Initial Evaluation of the Performance of Novel Inorganic Scintillating Detectors for Small Animal Irradiation Dosimetry

Byrne, Kevin; Alharbi, Majed; Esplen, Nolan; Woulfe, Peter; O'Keeffe, Sinéad; Bazalova‐Carter, Magdalena; Foley, Mark

doi:10.1109/jsen.2020.2964989

Cited by 13 publications

(5 citation statements)

References 25 publications

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“…Cerenkov radiation seems to have less prominence in the response of inorganic scintillators due to their higher light yield [26]. Despite the increased popularity of scintillator detectors for dosimetry among different energy ranges, including those of IGSARTP [28], characterization of the energy dependence in the medium-energy X-ray range has been rarely reported in the literature. The small size of the detectors makes them attractive for measurements in the typically small fields delivered by small animal irradiation platforms.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Inorganic Scintillator Detectors for Dosimetry in Image-Guided Small Animal Radiotherapy Platforms

Patallo

Subiel

Carter

et al. 2023

Cancers

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The purpose of the study was to characterize a detection system based on inorganic scintillators and determine its suitability for dosimetry in preclinical radiation research. Dose rate, linearity, and repeatability of the response (among others) were assessed for medium-energy X-ray beam qualities. The response’s variation with temperature and beam angle incidence was also evaluated. Absorbed dose quality-dependent calibration coefficients, based on a cross-calibration against air kerma secondary standard ionization chambers, were determined. Relative output factors (ROF) for small, collimated fields (≤10 mm × 10 mm) were measured and compared with Gafchromic film and to a CMOS imaging sensor. Independently of the beam quality, the scintillator signal repeatability was adequate and linear with dose. Compared with EBT3 films and CMOS, ROF was within 5% (except for smaller circular fields). We demonstrated that when the detector is cross-calibrated in the user’s beam, it is a useful tool for dosimetry in medium-energy X-rays with small fields delivered by Image-Guided Small Animal Radiotherapy Platforms. It supports the development of procedures for independent “live” dose verification of complex preclinical radiotherapy plans with the possibility to insert the detectors in phantoms.

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Section: Introductionmentioning

confidence: 99%

Characterization of Inorganic Scintillator Detectors for Dosimetry in Image-Guided Small Animal Radiotherapy Platforms

Patallo

Subiel

Carter

et al. 2023

Cancers

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“…Fiber-coupled luminescence detectors such as scintillators offer real-time measurements and have been used for dosimetry for external proton 12,13 and photon beams 14,15 as well as in brachytherapy. 16,17 Another candidate for dose rate QA in PBS proton FLASH delivery foresees the use of machine log files.…”

Section: Introductionmentioning

confidence: 99%

“…Luminescence detectors have been suggested as good candidates for dosimetry of FLASH radiotherapy 11 . Fiber‐coupled luminescence detectors such as scintillators offer real‐time measurements and have been used for dosimetry for external proton 12,13 and photon beams 14,15 as well as in brachytherapy 16,17 . Another candidate for dose rate QA in PBS proton FLASH delivery foresees the use of machine log files.…”

Section: Introductionmentioning

confidence: 99%

Time structure of pencil beam scanning proton FLASH beams measured with scintillator detectors and compared with log files

et al. 2022

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Purpose Key factors in FLASH treatments are the ultra‐high dose rate (UHDR) and the time structure of the beam delivery. Measurement of the time structure in pencil beam scanning (PBS) proton FLASH treatments is challenging for many types of detectors since high temporal resolution is needed. In this study, a fast scintillator detector system was developed and used to measure the individual spot durations as well as the time when the beam moves between two positions (transition duration) during PBS proton FLASH and UHDR treatments. The spot durations were compared with machine log‐file recordings. Methods A detector system based on inorganic scintillating crystals was developed. The system consisted of four detector probes made of a sub‐millimeter ZnSe:O crystal that was coupled via an optical fiber to an optical reader with 50 kHz sampling rate. The detector system was used in two experiments, both performed with a PBS proton beam with 250 MeV beam energy and 215 nA requested nozzle beam current. The sampling rate enabled multiple measurements during each spot delivery and during the beam transition between spots. First, the detector was tested in a phantom experiment, where a total of 305 scan sequences were delivered to the four detectors. The number of spots delivered without beam interruption in a single scan sequence ranged from one to 35. The spot duration and transition duration were measured for each individual spot. Secondly, the detector system was used in vivo in preclinical experiments with FLASH irradiation of mouse legs placed in the entrance plateau of the beam. A single detector was placed 1 cm downstream of the irradiated mouse leg. The mouse dose ranged from 30.5 to 44.2 Gy and the field consisted of 35 spots. The spot durations as well as the mean dose rate (field dose divided by the measured field duration) for each mouse were determined using the detector and then compared with the corresponding log files. Results The phantom experiment showed that the logged total duration of an uninterrupted spot sequence was consistently shorter than the measured duration with a difference of −0.252 ms (95% confidence interval: [‐0.255, −0.249 ms]). This corresponded to 0.05%–0.07% of the spot sequence duration in the mice experiments. For individual spots, the mean ± 1SD difference between logged and measured spot duration was −0.39 ± 0.05 ms for the first spot in a sequence, 0.13 ± 0.04 ms for the last spot in a sequence, and −0.0017 ± 0.09 ms for the intermediate spots in a sequence. The measured spot transition durations were 0.20 ± 0.04 ms (5.1 mm horizontal steps) and 0.50 ± 0.04 ms (5.0 mm vertical steps). For the mouse experiments, the mean dose rate calculated from the measured field duration was 84.1–92.5 Gy/s. It agreed with log files with a root mean square difference of 0.02 Gy/s. Conclusions Fiber‐coupled scintillator detectors were designed with sufficient temporal resolution to measure the spot and transition duration during PBS proton UHDR deliveries. Their small volume makes the...

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“…More recently, several novel ISDs were fabricated for in vivo optical fiber dosimetry of small animal irradiators 14 . An initial evaluation of some key dosimetry characteristics was carried out for the 40 and 80 kVp imaging beams and 220 kVp therapy beam of the Small Animal Research Platform (SARRP) at the University of Victoria, BC, Canada.…”

Section: Introductionmentioning

confidence: 99%

“…Schematic of the gadox-based detector14 (left) and a 3-D representation of the virtual sensing tip model created in DOSXYZnrc (right).…”

mentioning

confidence: 99%

Novel inorganic scintillating detectors and their applications in small animal irradiators: measurements and Monte Carlo simulations

Byrne

Alharbi

O'Keeffe

et al. 2020

Optical Sensing and Detection VI

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In the field of radiation therapy, optical fiber dosimeters (OFD) offer several advantages over conventional dosimeters for real-time dosimetry. Their sensing tips can be small in size affording them the potential for high spatial resolution capabilities. In previous work, a novel inorganic scintillating detector (ISD) based on Gadolinium Oxysulfide (gadox) was fabricated for in vivo optical fiber dosimetry of conformal small animal irradiators. The performance of this detector was evaluated for 40 and 80 kVp imaging beams and the 220 kVp therapy beam of the Small Animal Research Platform (SARRP). The purpose of this study was to use a validated Monte Carlo (MC) model of the SARRP to investigate (i) dose absorption in the ISD active volume and (ii) dose perturbation by the inorganic scintillating phosphor volume. A comparison was also drawn between the perturbation by the gadox phosphor and a ZnS-based phosphor. The gadox-based detector was seen to cause high levels of dose perturbation in the radiation field, leaving significant dose shadows in the irradiated media. The use of ZnS:Ag phosphor reduces the perturbations with just over half as much dose absorbed relative to the gadox phosphor. An optimized ISD design which utilizes the higher light yield of the less perturbing ZnS:Ag phosphor to allow for a smaller high-density active volume, and significantly mitigating kV dose perturbation, has been proposed.

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Initial Evaluation of the Performance of Novel Inorganic Scintillating Detectors for Small Animal Irradiation Dosimetry

Cited by 13 publications

References 25 publications

Characterization of Inorganic Scintillator Detectors for Dosimetry in Image-Guided Small Animal Radiotherapy Platforms

Characterization of Inorganic Scintillator Detectors for Dosimetry in Image-Guided Small Animal Radiotherapy Platforms

Time structure of pencil beam scanning proton FLASH beams measured with scintillator detectors and compared with log files

Novel inorganic scintillating detectors and their applications in small animal irradiators: measurements and Monte Carlo simulations

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