Generation of photon energy deposition kernels using the EGS Monte Carlo code

Abstract

The EGS Monte Carlo code was used to generate photon energy deposition kernels which describe the energy deposited by charged particles set in motion by primary, first scattered, second scattered, multiple scattered and bremsstrahlung plus annihilation photons. These were calculated for a water medium irradiated with monoenergetic photons with energies in the range 0.1-50 MeV. In addition to the primary energy deposition kernels, primary charged particle transport was further characterised by computing the effective centre of the voxels, and the effective penetration depth, effective radius and effective lateral distance travelled by these particles. The dose per unit collision kerma for parallel monoenergetic primary photons beta' was calculated. Additional applications of the energy deposition kernels are discussed.

Dosimetric verification of the anisotropic analytical algorithm for radiotherapy treatment planning

“…The AAA is just one of many convolution-superposition models implemented in commercial treatment planning systems; the collapsed cone convolution (CCC) models of the Pinnacle [16,21] and Helax-TMS [1] planning systems (ADAC, Milpitas, CA, USA and Nucletron, Veenendaal, Netherlands respectively) are perhaps the most widely studied in the literature. The accuracy of these two algorithms has been evaluated in several studies; while exact comparison of the results in those reports with the results obtained in this study is not practical, some general comments can be made.…”

Dose calculation algorithms in external beam photon radiation therapy

“…These physical processes are simplified by using a convolution equation that convolutes the primary photon energy fluence (terma -total energy released in unit of mass) with a kernel that describes the contribution from scattering photons and electrons, and the method is called the convolution algorithm. [7][8][9][10][11][12][13][14][15][16][17][18][19][20] If the path length is replaced by radiological path length to describe the inhomogeneity of media, the method is called convolution-superposition. The details of how to handle this convolution kernel give rise to sub-difference algorithms that are applied in different commercial treatment plan systems: Pencil Beam Convolution (PBC) [12][13][14] , the Analytical Anisotropic Algorithm (AAA) 15,18 (Varian Medical System, Inc. Palo Alto, CA, USA ), and Collapse Cone Convolution (CCC) algorithms 16,19,20 (Pinnacle, CMS XiO, etc).…”

“…15,18 In CCC, the kernel is replaced by a certain number of discrete elements and the mean for all elements is used to simplify and reduce the calculation time. 16,19,20 Many research results imply that CCC is more accurate than AAA when an inhomogeneity correction needs to be applied [21][22][23] , which indicates that CCC handles the lateral scattering better than does AAA in a heterogeneous environment. Monte-Carlo algorithm is not a new technique but has been used as a benchmark to check the accuracy of other dose calculation algorithms.…”

“…To take advantage of the accuracy of the Monte-Carlo algorithm and avoid its slow speed, simplification of beam particle transport in patient body was made, leading to the AAA and CCC algorithms. [15][16][17][18][19][20][21] Similar to Monte-Carlo algorithm, Acuros XB tries to simulate all the physical processes that beam particles involveinstead of generating beam particles one by one in the simulation process, Acuros XB uses a group of Boltzmann transport equations (BTE) to describe all the physical processes involved 31 , and these equations are solved using numerical methods in the computer world, which is much faster than Monte-Carlo (and even the AAA algorithm) but still provides a comparable accuracy to the Monte-Carlo algorithm. The Acuros XB algorithm was recently implemented in the Varian Eclipse Version 10.1, and is available in clinic.…”

Towards real-time radiation therapy: GPU accelerated superposition/convolution

“…However, this effect is negligible and a single poly-energetic kernel has been shown to be sufficiently accurate for clinical use and is the current standard of care. Poly-energetic kernels are created by combining a spectrum of mono-energetic kernels, which are generated using Monte Carlo simulations that forces monoenergetic photons to interact at the center of a water sphere and tallying the dose deposited everywhere in that sphere [10,11].…”