Al<sub>2</sub>O<sub>3</sub>:C optically stimulated luminescence dosimeters (OSLDs) for ultra-high dose rate proton dosimetry

Christensen, Jeppe Brage; Togno, Michele; Nesteruk, Konrad Pawel; Psoroulas, S.; Meer, D.; Weber, Damien Charles; Lomax, Tony; Yukihara, E.G.; Safai, Sairos

doi:10.1088/1361-6560/abe554

“…3 does not necessarily exclude dose-linearity over a wider dose range. Previous studies have demonstrated OSL response to be dose-rate independent in :C 32 , 33 , but any dose-rate dependence in LYSO:Ce is subject to further investigation.…”

Section: Discussionmentioning

confidence: 93%

Optically stimulated luminescence in state-of-the-art LYSO:Ce scintillators enables high spatial resolution 3D dose imaging

Jensen

¹

,

Nyemann

²

,

Muren

³

et al. 2022

Sci Rep

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In this contribution, we study the optically stimulated luminescence (OSL) exhibited by commercial $$\hbox {Lu}_{(2-x)}\hbox {Y}_x\hbox {SiO}_5$$ Lu ( 2 - x ) Y x SiO 5 :Ce crystals. This photon emission mechanism, complementary to scintillation, can trap a fraction of radiation energy deposited in the material and provides sufficient signal to develop a novel post-irradiation 3D dose readout. We characterize the OSL emission through spectrally and temporally resolved measurements and monitor the dose linearity response over a broad range. The measurements show that the $$\hbox {Ce}^{3+}$$ Ce 3 + centers responsible for scintillation also function as recombination centers for the OSL mechanism. The capture to OSL-active traps competes with scintillation originating from the direct non-radiative energy transfer to the luminescent centers. An OSL response on the order of 100 ph/MeV is estimated. We demonstrate the imaging capabilities provided by such an OSL photon yield using a proof-of-concept optical readout method. A 0.1 $$\hbox {mm}^3$$ mm 3 spatial resolution for doses as low as 0.5 Gy is projected using a cubic crystal to image volumetric dose profiles. While OSL degrades the intrinsic scintillating performance by reducing the number of scintillation photons emitted following the passage of ionizing radiation, it can encode highly resolved spatial information of the interaction point of the particle. This feature combines ionizing radiation spectroscopy and 3D reusable dose imaging in a single material.

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“…The saturating exponential in Eq. ( 1 a) was fitted to the OSLD response as a function of the dose measured with the ionization chamber in line with previous works 13 .…”

Section: Methodsmentioning

confidence: 97%

“…The optically stimulated luminescence (OSL) of allows the estimation of both dose and LET, but with the advantage of only requiring a single detector, and has been demonstrated 13 to be dose-rate independent in proton beams up to .…”

Section: Introductionmentioning

confidence: 99%

Improved simultaneous LET and dose measurements in proton therapy

Christensen

¹

,

Togno

²

,

Bossin

³

et al. 2022

Sci Rep

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The objective of this study was to improve the precision of linear energy transfer (LET) measurements using $$\text {Al}_2\text {O}_3\text {:C}$$ Al 2 O 3 :C optically stimulated luminescence detectors (OSLDs) in proton beams, and, with that, improve OSL dosimetry by correcting the readout for the LET-dependent ionization quenching. The OSLDs were irradiated in spot-scanning proton beams at different doses for fluence-averaged LET values in the (0.4–6.5) $$\hbox {keV}\, \upmu \hbox {m}^{-1}$$ keV μ m - 1 range (in water). A commercial automated OSL reader with a built-in beta source was used for the readouts, which enabled a reference irradiation and readout of each OSLD to establish individual corrections. Pulsed OSL was used to separately measure the blue (F-center) and UV ($$F^+$$ F + -center) emission bands of $$\text {Al}_2\text {O}_3\text {:C}$$ Al 2 O 3 :C and the ratio between them (UV/blue signal) was used for the LET measurements. The average deviation between the simulated and measured LET values along the central beam axis amounts to 5.5% if both the dose and LET are varied, but the average deviation is reduced to 3.5% if the OSLDs are irradiated with the same doses. With the measurement procedure and automated equipment used here, the variation in the signals used for LET estimates and quenching-corrections is reduced from 0.9 to 0.6%. The quenching-corrected OSLD doses are in agreement with ionization chamber measurements within the uncertainties. The automated OSLD corrections are demonstrated to improve the LET estimates and the ionization quenching-corrections in proton dosimetry for a clinically relevant energy range up to 230 MeV. It is also for the first time demonstrated how the LET can be estimated for different doses.

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“…Even for a FLASH dose rate of 1000 Gy/s, the dose per pulse is of the order of 10 μGy. Also in terms of ion recombination, the dose delivery can be considered continuous 19 …”

Section: Methodsmentioning

confidence: 99%

Commissioning of a clinical pencil beam scanning proton therapy unit for ultra‐high dose rates (FLASH)

Nesteruk

¹

,

Togno

²

,

Großmann

³

et al. 2021

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The purpose of this work was to provide a flexible platform for FLASH research with protons by adapting a former clinical pencil beam scanning gantry to irradiations with ultra-high dose rates. Methods: PSI Gantry 1 treated patients until December 2018. We optimized the beamline parameters to transport the 250 MeV beam extracted from the PSI COMET accelerator to the treatment room, maximizing the transmission of beam intensity to the sample. We characterized a dose monitor on the gantry to ensure good control of the dose, delivered in spot-scanning mode. We characterized the beam for different dose rates and field sizes for transmission irradiations. We explored scanning possibilities in order to enable conformal irradiations or transmission irradiations of large targets (with transverse scanning). Results: We achieved a transmission of 86% from the cyclotron to the treatment room. We reached a peak dose rate of 9000 Gy/s at 3 mm water equivalent depth, along the central axis of a single pencil beam. Field sizes of up to 5 × 5 mm 2 were achieved for single-spot FLASH irradiations. Fast transverse scanning allowed to cover a field of 16 × 1.2 cm 2 . With the use of a nozzle-mounted range shifter, we are able to span depths in water ranging from 19.6 to 37.9 cm. Various dose levels were delivered with precision within less than 1%. Conclusions: We have realized a proton FLASH irradiation setup able to investigate continuously a wide dose rate spectrum, from 1 to 9000 Gy/s in single-spot irradiation as well as in the pencil beam scanning mode. As such, we have developed a versatile test bench for FLASH research.

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Al₂O₃:C optically stimulated luminescence dosimeters (OSLDs) for ultra-high dose rate proton dosimetry

Cited by 44 publications

References 36 publications

Optically stimulated luminescence in state-of-the-art LYSO:Ce scintillators enables high spatial resolution 3D dose imaging

Optically stimulated luminescence in state-of-the-art LYSO:Ce scintillators enables high spatial resolution 3D dose imaging

Improved simultaneous LET and dose measurements in proton therapy

Commissioning of a clinical pencil beam scanning proton therapy unit for ultra‐high dose rates (FLASH)

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Al2O3:C optically stimulated luminescence dosimeters (OSLDs) for ultra-high dose rate proton dosimetry

Cited by 44 publications

References 36 publications

Optically stimulated luminescence in state-of-the-art LYSO:Ce scintillators enables high spatial resolution 3D dose imaging

Optically stimulated luminescence in state-of-the-art LYSO:Ce scintillators enables high spatial resolution 3D dose imaging

Improved simultaneous LET and dose measurements in proton therapy

Commissioning of a clinical pencil beam scanning proton therapy unit for ultra‐high dose rates (FLASH)

Contact Info

Product

Resources

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Al₂O₃:C optically stimulated luminescence dosimeters (OSLDs) for ultra-high dose rate proton dosimetry