Experimental determination and verification of the parameters used in a proton pencil beam algorithm

Szymanowski, H.; Mazal, A.; Nauraye, C.; Biensan, S.; Ferrand, R.; Murillo, M.-C.; Caneva, S.; Gaboriaud, G.; Rosenwald, J. C.

doi:10.1118/1.1376445

Cited by 48 publications

(52 citation statements)

References 24 publications

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“…Treatment planning Dose calculations were established with dose-scoring grid resolution of 1 3 1 3 1 mm 3 by the ISIS 3D treatment planning system (Technologie Diffusion, France), which comprises broad beam and pencil beam algorithms for proton beam calculations [22][23][24] and dose engine for photons. The photon algorithms are based on a double decomposition algorithm and Clarkson-Cunningham integration, with inhomogeneity corrections based on the 3D subtraction method.…”

Section: Methodsmentioning

confidence: 99%

Use of gEUD for predicting ear and pituitary gland damage following proton and photon radiation therapy

Marzi¹,

Feuvret²,

Boulé³

et al. 2015

BJR

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Objective: To determine the relationship between the dose to the inner ear or pituitary gland and radiationinduced late effects of skull base radiation therapy. Methods: 140 patients treated between 2000 and 2008 were considered for this study. Hearing loss and endocrine dysfunction were retrospectively reviewed on pre-and post-radiation therapy audiometry or endocrine assessments. Two normal tissue complication probability (NTCP) models were considered (LymanKutcher-Burman and log-logistic) whose parameters were fitted to patient data using receiver operating characteristics and maximum likelihood analysis. The method provided an estimation of the parameters of a generalized equivalent uniform dose (gEUD)-based NTCP after conversion of dose-volume histograms to equivalent doses.

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Section: Methodsmentioning

confidence: 99%

Use of gEUD for predicting ear and pituitary gland damage following proton and photon radiation therapy

Marzi¹,

Feuvret²,

Boulé³

et al. 2015

BJR

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“…10,12 This expression follows the assumption that the proton beamlet is directly incident on a uniform target. However, for the case of a trimmed dose distribution, in which the trimmer blades interact with the beamlet before it reaches the target, a simple symmetric Gaussian along each axis is insufficient to describe the lateral distribution of the now asymmetric beamlet.…”

Section: C Modeling Asymmetric Beamlets-lateral Distributionmentioning

confidence: 99%

A method for modeling laterally asymmetric proton beamlets resulting from collimation

et al. 2015

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Purpose: To introduce a method to model the 3D dose distribution of laterally asymmetric proton beamlets resulting from collimation. The model enables rapid beamlet calculation for spot scanning (SS) delivery using a novel penumbra-reducing dynamic collimation system (DCS) with two pairs of trimmers oriented perpendicular to each other. Methods: Trimmed beamlet dose distributions in water were simulated with MCNPX and the collimating effects noted in the simulations were validated by experimental measurement. The simulated beamlets were modeled analytically using integral depth dose curves along with an asymmetric Gaussian function to represent fluence in the beam's eye view (BEV). The BEV parameters consisted of Gaussian standard deviations (sigmas) along each primary axis (σ x1 ,σ x2 ,σ y1 ,σ y2 ) together with the spatial location of the maximum dose (µ x ,µ y ). Percent depth dose variation with trimmer position was accounted for with a depth-dependent correction function. Beamlet growth with depth was accounted for by combining the in-air divergence with Hong's fit of the Highland approximation along each axis in the BEV. Results: The beamlet model showed excellent agreement with the Monte Carlo simulation data used as a benchmark. The overall passing rate for a 3D gamma test with 3%/3 mm passing criteria was 96.1% between the analytical model and Monte Carlo data in an example treatment plan. Conclusions: The analytical model is capable of accurately representing individual asymmetric beamlets resulting from use of the DCS. This method enables integration of the DCS into a treatment planning system to perform dose computation in patient datasets. The method could be generalized for use with any SS collimation system in which blades, leaves, or trimmers are used to laterally sharpen beamlets. C 2015 American Association of Physicists in Medicine.

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“…For a more detailed treatment of 2D scaling theory, the reader is referred to the original papers by Szymanowski and Oelfke. 17,28 …”

Section: D Scaling Theorymentioning

confidence: 99%

A generalized 2D pencil beam scaling algorithm for proton dose calculation in heterogeneous slab geometries

Westerly¹,

Mo²,

Mackie³

et al. 2013

Medical Physics

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Purpose: Pencil beam algorithms are commonly used for proton therapy dose calculations. Szymanowski and Oelfke ["Two-dimensional pencil beam scaling: An improved proton dose algorithm for heterogeneous media," Phys. Med. Biol. 47, 3313-3330 (2002)] developed a two-dimensional (2D) scaling algorithm which accurately models the radial pencil beam width as a function of depth in heterogeneous slab geometries using a scaled expression for the radial kernel width in water as a function of depth and kinetic energy. However, an assumption made in the derivation of the technique limits its range of validity to cases where the input expression for the radial kernel width in water is derived from a local scattering power model. The goal of this work is to derive a generalized form of 2D pencil beam scaling that is independent of the scattering power model and appropriate for use with any expression for the radial kernel width in water as a function of depth. Methods: Using Fermi-Eyges transport theory, the authors derive an expression for the radial pencil beam width in heterogeneous slab geometries which is independent of the proton scattering power and related quantities. The authors then perform test calculations in homogeneous and heterogeneous slab phantoms using both the original 2D scaling model and the new model with expressions for the radial kernel width in water computed from both local and nonlocal scattering power models, as well as a nonlocal parameterization of Molière scattering theory. In addition to kernel width calculations, dose calculations are also performed for a narrow Gaussian proton beam. Results: Pencil beam width calculations indicate that both 2D scaling formalisms perform well when the radial kernel width in water is derived from a local scattering power model. Computing the radial kernel width from a nonlocal scattering model results in the local 2D scaling formula under-predicting the pencil beam width by as much as 1.4 mm (21%) at the depth of the Bragg peak for a 220 MeV proton beam in homogeneous water. This translates into a 32% dose discrepancy for a 5 mm Gaussian proton beam. Similar trends were observed for calculations made in heterogeneous slab phantoms where it was also noted that errors tend to increase with greater beam penetration. The generalized 2D scaling model performs well in all situations, with a maximum dose error of 0.3% at the Bragg peak in a heterogeneous phantom containing 3 cm of hard bone. Conclusions:The authors have derived a generalized form of 2D pencil beam scaling which is independent of the proton scattering power model and robust to the functional form of the radial kernel width in water used for the calculations. Sample calculations made with this model show excellent agreement with expected values in both homogeneous water and heterogeneous phantoms.

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Experimental determination and verification of the parameters used in a proton pencil beam algorithm

Cited by 48 publications

References 24 publications

Use of gEUD for predicting ear and pituitary gland damage following proton and photon radiation therapy

Use of gEUD for predicting ear and pituitary gland damage following proton and photon radiation therapy

A method for modeling laterally asymmetric proton beamlets resulting from collimation

A generalized 2D pencil beam scaling algorithm for proton dose calculation in heterogeneous slab geometries

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