A dosimetric study of small photon fields using polymer gel and Gafchromic EBT films

Hassani, Hossein; Nedaie, Hassan Ali; Zahmatkesh, Mohammad Hasan; Shirani, K.

doi:10.1016/j.meddos.2013.10.007

Cited by 16 publications

(13 citation statements)

References 26 publications

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“…Furthermore, with gel dosimetry, it is possible to have a continuous 3D detection volume. An excellent agreement among these types of dosimeters has been reported in the literature (De Deene et al, 1998;Hassani et al, 2014) with the exception of measurements in the penumbra regions.…”

Section: Introductionsupporting

confidence: 58%

Fricke and polymer gel 2D dosimetry validation using Monte Carlo simulation

Vedelago

Obando

Malano

et al. 2016

Radiation Measurements

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h i g h l i g h t sFricke and NIPAM gel dosimetry are tested in conformal radiotherapy. Rigorous (1 mme2%) Gamma test in 1D and 2D are performed for cross-comparisons. Very good agreements with TPS and MC simulations was obtained for gel dosimeters. Results suggest promising performance for quality assurance in radiotherapy. a b s t r a c tComplexity in modern radiotherapy treatments demands advanced dosimetry systems for quality control. These systems must have several characteristics, such as high spatial resolution, tissue equivalence, three-dimensional resolution, and dose-integrating capabilities. In this scenario, gel dosimetry has proved to be a very promising option for quality assurance. In this study, the feasibility of Fricke and polymer gel dosimeters suitably shaped in form of thin layers and optically analyzed by visible light transmission imaging has been investigated for quality assurance in external radiotherapy. Dosimeter irradiation was carried out with a 6-MV photon beam (CLINAC 600C). The analysis of the irradiated dosimeters was done using two-dimensional optical transmission images. These dosimeters were compared with a treatment plan system using Monte Carlo simulations as a reference by means of a gamma test with parameters of 1 mm and 2%. Results show very good agreement between the different dosimetric systems: in the worst-case scenario, 98% of the analyzed points meet the test quality requirements. Therefore, gel dosimetry may be considered as a potential tool for the validation of other dosimetric systems.

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Section: Introductionsupporting

confidence: 58%

Fricke and polymer gel 2D dosimetry validation using Monte Carlo simulation

Vedelago

Obando

Malano

et al. 2016

Radiation Measurements

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show abstract

“…The results of gamma evaluation with 2%/2 mm criteria showed that the dose maps had a 92.7% pass rate compared to the result of the treatment planning system (TPS). Hassani et al [ 12 ] measured 6-MV X-ray beams with field sizes of 5 × 5, 10 × 10, 20 × 20, and 30 × 30 mm 2 using the methacrylic and ascorbic acid in gelatin initiated by copper (MAGIC) polymer gel dosimeter, and the dose distribution was read out by MRI. The dose profiles of the MAGIC gel dosimeter had a maximum difference of 2.08% compared to those of the verification films at the edge of the penumbra.…”

Section: Introductionmentioning

confidence: 99%

Small-Field Measurements of 3D Polymer Gel Dosimeters through Optical Computed Tomography

Shih

et al. 2016

PLoS ONE

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With advances in therapeutic instruments and techniques, three-dimensional dose delivery has been widely used in radiotherapy. The verification of dose distribution in a small field becomes critical because of the obvious dose gradient within the field. The study investigates the dose distributions of various field sizes by using NIPAM polymer gel dosimeter. The dosimeter consists of 5% gelatin, 5% monomers, 3% cross linkers, and 5 mM THPC. After irradiation, a 24 to 96 hour delay was applied, and the gel dosimeters were read by a cone beam optical computed tomography (optical CT) scanner. The dose distributions measured by the NIPAM gel dosimeter were compared to the outputs of the treatment planning system using gamma evaluation. For the criteria of 3%/3 mm, the pass rates for 5 × 5, 3 × 3, 2 × 2, 1 × 1, and 0.5 × 0.5 cm2 were as high as 91.7%, 90.7%, 88.2%, 74.8%, and 37.3%, respectively. For the criteria of 5%/5 mm, the gamma pass rates of the 5 × 5, 3 × 3, and 2 × 2 cm2 fields were over 99%. The NIPAM gel dosimeter provides high chemical stability. With cone-beam optical CT readouts, the NIPAM polymer gel dosimeter has potential for clinical dose verification of small-field irradiation.

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“…Physically small film samples are often used in the verification of external beam small field dosimetry, or in brachytherapy applications, when small scales are required. As an example, Hassani et al (4) used film pieces of

3 cm \times 3 cm

and

5 \times 20 cm

, analyzed with a flatbed scanner, which is typical practice. Such film sizes are, however, susceptible to curling.…”

Section: Introductionmentioning

confidence: 99%

“…Radiochromic film dosimetry is an important tool in radiotherapy to validate absolute dose or dose distributions in challenging external beam or brachytherapy situations. (1)(2)(3)(4) The use of modern radiochromic films and advanced scanning techniques have seen improved accuracy of film dosimetry and widespread adoption of the technique. (5,6) Film dosimetry has several advantages over other dosimetry methods including very high spatial resolution in continuous 2D, low-energy dependence, and near water equivalence.…”

Section: Introductionmentioning

confidence: 99%

Evaluation and mitigation of potential errors in radiochromic film dosimetry due to film curvature at scanning

Palmer

Bradley

Nisbet

2015

J Applied Clin Med Phys

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This work considers a previously overlooked uncertainty present in film dosimetry which results from moderate curvature of films during the scanning process. Small film samples are particularly susceptible to film curling which may be undetected or deemed insignificant. In this study, we consider test cases with controlled induced curvature of film and with film raised horizontally above the scanner plate. We also evaluate the difference in scans of a film irradiated with a typical brachytherapy dose distribution with the film naturally curved and with the film held flat on the scanner. Typical naturally occurring curvature of film at scanning, giving rise to a maximum height 1 to 2 mm above the scan plane, may introduce dose errors of 1% to 4%, and considerably reduce gamma evaluation passing rates when comparing film‐measured doses with treatment planning system‐calculated dose distributions, a common application of film dosimetry in radiotherapy. The use of a triple‐channel dosimetry algorithm appeared to mitigate the error due to film curvature compared to conventional single‐channel film dosimetry. The change in pixel value and calibrated reported dose with film curling or height above the scanner plate may be due to variations in illumination characteristics, optical disturbances, or a Callier‐type effect. There is a clear requirement for physically flat films at scanning to avoid the introduction of a substantial error source in film dosimetry. Particularly for small film samples, a compression glass plate above the film is recommended to ensure flat‐film scanning. This effect has been overlooked to date in the literature.PACS numbers: 87.55.Qr, 87.56.bg, 87.55.km

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A dosimetric study of small photon fields using polymer gel and Gafchromic EBT films

Cited by 16 publications

References 26 publications

Fricke and polymer gel 2D dosimetry validation using Monte Carlo simulation

Fricke and polymer gel 2D dosimetry validation using Monte Carlo simulation

Small-Field Measurements of 3D Polymer Gel Dosimeters through Optical Computed Tomography

Evaluation and mitigation of potential errors in radiochromic film dosimetry due to film curvature at scanning

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