D Sawkey's research while affiliated with Siemens Healthineers and other places

... MaximumEpsilonStep Maximum relative tolerance of the position and momentum inaccuracy for the integration of a step standard_opt4 physics list in TOPAS, corresponding to G4EMStandardPhysics_option4 7 in Geant4, is used to define the electromagnetic processes, models and its parameters for all particles with settings which are appropriate for radiotherapy with photons and charged particle beams (Ivanchenko et al 2020). For photons, the pair production is handled by the BetheHeitler5D model, the Compton scattering by the G4LowEPComptonModel (<20 MeV) and both the photo-electric effect and the Rayleigh scattering by the Livermore models. ...

... Muon interactions with materials in Geant4 are simulated using the Wentzel-VI Combined Scattering Model for electromagnetic interactions. 28,29 The drift radius is the distance of the closest approach between muon tracks and the central anode wire as the muon travels through a drift tube. While muon tracks can be reconstructed from experimental drift radius measurements, secondary electrons (delta rays) produced by muons' interactions with electrons in the detector gas also deposit energy in the drift tube gas. ...

... Feng et al. used BEAMnrc and DOSXYZnrc codes to simulate the beam characteristics from small fields, based on the TrueBeam linear particle accelerator (LINAC) (Varian Medical Systems, Palo Alto, CA, USA) flattening-filter-free (FFF) mode [3]. The Geant4based MC model is used to evaluate the accuracy of out-of-field dose predictions at extended distances, which are comprised of scattering from within the patient and treatment head leakage, thus reflecting the accuracy of the head shielding model proposed by Wijsooriya et al. [12]. The MCNPX code was used by Chibani et al. to simulate three different photon beams from two machines: the Siemens 18 MV, Varian 15 MV (Varian Medical Systems) and Varian 18 MV (Varian Medical Systems) [7]. ...

... For our simulation, we used a GEANT4-based [17] framework where different configurations have been investigated as shown in figure 3. The standard emstandard with opt4 physics constructor was employed as it is suggested to be used for applications that require higher accuracy of electrons, hadrons and ion tracking. For more details on the implementation with a particular focus on the MS see [18,19] and references therein. The first simulation regarded the estimation of the MS effect in the case of a full Fe blast ( = 7.87 g/cm 3 ) furnace as the worst-case scenario (left side of figure 3). ...

... To understand what happens during these collisions, sophisticated simulations of the detectors inside the LHC are generated. The majority of these simulations are founded on Monte Carlo methods [2], which yield results of high quality, albeit with a significant computational expense. In response, researchers investigate strategies to optimize resource use, including the application of generative machine learning methods to lessen CPU consumption [3], [4]. ...

... Multiple general-purpose MC codes are currently available, such as EGS4 [4], MCNP [5], PENELOPE [6] and Geant4 [7]. Nowadays, Geant4, a software toolkit originally created for high energy physics applications, is considered by many the main reference in the field of medical physics [8]. It is the most common choice for nuclear medicine applications due to its accurate physics models [9]. ...

... The tortuous path of the energetic electron emitted by the gamma was modeled with a realistic inelastic mean free path in BGO at 511 keV in the order of a fraction of microns [19]. The optical photons produced by scintillation and Cerenkov emission from energetic electrons were simultaneously generated using the Livermore Model [28]. Optical photons transport was conducted using the LUT Davis model [15,18]. ...

... [23][24][25][26] Prior research indicates that a DQE(0) of at least 20% is needed for sufficient image quality without delivering excessive dose to the patient, with non-negligible dose concerns emerging due to daily imaging of patients for modern IGRT. 2,43 However, conventional linear accelerators typically acquire MV images using a cone-beam CT geometry and flat-panel electronic portal imaging device (EPID) with a much lower detective efficiency of 1% to 2%. 44 Thus, it is of interest to consider the applicability of our work in the context of conventional cone-beam CT. ...

... Rodrigues et al. previously validated the vendor-provided electron phase-space files for conventional electron therapy, with the MLCs fully retracted. 23 The number of particles in the vendor-provided phase space is not large enough for these simulations, so we assume rotational symmetry for the upper part of the treatment head (and hence the phase-space file), and each particle is randomly rotated about the central axis (CAX) of the beam prior to calculation. ...

... This approach allows for a precise and simultaneous evaluation of absorbed dose and average LETs, for a voxel size of arbitrary dimensions, with negligible dependence with the cut variations [18]. Electromagnetic and hadronic interactions were simulated with the G4EmStandardPhysics-option4 and the QGSP-BIC-HP physics list, respectively [19,20]. More details on the Monte Carlo simulations of absorbed dose and LET are given in [17]. ...