Abstract
The purpose of this work was to develop a user friendly, accurate, real‐time computer simulator to facilitate the design of dual foil scattering systems for electron beams on radiotherapy accelerators. The simulator allows for a relatively quick, initial design that can be refined and verified with subsequent Monte Carlo (MC) calculations and measurements. The simulator also is a powerful educational tool. The simulator consists of an analytical algorithm for calculating electron fluence and X‐ray dose and a graphical user interface (GUI) C++ program. The algorithm predicts electron fluence using Fermi‐Eyges multiple Coulomb scattering theory with the reduced Gaussian formalism for scattering powers. The simulator also estimates central‐axis and off‐axis X‐ray dose arising from the dual foil system. Once the geometry of the accelerator is specified, the simulator allows the user to continuously vary primary scattering foil material and thickness, secondary scattering foil material and Gaussian shape (thickness and sigma), and beam energy. The off‐axis electron relative fluence or total dose profile and central‐axis X‐ray dose contamination are computed and displayed in real time. The simulator was validated by comparison of off‐axis electron relative fluence and X‐ray percent dose profiles with those calculated using EGSnrc MC. Over the energy range 7–20 MeV, using present foils on an Elekta radiotherapy accelerator, the simulator was able to reproduce MC profiles to within 2% out to 20 cm from the central axis. The central‐axis X‐ray percent dose predictions matched measured data to within 0.5%. The calculation time was approximately 100 ms using a single Intel 2.93 GHz processor, which allows for real‐time variation of foil geometrical parameters using slider bars. This work demonstrates how the user‐friendly GUI and real‐time nature of the simulator make it an effective educational tool for gaining a better understanding of the effects that various system parameters have on a relative dose profile. This work also demonstrates a method for using the simulator as a design tool for creating custom dual scattering foil systems in the clinical range of beam energies (6–20 MeV).PACS number: 87.10.Ca
Highlights
324 Carver et al.: Real-time dual scattering foil simulator underlying critical structures
The analytical and Monte Carlo (MC)-calculated central-axis X-ray percent dose at a depth of Rp + 2 cm and off-axis X-ray percent dose profiles were compared
As mentioned in the Methods section, the MC model used for these comparisons was previously validated by Harris.(13)
Summary
324 Carver et al.: Real-time dual scattering foil simulator underlying critical structures. Hogstrom,(1) Tapley,(2) Vaeth and Meyer,(3) and Gerbi et al(4) enumerate a number of patient sites for which electron beam therapy may be utilized. It is useful in treatment of cancer of the skin such as eyelids, nose, ear, scalp, and lips, as well as more widely spread diseases of limbs (e.g., melanoma, lymphoma, and sarcoma) or total skin (mycosis fungoides). Electron beam therapy is used to treat disease of the upper respiratory and digestive tract (e.g., floor of mouth, soft palate, retromolar trigone, and salivary glands), postmastectomy chest wall, postlumpectomy tumor bed, and lymph nodes. Electron beam therapy has been used intracavitarily and intraoperatively
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