation hardness means that it can be reused numerous times. Any potential measurement artifacts encountered in complex irradiation conditions should be able to be corrected for using known physical quantities.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Quantitative proton radiation therapy dosimetry using the storage phosphor europium‐doped potassium chloride

et al. 2020

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“…Additionally, they noted that the gas scintillator was able to measure up to a dose rate of 350 Gy/s, whereas an ionization chamber started exhibiting ion-recombination effects at much smaller dose-rates. In another study, Darne et al [98,99] used three CMOS cameras to image proton pencil beam scanning inside a phantom filled with a liquid scintillator. The authors were able to image at 91 frames per second with sub millimeter resolution.…”

Section: Scintillatorsmentioning

confidence: 99%

Dosimetry for FLASH Radiotherapy: A Review of Tools and the Role of Radioluminescence and Cherenkov Emission

et al. 2020

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While spatial dose conformity delivered to a target volume has been pushed to its practical limits with advanced treatment planning and delivery, investigations in novel temporal dose delivery are unfolding new mechanisms. Recent advances in ultra-high dose radiotherapy, abbreviated as FLASH, indicate the potential for reduction in healthy tissue damage while preserving tumor control. FLASH therapy relies on very high dose rate of > 40Gy/s with sub-second temporal beam modulation, taking a seemingly opposite direction from the conventional paradigm of fractionated therapy. FLASH brings unique challenges to dosimetry, beam control, and verification, as well as complexity of radiobiological effective dose through altered tissue response. In this review, we compare the dosimetric methods capable of operating under high dose rate environments. Due to excellent dose-rate independence, superior spatial (∼ <1 mm) and temporal (∼ns) resolution achievable with Cherenkov and scintillation-based detectors, we show that luminescent detectors have a key role to play in the development of FLASH, as the field rapidly progresses toward clinical adaptation. Additionally, we show that the unique ability of certain luminescence-based methods to provide tumor oxygenation maps in real-time with submillimeter resolution can elucidate the radiobiological mechanisms behind the FLASH effect. In particular, such techniques will be crucial for understanding the role of oxygen in mediating the FLASH effect.

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“…It relies on the accurate matching of the predicted and the measured LET distributions and is therefore prone to small shifts between the simulated and the measured Bragg curve . Range information has also been extracted from the scintillation light output without applying any correction for quenching at all …”

Section: Introductionmentioning

confidence: 99%

A mathematical expression for depth‐light curves of therapeutic proton beams in a quenching scintillator

Kelleter

Jolly

2020

Medical Physics

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Purpose: Recently, there has been increasing interest in the development of scintillator-based detectors for the measurement of depth-dose curves of therapeutic proton beams (Beaulieu and Beddar [2016], Phys Med Biol., 61:R305-R343). These detectors allow the measurement of single beam parameters such as the proton range or the reconstruction of the full three-dimensional dose distribution. Thus, scintillation detectors could play an important role in beam quality assurance, online beam monitoring, and proton imaging. However, the light output of the scintillator as a function of dose deposition is subject to quenching effects due to the high-specific energy loss of incident protons, particularly in the Bragg peak. The aim of this work is to develop a model that describes the percent depth-light curve in a quenching scintillator and allow the extraction of information about the beam range and the strength of the quenching. Methods: A mathematical expression of a depth-light curve, derived from a combination of Birks' law (Birks [1951], Proc Phys Soc A., 64:874) and Bortfeld's Bragg curve (Bortfeld [1997], Med Phys., 24:2024-2033) that is termed a "quenched Bragg" curve, is presented. The model is validated against simulation and measurement. Results: A fit of the quenched Bragg model to simulated depth-light curves in a polystyrene-based scintillator shows good agreement between the two, with a maximum deviation of 2.5% at the Bragg peak. The differences are larger behind the Bragg peak and in the dose build-up region. In the same simulation, the difference between the reconstructed range and the reference proton range is found to be always smaller than 0.16 mm. The comparison with measured data shows that the fitted beam range agrees with the reference range within their respective uncertainties. Conclusions: The quenched Bragg model is, therefore, an accurate tool for the range measurement from quenched depth-dose curves. Moreover, it allows the reconstruction of the beam energy spread, the particle fluence, and the magnitude of the quenching effect from a measured depth-light curve.

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Performance characterization of a 3D liquid scintillation detector for discrete spot scanning proton beam systems

Cited by 27 publications

References 24 publications

Quantitative proton radiation therapy dosimetry using the storage phosphor europium‐doped potassium chloride

Quantitative proton radiation therapy dosimetry using the storage phosphor europium‐doped potassium chloride

Dosimetry for FLASH Radiotherapy: A Review of Tools and the Role of Radioluminescence and Cherenkov Emission

A mathematical expression for depth‐light curves of therapeutic proton beams in a quenching scintillator

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