Systematic evaluation of photodetector performance for plastic scintillation dosimetry

Boivin, Jonathan; Beddar, Sam; Guillemette, Maxime; Beaulieu, Luc

doi:10.1118/1.4931979

Cited by 19 publications

(24 citation statements)

References 54 publications

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“…In those conditions, precise measurements can be made by either short (about 2 s) or long (.30 s) exposure times. These conclusions are in agreement with Boivin et al 31 recommendations concerning the dose rate ranges of use for one-dimensional plastic scintillation detector with a PIN diode photodetector.…”

Section: Linearitysupporting

confidence: 81%

Characterization of a scintillating fibre detector for small animal imaging and irradiation dosimetry

Deroff

Frelin-Labalme

Ledoux

2017

BJR

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Objective: Small animal image-guided irradiators have recently been developed to mimic the delivery techniques of clinical radiotherapy. A dosemeter adapted to millimetric beams of medium-energy X-rays is then required. This work presents the characterization of a dosemeter prototype for this particular application. Methods: A scintillating optical fibre dosemeter (called DosiRat) has been implemented to perform real-time dose measurements with the dedicated small animal X-RAD® 225Cx (Precision X-Ray, Inc., North Branford, CT) irradiator. Its sensitivity, stem effect, stability, linearity and measurement precision were determined in large field conditions for three different beam qualities, consistent with small animal irradiation and imaging parameters. Results: DosiRat demonstrates good sensitivity and stability; excellent air kerma and air kerma rate linearity; and a good repeatability for air kerma rates .1 mGy s 21. The stem effect was found to be negligible. DosiRat showed limited precision for low air kerma rate measurements (,1 mGy s 21 ), typically for imaging protocols. A positive energy dependence was found that can be accounted for by calibrating the dosemeter at the needed beam qualities. Conclusion: The dosimetric performances of DosiRat are very promising. Extensive studies of DosiRat energy dependence are still required. Further developments will allow to reduce the dosemeter size to ensure millimetric beams dosimetry and perform small animal in vivo dosimetry. Advances in knowledge: Among existing point dosemeters, very few are dedicated to both medium-energy X-rays and millimetric beams. Our work demonstrated that scintillating fibre dosemeters are suitable and promising tools for real-time dose measurements in the small animal field of interest.

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Section: Linearitysupporting

confidence: 81%

Characterization of a scintillating fibre detector for small animal imaging and irradiation dosimetry

Deroff

Frelin-Labalme

Ledoux

2017

BJR

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“…When developing ISDs based on Eu-activated phosphors, the scintillation intensity should be maximized by optimizing the phosphor-glue ratio to limit the influence of stem signal contamination and to minimize the statistical uncertainty of time-resolved measurements. In addition to shortening the fiber-optic cable to about 2 m, choosing a more sensitive photodetector than the one we used could further minimize the statistical uncertainty (Boivin et al 2015). …”

Section: Discussionmentioning

confidence: 99%

Inorganic scintillation detectors based on Eu-activated phosphors for¹⁹²Ir brachytherapy

Kertzscher

Beddar

2017

Phys. Med. Biol.

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The availability of real-time treatment verification during high-dose-rate (HDR) brachytherapy is currently limited. Therefore, we studied the luminescence properties of the widely commercially available scintillators using the inorganic materials Eu-activated phosphors Y2O3:Eu, YVO4:Eu, Y2O2S:Eu, and Gd2O2S:Eu to determine whether they could be used to accurately and precisely verify HDR brachytherapy doses in real time. The suitability for HDR brachytherapy of inorganic scintillation detectors (ISDs) based on the 4 Eu-activated phosphors in powder form was determined based on experiments with a 192Ir HDR brachytherapy source. The scintillation intensities of the phosphors were 16 to 134 times greater than that of the commonly used organic plastic scintillator BCF-12. High signal intensities were achieved with an optimized packing density of the phosphor mixture and with a shortened fiber-optic cable. The influence of contaminating Cerenkov and fluorescence light induced in the fiber-optic cable (stem signal) was adequately suppressed by inserting between the fiber-optic cable and the photodetector a 25-nm band-pass filter centered at the emission peak. The spurious photoluminescence signal induced by the stem signal was suppressed by placing a long-pass filter between the scintillation detector volume and the fiber-optic cable. The time-dependent luminescence properties of the phosphors were quantified by measuring the non-constant scintillation during irradiation and the afterglow after the brachytherapy source had retracted. We demonstrated that a mixture of Y2O3:Eu and YVO4:Eu suppressed the time-dependence of the ISDs and that the time-dependence of Y2O2S:Eu and Gd2O2S:Eu introduced large measurement inaccuracies. We conclude that ISDs based on a mixture of Y2O3:Eu and YVO4:Eu are promising candidates for accurate and precise real-time verification technology for HDR BT that is cost effective and straightforward to manufacture. Widespread dissemination of this technology could lead to an improved understanding of error types and frequencies during BT and to improved patient safety during treatment.

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“…PMTs were chosen as the photodetectors because they have a high signal to noise ratio (SNR) and readout speed that overcomes many of the sensitivity issues of charge‐coupled device‐based systems. Generally, PMTs more accurately measure low light signals and have a faster response, making them more suitable for the demands of in vivo dosimetry applications . Henceforth, an assembly composed of a dichroic mirror, filter, and PMT will be referred to as a “channel.” From an optimization perspective, the signal produced in each channel was calculated, taking into account the measured scintillation spectrum and light yield, the manufacturer‐reported transmission and attenuation of the optical components, and the experimentally characterized PMT noise.…”

Section: Methodsmentioning

confidence: 99%

Optimization of a multipoint plastic scintillator dosimeter for high dose rate brachytherapy

et al. 2019

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Purpose This study is devoted to optimizing and characterizing the response of a multipoint plastic scintillator detector (mPSD) for application to in vivo dosimetry in high dose rate (HDR) brachytherapy. Methods An exhaustive analysis was carried out in order to obtain an optimized mPSD design that maximizes the scintillation light collection produced by the interaction of ionizing photons. More than 20 prototypes of mPSD were built and tested in order to determine the appropriate order of scintillators relative to the photodetector (distal, center, or proximal) as well as their length as a function of the scintillation light emitted. The available detecting elements are the BCF‐60, BCF‐12, and BCF‐10 scintillators (Saint Gobain Crystals, Hiram, OH, USA), separated from each other by segments of Eska GH‐4001 clear optical fibers (Mitsubishi Rayon Co., Ltd., Tokyo, Japan). The contribution of each scintillator to the total spectrum was determined by irradiations in the low energy range (<120 keV). For the best mPSD design, a numerical optimization was done in order to select the optical components [dichroic mirrors, filters, and photomultipliers tubes (PMTs)] that best match the light emission profile. Calculations were performed taking into account the measured scintillation spectrum and light yield, the manufacturer‐reported transmission and attenuation of the optical components, and the experimentally characterized PMT noise. The optimized dosimetric system was used for HDR brachytherapy measurements. The system was independently controlled from the 192Ir source via LabVIEW and read simultaneously using an NI‐DAQ board. Dose measurements as a function of distance from the source were carried out according to TG‐43U1 recommendations. The system performance was quantified in terms of signal to noise ratio (SNR) and signal to background ratio (SBR). Results For best overall light‐yield emission, it was determined that BCF‐60 should be placed at the distal position, BCF‐12 in the center, and BCF‐10 at the proximal position with respect to the photodetector. This configuration allowed for optimized light transmission through the collecting fiber and avoided inter‐scintillator excitation and self‐absorption effects. The optimal scintillator length found was of 3, 6, and 7 mm for BCF‐10, BCF‐ 12, and BCF‐60, respectively. The optimized luminescence system allowed for signal deconvolution using a multispectral approach, extracting the dose to each element while taking into account the Cerenkov stem effect. Differences between the mPSD measurements and TG‐43U1 remain below 5% in the range of 0.5 to 6.5 cm from the source. The dosimetric system can properly differentiate the scintillation signal from the background for a wide range of dose rate conditions; the SNR was found to be above 5 for dose rates above 22 mGy/s while the minimum SBR measured was 1.8 at 6 mGy/s. Conclusion Based on the spectral response at different conditions, an mPSD was constructed and optimized for HDR brachytherapy dosimetry. It is sensitive e...

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Systematic evaluation of photodetector performance for plastic scintillation dosimetry

Abstract: For dose rates higher than 3 mGy/s, the PIN diode is the most effective photodetector in terms of performance/cost ratio. For lower dose rates, such as those seen in interventional radiology or high-gradient radiotherapy, PMTs are the optimal choice.

Cited by 19 publications

References 54 publications

Characterization of a scintillating fibre detector for small animal imaging and irradiation dosimetry

Characterization of a scintillating fibre detector for small animal imaging and irradiation dosimetry

Inorganic scintillation detectors based on Eu-activated phosphors for¹⁹²Ir brachytherapy

Optimization of a multipoint plastic scintillator dosimeter for high dose rate brachytherapy

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Systematic evaluation of photodetector performance for plastic scintillation dosimetry

Abstract: For dose rates higher than 3 mGy/s, the PIN diode is the most effective photodetector in terms of performance/cost ratio. For lower dose rates, such as those seen in interventional radiology or high-gradient radiotherapy, PMTs are the optimal choice.

Cited by 19 publications

References 54 publications

Characterization of a scintillating fibre detector for small animal imaging and irradiation dosimetry

Characterization of a scintillating fibre detector for small animal imaging and irradiation dosimetry

Inorganic scintillation detectors based on Eu-activated phosphors for192Ir brachytherapy

Optimization of a multipoint plastic scintillator dosimeter for high dose rate brachytherapy

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Product

Resources

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Inorganic scintillation detectors based on Eu-activated phosphors for¹⁹²Ir brachytherapy