Improving the calibration of radiochromic films by the use of uncertainties in optical density and dose

García, Luis Isaac Ramos; Azorín, José Fernando Pérez

doi:10.1118/1.4811238

Cited by 18 publications

(12 citation statements)

References 31 publications

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“…Fields were delivered at 70 cm SSD with film placed between slabs of Solid Water (Gammex Inc., Middleton, WI) perpendicular to the beam axis at depths of 1.5 and 2.0 cm for 6 and 20 MeV electrons, respectively. Irradiated films were scanned on an Epson Expression 10000XL scanner (Seiko Epson Corporation, Suwa, Japan) in transmission mode at 150 dpi and processed using MATLAB (Mathworks, Natick, MA), according to the procedure outlined by Garcia and Azorin (9) . Using the red channel from each scan, images were corrected for scanner and film nonuniformities by subtracting a scan of an unirradiated film.…”

Section: Methodsmentioning

confidence: 99%

Comparison of measured Varian Clinac 21EX and TrueBeam accelerator electron field characteristics

Lloyd

Zavgorodni

Gagne

2015

J Applied Clin Med Phys

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Dosimetric comparisons of radiation fields produced by Varian's newest linear accelerator, the TrueBeam, with those produced by older Varian accelerators are of interest from both practical and research standpoints. While photon fields have been compared in the literature, similar comparisons of electron fields have not yet been reported. In this work, electron fields produced by the TrueBeam are compared with those produced by Varian's Clinac 21EX accelerator. Diode measurements were taken of fields shaped with electron applicators and delivered at 100 cm SSD, as well as those shaped with photon MLCs without applicators and delivered at 70 cm SSD for field sizes ranging from 5×5 to 25×25 cm2 at energies between 6 and 20 MeV. Additionally, EBT2 and EBT3 radio‐chromic film measurements were taken of an MLC‐shaped aperture with closed leaf pairs delivered at 70 cm SSD using 6 and 20 MeV electrons. The 6 MeV fields produced by the TrueBeam and Clinac 21EX were found to be almost indistinguishable. At higher energies, TrueBeam fields shaped by electron applicators were generally flatter and had less photon contamination compared to the Clinac 21EX. Differences in PDDs and profiles fell within 3% and 3 mm for the majority of measurements. The most notable differences for open fields occurred in the profile shoulders for the largest applicator field sizes. In these cases, the TrueBeam and Clinac 21EX data differed by as much as 8%. Our data indicate that an accurate electron beam model of the Clinac 21EX could be used as a starting point to simulate electron fields that are dosimetrically equivalent to those produced by the TrueBeam. Given that the Clinac 21EX shares head geometry with Varian's iX, Trilogy, and Novalis TX accelerators, our findings should also be applicable to these machines.PACS number: 87.56.bd

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Section: Methodsmentioning

confidence: 99%

Comparison of measured Varian Clinac 21EX and TrueBeam accelerator electron field characteristics

Lloyd

Zavgorodni

Gagne

2015

J Applied Clin Med Phys

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“…arabiensis mosquitoes were reared as described above, and batches of approximately 1000 pupae that had been quantified volumetrically in netted spoons were irradiated (20–26 h after pupation) in a 60 Co Gamma cell 220 (Nordion, Ottawa, Canada) with a dose of 70 Gy which induces partial sterility (~83%) as described by Helinski et al [27]. A dosimetry system was used to verify the dose received by the batches based on the Gafchromic HD-810 film (International Speciality Products, NJ, USA) [28]. Each group of pupae was then placed in each of 9 (30 × 30 × 30 cm) cages (3 for ivermectin treatment, 3 control cages, and 3 cages with virgin sterile males only) and allowed to emerge.…”

Section: Methodsmentioning

confidence: 99%

Eliminating female Anopheles arabiensis by spiking blood meals with toxicants as a sex separation method in the context of the sterile insect technique

et al. 2013

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BackgroundIvermectin has longevity reducing effects in several insect species, including disease transmitting mosquitoes after feeding on hosts that have received ivermectin treatment. This has important implications in mosquito population control and thus the reduction of disease transmission. In addition, ivermectin could play an enormous role in mosquito control operations by its use in the female elimination process during mass-rearing, enabling the release of only sterile males in the context of the sterile insect technique (SIT).MethodsBlood meals were spiked with various toxicants and were then offered to adult Anopheles arabiensis and killing effects were observed. Varying concentrations of the most effective substance were then tested in subsequent trials to obtain an optimal dose for quick and total female elimination. The remaining males were mated with untreated virgin females to assess whether their mating efficiency had been compromised. The most promising substance at the optimal concentration was further tested on a larger number of adults, after they had been irradiated and partially sterilised as pupae with 70 Gy to evaluate the feasibility of the method in a mass-rearing, and SIT context. The males resulting from the latter trial were also checked for mating efficiency post treatments.ResultsIvermectin (Virbamec®) at a concentration of 7.5 ppm was chosen from the toxicants tested as sufficiently effective in eliminating all female An. arabiensis in 4 days, the shortest time required for female elimination of all chemicals tested. Mating efficiency of the non-blood feeding male mosquitoes was not compromised significantly compared to controls even when they were kept for a total of 4 days (from emergence) before theoretical release. The irradiation treatment did not affect overall female feeding behaviour in this setting, nor were the sterile males less competitive for mating with virgin females after the treatments than virgin sterile males that had not been in the ivermectin treatment environment.ConclusionsSpiking bloodmeals with ivermectin has shown potential as a viable treatment to eliminate female An. arabiensis from laboratory colonies although its practical use in a mass-rearing facility still needs to be tested.

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“…Calibration curves at all energies were determined using both FilmQA Pro, as well as a recently published method which includes the error in reference dose and in measured OD when performing nonlinear least square minimization to determine the calibration fit parameters. 39 The effective variance method solved by direct optimization (EV opt ) was implemented in a MATLAB code provided by the authors and modified to use a rational linear calibration function. This method, as the name suggests, uses an effective variance in the y variable, calculated using the following formula:…”

Section: D Film Calibration and Curve Fittingmentioning

confidence: 99%

“…If using the polynomial functions with netOD over the extended dose range, the fitted functions were found to oscillate between data points, while the rational linear function was found to fit the data well, with the exception of the region with the greatest curvature in the calibration curve (60-500 cGy), particularly in the red channel, where there was a larger deviation. When performing the curve fitting using the Ramos et al 39 nonlinear least squares minimization method the data was fit in three different ways: using equal weightings (i.e., no error included), including error in only the OD values, and including error in both OD and reference dose. For these fittings, the PVs were converted to OD using Eq.…”

Section: D Film Calibration and Curve Fittingmentioning

confidence: 99%

Radiochromic film calibration for low-energy seed brachytherapy dose measurement

2014

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A modified procedure for performing EBT3 film calibration was established for use with low-energy brachytherapy seeds and high dose exposures. The energy dependence between 6 MV and I-125 photons is significant such that film calibrations should be done with an appropriately low-energy source when performing low-energy brachytherapy dose measurements. Two-segment piecewise fitting with the inclusion of errors in measured optical density as well as dose was found to result in the most accurate calibration curves. Above doses of 1 Gy, absolute dose measurements can be made with an accuracy of 1.6% for 6 MV beams and 5.7% for I-125 seed exposures if using the I-125 source for calibration, or 2.3% if using the 75 kVp photon beam for calibration.

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Improving the calibration of radiochromic films by the use of uncertainties in optical density and dose

Abstract: Methods that take into account all the variability both in dose and in optical density should be used in the calibration process.

Cited by 18 publications

References 31 publications

Comparison of measured Varian Clinac 21EX and TrueBeam accelerator electron field characteristics

Comparison of measured Varian Clinac 21EX and TrueBeam accelerator electron field characteristics

Eliminating female Anopheles arabiensis by spiking blood meals with toxicants as a sex separation method in the context of the sterile insect technique

Radiochromic film calibration for low-energy seed brachytherapy dose measurement

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