Treatment planning of a skin‐sparing conical breast brachytherapy applicator using conventional brachytherapy software

Yang, Yun; Melhus, Christopher S.; Sioshansi, Shirin; Rivard, Mark J.

doi:10.1118/1.3552921

Cited by 18 publications

(12 citation statements)

References 21 publications

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“…Thus, an alternate application of the gamma-index method for brachytherapy dose distributions is to compare reference and planned results as investigated in Yang et al . [25]. The uniformly-loaded 125 I plaque MC results represent the reference dose distributions in this study.…”

Section: Discussionmentioning

confidence: 99%

“…[25] was employed to quantitatively compare the raw MC dose distribution data from a uniformly-loaded 16 mm plaque with the TPS dose distribution data from a summation of the plaque's three constituent rings using the OmniPro I'mRT software suite (IBA Dosimetry, Bartlett, TN). Both dose distributions were calculated with (0.2 mm) 2 dose grid resolution, were normalized to 75 Gy at a depth of 5 mm, and comprised a (50 mm) 2 field-of-view.…”

Section: Methodsmentioning

confidence: 99%

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Keeping an eye on the ring: COMS plaque loading optimization for improved dose conformity and homogeneity

Gagne¹,

Cutright²,

Rivard³

2012

jcb

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PurposeTo improve tumor dose conformity and homogeneity for COMS plaque brachytherapy by investigating the dosimetric effects of varying component source ring radionuclides and source strengths.Material and methodsThe MCNP5 Monte Carlo (MC) radiation transport code was used to simulate plaque heterogeneity-corrected dose distributions for individually-activated source rings of 14, 16 and 18 mm diameter COMS plaques, populated with 103Pd, 125I and 131Cs sources. Ellipsoidal tumors were contoured for each plaque size and MATLAB programming was developed to generate tumor dose distributions for all possible ring weighting and radionuclide permutations for a given plaque size and source strength resolution, assuming a 75 Gy apical prescription dose. These dose distributions were analyzed for conformity and homogeneity and compared to reference dose distributions from uniformly-loaded 125I plaques. The most conformal and homogeneous dose distributions were reproduced within a reference eye environment to assess organ-at-risk (OAR) doses in the Pinnacle3 treatment planning system (TPS). The gamma-index analysis method was used to quantitatively compare MC and TPS-generated dose distributions.ResultsConcentrating > 97% of the total source strength in a single or pair of central 103Pd seeds produced the most conformal dose distributions, with tumor basal doses a factor of 2-3 higher and OAR doses a factor of 2-3 lower than those of corresponding uniformly-loaded 125I plaques. Concentrating 82-86% of the total source strength in peripherally-loaded 131Cs seeds produced the most homogeneous dose distributions, with tumor basal doses 17-25% lower and OAR doses typically 20% higher than those of corresponding uniformly-loaded 125I plaques. Gamma-index analysis found > 99% agreement between MC and TPS dose distributions.ConclusionsA method was developed to select intra-plaque ring radionuclide compositions and source strengths to deliver more conformal and homogeneous tumor dose distributions than uniformly-loaded 125I plaques. This method may support coordinated investigations of an appropriate clinical target for eye plaque brachytherapy.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Keeping an eye on the ring: COMS plaque loading optimization for improved dose conformity and homogeneity

Gagne¹,

Cutright²,

Rivard³

2012

jcb

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“…An additional approach uses a TG-43 hybrid technique where MC calculations for rigid brachytherapy geometries are performed for input to conventional brachytherapy planning systems. [52][53][54][55][56] This technique has been performed for HDR 192 Ir gynecological implants, skin applicators, deepseated breast lumpectomy cavities, and for LDR eye plaque brachytherapy planning.…”

Section: Iia Semiempirical Approachesmentioning

confidence: 99%

“…Since then, a number of investigators have applied the gamma-index concept to brachytherapy. Yang et al 56 compared MC dosimetry results for HDR 192 Ir breast applicator to those obtained using a TG-43 hybrid MBDCA approach and found a 99.24% gamma-index pass rate with 1% and 1 mm criterion, and a 99.95% pass rate for a 2% and 2 mm criterion. Petrokokkinos et al 72 examined the accuracy of the Acuros R system in comparison to MCNPX-based MC simulations for the dose distribution from a HDR 192 Ir source in the presence of a shielded vaginal applicator.…”

Section: Vc3 Gamma-index Comparisonsmentioning

confidence: 99%

Report of the Task Group 186 on model‐based dose calculation methods in brachytherapy beyond the TG‐43 formalism: Current status and recommendations for clinical implementation

et al. 2012

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The charge of Task Group 186 (TG-186) is to provide guidance for early adopters of model-based dose calculation algorithms (MBDCAs) for brachytherapy (BT) dose calculations to ensure practice uniformity. Contrary to external beam radiotherapy, heterogeneity correction algorithms have only recently been made available to the BT community. Yet, BT dose calculation accuracy is highly dependent on scatter conditions and photoelectric effect cross-sections relative to water. In specific situations, differences between the current water-based BT dose calculation formalism (TG-43) and MBDCAs can lead to differences in calculated doses exceeding a factor of 10. MBDCAs raise three major issues that are not addressed by current guidance documents: (1) MBDCA calculated doses are sensitive to the dose specification medium, resulting in energy-dependent differences between dose calculated to water in a homogeneous water geometry (TG-43), dose calculated to the local medium in the heterogeneous medium, and the intermediate scenario of dose calculated to a small volume of water in the heterogeneous medium. (2) MBDCA doses are sensitive to voxel-by-voxel interaction cross sections. Neither conventional single-energy CT nor ICRU∕ICRP tissue composition compilations provide useful guidance for the task of assigning interaction cross sections to each voxel. (3) Since each patient-source-applicator combination is unique, having reference data for each possible combination to benchmark MBDCAs is an impractical strategy. Hence, a new commissioning process is required. TG-186 addresses in detail the above issues through the literature review and provides explicit recommendations based on the current state of knowledge. TG-43-based dose prescription and dose calculation remain in effect, with MBDCA dose reporting performed in parallel when available. In using MBDCAs, it is recommended that the radiation transport should be performed in the heterogeneous medium and, at minimum, the dose to the local medium be reported along with the TG-43 calculated doses. Assignments of voxel-by-voxel cross sections represent a particular challenge. Electron density information is readily extracted from CT imaging, but cannot be used to distinguish between different materials having the same density. Therefore, a recommendation is made to use a number of standardized materials to maintain uniformity across institutions. Sensitivity analysis shows that this recommendation offers increased accuracy over TG-43. MBDCA commissioning will share commonalities with current TG-43-based systems, but in addition there will be algorithm-specific tasks. Two levels of commissioning are recommended: reproducing TG-43 dose parameters and testing the advanced capabilities of MBDCAs. For validation of heterogeneity and scatter conditions, MBDCAs should mimic the 3D dose distributions from reference virtual geometries. Potential changes in BT dose prescriptions and MBDCA limitations are discussed. When data required for full MBDCA implementation are insufficient, interim ...

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“…Also, a new technique which may be applicable to these shielded applicators, called tufts, has been developed recently for complex MC-based brachytherapy dose distributions using conventional TPS. 29,30 Furthermore, there has been more and more work done on programs capable of accounting for inhomogeneity in the surrounding materials, such as with the grid-based Boltzmann solvers. 31,32 In 2012, the Task Group 186 report strongly recommended using these sorts of programs for calculating brachytherapy doses and specifically mentioned the need to be able to account for shielded applicators.…”

Section: Discussionmentioning

confidence: 99%

HDR brachytherapy of rectal cancer using a novel grooved‐shielding applicator design

et al. 2013

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Treatment planning of a skin‐sparing conical breast brachytherapy applicator using conventional brachytherapy software

Cited by 18 publications

References 21 publications

Keeping an eye on the ring: COMS plaque loading optimization for improved dose conformity and homogeneity

Keeping an eye on the ring: COMS plaque loading optimization for improved dose conformity and homogeneity

Report of the Task Group 186 on model‐based dose calculation methods in brachytherapy beyond the TG‐43 formalism: Current status and recommendations for clinical implementation

HDR brachytherapy of rectal cancer using a novel grooved‐shielding applicator design

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