An interface tool to parametrize treatment plans for the TrueBeam radiotherapy system into TOPAS parameter control files for Monte Carlo simulation.

Purpose: The Monte Carlo (MC) method, the gold standard method for radiotherapy dose calculations, is underused in clinical research applications mainly due to computational speed limitations. Another reason is the time-consuming and error prone conversion of treatment plan specifications into MC parameters. To address this issue, we developed an interface tool that creates a set of TOPAS parameter control files (PCF) from information exported from a clinical treatment planning system (TPS) for plans delivered by the TrueBeam radiotherapy system.

Technical Note: A dose calculation framework for dynamic electron arc radiotherapy (DEAR) using VirtuaLinac Monte Carlo simulation tool.

Purpose: Dynamic electron arc radiotherapy (DEAR) is a novel dynamic technique that achieves highly conformal dose through simultaneous couch and gantry motion during delivery. The purpose of this study is to develop a framework integrating a Monte Carlo dose engine (VirtuaLinac) to a treatment planning system (TPS, Eclipse) for DEAR. A quality assurance (QA) procedure is also developed.

Part II: Verification of the TrueBeam head shielding model in Varian VirtuaLinac via out-of-field doses.

Purpose: A good Monte Carlo model with an accurate head shielding model is important in estimating the long-term risks of unwanted radiation exposure during radiation therapy. The aim of this paper was to validate the Monte Carlo simulation of a TrueBeam linear accelerator (linac) head shielding model. We approach this by evaluating the accuracy of out-of-field dose predictions at extended distances which are comprised of scatter from within the patient and treatment head leakage and thus reflect the accuracy of the head shielding model.

Abstract ID: 142 Monte Carlo modeling of Varian TrueBeam with Geant4-based VirtuaLinac and comparison to experiments.

Monte Carlo simulations can provide powerful insight into the physical phenomena and geometrical interactions of linear accelerator beams. This insight can be used to understand the phenomena that govern the beam characteristic and, for instance, to guide the development of treatment planning systems. In this study, we use the VirtuaLinac, a cloud-based application to model the treatment head of the Varian TrueBeam linear accelerator.

A piecewise-focused high DQE detector for MV imaging.

Purpose: Electronic portal imagers (EPIDs) with high detective quantum efficiencies (DQEs) are sought to facilitate the use of the megavoltage (MV) radiotherapy treatment beam for image guidance. Potential advantages include high quality (treatment) beam's eye view imaging, and improved cone-beam computed tomography (CBCT) generating images with more accurate electron density maps with immunity to metal artifacts. One approach to increasing detector sensitivity is to couple a thick pixelated scintillator array to an active matrix flat panel imager (AMFPI) incorporating amorphous silicon thin film electronics.

A Monte Carlo simulation framework for electron beam dose calculations using Varian phase space files for TrueBeam Linacs.

Purpose: To develop a framework for accurate electron Monte Carlo dose calculation. In this study, comprehensive validations of vendor provided electron beam phase space files for Varian TrueBeam Linacs against measurement data are presented.

Methods: In this framework, the Monte Carlo generated phase space files were provided by the vendor and used as input to the downstream plan-specific simulations including jaws, electron applicators, and water phantom computed in the EGSnrc environment.

A Monte Carlo investigation of low-Z target image quality generated in a linear accelerator using Varian's VirtuaLinac.

Purpose: The focus of this work was the demonstration and validation of VirtuaLinac with clinical photon beams and to investigate the implementation of low-Z targets in a TrueBeam linear accelerator (Linac) using Monte Carlo modeling.

Methods: VirtuaLinac, a cloud based web application utilizing Geant4 Monte Carlo code, was used to model the Linac treatment head components. Particles were propagated through the lower portion of the treatment head using BEAMnrc.

Sensitivity analysis of an asymmetric Monte Carlo beam model of a Siemens Primus accelerator.

The assumption of cylindrical symmetry in radiotherapy accelerator models can pose a challenge for precise Monte Carlo modeling. This assumption makes it difficult to account for measured asymmetries in clinical dose distributions. We have performed a sensitivity study examining the effect of varying symmetric and asymmetric beam and geometric parameters of a Monte Carlo model for a Siemens PRIMUS accelerator.

Monte Carlo commissioning of clinical electron beams using large field measurements.

Monte Carlo simulation can accurately calculate electron fluence at the patient surface and the resultant dose deposition if the initial source electron beam and linear accelerator treatment head geometry parameters are well characterized. A recent approach used large electron fields to extract these simulation parameters. This method took advantage of the absence of lower energy, widely scattered electrons from the applicator resulting in more accurate data.

Comparison of patient megavoltage cone beam CT images acquired with an unflattened beam from a carbon target and a flattened treatment beam.

Purpose: To use an imaging beam line (IBL) to obtain the first megavoltage cone-beam computed tomography (MV CBCT) images of patients with a low atomic number (Z) target, and to compare these images to those taken of the same patients with the 6 MV flattened beam from the treatment beam line (TBL).

Methods: The IBL, which produces a 4.2 MV unflattened beam from a carbon target, was installed on a linear accelerator in use for radiotherapy.

Treatment head disassembly to improve the accuracy of large electron field simulation.

Purpose: The purposes of this study are to improve the accuracy of source and geometry parameters used in the simulation of large electron fields from a clinical linear accelerator and to evaluate improvement in the accuracy of the calculated dose distributions.

Methods: The monitor chamber and scattering foils of a clinical machine not in clinical service were removed for direct measurement of component geometry. Dose distributions were measured at various stages of reassembly, reducing the number of geometry variables in the simulation.

Liquid 3He thermomechanical effect in regular cylinders.

We have measured the normal liquid 3He thermomechanical effect with the liquid confined in the regular 210 nm diameter cylinders of Anopore. The pressure difference resulting from the temperature difference was deltaP/deltaT=25 Pa/mK, independent of temperature, from 0.7 to 12 mK.