Simple variance reduction in Monte Carlo calculations of specific absorbed fractions: Russian roulette and splitting at the source organ.

Purpose: To investigate the capabilities of several variance reduction techniques in the calculation of specific absorbed fractions in cases where the source and the target organs are far away and/or the target organs have a small volume.

Methods: The specific absorbed fractions have been calculated by using the Monte Carlo code PENELOPE and by assuming the thyroid gland as the source organ and the testicles, the urinary bladder, the uterus, and the ovaries as the target ones. A mathematical anthropomorphic phantom, similar to the MIRD-type phantoms, has been considered.

Monte Carlo calculation of specific absorbed fractions: variance reduction techniques.

The purpose of the present work is to calculate specific absorbed fractions using variance reduction techniques and assess the effectiveness of these techniques in improving the efficiency (i.e. reducing the statistical uncertainties) of simulation results in cases where the distance between the source and the target organs is large and/or the target organ is small.

A jaw calibration method to provide a homogeneous dose distribution in the matching region when using a monoisocentric beam split technique.

Purpose: Asymmetric collimators are currently available in most of linear accelerators. They involve a lot of clinical improvements, such as the monoisocentric beam split technique that is more and more used in many external radiotherapy treatments. The tolerance established for each independent jaw positioning is 1 mm.

Ant colony algorithm implementation in electron and photon Monte Carlo transport: application to the commissioning of radiosurgery photon beams.

Purpose: In this work, the authors describe an approach which has been developed to drive the application of different variance-reduction techniques to the Monte Carlo simulation of photon and electron transport in clinical accelerators.

Methods: The new approach considers the following techniques: Russian roulette, splitting, a modified version of the directional bremsstrahlung splitting, and the azimuthal particle redistribution. Their application is controlled by an ant colony algorithm based on an importance map.

Dosimetric characterization of an 192Ir brachytherapy source with the Monte Carlo code PENELOPE.

Monte Carlo calculations are highly spread and settled practice to calculate brachytherapy sources dosimetric parameters. In this study, recommendations of the AAPM TG-43U1 report have been followed to characterize the Varisource VS2000 (192)Ir high dose rate source, provided by Varian Oncology Systems. In order to obtain dosimetric parameters for this source, Monte Carlo calculations with PENELOPE code have been carried out.

Multiple scattering of 13 and 20 MeV electrons by thin foils: a Monte Carlo study with GEANT, Geant4, and PENELOPE.

Purpose: In this work, recent results from experiments and simulations (with EGSnrc) performed by Ross et al. [Med. Phys.

Monte Carlo simulation using the PENELOPE code with an ant colony algorithm to study MOSFET detectors.

In this work we have developed a simulation tool, based on the PENELOPE code, to study the response of MOSFET devices to irradiation with high-energy photons. The energy deposited in the extremely thin silicon dioxide layer has been calculated. To reduce the statistical uncertainties, an ant colony algorithm has been implemented to drive the application of splitting and Russian roulette as variance reduction techniques.

Effect of the multiple scattering of electrons in Monte Carlo simulation of LINACS.

Results obtained from Monte Carlo simulations of the transport of electrons in thin slabs of dense material media and air slabs with different widths are analyzed. Various general purpose Monte Carlo codes have been used: PENELOPE, GEANT3, GEANT4, EGSNRC, MCNPX. Non-negligible differences between the angular and radial distributions after the slabs have been found.