A method to correct for temperature dependence and measure simultaneously dose and temperature using a plastic scintillation detector

Therriault‐Proulx, François; Wootton, Landon; Beddar, Sam

doi:10.1088/0031-9155/60/20/7927

Cited by 17 publications

(17 citation statements)

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“…Furthermore, online self -correcting technology for temperature dependence of detector probes has been developed for a detector system using multipoint plastic scintillators. 39 Developing a similar self -correcting algorithm for ZnSe:O could be considered, as ZnSe:O displays a large temperature dependence. However, manual correction for the difference between calibration and patient temperatures is still feasible.…”

Section: Temperature Dependence Of the Znse:o Crystal's Responsementioning

confidence: 99%

A high‐Z inorganic scintillator–based detector for time‐resolved in vivo dosimetry during brachytherapy

et al. 2021

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Purpose High‐dose rate (HDR) and pulsed‐dose rate (PDR) brachytherapy would benefit from an independent treatment verification system to monitor treatment delivery and to detect errors in real time. This paper characterizes and provides an uncertainty budget for a detector based on a fiber‐coupled high‐Z inorganic scintillator capable of performing time‐resolved in vivo dosimetry during HDR and PDR brachytherapy. Method The detector was composed of a detector probe and an optical reader. The detector probe consisted of either a 0.5 × 0.4 × 0.4 mm3 (HDR) or a 1.0 × 0.4 × 0.4 mm3 (PDR) cuboid ZnSe:O crystal glued onto an optical‐fiber cable. The outer diameter of the detector probes was 1 mm, and fit inside standard brachytherapy catheters. The signal from the detector probe was read out at 20 Hz by a photodiode and a data acquisition device inside the optical reader. In order to construct an uncertainty budget for the detector, six characteristics were determined: (1) temperature dependence of the detector probe, (2) energy dependence as a function of the probe‐to‐source position in 2D (determined with 2 mm resolution using a robotic arm), (3) the signal‐to‐noise ratio (SNR), (4) short‐term stability over 8 h, and (5) long‐term stability of three optical readers and four probes used for in vivo monitoring in HDR and PDR treatments over 21 months (196 treatments and 189 detector calibrations, and (6) dose‐rate dependence. Results The total uncertainty of the detector at a 20 mm probe‐to‐source distance was < 5.1% and < 5.8% for the HDR and PDR versions, respectively. Regarding the above characteristics, (1) the sensitivity of the detector decreased by an average of 1.4%/°C for detector probe temperatures varying from 22 to 37°C; (2) the energy dependence of the detector was nonlinear and depended on both probe‐to‐source distance and the angle between the probe and the brachytherapy source; (3) the median SNRs were 187 and 34 at a 20 mm probe‐to‐source distance for the HDR and PDR versions, respectively (corresponding median source activities of 4.8 and 0.56 Ci, respectively); (4) the detector response varied by 0.6% in 11 identical irradiations over 8 h; (5) the sensitivity of the four detector probes decreased systematically by 0–1.2%/100 Gy of dose delivered to the probes, and random fluctuations of 4.8% in the sensitivity were observed for the three probes used in PDR and 1.9% for the probe used in HDR; and (6) the detector response was linear with dose rate. Conclusion ZnSe:O detectors can be used effectively for in vivo dosimetry and with high accuracy for HDR and PDR brachytherapy applications.

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Section: Temperature Dependence Of the Znse:o Crystal's Responsementioning

confidence: 99%

A high‐Z inorganic scintillator–based detector for time‐resolved in vivo dosimetry during brachytherapy

et al. 2021

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“…One such detector, the plastic scintillation detector (PSD), has several advantages that have been recently highlighted in the literature, a key one being their real-time response. [7][8][9][10][11][12][13][14][15][16][17] Although PSDs are affected by the stem effect and temperature variations, 12,13 several investigations have developed methods to correct both of these dependencies in the detector response. 7,9,14,15,[18][19][20][21] Most of the studies characterizing PSD response were conducted using an optical fiber connected to a single point of measurement as a sensitive volume.…”

Section: Introductionmentioning

confidence: 99%

“…A review by Tanderup et al highlighted the main aspects of various detectors that could be used as in vivo dosimeters in brachytherapy. One such detector, the plastic scintillation detector (PSD), has several advantages that have been recently highlighted in the literature, a key one being their real‐time response . Although PSDs are affected by the stem effect and temperature variations, several investigations have developed methods to correct both of these dependencies in the detector response …”

Section: Introductionmentioning

confidence: 99%

Dosimetric performance of a multipoint plastic scintillator dosimeter as a tool for real‐time source tracking in high dose rate Ir brachytherapy

et al. 2020

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This study aims to present the performance of a multipoint plastic scintillation detector (mPSD) as a tool for real-time dose measurements (covering three orders of magnitude in dose rate), source-position triangulation, and dwell time assessment in high dose rate (HDR) brachytherapy. Methods: A previously characterized and optimized three-point sensor system was used for HDR brachytherapy measurements. The detector was composed of three scintillators: BCF60, BCF12, and BCF10. Scintillation light was transmitted through a single 1-mm-diameter clear optical fiber and read by a compact assembly of photomultiplier tubes (PMTs). Each component was numerically optimized to allow for signal deconvolution using a multispectral approach, taking care of the Cerenkov stem effect as well as extracting the dose from each scintillator. The PMTs were read simultaneously using a data acquisition board at a rate of 100 KHz and controlled with in-house software based on Python. An 192 Ir source (Flexitron, Elekta-Brachy) was remotely controlled and sent to various positions in a in-house PMMA holder, ensuring 0.1 mm positional accuracy. Dose measurements covering a range of 10 cm of source movement were carried out according to TG-43 U1 recommendations. Water measurements were performed in order to: (a) characterize the system's response in terms of angular dependence; (b) obtain the relative contribution of positioning and measurement uncertainties to the total system uncertainty; (c) assess the system's temporal resolution; and (d) track the source position in real time. The triangulation principle was applied to report the source position in three-dimensional space. Results: As expected, the positioning uncertainty dominated close to the source, whereas the measurement uncertainty dominated at larger distances. A maximum measurement uncertainty of 17 % was observed for the BCF60 scintillator at 10 cm from the source. Based on the uncertainty chain, the best compromises between positioning and measurement uncertainties were reached at 17.2, 17.4, and 17.5 mm for the BCF10, BCF12, and BCF60 scintillators, respectively, which also corresponded to the recommended optimal distances to the source for calibration purposes. The detector further exhibited no angular dependence. All dose values were found to be within 2% of the dose value at 90. In the experiments performed for source-position determination, the system provided an average location with a standard deviation under 1.7 mm. The maximum observed differences between measured and expected values were 1.82 and 1.8 mm in the x-and z-directions, respectively. Deviations between the mPSD measurements and expected TG-43 values were below 5% in all the explored measurement conditions. With regard to dwell time measurement accuracy, the maximum deviation observed at all distances was 0.56 AE 0.25 s, with a weighted average of the three scintillators below 0.33 AE 0.37 s at all distances covered in this study. Conclusions: Real-time HDR brachytherapy measurements were performed with a...

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“…Plastic scintillator detectors (PSDs) show promise for obtaining accurate real‐time radiotherapy dose measurements. Previous studies have demonstrated that PSDs can accurately measure dose in external beam radiotherapy and that they have high spatial resolution, linearity with dose, energy independence in the megavolt energy range, and water equivalence . In addition, some authors have found PSDs to be feasible for use in brachytherapy applications .…”

Section: Introductionmentioning

confidence: 99%

“…Previous studies have demonstrated that PSDs can accurately measure dose in external beam radiotherapy and that they have high spatial resolution, linearity with dose, energy independence in the megavolt energy range, and water equivalence. [3][4][5][6][7][8][9][10][11][12] In addition, some authors have found PSDs to be feasible for use in brachytherapy applications. [13][14][15][16][17] Despite the aforementioned advantages, PSD response is affected by the stem effect and temperature dependence.…”

Section: Introductionmentioning

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...

show abstract

A method to correct for temperature dependence and measure simultaneously dose and temperature using a plastic scintillation detector

Cited by 17 publications

References 43 publications

A high‐Z inorganic scintillator–based detector for time‐resolved in vivo dosimetry during brachytherapy

A high‐Z inorganic scintillator–based detector for time‐resolved in vivo dosimetry during brachytherapy

Dosimetric performance of a multipoint plastic scintillator dosimeter as a tool for real‐time source tracking in high dose rate Ir brachytherapy

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

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