Comparison of Monte Carlo calculations around a Fletcher Suit Delclos ovoid with radiochromic film and normoxic polymer gel dosimetry

Gifford, Kent A; Horton, John L.; Jackson, Edward F.; Steger, Theodore R.; Heard, M; Mourtada, Firas; Lawyer, Ann A.

doi:10.1118/1.1944247

Cited by 24 publications

(15 citation statements)

References 23 publications

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“…In Monte Carlo studies at low energies, such as those encountered in brachytherapy, kerma is commonly scored as an approximation of dose. 33 Such an approximation was a possibility for the current study, at least where electronic equilibrium exists ͑such as depths below d max ͒. For a 6 MV beam a difference is expected between dose and kerma, but this difference may be small because large voxels are used and relatively small dose gradients are encountered out-of-field ͑so electronic equilibrium is very nearly achieved͒, and the required accuracy of the final answer for out-of-field studies is less than is typically required for other Monte Carlo studies.…”

Section: B Monte Carlo Talliesmentioning

confidence: 99%

A Monte Carlo model for calculating out‐of‐field dose from a Varian beam

et al. 2006

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Dose to the patient outside of the treatment field is important when evaluating the outcome of radiotherapy treatments. However, determining out-of-field doses for any particular treatment plan currently requires either time-consuming measurements or calculated estimations that may be highly uncertain. A Monte Carlo model may allow these doses to be determined quickly, accurately, and with a great degree of flexibility. MCNPX was used to create a Monte Carlo model of a Varian Clinac 2100 accelerator head operated at 6 MV. Simulations of the dose out-of-field were made and measurements were taken with thermoluminescent dosimeters in an acrylic phantom and with an ion chamber in a water tank to validate the Monte Carlo model. Although local differences between the out-of-field doses calculated by the model and those measured did exceed 50% at some points far from the treatment field, the average local difference was only 16%. This included a range of doses as low as 0.01% of the central axis dose, and at distances in excess of 50 cm from the central axis of the treatment field. The out-of-field dose was found to vary with field size and distance from the central axis, but was almost independent of the depth in the phantom except where the dose increased substantially at depths less than dmax. The relationship between dose and kerma was also investigated, and kerma was found to be a good estimate of dose (within 3% on average) except near the surface and in the field penumbra. Our Monte Carlo model was found to well represent typical Varian 2100 accelerators operated at 6 MV.

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Section: B Monte Carlo Talliesmentioning

confidence: 99%

A Monte Carlo model for calculating out‐of‐field dose from a Varian beam

et al. 2006

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“…Use of RCF to measure absolute dose distributions around LDR 125 I- 7 and a 137 Cs-bearing intracavitary applicator 30,31 have reported previously. Monroe, etc.…”

Section: Discussionmentioning

confidence: 99%

Prospects for quantitative two‐dimensional radiochromic film dosimetry for low dose‐rate brachytherapy sources

Le¹,

Ali²,

Dempsey³

et al. 2006

Medical Physics

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Radiochromic film (RCF) has been shown to be a precise and accurate two-dimensional dosimeter for acute exposure radiation fields. However, "temporal history" mismatch between calibration and brachytherapy films due to RCF dose-rate effects could introduce potentially large uncertainties in low dose-rate (LDR) brachytherapy absolute dose measurement. This article presents a quantitative evaluation of the precision and accuracy of a laser scanner-based RCF-dosimetry system and the effect of the temporal history mismatch in LDR absolute dose measurement. MD-55-2 RCF was used to measure absolute dose for a low dose-rate 137Cs brachytherapy source using both single- and double-exposure techniques. Dose-measurement accuracy was evaluated by comparing RCF to Monte Carlo photon-transport simulation. The temporal history mismatch effect was investigated by examining dependence of RCF accuracy on irradiation-to-densitometry time interval. The predictions of the empirical cumulative dose superposition model (CDSM) were compared with measurements. For the double-exposure technique, the agreement between measurement and Monte Carlo simulation was better than 4% in the 3-60 Gy dose range with measurement precisions (coverage factor k = 1) of<2% and <6% for the doses greater or less than 3 Gy, respectively. The overall uncertainty (k = 1) of dose rate/air-kerma strength measurements achievable by this dosimetry system for a spatial resolution of 0.1 mm is less than 4% for doses greater than 5 Gy. The measured temporal history mismatch systematic error is about 1.8% for a 48 h postexposure time when using the double exposure technique and agrees with CDSM's prediction qualitatively. This work demonstrates that the model MD-55-2 RCF detector has the potential to support quantitative dose measurements about LDR brachytherapy sources with precision and accuracy better than that of previously described dosimeters. The impacts of this work on the future use of new type of RCF were also discussed.

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“…[47][48][49][50] While gel dosimetry looks appealing because it conceptually could provide an entire set of three-dimensional data with a single exposure, characteristics such as the high dose required for adequate signals and a marked gradient effect pose challenges for widespread use. [51][52][53][54][55]…”

Section: Iic Measurement Of Dosimetric Parametersmentioning

confidence: 99%

Anniversary Paper: Past and current issues, and trends in brachytherapy physics

et al. 2008

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Brachytherapy began at the turn of the 20th century, contemporary with external-beam radiotherapy. Physicists and physicians together developed the field. There has not been a period since the beginning that has not witnessed innovations and progress in brachytherapy. At the time of this article, the pace of change in the field has never been more rapid, particularly in image-guided brachytherapy and the development of unconventional sources and treatment techniques.

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Comparison of Monte Carlo calculations around a Fletcher Suit Delclos ovoid with radiochromic film and normoxic polymer gel dosimetry

Cited by 24 publications

References 23 publications

A Monte Carlo model for calculating out‐of‐field dose from a Varian beam

A Monte Carlo model for calculating out‐of‐field dose from a Varian beam

Prospects for quantitative two‐dimensional radiochromic film dosimetry for low dose‐rate brachytherapy sources

Anniversary Paper: Past and current issues, and trends in brachytherapy physics

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