Enhanced epidermal dose caused by localized electron contamination from lead cutouts used in kilovoltage radiotherapy

Lye, Jessica; Butler, Duncan; Webb, Douglas

doi:10.1118/1.3458722

Cited by 21 publications

(12 citation statements)

References 10 publications

(9 reference statements)

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“…1, it is apparent that EBT2 film is not symmetrical. However the depth of the active layer is 70 lm, which corresponds to the ICRP skin depth [36,37].…”

Section: Gafchromic Ebt2 Filmmentioning

confidence: 99%

“…For the in-air measurements, no scattering material was present within at least 1 m from the cone to prevent unwanted scattered radiation interacting with the film. For both the in-air and on-phantom measurements, cling wrap was used to attach the films to the end of the cone and remove the effect of very-low energy secondary electrons [37,[42][43][44]. Measurements on the phantom surface were performed in full scatter conditions, with a thickness of at least 10 cm as specified in the AAPM TG-61 protocol [4].…”

Section: Measurement Of B Wmentioning

confidence: 99%

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The measurement of backscatter factors of kilovoltage X-ray beams using Gafchromic™ EBT2 film

Smith

Hill

Nakano

et al. 2011

Australas Phys Eng Sci Med

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Backscatter factors are essential in the determination of radiation dose for kilovoltage X-ray beams. The accurate measurement of backscatter factors in water (B (W)) is difficult and published values are based largely on Monte Carlo calculations. A number of studies have found that the measurement of B (W) in the energy range from 50 to 300 kVp is possible using Gafchromic EBT film, but this film is no longer commercially available. In this work, we evaluated whether the newer Gafchromic EBT2 film is suitable for the determination of B (W) for kilovoltage X-ray beams. B (W) were measured with Gafchromic EBT2 film for beam qualities of 50, 100 and 280 kVp and field sizes of 2, 3, 4 and 6 cm diameter and compared with tabulated values published in the AAPM TG-61 protocol. We found that rotation of the film position during readout had a small but non-negligible effect on the optical density readings. The agreement between measured and published B (W) was better than 3%, with the largest difference of occurring for the 2 cm diameter field with the 50 kVp X-ray beam. However, these differences are consistent with the total estimated uncertainty for the measurements, as calculated by the ISO GUM. Our results demonstrate that Gafchromic EBT2 film is a suitable dosimeter for B (W) measurements for clinical kilovoltage X-ray beams.

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“…1, it is apparent that EBT2 film is not symmetrical. However the depth of the active layer is 70 lm, which corresponds to the ICRP skin depth [36,37].…”

Section: Gafchromic Ebt2 Filmmentioning

confidence: 99%

Section: Measurement Of B Wmentioning

confidence: 99%

The measurement of backscatter factors of kilovoltage X-ray beams using Gafchromic™ EBT2 film

Smith

Hill

Nakano

et al. 2011

Australas Phys Eng Sci Med

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“…Since Gafchromic radiochromic films produce colored images when exposed to radiation, it has long been recognized that multichannel flatbed scanners offer better usability than white-light scanners. The red color channel has greater sensitivity at lower doses while the signal from the green or blue channels provides extension of the dynamic range of the film to higher doses [ 15 , 23 – 25 ]. Multichannel dosimetry has shown to have significant advantages over single channel dosimetry by its better dosimetric accuracy [ 26 ].…”

Section: Introductionmentioning

confidence: 99%

Is It Possible to Publish a Calibration Function for Radiochromic Film?

Chan¹,

Lewis²,

Yu³

2014

IJMPCERO

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Purpose To assess the possibility of using a public calibration function for radiochromic film dosimetry in dose QA of highly conformal treatment plans. Methods EBT3 film calibration strips (3.5 × 20 cm2 from lots A101212 and A011713) were exposed on a Varian Trilogy at a facility to a 10 × 10 cm2 open field at doses of 80, 160, 320 cGy using 6MV photons. Together with a strip of unexposed film from the same lot the exposed films were digitized in a single scan using different Epson 10,000 XL scanners at two different facilities. The dose-response data for each color-channel from each facility were generated using the same calibration function X(D) = a + b/(D − c), where X(D) is the response at dose D and a, b and c are the coefficients. Different batches of EBT3 film were exposed to a VMAT beam. These films, plus two reference strips exposed to doses of zero and 160 cGy, were digitized on the scanners at the two facilities. Using the multi-channel dosimetry method and One-scan protocol (Med Phys, 39:6339–49, 2012) the recorded doses on the VMAT films were calculated and the results were compared with the VMAT plan using a Gamma index of 3%/3 mm. Results The passing rates obtained for dose maps calculated for all combinations of VMAT images and calibration functions were nearly unchanged, using the One-scan protocol. Also, in all cases a passing rate of >99% was obtained for Gamma index of 3%/3 mm. On the other hand, if the One-scan protocol was not employed, the dose maps for VMAT images and calibration functions from different scanners showed poor correlation with the treatment plan. This is probably due to the scan-to-scan variability. Conclusions The authors have found that it is feasible to use a public calibration function for a given radiochromic film lot using the same methodology, One-scan protocol, for patient-specific QA.

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“…Thus, without attenuation of the surface dose, total doses for a single fraction dose at 2 mm depth would be limited to approximately 4–5 Gy; in a pilot study, one mouse developed a severe skin reaction two weeks after being exposed to a surface dose of 20 Gy. Several other authors have reported similarly high surface doses when using metallic collimating devices for orthovoltage radiotherapy (Podgorsak, 1990, Lye et al 2010, Arndt et al 2011). The acrylic insert within the collimator reduced the surface dose without significantly reducing the dose rate at depth since the inherent attenuation is partially offset by the increased dose due to scatter within the acrylic.…”

Section: Discussionmentioning

confidence: 76%

Design and characterization of an economical¹⁹²Ir hemi-brain small animal irradiator

Grams

Wilson

Sio

et al. 2014

International Journal of Radiation Biology

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Purpose To describe the design and dosimetric characterization of a simple and economical small animal irradiator. Materials and methods A high dose rate (HDR) 192Ir brachytherapy source from a commercially available afterloader was used with a 1.3 cm thick tungsten collimator to provide sharp beam penumbra suitable for hemi-brain irradiation of mice. The unit was equipped with continuous gas anesthesia to allow robust animal immobilization. Dosimetric characterization of the device was performed with Gafchromic film measurements. Results The tungsten collimator provided a sharp penumbra suitable for hemi-brain irradiation, and dose rates on the order of 200 cGy/minute were achieved. The sharpness of the penumbra attainable with this device compares favorably to those measured experimentally for 6 MV photons, and 6 and 20 MeV electron beams from a linear accelerator, and was comparable to those measured for a 300 kVp orthovoltage beam and a Monte Carlo simulated 90 MeV proton beam. Conclusions Due to its simplicity and low cost, the apparatus described is an attractive alternative for small animal irradiation experiments requiring steep dose gradients.

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Enhanced epidermal dose caused by localized electron contamination from lead cutouts used in kilovoltage radiotherapy

Cited by 21 publications

References 10 publications

The measurement of backscatter factors of kilovoltage X-ray beams using Gafchromic™ EBT2 film

The measurement of backscatter factors of kilovoltage X-ray beams using Gafchromic™ EBT2 film

Is It Possible to Publish a Calibration Function for Radiochromic Film?

Design and characterization of an economical¹⁹²Ir hemi-brain small animal irradiator

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Enhanced epidermal dose caused by localized electron contamination from lead cutouts used in kilovoltage radiotherapy

Cited by 21 publications

References 10 publications

The measurement of backscatter factors of kilovoltage X-ray beams using Gafchromic™ EBT2 film

The measurement of backscatter factors of kilovoltage X-ray beams using Gafchromic™ EBT2 film

Is It Possible to Publish a Calibration Function for Radiochromic Film?

Design and characterization of an economical192Ir hemi-brain small animal irradiator

Contact Info

Product

Resources

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Design and characterization of an economical¹⁹²Ir hemi-brain small animal irradiator