Spectral discrimination of Čerenkov radiation in scintillating dosimeters

Frelin, Anne-Marie; Jm, Fontbonne; Ban, G.; Colin, J.; Labalme, M.; Batalla, A.; Isambert, A.; Véla, A.; Leroux, Thierry

doi:10.1118/1.2008487

Cited by 183 publications

(158 citation statements)

References 19 publications

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“…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. A calibration is then performed to determine the relative contributions of scintillation and Cerenkov light to the resulting signal that is proportional to a measured dose.…”

Section: Iid Cerenkov Light Removalmentioning

confidence: 99%

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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%

“…Thus, Cerenkov light can be effectively removed. 19,29 The chromatic removal technique was used for all measurements discussed below.…”

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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“…Various methods for the correction or subtraction of the stem effect have been proposed in the literature [20][21][22][23][24] . Unfortunately, all of them have showed some limits in various applications and therefore new solutions are welcome.…”

Section: Doped Portionmentioning

confidence: 99%

Characterization of Yb-doped silica optical fiber as real-time dosimeter

Veronese

Chiodini

Cialdi

et al. 2017

Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XIX

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The near-infrared radioluminescence and dosimetric properties of Yb-doped silica optical fibers, coupled with an optical detector prototype based on an avalanche photo-diode, were studied by irradiating the fibers with clinical beams generated by a Varian Trilogy accelerator. The performances of the system in standard and small field sizes have been also investigated comparing the output factor, percent depth dose and off axis ratio measurements of the prototypal dosimetric system with other commercial sensors.The results demonstrated that the drawback due to the stem effect in Yb-doped silica optical fibers can be managed in a simple but effective way by optical filtering. These features, together with the accuracy and precision achieved by Ybdoped fibers in relative dose assessments make the device promising for in-vivo dosimetry studies in radiation therapy.

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“…2,16,17 Various methods have been described to remove the Čerenkov radiation from the detector's signal. 2,4,[18][19][20] An elegant method of circumventing the production of Čerenkov radiation in the optical fiber has also been proposed. 21,22 Since air has a refractive index very close to 1, those investigators used a hollow optical fiber ͑filled with air͒ instead of one with a solid fiber core to minimize the generation of Čerenkov radiation.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo study of the energy and angular dependence of the response of plastic scintillation detectors in photon beams

2010

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Purpose: By using Monte Carlo simulations, the authors investigated the energy and angular dependence of the response of plastic scintillation detectors ͑PSDs͒ in photon beams. Methods: Three PSDs were modeled in this study: A plastic scintillator ͑BC-400͒ and a scintillating fiber ͑BCF-12͒, both attached by a plastic-core optical fiber stem, and a plastic scintillator ͑BC-400͒ attached by an air-core optical fiber stem with a silica tube coated with silver. The authors then calculated, with low statistical uncertainty, the energy and angular dependences of the PSDs' responses in a water phantom. For energy dependence, the response of the detectors is calculated as the detector dose per unit water dose. The perturbation caused by the optical fiber stem connected to the PSD to guide the optical light to a photodetector was studied in simulations using different optical fiber materials. Results: For the energy dependence of the PSDs in photon beams, the PSDs with plastic-core fiber have excellent energy independence within about 0.5% at photon energies ranging from 300 keV ͑monoenergetic͒ to 18 MV ͑linac beam͒. The PSD with an air-core optical fiber with a silica tube also has good energy independence within 1% in the same photon energy range. For the angular dependence, the relative response of all the three modeled PSDs is within 2% for all the angles in a 6 MV photon beam. This is also true in a 300 keV monoenergetic photon beam for PSDs with plastic-core fiber. For the PSD with an air-core fiber with a silica tube in the 300 keV beam, the relative response varies within 1% for most of the angles, except in the case when the fiber stem is pointing right to the radiation source in which case the PSD may over-response by more than 10%. Conclusions: At Ϯ1% level, no beam energy correction is necessary for the response of all three PSDs modeled in this study in the photon energy ranges from 200 keV ͑monoenergetic͒ to 18 MV ͑linac beam͒. The PSD would be even closer to water equivalent if there is a silica tube around the sensitive volume. The angular dependence of the response of the three PSDs in a 6 MV photon beam is not of concern at 2% level.

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Spectral discrimination of Čerenkov radiation in scintillating dosimeters

Cited by 183 publications

References 19 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

Characterization of Yb-doped silica optical fiber as real-time dosimeter

Monte Carlo study of the energy and angular dependence of the response of plastic scintillation detectors in photon beams

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