Optical filtering and spectral measurements of radiation-induced light in plastic scintillation dosimetry

Boer, Steven F. de; Beddar, Sam; Rawlinson, J. A.

doi:10.1088/0031-9155/38/7/005

Cited by 149 publications

(121 citation statements)

References 12 publications

(3 reference statements)

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“…Cerenkov light is emitted in a broad band over which the intensity decreases as a function of wavelength and, in the case of optical fiber, the collection of Cerenkov light is highly dependent on the angle at which the radiation beam is incident to the fiber. 27,28 A technique was developed that uses optical filtration to spectrally segregate the scintillation light and background light output by a single scintillator/fiber cable. 18,29 The socalled chromatic removal technique involves measuring light from different spectral bands of the multicomponent signal produced by the scintillator and optical fiber.…”

Section: Iid Cerenkov Light Removalmentioning

confidence: 99%

Measuring output factors of small fields formed by collimator jaws and multileaf collimator using plastic scintillation detectors

et al. 2010

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Purpose: As the practice of using high-energy photon beams to create therapeutic radiation fields of subcentimeter dimensions ͑as in intensity-modulated radiotherapy or stereotactic radiosurgery͒ grows, so too does the need for accurate verification of beam output at these small fields in which standard practices of dose verification break down. This study investigates small-field output factors measured using a small plastic scintillation detector ͑PSD͒, as well as a 0.01 cm 3 ionization chamber. Specifically, output factors were measured with both detectors using small fields that were defined by either the X-Y collimator jaws or the multileaf collimator ͑MLC͒. Methods: A PSD of 0.5 mm diameter and 2 mm length was irradiated with 6 and 18 MV linac beams. The PSD was positioned vertically at a source-to-axis distance of 100 cm, at 10 cm depth in a water phantom, and irradiated with fields ranging in size from 0.5ϫ 0.5 to 10ϫ 10 cm 2 . The field sizes were defined either by the collimator jaws alone or by a MLC alone. The MLC fields were constructed in two ways: with the closed leaves ͑i.e., those leaves that were not opened to define the square field͒ meeting at either the field center line or at a 4 cm offset from the center line. Scintillation light was recorded using a CCD camera and an estimation of error in the medianfiltered signals was made using the bootstrapping technique. Measurements were made using a CC01 ionization chamber under conditions identical to those used for the PSD. Results: Output factors measured by the PSD showed close agreement with those measured using the ionization chamber for field sizes of 2.0ϫ 2.0 cm 2 and above. At smaller field sizes, the PSD obtained output factors as much as 15% higher than those found using the ionization chamber by 0.6ϫ 0.6 cm 2 jaw-defined fields. Output factors measured with no offset of the closed MLC leaves were as much as 20% higher than those measured using a 4 cm leaf offset. Conclusions:The authors' results suggest that PSDs provide a useful and possibly superior alternative to existing dosimetry systems for small fields, as they are inherently less susceptible to volume-averaging and perturbation effects than larger, air-filled ionization chambers. Therefore, PSDs may provide more accurate small-field output factor determination, regardless of the collimation mechanism.

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Section: Iid Cerenkov Light Removalmentioning

confidence: 99%

Measuring output factors of small fields formed by collimator jaws and multileaf collimator using plastic scintillation detectors

et al. 2010

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“…The detectors were irradiated from a direction normal to the phantom surface, with the detectors placed at the centre of the radiation field throughout the experiments. The dose was measured at depths ranging from 0 mm (at the surface of the phantom) to 100 mm, using radiation field sizes of 5 5, 10 10, 20 20, and 40 40 cm 2 and SSD of 100 cm. The ion chamber has a finite water-equivalent depth due to the thickness of the walls, so dosimetry at shallow depths (<0.5 mm) is not possible.…”

Section: Depth Dose Determinationmentioning

confidence: 99%

“…The main issue with fiber optic dosimetry has always been the background radiation due to * Corresponding Author, Tel No: +61-2-4221-4574, Fax No: +61-2-4221-5944, E-Mail: anatoly@uow.edu.au ** B. Lee is currently a visiting fellow at CMRP on subbatical Cerenkov radiation. 1,2) Cerenkov radiation is produced when charged particles, (electrons in this case) pass through the fiber at a speed greater than the speed of light in the fiber. The Cerenkov radiation produced when a high energy photon beam is delivered from a linear accelerator (LINAC) has a wavelength in the 400-480 nm range, which is in the violet and blue end of the visible spectrum.…”

Section: Introductionmentioning

confidence: 99%

“…Since the amount of Cerenkov produced in the fiber is not directly proportional to the dose delivered to the fiber, the Cerenkov contribution to the signal is considered background noise. 2,3,4) Methods such as background subtraction and optical filtering are used to reduce the majority of this noise 2,3) . MOSFET-based dosimeters utilize a different technology to measure dose, but share many characteristics with fiber optic dosimeters such as small size, water equivalence for MV X-ray, and the ability to measure dose in real-time.…”

Section: Introductionmentioning

confidence: 99%

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Comparison of the New MOSkin Detector and Fiber Optic Dosimetry System for Radiotherapy

Kwan

Lee

Yoo

et al. 2008

Journal of Nuclear Science and Technology

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In radiotherapy, interest in real-time dosimetry stems from the desire to monitor the dose delivered to the target volume and the surrounding normal tissue to enable clinicians to track the progress of the treatment, and prevent surrounding tissue from receiving too much radiation dose. In this study, the dosimetric performance of the new MOSkin dosimeter and a Bicron BCF-20 scintillating fiber was compared to depth dose measurements taken with a Farmer-type ionization chamber. The performance of the MOSkin and BCF-20 detectors in the build-up region of the depth dose curve, where the dose gradient is steep, is also compared to readings taken with an Attix chamber. At depths greater than 15 mm, the MOSkin readings deviated from the ion chamber readings by up to 4%, while the fiber optic dosimeter always remained within 3% of the ionization chamber reading. In the build-up region, the MOSkin proved quite capable of measuring the dose at build up when compared to the Attix chamber results, while the fiber optic dosimeter was not able to measure the dose in this region with a high level of precision due to the thick sensitive volume of the scintillating crystal.

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“…Therefore the stem effect must be removed. Promising solutions to do so have been investigated in the past [1][2][3].…”

Section: Introductionmentioning

confidence: 99%

Fiber optical dose rate measurement based on the luminescence of beryllium oxide

2018

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Abstract-This work presents a fiber optical dose rate measurement system based on the radioluminescence and optically stimulated luminescence of beryllium oxide. The system consists of a small, radiation sensitive probe which is coupled to a light detection unit with a long and flexible light guide. Exposing the beryllium oxide probe to ionizing radiation results in the emission of light with an intensity which is proportional to the dose rate. Additionally, optically stimulated luminescence can be used to obtain dose and dose rate information during irradiation or retrospectively. The system is capable of real time dose rate measurements in fields of high dose rates and dose rate gradients and in complex, narrow geometries. This enables the application for radiation protection measurements as well as for quality control in radiotherapy. One inherent drawback of fiber optical dosimetry systems is the generation of Cherenkov radiation and luminescence in the light guide itself when it is exposed to ionizing radiation. This so called "stem" effect leads to an additional signal which introduces a deviation in the dose rate measurement and reduces the spatial resolution of the system, hence it has to be removed. The current system uses temporal discrimination of the effect for radioluminescence measurements in pulsed radiation fields and modulated optically stimulated luminescence for continuous irradiation conditions. This work gives an overview of the major results and discusses new-found obstacles of the applied methods of stem discrimination.Index Terms-Beryllium oxide, Fiber optic dose rate measurements, Optically Stimulated Luminescence, Radioluminescence I. INTRODUCTIONIBER OPTICAL DOSIMETERS (FODs) allow real time dose rate measurements with high spatial resolution. FODs consist of a small, radiation sensitive probe which is coupled to a light detection unit with a long and flexible light guide. Exposing the probe to ionizing radiation results in the emission of radioluminescence light (RL) with a characteristic spectrum and an intensity which is, under certain circumstances, proportional to the dose rate. Additional dose ANIMMA

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Optical filtering and spectral measurements of radiation-induced light in plastic scintillation dosimetry

Cited by 149 publications

References 12 publications

Measuring output factors of small fields formed by collimator jaws and multileaf collimator using plastic scintillation detectors

Measuring output factors of small fields formed by collimator jaws and multileaf collimator using plastic scintillation detectors

Comparison of the New MOSkin Detector and Fiber Optic Dosimetry System for Radiotherapy

Fiber optical dose rate measurement based on the luminescence of beryllium oxide

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