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In this study, we have studied the effects of temperature and X-ray energy variations on the light output signals from two different fiber-optic sensors, a fiber-optic dosimeter (FOD) based on a BCF-12 as a plastic scintillating fiber (PSF) and a fiber-optic thermometer (FOT) using a silver halide optical fiber as an infrared optical fiber (IR fibe...
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... main study concerns the impact of temperature or X-ray energy variation on the light output signals from a fiber-optic sensor based on a PSF or an IR fiber. Figures 1 and 2 show the internal structures of the two different types of sensing probes, which can produce scintillating light and transmit an IR signal, respectively. First, we fabricated a typical dosimeter probe (CH 1) of a FOD to measure scintillating light signals induced by an X-ray beam. ...
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... POF is covered by a black polyethylene (PE) jacket with an outer diameter of 2.2 mm to block external light noise and to protect the POF from ambient contamination. Figure 1 illustrates the internal structure of the dosimeter probe. In fabricating the typical dosimeter probe of the FOD, first, both ends of the PSF and POF, respectively, were polished with various types of lapping films (LFG series, Thorlabs, Newton, NJ, USA). ...
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... this test, the exposure parameters were set to the same values as those of Section 3.1. Figure 10 shows the temperature of water, which was measured using a thermocouple, versus the output voltage of FOT as a function of the IR signal. The output voltage of the FOT increased as the temperature of water increased because the intensity of the IR signal transmitted through the IR fiber is proportional to the temperature of the heat source [17][18][19][20][21][22]. ...
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... output voltage of the FOT increased as the temperature of water increased because the intensity of the IR signal transmitted through the IR fiber is proportional to the temperature of the heat source [17][18][19][20][21][22]. The mathematical form of the linear fit line to the curve is also presented in Figure 10 and R 2 was found to be 0.9982. Fortunately, the IR signal at the given temperature is fairly constant even when the tube potential was changed from 50 to 150 kVp. ...
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For technical and radioprotection reasons, it has become essential to develop new dosimetric tools adapted to the specificities of computed tomography (CT) to ensure precise and efficient dosimetry since the current standards are not suitable for clinical use and for new CT technological evolution. Thanks to its many advantages, plastic scintillati...
Citations
... Despite the low temperature dependence of PSDs [9], it is known that the PSD signal in the case of BCF-12 decreases linearly with increasing temperature [15][16][17][19][20][21][22]. All these studies used kilovoltage, megavoltage, or Co-60 sources of radiation, but BCF-12 PSD temperature dependence has not yet been reported under Ir-192 HDR source irradiations. ...
... Other PSDs using BCF-12 irradiated with different sources of radiation have also shown negative temperature dependencies of −0.15%/ • C (50 kVp) [19], −0.09%/ • C (Co-60) [20], −0.225%/ • C (6 MV, 15 MV) [17], −0.263%/ • C (50-150 kVp) [21], −0.25%/ • C (6 MV, 10 MV, 15 MV, Co-60) [16], −0.18%/ • C (6 MV) [22], and −0.18%/ • C (6 MV FFF) [15]. The mean value of all these works is around −0.2%/ • C, which coincides with the value obtained in the present work considering the associated uncertainty. ...
(1) Background: High dose gradients and manual steps in brachytherapy treatment procedures can lead to dose errors which make the use of in vivo dosimetry (IVD) highly recommended for verifying brachytherapy treatments. A new procedure was presented to obtain a calibration factor which allows fast and robust calibration of plastic scintillation detector (PSD) probes for the geometry of a compact phantom using Monte Carlo simulations. Additionally, characterization of PSD energy, angular, and temperature dependences was performed. (2) Methods: PENELOPE/PenEasy code was used to obtain the calibration factor. To characterize the energy dependence of the PSD, the signal was measured at different radial and transversal distances. The sensitivity to the angular position was characterized in axial and azimuthal planes. (3) Results: The calibration factor obtained allows for an absorbed dose to water determination in full scatter conditions from ionization measured in a mini polymethylmethacrylate (PMMA) phantom. The energy dependence of the PSD along the radial distances obtained was (2.3 ± 2.1)% (k = 1). The azimuthal angular dependence measured was (2.6 ± 3.4)% (k = 1). The PSD response decreased by (0.19 ± 0.02)%/°C with increasing detector probe temperature. (4) Conclusions: The energy, angular, and temperature dependence of a PSD is compatible with IVD.
... Later, in 2013 two papers [4,5] presented measurements on the BCF-12 and BCF-60 (also polystyrene based) reporting non-vanishing temperature coefficients for both scintillators. The results for BCF-12 have been confirmed by Lee et al. in a work published in 2015 [6]. These works focused on the widely used BCF-12 and BCF-60 scintillators, being the information on other plastic scintillators scarce. ...
... Ideally, the response from the dosimeter should be constant for a sufficiently wide range of temperatures. However, several studies now suggest that PSDs might have temperature dependency [3][4][5][6]. In order to correct the dosimeter readings, it is critical to study the scintillator's temperature dependence. ...
... Except for BC-404, all the other scintillators present a clear temperature dependence within the measured range. The measured temperature coefficient value for BCF-10 is similar to the BCF-12 scintillator (α= (-0.26 ± 0.03) ×10 -3 ºC -1 ) [6] (also a blue-emitting scintillator [14]). On the other hand, the value obtained for the BCF-60 scintillator is less than the values reported by earlier works [4,5] of about 0.5×10 -3 ºC -1 , but still showing a significant decrease on light yield with temperature. ...
Plastic scintillator detectors have been studied as dosimeters, since they provide a cost-effective alternative to conventional ionization chambers. On the other hand, several articles have reported undesired response dependencies on beam energy and temperature, which enhances the necessity to determine appropriate correction factors. In this work, we studied the light yield temperature dependency of four plastic scintillators (BCF-10, BCF-60, BC-404 and RP-200A) and two clear fibers (BCF-98 and SK-80). Measurements were made using a 50 kVp X-ray beam to produce the scintillation and/or radioluminescence signal. The 0 to 40 degrees celsius range was scanned for each scintillator, and temperature coefficients obtained.
... 9 Small dependence to temperature has also been reported with a small decrease of the plastic scintillator light output with increasing temperature. [10][11][12] This temperature dependence is an important consideration for a detector dedicated to in vivo dosimetry. Nevertheless, it becomes negligible in a temperature-controlled environment. ...
... The temperature inside the X-RAD® cabinet was stable during measurements (21 6 2°C). Thus, the uncertainty generated by the small temperature dependence of the BCF-12 light output (20.263 6 0.028%/°C reported by Lee et al 12 ) was not taken into account. It should not exceed 1% in our conditions. ...
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(-1). The stem effect was found to be negligible. DosiRat showed limited precision for low air kerma rate measurements (<1 mGy s(-1)), 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.
In this study, we developed a remote gamma spectroscopy system based on fiber-optic radiation sensor (FORS) to detect species of gamma-emitting sources at large distances. In order to evaluate the performance of the gamma spectroscopy system, we measured the scintillating light intensity and gamma energy spectra as a function of the length of the plastic optical fiber (POF) and radioactivity of the gamma-ray source. Using the obtained experimental results, we selected the optimal inorganic scintillator as the FORS sensing material and measured the energy spectra. In addition, the photopeaks of the gamma-emitting sources were detected for different lengths of the POF and radioactivity of the ¹³⁷Cs gamma-ray source. It is expected that the remote gamma spectroscopy system based on FORS can be an effective and convenient tool that can detect gamma-emitting sources at large distances, and can identify species of radioactive sources by measuring gamma energy spectra in nuclear facilities.
In this paper, we present the first results regarding the on-line monitoring of gamma-ray exposure effects on a commercial multi-mode perfluorinated polymer optical fiber (PF-POF), type GigaPOF-50SR from Chromis Fiberoptics. Our focus was to evaluate on-line the radiation induced attenuation (RIA) over a wide spectral range (320 nm – 1700 nm), in order to assess the fiber’s radiation hardness and its possible use in radiation detection. An Ocean Optics QE65000 high sensitivity spectrometer and a StellarNet near-IR spectrometer were used to cover the spectral ranges 200 nm – 1μm and 900 nm – 1.6 μm, respectively. Electron paramagnetic resonance was used to monitor the recovery of the irradiation induced centers at room temperature. The study indicated that the optical fiber can be used as radiation monitor at low dose rates by measuring the attenuation in the UV, while higher dose rates irradiation can be observed by RIA monitoring at specific wavelengths in the visible spectral range.
