E.M. Souza

Methodology for digital radiography simulation using the Monte Carlo code MCNPX for industrial applications.

This work presents a methodology for digital radiography simulation for industrial applications using the MCNPX radiography tally. In order to perform the simulation, the energy-dependent response of a BaFBr imaging plate detector was modeled and introduced in the MCNPX radiography tally input. In addition, a post-processing program was used to convert the MCNPX radiography tally output into 16-bit digital images. Simulated and experimental images of a steel pipe containing corrosion alveoli and stress corrosion cracking were compared, and the results showed good agreement between both images.

Computed radiography simulation using the Monte Carlo code MCNPX

Simulating X-ray images has been of great interest in recent years as it makes possible an analysis of how X-ray images are affected owing to relevant operating parameters. In this paper, a procedure for simulating computed radiographic images using the Monte Carlo code MCNPX is proposed. The sensitivity curve of the BaFBr image plate detector as well as the characteristic noise of a 16-bit computed radiography system were considered during the methodologys development. The results obtained confirm that the proposed procedure for simulating computed radiographic images is satisfactory, as it allows obtaining results comparable with experimental data.

Dose–image quality study in digital chest radiography using Monte Carlo simulation

One of the main preoccupations of diagnostic radiology is to guarantee a good image-sparing dose to the patient. In the present study, Monte Carlo simulations, with MCNPX code, coupled with an adult voxel female model (FAX) were performed to investigate how image quality and dose in digital chest radiography vary with tube voltage (80-150 kV) using air-gap technique and a computed radiography system. Calculated quantities were normalized to a fixed value of entrance skin exposure (ESE) of 0.0136 R. The results of the present analysis show that the image quality for chest radiography with imaging plate is improved and the dose reduced at lower tube voltage.

Assessment of weld thickness loss in offshore pipelines using computed radiography and computational modeling.

In order to guarantee the structural integrity of oil plants it is crucial to monitor the amount of weld thickness loss in offshore pipelines. However, in spite of its relevance, this parameter is very difficult to determine, due to both the large diameter of most pipes and the complexity of the multi-variable system involved. In this study, a computational modeling based on Monte Carlo MCNPX code is combined with computed radiography to estimate the weld thickness loss in large-diameter offshore pipelines. Results show that computational modeling is a powerful tool to estimate intensity variations in radiographic images generated by weld thickness variations, and it can be combined with computed radiography to assess weld thickness loss in offshore and subsea pipelines.

Evaluation of the dose and of the risk of cancer induction associated with the use of transmission X–ray body scanners using the Monte Carlo MCNPX code

In recent years, X–ray body scanners have been introduced at airports, penitentiaries and other places with considerable movement of people in order to combat drug trafficking, the entry of illegal materials and terrorism. However, although the application of this equipment in the national security area is indeed relevant, its use has caused a great deal of controversy, especially with regard to the doses absorbed and to the cancer induction risk associated with these exposures. The aim of this study is to use the Monte Carlo MCNPX code and the male adult voxel (MAX) and female adult voxel (FAX) phantoms, to evaluate the absorbed dose, effective dose and risk of cancer incidence attributable to exposures of individuals submitted to transmission X–ray body scanners in several projections. The effective dose values were calculated as recommended by the ICRP Publication 103 and the risk of cancer incidence were estimated through the BEIR VII Report.

Dose optimization in 125I permanent prostate seed implants using the Monte Carlo method

Abstract The aim of this work consisted in using the Monte Carlo code MCNP and computational phantoms to assess the absorbed dose distributions in the prostate, due to a radiotherapy treatment using 125 I radioactive seeds. The intention was to develop a tool that can serve as a complement of the treatment planning system of radiotherapy procedures, reproducing accurately the exact geometry of the sources and the composition of the media where the seeds are inserted. The radiation activities of the simulated seeds varied from 0.27 mCi to 0.38 mCi, for hypothetical treatments employing 80, 88 or 100 125 I sources, typical parameters for this technique. The prostate volumes where the seeds were virtually inserted were simulated with spherical or voxel computational phantoms. The configuration containing 88 seeds with initial radiation activity of 0.27 mCi resulted in a final absorbed dose near 144 Gy, in accordance with the recommendations of the American Association of Physicists in Medicine (AAPM). Based on this configuration, it was possible to obtain the radiation absorbed dose distributions for the voxel phantom, which allowed the determination of treatment quality indicators. The obtained results are in good agreement with experimental data presented by other authors.

Dose and risk evaluation in thoracic radiology using male and female voxel phantoms

Thoracic radiology is of great concern because of its routine nature. It is important to avoid conditions where the amount of radiation used is more than that needed for the procedure. The purpose of this work is to use the Monte Carlo code MCNPX and the Female Adult voxel (FAX) and Male Adult voxel (MAX) phantoms to investigate how the effective doses, absorbed doses to organs and risk of cancer incidence vary for routine thoracic examinations. The risks attributable to thoracic radiological exams were estimated using the Biological Effects of Ionizing Radiations (BEIR) VII Committee Report. The results obtained suggest that different precautionary measures should be taken depending on the chosen geometric projection, and that the application of higher voltages to the X-ray tube appeared as an alternative to reduce the doses and the risk of cancer incidence.

AP and PA thorax radiographs: dose evaluation using the FAX phantom

Considering that the risks associated with ionising radiation are dependent on the characteristics of the exposed individual and that the structures and sizes of the human body vary considerably as a function of gender, efforts must be made in order to study the effective and absorbed doses in thoracic radiological examinations, taking into account the special features of the female anatomy. In this work, the Monte Carlo code Monte Carlo N-Particle eXtended (MCNPX) and the Female Adult voXel (FAX) phantom are combined in order to investigate how the effective and absorbed doses vary in thoracic radiological examinations. The results suggest that different precautionary measures should be taken depending on the chosen geometric projection and that the application of higher voltages to the X-ray tube appears to be an alternative to reduce the effective and absorbed doses.

Equivalent dose calculation in simulation of lung cancer treatment and analysis of dose distribution profile

Currently, lung cancer is one of the most lethal types of cancer (IARC, 2012), the pathology being detected in advanced stage, when the tumor has considerable volume because the disease in most cases asymptomatic in the early stages (INCA, 2016). Dosimetry analysis of healthy organs under real conditions is not feasible. Therefore, computational simulations are used to aid in dose verification in organs of patients submitted to radiotherapy. The goal of this study was to calculate the equivalent dose, due to photons, in the surrounding of healthy organs of patients submitted to radiotherapy for lung cancer, through computational modeling. The simulation was performed using the MCNPX code (MNCPX, 2006), Rex and Regina phantoms (ICRP 110, 2009), radiotherapy room, Siemens Oncor Expression accelerator operating at 6 MV and treatment protocol adopted at the INCA (National Cancer Institute - Brazil). The results obtained, considering the dose due to photons for both phantoms indicate that organs located inside the thoracic cavity received higher dose, being the bronchi, heart and esophagus more affected, due to their anatomical positioning. Clinical data describe the development of bronchiolitis, esophagitis and cardiomyopathies with decreased cardiopulmonary function as one of the major effects of lung cancer treatment. In the Regina phantom, the second largest dose was in the region of the breasts with 615.73 mSv/Gy, while in the Rex the dose was 514.06 mSv/Gy, event related to the difference of anatomical structure of the organ. A qualitative analysis was performed between the dose deposition profile of the treatment planning system and the simulated treatment through the tmesh command and a similar profile of dose distribution was verified throughout the patients body.

ANALYSIS OF THE INFLUENCE OF LIQUID AND OF EXTERNAL COATING MATERIAL ON THE QUALITY OF THE RADIOGRAPHIC IMAGE OF OFFSHORE PIPES USING COMPUTATIONAL MODELING

The aim of this work is to evaluate different forms to minimize the scattered radiation contribution in digital radiographic images of offshore pipelines using MCNPX simulations. The influence of oil inside the pipe, seawater surrounded the pipelines and external coating in the scattering component of the radiation beam will be analyzed. The use of backscattering shielding and lead screen will be discussed.