Walmir Belinato

Exposures in interventional radiology using Monte Carlo simulation coupled with virtual anthropomorphic phantoms

In this work we investigated the way in which conversion coefficients from air kerma-area product for effective doses (CCE) and entrance skin doses (CCESD) in interventional radiology (IR) are affected by variations in the filtration, projection angle of the X-ray beam, lead curtain attached to the surgical table, and suspended shield lead glass in regular conditions of medical practice. Computer simulations were used to model an exposure scenario similar to a real IR room. The patient and the physician were represented by MASH virtual anthropomorphic phantoms, inserted in the MCNPX 2.7.0 radiation transport code. In all cases, the addition of copper filtration also increased the CCE and CCESD values. The highest CCE values were obtained for lateral, cranial and caudal projections. In these projections, the X-ray tube was located above the table, and more scattered radiation reached the middle and upper portions of the physician trunk, where most of the radiosensitive organs are located. Another important result of this study was to show that the physicians protection is 358% higher when the lead curtain and suspended shield lead glasses are used. The values of CCE and CCESD, presented in this study, are an important resource for calculation of effective doses and entrance skin doses in clinical practice.

Occupational exposures during abdominal fluoroscopically guided interventional procedures for different patient sizes — A Monte Carlo approach

In this study we evaluated the occupational exposures during an abdominal fluoroscopically guided interventional radiology procedure. We investigated the relation between the Body Mass Index (BMI), of the patient, and the conversion coefficient values (CC) for a set of dosimetric quantities, used to assess the exposure risks of medical radiation workers. The study was performed using a set of male and female virtual anthropomorphic phantoms, of different body weights and sizes. In addition to these phantoms, a female and a male phantom, named FASH3 and MASH3 (reference virtual anthropomorphic phantoms), were also used to represent the medical radiation workers. The CC values, obtained as a function of the dose area product, were calculated for 87 exposure scenarios. In each exposure scenario, three phantoms, implemented in the MCNPX 2.7.0 code, were simultaneously used. These phantoms were utilized to represent a patient and medical radiation workers. The results showed that increasing the BMI of the patient, adjusted for each patient protocol, the CC values for medical radiation workers decrease. It is important to note that these results were obtained with fixed exposure parameters.

Exposition to 137Cs deposited in soil – a Monte Carlo study

In the event of an environmental contamination with radioactive materials, one of the most dangerous materials is 137Cs. In order to evaluate the radiation doses involved in an environmental contamination of soil, with 137Cs, we carried out a computational dosimetric study. We determined the radiation conversion coefficients (CC) for effective (E) and equivalent (H T) doses, using a male and a female anthropomorphic phantoms. These phantoms were coupled with the MCNPX (2.7.0) Monte Carlo simulation software, for three different types of soil. The highest CC[H T] values were for the gonads and skin (male) and bone marrow and skin (female). We found no difference for the different types of soil.

The influence of different 192Ir sources geometries to the energy deposition

In this paper, various simplifications of the HDR source Varian VariSource Classic model, in which 192Ir as a radionuclide is used, were compared. These simplifications were carried out by Monte Carlo simulations, using the MCNPX 2.7.0 code. The different sources were compared through a distribution of energy deposition in a water phantom. Our results indicated that small simplifications will present no influence on the source response, and the removal of the entire capsule surrounding the radionuclide will present a difference of just 0.53% in the final response.

Anthropomorphic phantom to investigate the bladder dose in gynecological high-dose-rate brachytherapy

PURPOSE This study presents a prototype of a phantom appropriate for experimental bladder dosimetry. This work presents details of the phantom construction and dosimetric results obtained using radiochromic film and optically stimulated luminescence dosimeters (OSLDs). METHODS AND MATERIALS The phantom was constructed of polymethyl methacrylate. Two artificial bladders were three-dimensional printed using previous computed tomography images. Radiochromic films and OSLDs were positioned on the artificial bladder walls, and the applicators were placed according to the original computed tomography image. RESULTS The prototype phantom simulated the behavior of the dose on the bladder surface, enabling bladder movement in all directions. The dosimetric study that was performed using radiochromic film and OSLDs exhibited concordance, in most cases, with the results obtained from the planning system. CONCLUSIONS The methodology presented offers conditions for researchers to investigate more accurately the behavior of the dose on the bladder surface during intracavitary brachytherapy procedures.