Parameterization of photon beam dosimetry for a linear accelerator

Lebron, S; Lü, Bo; Yan, G; Kahler, Darren; Li, Jonathan G.; Barraclough, B; Liu, Chihray

doi:10.1118/1.4939261

Cited by 9 publications

(16 citation statements)

References 12 publications

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“…In our previous work, we demonstrated that the penumbra region (P) can be characterized with a modified sigmoid function,

P false(r false) = {italicβ}_{1} - (\frac{{italicβ}_{2}}{1 + e^{- \frac{r - α_{1}}{{italicα}_{2}}}})

where r is the radial distance from the CAX; α and β are field size‐, energy‐ and depth‐dependent parameters. The physical meaning of the parameters and the method to segment the profiles can be found in our previous paper . We have demonstrated that this function can successfully parameterize the penumbra region of beam profiles with field sizes ranging from 2 × 2 to 40 × 40 cm .…”

Section: Methodsmentioning

confidence: 99%

“…The physical meaning of the parameters and the method to segment the profiles can be found in our previous paper . We have demonstrated that this function can successfully parameterize the penumbra region of beam profiles with field sizes ranging from 2 × 2 to 40 × 40 cm . Figure (a) shows the penumbra region to be fitted with Eq.…”

Section: Methodsmentioning

confidence: 99%

“…The 6 mm extension was empirically chosen such that the analytical model can be equally applied to different field sizes (2 × 2 cm 2 to 40 × 40 cm 2 ). The optimal parameters can be found using a least square optimization method . The inflection point of the curve (i.e., field edge) was determined by setting the second derivative of Eq.…”

Section: Methodsmentioning

confidence: 99%

“…The authors recently proposed a method to parameterize photon beam profiles. The method characterizes the penumbra region of a photon beam profile with an analytical function where the location of the inflection point can be exactly determined, making it suitable for field size determination.…”

Section: Introductionmentioning

confidence: 99%

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A universal parameterized gradient‐based method for photon beam field size determination

Lebron

Yan

et al. 2017

Medical Physics

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“…In our previous work, we demonstrated that the penumbra region (P) can be characterized with a modified sigmoid function,

P false(r false) = {italicβ}_{1} - (\frac{{italicβ}_{2}}{1 + e^{- \frac{r - α_{1}}{{italicα}_{2}}}})

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A universal parameterized gradient‐based method for photon beam field size determination

Lebron

Yan

et al. 2017

Medical Physics

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“…Second, interpolation and correlation can be used to incorporate data published by other sources into the model, thereby reducing the number of measurements that needs to be collected on site. LeBron et al [9] echo this assertion by advocating the portability of data sets and the ease of evaluating the characteristics of different materials. For instance, Du Plessis et al [7] present a detailed analysis of linear attenuation measurements in several materials with different atomic numbers.…”

Section: Introductionmentioning

confidence: 90%

Analytical Derivation and Validation of Dosimetric Parameters for Gamma Putty Attenuators with Megavoltage Photon Beams

Gloi¹

2017

Am. J. Biomed. Sci.

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Background: Several descriptors are used to characterize the dosimetric parameters of a photon beam through an attenuator. This study evaluates these descriptors analytically through various thicknesses of Gamma Putty. Specifically, we measure percent ionization depth doses as a function of depth and field size, and fit three models to the data. Materials and Methods: Measurements of percent ionization at various depths along the central axis were generated from 6 MV and 18 MV photon beams at a source-axis distance of 100 cm with an ionization in solid water phantom. We fit analytic models to the data to determine linear attenuation, beam hardening, beam quality, and electron contamination. Results: We report best-fit parameters for all the analytical models. All models yielded a root mean square (RMS) error of less than 1% with respect to the data. At depths below 5cm in the phantom, the largest attenuation coefficients (μ) were observed for the 6 MV beam, regardless of Gamma Putty thickness. Also, the smallest field sizes (4×4 and 5×5 cm 2 ) have the largest attenuation coefficients at these depths, for both beam energies. At a depth of 10 cm, the variation in μ was negligible for both beam energies. Conclusions: By fitting parametric models to axial ionization profiles, it is possible to characterize the dosimetric parameters of any attenuator as a function of thickness and field size, without knowing the precise spectral distribution of the beam. Parameters such as attenuation coefficients, beam hardening, and electron contamination can then be calculated accurately for any combination of field size and attenuator thickness.

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Dynamic range and optimization strategies for radiochromic film calibration using gradient radiation fields

Pecic,

Belca,

Stojadinovic

et al. 2024

J Applied Clin Med Phys

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This investigation aimed to optimize gradient positioning for radiochromic film calibration to facilitate a uniform distribution of calibration points. The study investigated the influence of various parameters on gradient dose profiles generated by a physical wedge, assessing their impact on the field's dose dynamic range, a scalar quantity representing the span of absorbed doses. Numerical parameterization of the physical wedge profile was used to visualize and quantify the impact of field size, depth, and energy on the dynamic range of dose gradients. This concept enabled the optimization of the gradient positioning and estimation of the necessary number of exposures for the desired calibration dose range. An optimization algorithm based on histogram bin height minimization was developed and presented. The maximum dynamic range was achieved with a 20 20 field size at 5 cm depth. Optimization of wedge gradient positioning yielded the most uniform dose distribution with 7 exposures for the [1,10] Gy range and 8 exposures for the [1,20] Gy range. Film calibration using gradients centered at 1.6, 3, 3.5, and 7 Gy central axis (CAX), obtained through optimized gradient positioning, was showcased. The presented work demonstrates the potential for an improved film calibration process, with efficient material utilization and enhanced dosimetric accuracy for clinical applications. While the method was described for the use of a physical wedge, the methodology can be easily extended to the use of a more convenient dynamic wedge.

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Parameterization of photon beam dosimetry for a linear accelerator

Abstract: This novel analytical model with minimum measurement requirements was proved to accurately calculate PDDs, profiles, and S(cp) for different field sizes, depths, and energies.

Cited by 9 publications

References 12 publications

A universal parameterized gradient‐based method for photon beam field size determination

A universal parameterized gradient‐based method for photon beam field size determination

Analytical Derivation and Validation of Dosimetric Parameters for Gamma Putty Attenuators with Megavoltage Photon Beams

Dynamic range and optimization strategies for radiochromic film calibration using gradient radiation fields

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