Toolkit implementation to exchange phase-space files between IAEA and MCNP6 monte Carlo code format.

Purpose: Some Monte Carlo simulation codes can read and write phase space files in IAEA format, which are used to characterize accelerators, brachytherapy seeds and other radiation sources. Moreover, as the format has been standardized, these files can be used with different simulation codes. However, MCNP6 has not still implemented this capability, which complicate the studies involving this kind of sources and the reproducibility of results among independent researchers.

Brachytherapy organ dose estimation using Monte Carlo simulations of realistic patient models.

Radiation Therapy Planning Systems (RTPS) currently used in hospitals contain algorithms based on deterministic simplifications that do not properly consider electrons lateral transport in the areas where there are changes of density, and as a result, erroneous dose predictions could be produced. According to this, the present work proposes the use of Monte Carlo method in brachytherapy planning systems, which could affect positively on the radiotherapy treatment planning, since it provides results that are more accurate and takes into account the in homogeneities density variations. This paper presents a Monte Carlo (MC) simulation of a brachytherapy prostate treatment with I-125 seeds, using the latest version of MCNP, v.

Study of the photoneutron generation caused by a LinAc Beryllium window with a 6 MeV treatment beam.

In most conventional radiation therapy treatments, special attention is payed for neutron contamination when working with energy beams above 8 MeV and generally it is only considered for shielding requirements, not for dose study in patients or employees. The present work is focused on studying the unwanted generated photoneutrons in a Medical Linear Accelerator (LinAc) Varian TrueBeam using a 6 MeV radiation treatment beam. To that, Monte Carlo (MC) simulation code MCNP6.

Dose calculation in computerized tomography.

The purpose of this work is to develop an automatic methodology to obtain the dose received by a patient, (classified by organs), after being subjected to ionizing radiation because of CT images acquisition. The methodology starts from CT images, these images are automatically segmented and voxelized taking into account the CT numbers in order to obtain a 3D model used in Monte Carlo Simulations to calculate the dose inside the patient.Monte Carlo codes used in this work are MCNP.

Experimental validation of neutron activation simulation of a varian medical linear accelerator.

This work presents a Monte Carlo simulation using the last version of MCNP, v. 6.1.

Neutron distribution and induced activity inside a Linac treatment room.

Induced radioactivity and photoneutron contamination inside a radiation therapy bunker of a medical linear accelerator (Linac) is investigated in this work. The Linac studied is an Elekta Precise electron accelerator which maximum treatment photon energy is 15 MeV. This energy exceeds the photonuclear reaction threshold (around 7 MeV for high atomic number metals).

Air radon concentration decrease in a waste water treatment plant.

(222)Rn is a naturally occurring gas created from the decay of (226)Ra. The long-term health risk of breathing radon is lung cancer. One particular place where indoor radon concentrations can exceed national guidelines is in wastewater treatment plants (WWTPs) where treatment processes may contribute to ambient airborne concentrations.

Neutron activation processes simulation in an Elekta medical linear accelerator head.

Monte Carlo estimation of the giant-dipole-resonance (GRN) photoneutrons inside the Elekta Precise LINAC head (emitting a 15 MV photon beam) were performed using the MCNP6 (general-purpose Monte Carlo N-Particle code, version 6). Each component of LINAC head geometry and materials were modelled in detail using the given manufacturer information. Primary photons generate photoneutrons and its transport across the treatment head was simulated, including the (n, γ) reactions which undergo activation products.

Unfolding X-ray spectra using a flat panel detector.

It is difficult to measure the energy spectrum of X-ray tubes due to the pile up effect produced by the high fluence of photons. Using attenuating materials, appropriate detector devices and the Monte Carlo method, primary X-ray spectrum of these devices can be estimated. In this work, a flat panel detector with a PMMA wedge has been used to obtain a dose curve corresponding to certain working conditions of a radiodiagnostic X-ray tube.

Comparison between transmission and scattering spectrum reconstruction methods based on EPID images.

Numerous improved physics-based methods for Linac photon spectra reconstruction have been published; some of them are based on transmission data analysis and others on scattering data. In this work, the two spectrum unfolding approaches are compared in order to experimentally validate its robustness and to determine which is the optimal methodology for application on a clinical quality assurance routine. Both studied methods are based on EPID images generated when the incident photon beam impinges onto plastic blocks.

MCNP5 Monte Carlo simulation of amorphous silicon EPID dosimetry from MLC radiation therapy treatment beams.

The present work is focused on a MCNP Monte Carlo (MC) simulation of a multi-leaf collimator (MLC) radiation therapy treatment unit including its corresponding Electronic Portal Imaging Device (EPID). We have developed a methodology to perform a spatial calibration of the EPID signal to obtain dose distribution using MC simulations. This calibration is based on several images acquisition and simulation considering different thicknesses of solid water slabs, using a 6 MeV photon beam and a square field size of 20 cm x 20 cm.

Estimated radiation dose reduction using non-linear diffusion method in computed radiography.

In this paper we use a non-linear diffusion method to filter the inherent noise in a Computed Radiography (CR) for reducing the dose absorbed by the patients especially children in pediatric applications, related with the exposure mAs. The method is implemented in order to create a lower CR dose based on the selection of lower X-ray exposure and with a reduction of the noise using a non-linear diffusion method. The impact of several milliAmpere-seconds (mAs) setting on image quality has been studied using the RANDO phantom.

Uncertainty and sensitivity analysis of the effect of the mean energy and FWHM of the initial electron fluence on the Bremsstrahlung photon spectra of linear accelerators.

A calculation of the correct dose in radiation therapy requires an accurate description of the radiation source because uncertainties in characterization of the linac photon spectrum are propagated through the dose calculations. Unfortunately, detailed knowledge of the initial electron beam parameters is not readily available, and many researchers adjust the initial electron fluence values by trial-and-error methods. The main goal of this work was to develop a methodology to characterize the fluence of initial electrons before they hit the tungsten target of an Elekta Precise medical linear accelerator.

6 and 15 MeV photon spectra reconstruction using an unfolding depth dose gradient methodology.

An accurate knowledge of the spectral distribution emission is essential for precise dose calculations in radiotherapy treatment planning. Reconstruction of photon spectra emitted by medical accelerators from measured depth dose distributions in a water cube is an important tool for commissioning a Monte Carlo treatment planning system. However, the reconstruction problem is an inverse radiation transport function which is poorly conditioned and its solution may become unstable due to small perturbations in the input data.

Electron influence on the reconstruction of a linac 6 MeV photon spectra by unfolding methods.

Megavoltage photon sources are normally used for radiotherapy treatments. For these equipments an accurate knowledge of their spectral distribution is essential for accurate dose calculations planning. There are several ways to determine the spectrum of a clinical photon beam: direct measurement, electron source modelling or reconstruction from experimental measures.

Indoor radon measurements in the city of Valencia.

The indoor radon risk in Valencia (Spain) was studied more than twenty years ago in two surveys using different methodologies and leading to contradictory results. We report here on new indoor radon measurements with the charcoal canister technique, which confirm the low average level of indoor radon in the city, with a geometrical mean of 24 Bq/m(3) and an arithmetic mean of 27 Bq/m(3).

Dosimetric capabilities of the Iview GT portal imager using MCNP5 Monte Carlo simulations.

This work is focused on developing a methodology to obtain portal dosimetry with an amorphous silicon Electronic Portal Image Device (a-Si EPID) used in radiotherapy by means of Monte Carlo simulations and experimental measures. Pixel intensity values from portal images have been compared with dose measured from an ionization chamber and dose calculated from Monte Carlo simulations. To this end, several images were acquired with the Elekta iView GT EPID using an attenuator phantom slab (10 cm thickness of solid water) and a 6 MeV photon energy beam with different monitor units settings (MU).

Comparison between voxelized, volumized and analytical phantoms applied to radiotherapy simulation with Monte Carlo.

The purpose of this paper is to provide a comparison between the different methods utilized for building up anthropomorphic phantoms in Radiotherapy Treatment Plans. A simplified model of the Snyder Head Phantom was used in order to construct an analytical, voxelized and volumized phantom, throughout a segmentation program and different algorithms programmed in Matlab code. The irradiation of the resulting phantoms was simulated with the MCNP5 (Monte Carlo N-Particle) transport code, version 5, and the calculations presented in particle flux maps inside the phantoms by utilizing the FMESH tool, superimposed mesh tally.

Comparison of experimental 3D dose curves in a heterogeneous phantom with results obtained by MCNP5 simulation and those extracted from a commercial treatment planning system.

Commercial planning systems used in radiotherapy treatments use determinist correlations to evaluate dose distribution around regions of interest. Estimated dose with this type of planners can be problematic, especially when analyzing heterogeneous zones. The present work is focused in quantifying the dose distribution in a heterogeneous medium irradiated by a 6 MeV photon beam emitted by an Elekta Precise Radiotherapy Unit head.

Monte Carlo simulation of the iView GT portal imager dosimetry.

This work is mainly focused on developing a methodology to obtain portal dosimetry with an amorphous silicon electronic portal image device (EPID) by means of Monte Carlo simulations and experimental measures. According to this, pixel intensity values of portal images have been compared with dose measured from an ionization chamber and dose obtained from Monte Carlo simulations. To that, several images were acquired with the Elekta iView GT EPID using an attenuator phantom slab (10 cm thickness of solid water) and a 6 MV photon energy beam with different monitor units.

3D dose distribution calculation in a voxelized human phantom by means of Monte Carlo method.

The aim of this work is to provide the reconstruction of a real human voxelized phantom by means of a MatLab program and the simulation of the irradiation of such phantom with the photon beam generated in a Theratron 780 (MDS Nordion) (60)Co radiotherapy unit, by using the Monte Carlo transport code MCNP (Monte Carlo N-Particle), version 5. The project results in 3D dose mapping calculations inside the voxelized antropomorphic head phantom. The program provides the voxelization by first processing the CT slices; the process follows a two-dimensional pixel and material identification algorithm on each slice and three-dimensional interpolation in order to describe the phantom geometry via small cubic cells, resulting in an MCNP input deck format output.

Photon spectra calculation for an Elekta linac beam using experimental scatter measurements and Monte Carlo techniques.

The present work is centered in reconstructing by means of a scatter analysis method the primary beam photon spectrum of a linear accelerator. This technique is based on irradiating the isocenter of a rectangular block made of methacrylate placed at 100 cm distance from surface and measuring scattered particles around the plastic at several specific positions with different scatter angles. The MCNP5 Monte Carlo code has been used to simulate the particles transport of mono-energetic beams to register the scatter measurement after contact the attenuator.

Analysis of CR dose reduction in pediatric patients, based on computer-simulated noise addition.

This paper validates a technique to add statistical noise to a Computed Radiography (CR) in order to simulate accurately how the same image would appear if taken at a reduced tube current. To that, a noise addition software has been developed to create lower dose CR using existing pediatric radiographies based on the selection of lower X-ray tube current. The effect of different milliAmpere-seconds (mAs) setting on image quality has been evaluated using the CDMAM 3.

Improving pediatric radiation dose management using Agfa digital radiography DICOM header information.

Dose reduction in pediatric explorations is especially important because of children radiation sensitivity. According to this, with the aim of saving radiation exposure in future clinical practice, we have developed a technique to control delivered dose in pediatric radiographic exams. To that, a computer science program has been developed to calculate entrance skin dose (ESD) provided by AGFA radiology digital system, using the "lgM" parameter exported from Dicom files.

Tally and geometry definition influence on the computing time in radiotherapy treatment planning with MCNP Monte Carlo code.

The present work has simulated the photon and electron transport in a Theratron 780 (MDS Nordion) (60)Co radiotherapy unit, using the Monte Carlo transport code, MCNP (Monte Carlo N-Particle), version 5. In order to become computationally more efficient in view of taking part in the practical field of radiotherapy treatment planning, this work is focused mainly on the analysis of dose results and on the required computing time of different tallies applied in the model to speed up calculations.