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The objective of this study was to estimate the risk of radiation-induced injury to the organs due to ionizing radiation following breast screening recommendations employing digital breast tomosynthesis (DBT) and digital mammography (DM). Using the Monte Carlo method, absorbed doses in the tissues and organs were calculated on an adult female phantom, considering two-view craniocaudal (CC) and mediolateral oblique (MLO) projections for each breast. The results showed differences in the total effective risk due to DM (CC + MLO) and DBT (CC + MLO) examinations in Brazil, ranging from 20.73 cases 10-5(DM) to 27.19 cases 10-5(DBT). Significant differences were also observed in the total effective risk of cancer incidence in the lungs due to DM (CC + MLO) and DBT (CC + MLO), ranging from 1.75×10-01cases 10-5(DM) to 1.76×10-01cases 10-5(DBT). The results indicate that the total effective risk of incidence should be considered as an additional parameter for the evaluation of DBT or DBT + DM program performance.

Purpose Uterine fibroids affect women mainly of childbearing age, an alternative for the treatment of these fibroids is uterine artery embolization (UAE), a minimally invasive procedure which uses fluoroscopy, providing radiation doses often high, due to the fact that professionals remain in the room throughout the procedure. In this work, equivalent and effective doses were evaluated for the main physician, for the assistant and for the patient during the UAE procedure. Methods Doses were calculated using computer simulation with the Monte Carlo Method, and virtual anthropomorphic phantoms, in a typical scenario of interventional radiology with field sizes of 20 × 20, 25 × 25 and 32 × 32 cm2, tube voltages of 70, 80, 90 and 100 kV, and projections of LAO45, RAO45 and PA. Results The results showed that the highest doses received by the professionals were for the LAO45 projection with 32 × 32 cm2 field size and 100 kV tube voltage, which is in accordance with the existing literature. The highest equivalent doses, without the protective equipment, were in the eyes, skin, breast and stomach for the main physician, and for the assistant they were in the eyes, breast, thyroid and skin. When she used the protective equipment, the highest equivalent doses for the main physician were on the skin, brain, bone marrow and bone surface, and for the assistant they were on the skin, brain, red bone marrow and bone surface. Conclusions Effective doses increased up to 3186% for the main physician, and 2462% for the assistant, without protective equipment, thus showing their importance.

The influence of the angular deviation of the tube during digital breast tomosynthesis (DBT) acquisition to the dose in the examined breast and in other organs and tissues is not well known. In this work, the Monte Carlo method was used with an adult female virtual anthropomorphic phantom to investigate the impact of this angular variation on the breast dose. The absorbed dose in the examined breast was normalized by the air kerma, which resulted in an absorbed dose coefficient (DT/Kair) for the breast. The absorbed dose in each organ was normalized by the glandular dose in the breast, resulting in the relative organ dose (ROD). An adult female virtual anthropomorphic phantom (FSTA_M50_H50) was incorporated into a scenario containing tomosynthesis equipment with Mo/Mo, Mo/Rh, and W/Rh target/filter combinations and tube voltages of 28 kV. The comparison between the results of the simulations considering digital mammography (DM) and DBT data showed that the DT/Kair values for the examined breast obtained with the DBT parameters were up to 24 times higher than with the DT/Kair obtained with DM parameters. A DT/Kair of 0.97 × 10-1 mGy mGy-1 was obtained in a DBT exam of the right breast. Considering the other organs, the highest ROD values were observed in the thyroid (6.45 × 10-4), eyes (3.87 × 10-4), liver (1.95 × 10-5), and eye lenses (3.21 × 10-3). A variation in the absorbed dose values for the breast and other organs was observed for all projections different from 0°.

Purpose Evaluation of the out-of-field dose is an important aspect in radiotherapy. Due to the fetus radiosensitivity, this evaluation becomes even more conclusive when the patient is pregnant. In this work, a linear accelerator Varian Clinac 2100c operating at 6 MV, a pregnant anthropomorphic phantom (Maria), and different shields added above the abdominal region of the phantom were used for the analysis based on MCNPX. Methods: The simulations were performed for the medial and lateral projections, using either an open field collimation (10×16 cm2) or a multileaf collimator. The added shields (M1 and M2) were designed based on models proposed by Stovall et al. [1] , intending to reduce the deposited dose on the fetus and related structures. Results: The presence of the shields showed to be effective in reducing the doses on the fetus, amniotic sac, and placenta, for example. A reduction of about 43% was found in the dose on the fetus when M2 was added, using the open field collimation, in comparison with the situation with no shield, being the lateral projection the main responsible for the dose. The use of MLC significatively reduced the doses in different structures, including on the fetus and amniotic sac, for example, in comparison to the open field situation. A slight increment on the dose in organs such as the eyes, thyroid and brain was found in both collimation systems, due to the presence of the shields. The contribution of the leakage radiation from the tube head of the linear accelerator was found to be in the order of µGy, being reduced by the presence of the M2 shield. Conclusion: Using the shields showed to be an essential feature in order to reduce the dose not only on the fetus, but also in important structures responsible to its development.

In 2020, the International Commission on Radiation Units and Measurements’ Report Committee 26 (RC 26) proposed new operational quantities to be used in personal monitoring for external radiation. METROBRAS is a Brazilian laboratory that uses a TLD-based personal dosimeter calibrated in terms of the personal dose equivalent, Hp(10, θ). In this paper, an evaluation of the METROBRAS personal dosimeter to the new operational quantity personal dose, Hp(θ), was performed. This assessment was based on the determination of Hp(10, θ) and Hp(θ) using Monte Carlo simulation. The basic personal dosimeter design includes three CaSO4:Dy plus polytetrafluoroethylene (PTFE) detectors sandwiched between different filters inside of an acrylic badge. The determination of the relative response for six X-ray qualities and for gamma-rays from Cs-137 (662 keV) was carried out using the Monte Carlo transport code MCNPX. TLD detectors, filters and the plastic badge were simulated on the surface of a water ISO phantom with 30 cm × 30 cm x 15 cm with PMMA walls. The effect of the direction of radiation incidence has been determined for angles of 0° (anterior-posterior, AP), ±45° and ±60°. The new Hp(θ) quantity affected the relative energy and angular response of the TLD badge mainly for the low photon energies with maximum factors of ∼1.94 and ∼2.91 for 33 keV and 24 keV, respectively. The TLD-badge exhibited not only photon energy but also angular dependence, that was larger for Hp(θ). The major differences between the relative angular responses with respect to the response at 0o were found for the exposures at ± 60o. To comply with the requirements of the new quantity, an upgrade on the calculation algorithm and a new design of the filter set (that allows energy discrimination) should be made. The information provided by the Monte Carlo data helped to predict the METROBRAS badge response to the new operational quantity Hp(θ).

This study aimed to calculate the Conversion Coefficients (CC) of Equivalent and Effective doses by air kerma considering Total Body Irradiation scenarios with Varian linear accelerator with photon beams energy of 4, 6, 10, 15, 18, and 25 MV. The simulations were performed in the MCNPX code and the University of Florida (UF) phantoms were used to represent exposed lying down adult patients in the AP, PA, RLAT, and LLAT irradiation geometries. Lead attenuators were inserted in the scenarios for the preservation of organs of risk and their contribution were analyzed for CC. For most counts, the statistical uncertainty was approximately 5%. For the gonads, CC values for the male phantom decreased with the increase of energy in the AP geometry, which did not occur for the female phantom. As the beam becomes more penetrating, the ovary absorbs more energy because of its internal position. Considering the lung, an organ of risk in TBI, the insertion of the attenuators in the scenarios caused the CC values to reduce by more than 30%. For organs and tissues such as skin and male breasts, the attenuators caused the dose to increase. As for the active bone marrow, which is the TBI target tissue, it was not possible to obtain a good estimate for CC at 15, 18, and 25 MV due to a limitation of the method used to calculate the dose in the bone areas. Nevertheless, for lower energies the CC values for the marrow were valid.

Granites are widely used in construction and they may be potential sources of ionizing radiation, due to the presence of radionuclides such as 40K and decay products from 238U series and 232Th series. These radionuclides occur in the minerals constituting the rocks. To evaluate the doses in humans exposed to 40K, and decay products from 238U series and 232Th series γ radiation, a room with dimensions of 4.0 × 5.0 × 2.8 m3, with uniformly distributed radiation source on the floor of granitic rocks, was computationally modeled. Adult individuals were represented in the virtual scenario by two virtual anthropomorphic phantoms FASH3 and MASH3, incorporated simultaneously in the software MCNPX 2.7.0. The mean energy deposited on each organ and tissue of FASH3 and MASH3 phantoms was determined using the MCNPX F6 tally (MeV/g/particle), while the photon flux within the room was calculated with the MCNPX F4 tally (MeV/cm2/particle). The organs that obtained the highest conversion coefficients CC[HT] (Sv/Gy) were the red bone marrow (0.94), skin (0.90), breast (0.81) and bladder (0.73) for the FASH3; skin (0.89), gonads (0.88), breast (0.79) and bladder (0.70) for the MASH3. The simulated air absorbed dose rates varied between 23.4 (11%) and 25.8 (12%) nGy/h, and the annual dose rates were 0.10 (6%) and 0.11 (6%) mSv/year. These results presented acceptable statistical uncertainties and they are in agreement with the literature. Fluency of photons pointed to the central region of the room floor as the place of greatest exposure. The results showed that the organs closer to the radiation source had the highest deposited energy values. Based on the annual effective dose data obtained, it was possible to note that the values are within the literature. We believe that the methodology used will allow the investigation of any ornamental material that emits natural radiation.

The scattered radiation from interventional procedures is an important source of radiological risk for the medical staff. Considering all affected organs, the eye lens are among the most critical organs. As pointed out by several studies, even for low radiation doses, the appearance of cataract may occur. Considering this scenario, the radiation doses to the eye lens were determined using three different lead eyewear models commonly employed. The fluoroscopist was represented by an adult virtual anthropomorphic phantom (MASH3), coupled to the Monte Carlo code MCNP6.1™, in a typical cardiac interventional radiology procedure. The eyewear had thickness 0.5 mmPb each, and the evaluation was carried out for four different beam angulations (PA, LAO90, LAO65 e RAO65), 80 kVp of tube voltage and HVL of 4 mmAl. The results pointed out that the shielding efficiency has a strong dependence on the eyewear type utilized, which may be very useful for the decision-making during the acquisition of such equipments.

Considering the higher radiosensitivity of children in comparison to adults, studies related to children’s exposure to ionising radiation have been long considered of relevance. For this study, the MCNPX2.7.0 Monte Carlo code and four paediatric voxel computational anthropomorphic phantoms, of both genders and aged 5 and 10 years, were used to simulate scenarios, where children are exposed to natural radiation emitted by sources in the ground by radionuclides of 40K and of 232Th and 238U radioactive series. These elements are part of the composition of ten different types of ornamental rocks obtained from three regions of Brazil, and used as architectural material for flooring of houses. The virtual paediatric anthropomorphic phantoms were positioned in a room with dimensions of (4.0 × 5.0 × 2.8) m3 filled with atmospheric air and a 3 cm thick granitic floor acting as a uniformly distributed planar gamma radiation source. The walls of the room were composed of 20 cm thick concrete. Gonads, bone marrow, bladder, colon, and skin were found to be the organs which receive the highest doses. The mean values of effective dose per air kerma at 1 m above the ground summed for all three radionuclides, were 0.96 and 0.68 Sv Gy−1 for the 5 and 10 year old phantoms, respectively. The obtained results showed that the granitic rocks considered implicate annual effective doses which are 69%–78% lower than the annual limits, recommended by ICRP Publication 103.

The influence of the angular deviation of the tube during digital breast tomosynthesis (DBT) acquisition to the dose in the examined breast and in other organs and tissues is not well known. In this work, the Monte Carlo method was used with an adult female virtual anthropomorphic phantom to investigate the impact of this angular variation on the breast dose. The absorbed dose in the examined breast was normalized by the air kerma, which resulted in an absorbed dose coefficient (DT/Kair) for the breast. The absorbed dose in each organ was normalized by the glandular dose in the breast, resulting in the relative organ dose (ROD). An adult female virtual anthropomorphic phantom (FSTA_M50_H50) was incorporated into a scenario containing tomosynthesis equipment with Mo/Mo, Mo/Rh, and W/Rh target/filter combinations and tube voltages of 28 kV. The comparison between the results of the simulations considering digital mammography (DM) and DBT data showed that the DT/Kair values for the examined breast obtained with the DBT parameters were up to 24 times higher than with the DT/Kair obtained with DM parameters. A DT/Kair of 0.97 × 10-1 mGy mGy-1 was obtained in a DBT exam of the right breast. Considering the other organs, the highest ROD values were observed in the thyroid (6.45 × 10-4), eyes (3.87 × 10-4), liver (1.95 × 10-5), and eye lenses (3.21 × 10-3). A variation in the absorbed dose values for the breast and other organs was observed for all projections different from 0°.

Normally, during medical procedures, special attention must be given to pediatric patients when compared to adults. This is specially relevant during procedures involving ionizing radiation, as CT scans, given that children are considerably more sensitive to radiation induced stochastic effects than adults. In order to investigate the radiation doses on radiosensitive organs of pediatric patients, undergoing head, chest and abdomen CT procedures, numerical dosimetry was employed in this work. The novelty is the use of a new set of pediatric virtual anthropomorphic phantoms, coupled with Monte Carlo simulation, to determine the conversion coefficients for absorbed and effective doses. Two CT equipment were simulated, taking into account the main characteristics of those commercially available. The results were converted to conversion coefficients (mGy/100 mA) for several organs and tissues, and the highest values were obtained for the newborn phantom. This numerical approach employed a new and reliable technique for pediatric CT dosimetry.

Cone beam computed tomography (CBCT) has become essential for dental diagnoses in the last decade. This is supported by its low cost and low doses, when compared to medical CT. Following this increase in CBCT procedures, it is necessary to ensure the image quality within low radiation doses to the patients. This is an especially difficult challenge in CBCT, given the number of equipment models (more than 50), radiographic techniques that may be employed, and technical information not available to the users by the manufacturers. The objective of this study was to estimate the cancer risk, effective and absorbed doses in tissues and organs for CBCT protocols intended for dental use. Monte Carlo (MC) simulations were used to estimate these quantities in tissues and organs with radiological importance, as those suggested by the International Commission of Radiological Protection (ICPR) report ICRP 103. Five different fields of view (FOV) were simulated to i-Cat Classic CBCT, using the MCNPX code. The virtual anthropomorphic phantoms FASH3 (Female Adult MeSH) and MASH3 (Male Adult MeSH) were also used. The effective dose estimative was in the range 75.15–142.20 μSv. The largest contribution to the effective dose was from the salivary glands (17%), thyroid (27%) and remainder tissues (28%). The results of this work showed that the effective and absorbed doses in tissues/organs vary according to the FOV, exposure parameters, and the positioning of the beam, relative to the radiosensitive organs. Furthermore, for the same exposure conditions, women can exceed the total risk of cancer by 26–34%, when compared to men.

The absorbed dose rate is the main characterization quantity for beta radiation. The extrapolation chamber is considered the primary standard instrument. To determine absorbed dose rates in beta radiation beams, it is necessary to establish several correction factors. In this work, the correction factors for the backscatter due to the collecting electrode and to the guard ring, and the correction factor for Bremsstrahlung in beta secondary standard radiation beams are presented. For this purpose, the Monte Carlo method was applied. The results obtained are considered acceptable, and they agree within the uncertainties. The differences between the backscatter factors determined by the Monte Carlo method and those of the ISO standard were 0.6%, 0.9% and 2.04% for 90Sr/90Y, 85Kr and 147Pm sources respectively. The differences between the Bremsstrahlung factors determined by the Monte Carlo method and those of the ISO were 0.25%, 0.6% and 1% for 90Sr/90Y, 85Kr and 147Pm sources respectively.

In recent years, positron emission tomography (PET), associated with multi-detector computed tomography (MDCT), has become a diagnostic technique widely disseminated to evaluate various malignant tumors and other diseases. However, during PET/CT examinations, the doses of ionizing radiation experienced by the internal organs of the patients due to 18F are unknown, and may be substantial. The aim of this study was to determine a set of S values derived from the 18F-FDG and to use them to determine the absorbed and effective doses of 8 different virtual anthropomorphic phantoms (4 of each gender). These phantoms have different Body Mass Index (BMI), to represent different anatomical characteristics of patients examined in PET. The results of the S values were calculated using the MCNPX (2.7.0) Monte Carlo code. These results were compared to the ICRP 106 reference values, obtained with mathematical anthropomorphic phantoms (MIRD model). Our results of the S values were higher than those obtained and presented at the ICRP 106, mainly due to the differences between the phantoms. The differences between the relative distances of the organs and the chemical and physical characteristics of the phantoms used in this study, in relation to mathematical model, reflected the use of a detailed set of phantoms. Therefore, the results presented in this study provide accurate and reliable data for internal dose calculations for patients undergoing PET examinations.

The dosimetric measurements of 147Pm beta radiation beams have limitations due to their low energy, low dose rate, great dispersion and attenuation in air or tissue. In this work, the Monte Carlo model was developed for a 147Pm absorbed dose rate determination. This model consists of an extrapolation chamber and a 147Pm beta radiation source. Moreover, the absorbed dose rate was determined by experimental measurements and the MCNP Monte Carlo code was used. The relative number of particles that crossed the radioactive source window and the particles that crossed the extrapolation chamber entrance window were determined. The source fluence spectrum was also determined. The results of the simulation and the experimental calculations are in agreement with the absorbed dose rate from the PTB calibration certificate. The results obtained are considered acceptable, and they agree within the uncertainties. The difference between the experimental result and that from the Monte Carlo model, compared to that from the calibration certificate, was only 0.8% in both cases.

The doses received by the patients during the computed tomography (CT) exams are the highest when compared to other diagnostic radiology procedures. This fact makes it so important to keep the quality control using the correct instrument. For dosimetry in CT, a pencil type ionization chamber is usually utilized with a sensitive volume length of 10 cm. A comparison of the performance of an extrapolation chamber in two different laboratories, at the Instrument Calibration Laboratory (LCI) from Instituto de Pesquisas Energeticas e Nucleares (IPEN, Brazil) and at the National Physical Laboratory (NPL, UK) was undertaken. Two chamber characteristics were determined (zero depth and extrapolation curve), and the main recommended characterization tests were performed (stabilization time, saturation curve, polarity effect, ion collection efficiency, linearity of response, and variation of response with source-detector distance). This extrapolation chamber was calibrated using the standard system of NPL laboratory, and the energy dependence was determined. The results obtained were within the international recommendations of IEC 61674, except for the energy dependence, as already expected. This study also established a reference system for the LCI of the IPEN, using a homemade extrapolation chamber for X-ray CT beams. Using the extrapolation curves obtained in the characterization tests and the correction factors of ionic recombination, and scattering and fluorescence, the air kerma rates were obtained, as a reference system in standard laboratory computed tomography beams. The last correction factor was obtained using computer simulations by the MCNP5 code (Monte Carlo). Moreover, two pencil type ionization chambers were calibrated using the replacement method in relation to the extrapolation chamber.

Diagnosis through positron emission tomography (PET) is an increasingly used procedure in cerebral, cardiac and especially oncology diseases. It is performed in nuclear medicine clinics, mainly using 18F-Fluorodeoxyglucose (18F-FDG), which has one of the longest half-lives among positron emitters. The gamma rays, produced in the annihilations, require strict radiation control to guarantee the safety of the occupationally exposed individuals working in PET exam facilities. To evaluate occupational exposures, in this study, the MCNPX2.7.0 radiation transport code was used. The professionals were represented by the FASH3 (female) and MASH3 (male) adult virtual anthropomorphic phantoms, which have anthropometric characteristics like those of real individuals. Four exposure scenarios were modeled: radiopharmaceutical preparation, administration to the patient, patient follow-up, and patient placement in PET equipment. The results are presented in terms of the mean effective dose by PET procedure (μSv/procedure) and the mean effective dose by radiopharmaceutical activity (nSv/MBq). Using the set of conversion coefficients presented in this study, it is possible to calculate the absolute values of effective doses for nuclear medicine professionals who are in contact with the radioactive material or the patient. The differences between our study and the literature were only 3%. The effective occupational doses, with an adult patient, were 14% higher than those with pediatric patients.

Aircrew members are exposed to primary cosmic rays as well as to secondary radiations from the interaction of cosmic rays with the atmosphere and with the aircraft. The radiation field at flight altitudes comprises neutrons, protons, electrons, positrons, photons, muons and pions. Generally, 50% of the effective dose to airplane passengers is due to neutrons. Care must be taken especially with pregnant aircrew members and frequent fliers so that the equivalent dose to the fetus will not exceed prescribed limits during pregnancy (1 mSv according to ICRP, and 5 mSv according to NCRP). Therefore, it is necessary to evaluate the equivalent dose to a fetus in the maternal womb. Up to now, the equivalent dose rate to a fetus at commercial flight altitudes was obtained using stylized pregnant-female phantom models. The aim of this study was calculating neutron fluence to dose conversion coefficients for a fetus of six months of gestation age using a new, realistic pregnant-female mesh-phantom. The equivalent dose rate to a fetus during an intercontinental flight was also calculated by folding our conversion coefficients with published spectral neutron flux data. The calculated equivalent dose rate to the fetus was 2.35 μSv.h −1 , that is 1.5 times higher than equivalent dose rates reported in the literature. The neutron fluence to dose conversion coefficients for the fetus calculated in this study were 2.7, 3.1 and 3.9 times higher than those from previous studies using fetus models of 3, 6 and 9 months of gestation age, respectively. The differences between our study and data from the literature highlight the importance of using more realistic anthropomorphic phantoms to estimate doses to a fetus in pregnant aircrew members.

One of the main criteria that must be held in Total Body Irradiation (TBI) is the uniformity of dose in the body. In TBI procedures the certification that the prescribed doses are absorbed in organs is made with dosimeters positioned on the patient skin. In this work, we modelled TBI scenarios in the MCNPX code to estimate the entrance dose rate in the skin for comparison and validation of simulations with experimental measurements from literature. Dose rates were estimated simulating an ionization chamber laterally positioned on thorax, abdomen, leg and thigh. Four exposure scenarios were simulated: ionization chamber (S1), TBI room (S2), and patient represented by hybrid phantom (S3) and water stylized phantom (S4) in sitting posture. The posture of the patient in experimental work was better represented by S4 compared with hybrid phantom, and this led to minimum and maximum percentage differences of 1.31% and 6.25% to experimental measurements for thorax and thigh regions, respectively. As for all simulations reported here the percentage differences in the estimated dose rates were less than 10%, we considered that the obtained results are consistent with experimental measurements and the modelled scenarios are suitable to estimate the absorbed dose in organs during TBI procedure.

Positron emission tomography (PET) has revolutionized the diagnosis of cancer since its conception. When combined with computed tomography (CT), PET/CT performed in children produces highly accurate diagnoses from images of regions affected by malignant tumors. Considering the high risk to children when exposed to ionizing radiation, a dosimetric study for PET/CT procedures is necessary. Specific absorbed fractions (SAF) were determined for monoenergetic photons and positrons, as well as the S-values for six positron emitting radionuclides ( 11 C, 13 N, 18 F, 68 Ga, 82 Rb, 15 O), and 22 source organs. The study was performed for six pediatric anthropomorphic hybrid models, including the newborn and 1 year hermaphrodite, 5 and 10-year-old male and female, using the Monte Carlo N-Particle eXtended code (MCNPX, version 2.7.0). The results of the SAF in source organs and S-values for all organs showed to be inversely related to the age of the phantoms, which includes the variation of body weight. The results also showed that radionuclides with higher energy peak emission produces larger auto absorbed S-values due to local dose deposition by positron decay. The S-values for the source organs are considerably larger due to the interaction of tissue with non-penetrating particles (electrons and positrons) and present a linear relationship with the phantom body masses. The results of the S-values determined for positron-emitting radionuclides can be used to assess the radiation dose delivered to pediatric patients subjected to PET examination in clinical settings. The novelty of this work is associated with the determination of auto absorbed S-values, in six new pediatric virtual anthropomorphic phantoms, for six emitting positrons, commonly employed in PET exams.

Kyphoplasty surgery is widely used for pain relief in patients with vertebral compression fracture (VCF). For this surgery, an X-ray emitter that provides real-time imaging is employed to guide the medical instruments and the surgical cement used to fill and strengthen the vertebra. Equivalent and effective doses related to high temporal resolution equipment has been studied to assess the damage and more recently cancer risk. For this study, a virtual scenario was prepared using MCNPX code and a pair of UF family simulators. Two projections with seven tube voltages for each one were simulated. The organ in the abdominal region were those who had higher cancer risk because they receive the primary beam. The risk of lethal cancer is on average 20% higher in AP projection than in LL projection. This study aims at estimating the risk of cancer in organs and the risk of lethal cancer for patient submitted to kyphoplasty surgery.

This paper aims to show how the variance reduction technique "Geometry splitting/Russian roulette" improves the statistical error and reduces uncertainties in the determination of the absorbed dose rate in tissue using an extrapolation chamber for beta radiation. The results show that the use of this technique can increase the number of events in the chamber cavity leading to a closer approximation of simulation result with the physical problem. There was a good agreement among the experimental measurements, the certificate of manufacture and the simulation results of the absorbed dose rate values and uncertainties. The absorbed dose rate variation coefficient using the variance reduction technique "Geometry splitting/Russian roulette" was 2.85%.

Clinical scenarios were virtually modeled to estimate both the equivalent and effective doses normalized by KAP ( K erma A rea P roduct) to vertebra compression fracture surgery in patient and surgeon. This surgery is known as kyphoplasty and involves the use of X-ray equipment, the C-arm, which provides real-time images to assist the surgeon in conducting instruments inserted into the patient and in the delivery of surgical cement into the fractured vertebra. The radiation transport code used was MCNPX ( M onte C arlo N - P article e X tended) and a pair of UFHADM ( U niversity of F lorida H ybrid AD ult M ale) virtual phantoms. The developed scenarios allowed us to calculate a set of equivalent dose (H T ) and effective dose (E) for patients and surgeons. In additional, the same scenario was calculated KAP in the tube output and was used for calculating conversion coefficients (E/KAP and H T /KAP). From the knowledge of the experimental values of KAP and the results presented in this study, it is possible to estimate absolute values of effective doses for different exposure conditions. In this work, we developed scenarios with and without the surgical table with the purpose of comparison with the existing data in the literature. The absence of the bed in the scenario promoted a percentage absolute difference of 56% in the patient effective doses in relation to scenarios calculated with a bed. Regarding the surgeon, the use of the personal protective equipment (PPE) reduces between 75% and 79% the effective dose and the use of the under table shield (UTS) reduces the effective dose of between 3% and 7%. All these variations emphasize the importance of the elaboration of virtual scenarios that approach the actual clinical conditions generating E/KAP and H T /KAP closer to the actual values.

There is a serious, and growing concern about the increased risk of the emergence of a secondary cancer, radio-induced, associated with radiotherapy treatments. To assess the radiation doses to organs outside the target volume, in this work, several computational exposure scenarios were modelled, based on Monte Carlo simulation (MCNPX code). A Varian 2100c accelerator, and a female virtual anthropomorphic phantom were used, in a simulated treatment of cervical cancer. The determination of the dispersed dose would be important for assessing the risk in different organs or tissues. Four treatment fields were applied, varying the gantry angle. It was possible to observe that the conversion factors for equivalent dose were higher for the AP projection. For the RLAT and LLAT projections, the results were similar, fact that may be attributed to the symmetrical distributions of the organs in relation to the radiation source. The results presented in this work showed that the computational exposure scenario provides a versatile and accurate tool to estimate in a ready way the absorbed doses during a cervical treatment.

In this work irradiation scenarios that simulated chest and abdomen examinations involving mobile X-ray equipment in hospitals were modeled with the purpose of calculating conversion coefficient for effective dose (CCE), normalized to entrance surface dose (ESD), applied to patients and public individuals. These coefficients can easily be used in this practice. Patients and public individuals were represented by a pair of anthropomorphic phantoms inserted in the MCNPX 2.7.0 radiation transport code. One of the phantoms (patient) was irradiated with the direct beam simulating examinations of the chest and abdomen, each with two fields of irradiation, ideal (IF) and extrapolated (EF). Using the software SPECGEN X-ray spectra from 60 to 100 kVp at 10 kVp intervals were generated and used in this work. The other phantom (public individual) was positioned 50–200 cm from the patient. In relation to the CCE calculated in the patient, the average increase obtained between the irradiation fields was 62.4% for the chest examinations, and for the same conditions the CCE was calculated for abdomen examinations and found to be 8.0%. Increasing the distance between public individual and patient, reductions of up to 81.7% in the CCE in abdomen examinations and 83.4% in chest examinations were observed. Through the assessment of CCE of these scenarios, it is possible to measure the damages relating to this practice for both patients and public individuals.

The aim of this work was to modify the standing posture of the anthropomorphic reference phantoms of ICRP publication 110, AM (Adult Male) and AF (Adult Female), to the sitting posture. The change of posture was performed using the Visual Monte Carlo software (VMC) to rotate the thigh region of the phantoms and position it between the region of the leg and trunk. Scion Image software was used to reconstruct and smooth the knee and hip contours of the phantoms in a sitting posture. For 3D visualization of phantoms, the VolView software was used. In the change of postures, the organ and tissue masses were preserved. The MCNPX was used to calculate the equivalent and effective dose conversion coefficients (CCs) per fluence for photons for six irradiation geometries suggested by ICRP publication 110 (AP, PA, RLAT, LLAT, ROT and ISO) and energy range 0.010–10 MeV. The results were compared between the standing and sitting postures, for both sexes, in order to evaluate the differences of scattering and absorption of radiation for different postures. Significant differences in the CCs for equivalent dose were observed in the gonads, colon, prostate, urinary bladder and uterus, which are present in the pelvic region, and in organs distributed throughout the body, such as the lymphatic nodes, muscle, skeleton and skin, for the phantoms of both sexes. CCs for effective dose showed significant differences of up to 16% in the AP irradiation geometry, 27% in the PA irradiation geometry and 13% in the ROT irradiation geometry. These results demonstrate the importance of using phantoms in different postures in order to obtain more precise conversion coefficients for a given exposure scenario.

In this study, computational modeling was applied to evaluate medical and occupational exposure, to ionizing radiation, during the Endoscopic Retrograde Cholangiopancreatography (ERCP) procedure of a pregnant woman in the second gestational trimester. The fetal dose evaluation and the construction of a photon fluence map inside the procedure room were also performed. The medical staff and patient were represented by virtual anthropomorphic phantoms. These phantoms were incorporated to the radiation transport code MCNPX (version 2.7.0). The photon beam was projected on the right lateral lower section of the liver of the patient, producing a FOV of 15×15 cm2. The spectral influence was evaluated using tube voltages of 70 kVp and 80 kVp with a total filtration of 5 mmAl. The influence of the suspended shield, lead curtain and fetal shield were evaluated on the Conversion Coefficients for Equivalent Dose (CC[HT]) and Effective Dose (CC[E]) for the medical staff and patient. The removal of the lead curtain and suspended shield was considered the most critical configuration to the medical staff. In this situation, an increase up to 633 % in the CC[HT]eye lens and 900 % in CC[E], for the medical staff, was reached. The CC[E]Patient ranged between 0.13 mSv/Gy.cm2 (70 kVp with all protective devices) and 0.15 mSv/Gy.cm2 (80 kVp without fetal shield) and the values obtained are in agreement with the literature. The CC[HT]fetus oscillated between 2.2E-1 mSv/Gy.cm2 (70 kV with fetal shield) and 2.7E-1 mSv/Gy.cm2 (80 kV without fetal shield). The outcomes of this work are useful in the prior monitoring of the radiation doses and risks, and a reduction on these may be reached for the medical team and patient, which is a complicated arrangement in ERCP procedures.

At the Calibration Laboratory (LCI) of the IPEN/CNEN, studies are in development on the establishment of a standard composed by the beta radiation sources for the dosimetry and calibration for personal monitoring in Brazil. For this purpose is used the Bohm extrapolation chamber (PTW model 23392). This chamber was already characterized at LCI in 90Sr/90Y beams using two different entrance windows: one of aluminized Mylar and another of PET (polyethylene terephthalate) known as Hostaphan. In this work, this extrapolation chamber was characterized in 85Kr and 147Pm beams. All tests were carried out with the reference 90Sr /90Y source, for comparison purposes. The Monte Carlo code MCNP5 code was used to obtain an extrapolation chamber and the BSS2 system sources computational model, based on the determination of the absorbed dose rate. Saturation curves, ion collection efficiency, ion recombination, polarity effect, stability of response, null depth, linearity of response, variation of response as a function of source-detector distance, extrapolation curves, correction factors and absorbed dose rates were obtained. The difference between the experimental absorbed dose rates and those obtained using the Monte Carlo model, compared to those from the calibration certificates, was less than 1.9% for the 108 histories for each BSS2 system source. All results of the performed tests are within the limits of the international recommendations. The results for the 90Sr/90Y source were in good agreement with previous works performed at LCI. These results are suitable for the establishment of a standard instrument for the dosimetry and calibration of beta radiation sources and detectors in the LCI/IPEN. This standard will allow the calibration of detectors in beta radiation beams in dosimetry services in Brazil.

Granites are widely used in construction and they may be potential sources of ionizing radiation, due to the presence of radionuclides such as

Thermoluminescence dosimeters containing boron, such as magnesium tetraborate (MgB4O7), are of interest because of their very high sensitivity, near tissue-equivalent absorption coefficients, low cost, easy handling, and very large linearity range for absorbed dose. Another important parameter that should be considered when working with thermoluminescent dosimeter (TLD) is the mass energy absorption coefficient (μen/ρ), which is a close approximation to the energy available for production of chemical, biological and other effects associated with exposure to ionizing radiation, therefore important in estimating dose in medical and health physics. In this study the mass energy absorption coefficients and energy responses of undoped and some doped magnesium tetraborates were calculated by Monte Carlo N-particle transport code for a range of photon energies between 20 keV and 20 MeV. The calculated parameters for MgB4O7, MgB4O7:Dy and MgB4O7:Dy,Li were evaluated in comparison with standard TLDs as Al2O3:C and TLD-100 (LiF: Mg, Ti) and ICRU tissue data. The influence of the dopant concentration in the MgB4O7 matrix on the energy dependence of TLD was also investigated. The analyses indicated a good agreement between the simulations and theoretical calculations. The μen/ρ and energy dependence of the materials are higher in the low energy range (E

A study of the influence of a dosimetric holder and its cover for the irradiation of the dosimeters in the Beta Secondary Standard BSS2 radiation fields is reported. The correction factors for attenuation or scattering were calculated taking into account the BSS2 beta source energy, as well as the detector source distance. The study and the determination of these factors were carried out using the Monte Carlo Method. The results of the correction factors showed that the absorption and scattering of the electrons depend greatly on the energy of beta radionuclides. The determined correction factors are in agreement with the international report ISO 6980.

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 physician's 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.

Cerebral angiography exams may provide valuable diagnostic information for the patients with suspect of cerebral diseases, but it may also deliver high doses of radiation to the patients and medical staff. In order to evaluate the medical and occupational expositions from different irradiation conditions, Monte Carlo (MC) simulations were employed. Virtual anthropomorphic phantoms (MASH) were used to represent the patient and the physician inside a typical fluoroscopy room, also simulated in details, incorporated in the MCNPX 2.7.0 MC code. The evaluation was carried out by means of dose conversion coefficients (CCs) for equivalent (H) and effective (E) doses normalized by the air kerma-area product (KAP). The CCs for the surface entrance dose of the patient (ESD) and equivalent dose for the eyes of the medical staff were determined, because CA exams present higher risks for those organs. The tube voltage was 80 kVp, and Al filters with thicknesses of 2.5 mm, 3.5 mm and 4.0 mm were positioned in the beams. Two projections were simulated: posterior–anterior (PA) and right-lateral (RLAT). In all situations there was an increase of the CC values with the increase of the Al filtration. The highest dose was obtained for a RLAT projection with a 4.0 mm Al filter. In this projection, the ESD/KAP and E/KAP values to patient were 11 (14%) mGy/Gy cm 2 and 0.12 (0.1%) mSv/Gy cm 2 , respectively. For the physician, the use of shield lead glass suspended and lead curtain attached to the surgical table resulted in a significant reduction of the CCs. The use of MC simulations proved to be a very important tool in radiation protection dosimetry, and specifically in this study several parameters could be evaluated, which would not be possible experimentally.

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.

This study presents a computational model of exposure of a patient, cardiologist and a nurse in a typical scenario of cardiac interventional procedures. In this case, a set of conversion coefficients (CC) for effective dose (E) in terms of the kerma-area product (KAP) was calculated for the individuals involved, using seven different energy spectra and eight beam projections. We also calculated the CC for the skin entrance dose (ESD) of the patient normalized by PKA. All individuals were represented by anthropomorphic computer simulators embedded in a radiation transport code based on Monte Carlo simulation.

In beta therapy, β particles from 90Sr+90Y are used for the prevention and treatment of ophthalmological and dermatological diseases. For such purposes, the radiation dose is deposited by planar and concave applicators positioned on the region to be treated. Although this therapy is effective on the diseases, several complications have been reported, making these types of radioactive applicators obsolete in current clinical practice. This paper proposes a methodology to prepare and evaluate the safety of a research irradiator that re-purposes and adapts dermatologic and ophthalmic 90Sr+90Y applicators. The irradiator was constructed using low cost materials and three applicator sources. The sources are positioned at the center and the upper end of acrylic rectangular prisms. Radiochromic film was used to obtain the dose distribution on the sample holder surface. Pellets of aluminum oxide doped with carbon (Al2O3:C) were used to evaluate the reproducibility of the irradiator. The MCNPX Monte Carlo code was used for the evaluation of safety conditions. The irradiator exhibits good reproducibility of irradiation of dosimeters in pellet form and is safe to handle.

The use of Monte Carlo simulations in dosimetry is a well established area of research, and several correction factors, for ionization chambers, were evaluated with these simulations. Some simulated values were considered even more reliable than the experimental measurements. Besides these uses with ionization chambers, Monte Carlo simulations may also be employed in the development and characterization of new dosimetric materials, as polymer gels. They are largely employed in radiotherapy dosimetry to mimic human tissue. New polymer gels were studied in order to better represent different organs or tissues, to provide more reliable results, or even to use different measurement techniques. The objective of this study was to evaluate the dosimetric properties of polymer gels, in relation to its mass-energy absorption coefficients, energy response and tissue equivalence. For this purpose the MCNPX Monte Carlo code was utilized. Three different materials, employed in radiotherapy dosimetry were evaluated in this work: MAGAS, MAGAT and AMPS. For all simulations carried out, the values were within an acceptable uncertainty and in accordance to the expected results.

The craniofacial structure is three-dimensional, and for a better visualization of these structures, Computed Tomography is often employed for diagnoses, even though being a high-cost procedure, leading to increased exposure to ionizing radiation. As a consequence, studies in dosimetry are necessary, since several radiosensitive structures are located in the head and neck, such as thyroid, crystalline and salivary glands. There is an overall consensus regarding the exposure of pediatric patients to ionizing radiation, with recommendations being that the procedures must occur with the shortest exposure time as possible, and it is only prescribed when they are effectively necessary. During the procedures, radiation effects are difficult to be measured. The use of either TL or OSL dosimeters can create artifacts within the images, and the positioning of a large number of dosimeters, necessary for the correct dose evaluation, is not feasible when it comes to a pediatric patient. Therefore pediatric virtual anthropomorphic phantoms and Monte Carlo simulations were used in this work. The absorbed and effective doses were determined during an i-CAT procedure, with 5 different fields of view, utilizing 5- and 10-year-old male virtual anthropomorphic phantoms. The results pointed out that the eye lens, salivary glands and thyroid received the highest doses. Besides, the effective dose values increase with the increasing of the FOV size, and the 5-year-old male virtual anthropomorphic phantom presented the highest effective dose values.

Several radioisotopes are produced at Instituto de Pesquisas Energeticas e Nucleares for the use in medical treatments, including the activation of 192 Ir sources. These sources are suitable for brachytherapy treatments, due to their low or high activity, depending on the concentration of 192 Ir, easiness to manufacture, small size, stable daughter products and the possibility of re-utilization. They may be used for the treatment of prostate, cervix, head and neck, skin, breast, gallbladder, uterus, vagina, lung, rectum, and eye cancer treatment. In this work, the use of some 192 Ir sources was studied for the treatment of esophagus cancer, especially the dose determination of important structures, such as those on the mediastinum. This was carried out utilizing a FASH anthropomorphic phantom and the MCNP5 Monte Carlo code to transport the radiation through matter. It was possible to observe that the doses at lungs, breast, esophagus, thyroid and heart were the highest, which was expected due to their proximity to the source. Therefore, the data are useful to assess the representative dose specific to brachytherapy treatments on the esophagus for radiation protection purposes.

The objective of this study was to estimate doses in the physician and the nurse assistant at different positions during interventional radiology procedures. In this study, effective doses obtained for the physician and at points occupied by other workers were normalised by air kerma-area product (KAP). The simulations were performed for two X-ray spectra (70 kVp and 87 kVp) using the radiation transport code MCNPX (version 2.7.0), and a pair of anthropomorphic voxel phantoms (MASH/FASH) used to represent both the patient and the medical professional at positions from 7 cm to 47 cm from the patient. The X-ray tube was represented by a point source positioned in the anterior posterior (AP) and posterior anterior (PA) projections. The CC can be useful to calculate effective doses, which in turn are related to stochastic effects. With the knowledge of the values of CCs and KAP measured in an X-ray equipment, at a similar exposure, medical professionals will be able to know their own effective dose.

Aircraft crew members are occupationally exposed to considerable levels of cosmic radiation at flight altitudes. Since aircrew (pilots and passengers) are in the sitting posture for most of the time during flight, and up to now there has been no data on the effective dose rate calculated for aircrew dosimetry in flight altitude using a sitting phantom, we therefore calculated the effective dose rate using a phantom in the sitting and standing postures in order to compare the influence of the posture on the radiation protection of aircrew members. We found that although the better description of the posture in which the aircrews are exposed, the results of the effective dose rate calculated with the phantom in the sitting posture were very similar to the results of the phantom in the standing posture. In fact we observed only a 1% difference. These findings indicate the adequacy of the use of dose conversion coefficients for the phantom in the standing posture in aircrew dosimetry. We also validated our results comparing the effective dose rate obtained using the standing phantom with values reported in the literature. It was observed that the results presented in this study are in good agreement with other authors (the differences are below 30%) who have measured and calculated effective dose rates using different phantoms.

The aim of this study was the calculation of conversion coefficients for absorbed doses per fluence (DT/Φ) using the sitting and standing male hybrid phantom (UFH/NCI) exposure to monoenergetic protons with energy ranging from 2 MeV to 10 GeV. Sex-averaged effective dose per fluence (E/Φ) using the results of DT/Φ for the male and female hybrid phantom in standing and sitting postures were also calculated. Results of E/Φ of UFH/NCI standing phantom were also compared with tabulated effective dose conversion coefficients provided in ICRP publication 116. To develop an exposure scenario implementing the male UFH/NCI phantom in sitting and standing postures was used the radiation transport code MCNPX. Whole-body irradiations were performed using the recommended irradiation geometries by ICRP publication 116 antero-posterior (AP), postero-anterior (PA), right and left lateral, rotational (ROT) and isotropic (ISO). In most organs, the conversion coefficients DT/Φ were similar for both postures. However, relative differences were significant for organs located in the lower abdominal region, such as prostate, testes and urinary bladder, especially in the AP geometry. Results of effective dose conversion coefficients were 18% higher in the standing posture of the UFH/NCI phantom, especially below 100 MeV in AP and PA. In lateral geometry, the conversion coefficients values below 20 MeV were 16% higher in the sitting posture. In ROT geometry, the differences were below 10%, for almost all energies. In ISO geometry, the differences in E/Φ were negligible. The results of E/Φ of UFH/NCI phantom were in general below the results of the conversion coefficients provided in ICRP publication 116.

In Brazilian public hospitals, the number of patients needing assistance is often much greater than the capacity of the hospital. In such situations, medical procedures are performed as quickly as possible, and mobile X-ray equipment is used intensively. This equipment is used for several types of examination, in different areas of the hospital. During the examination procedure, apart from the radiology technicians involved, there are always other people in the room who are also exposed to the radiation scattered by the patient. The objective of this study was to determine the exposure, due to the use of mobile X-ray equipment, of hospital personnel, divided into two categories named 'monitored' and 'non-monitored'. Evaluation of 413 radiographies was performed, the vast majority of them being chest examinations (75 %). During the procedures, specific information was collected to allow measurement in simulated situations. Air kerma rates were measured at different distances from the mobile X-ray equipment using an ionisation chamber and an acrylic phantom with dimensions of 30×30×15 cm(3). From the results, it was possible to estimate the personal dose equivalent received by the individuals in the room during the procedure and to determine the dose maps associated with the use of the mobile X-ray equipment. The results obtained in this study were in accordance with dose limits, but some observed situations were considered critical.