Values Of Conversion Coefficients Research Articles

Model of occupational exposure of workers performing inspection of welded joints

A model of occupational exposure to gamma flaw detector operators working with portable flaw detectors in the field has been developed. The initial data for the development and verification of the model were the results of measurements of the characteristics of the gamma radiation field at the workplaces of flaw detectors and data from individual dosimetric monitoring. The relationships between the measured (H*(10), Hp(10)) and protection (effective dose) quantities (conversion coefficients) were determined using calculations and phantom experiments simulating three main operations of the full production cycle: transportation of the flaw detector to the place of X-raying of the product, installation of a flaw detector to perform x-raying and X-raying of the product. As a result of the study, it was found that more than 90% of the dose contribution to the readings of an individual dosimeter is due to the installation of the flaw detector in the working position and X-raying of the product. The values of the conversion coefficients for these operations in the form of the ratio of the effective dose values and the readings of dosimeters (Hp(10)) located on the worker's body at chest level (standard place) and abdominal level differ little for both positions of individual dosimeters. The use of maximum conversion coefficient value of 0.8 Sv/Sv corresponding to the operation of X-raying of the product will ensure conservatism in the assessment of the effective dose for the entire production cycle by no more than 15% and 25% for dosimeters located at the chest level and abdominal level, respectively.

Energy efficiency of hydrogen production during dark fermentation

It is widely known that most of the world's energy is produced from non-renewable energy sources such as crude oil and coal. Hydrogen is an ideal fuel candidate with a high energy content and clean combustion product. Biohydrogen is an environmentally friendly, renewable biofuel with high energy density, making it a viable alternative to fossil fuels in the future. At the same time, despite the large number of articles on the intensification of both dark fermentation and anaerobic bioconversion in general, the operating costs of the proposed intensification methods are not well covered in the literature. The goal of the work was to estimate the conversion coefficient of thermal and electrical energy spent on the functioning of the process of dark fermentation of various organic wastes into the energy of produced hydrogen. A block diagram of the energy flows of the dark fermentation system and the structure of the energy consumption of the system were developed. The obtained literature and experimental data suggest that the conversion coefficient of energy into biohydrogen in the process of dark fermentation is less than 1, so to obtain 1 kWh of hydrogen it is necessary to expend more than 1 kWh of energy. At the same time, the use of a vortex layer apparatus for dark fermentation of the food waste model made it possible to increase the energy output of the process by more than 7 times, thereby bringing the values of the conversion coefficients of thermal and electrical energy closer to 1. Despite the fact that the energy efficiency of most known methods for producing hydrogen is higher than the energy efficiency of dark fermentation, it is worth noting that the raw material for producing hydrogen in the dark fermentation process is organic waste, and not high-energy fuel (natural gas, methane, coal) or water in the case of electrolysis. In addition, the use of a vortex layer apparatus for pre-treatment of the dark fermentation substrate made it possible to achieve electricity conversion coefficient values 40% higher than with water electrolysis.

Assessment of effective doses for fluoroscopy-guided balloon dilatation of benign esophageal strictures in pediatric medicine

Interventional examinations are associated with high levels of patient exposure per examination, which makes it particularly important to monitor individual patient doses and to assess radiation risks. The aim of this study was the assessment of effective doses for fluoroscopy-guided balloon dilatation of benign esophageal strictures, whichwasperformedonpediatricpatientsaged 1 to 2 yearsatthe Departmentof Radiosurgical Methodsof Diagnosis and Treatment of St. Petersburg State Pediatric Medical University. Patient exposure patterns were basedonourowndatacollection. Thecalculationofeffectiveandorgandosesofpatientsnormalizedbythevalue of the dose area product measured during the study was carried out using PCXMC 2.0 software. The conversion coefficients from the dose area product to the effective dose were calculated using tissue weighting coefficients from the ICRP Publications 60 and 103 their values were 10.7 and 11.7 µSv/cGy cm2, respectively. The results of verification of the method indicated that the use of inappropriate conversion coefficients leads to an almost double underestimation of children’s effective doses. Differences in the values of conversion coefficients are significant and are explained by differences in voltage, source to image distance, and irradiation field size. A simplified model of patient exposure was proposed, which is described by a single irradiation field. The assessment of effective doses using multi-field and single-field irradiation model shows comparable results, which allows using the differentiated approach to the assessment of radiation doses of patients.

Level structure and transition multipolarities of 54Mn

Excited states up to 3 MeV in the odd-odd 54Mn have been populated in the 54Cr(p,n)54Mn reaction at Ep = 4.5 MeV. Conversion coefficients (αK and απ ) were deduced using the NPG method for the first time in 54Mn. Multipolarities were unambiguously assigned in 16 transitions for the first time using the obtained conversion coefficient values. Spin and parity has been restricted for three transitions.

THE IMPACT OF NEW ICRU95 QUANTITIES AND SPECTRUM DATA ON THE DOSIMETRIC QUANTITIES OF THE NEUTRON REFERENCE FIELDS AT PTB.

In 2020, the ICRU released a new report which includes the re-definition of the operational quantities used in radiation protection and new conversion coefficients from physical quantities to operational radiation protection quantities. An assessment of the ambient and personal dose conversion coefficients for the reference neutron fields of radionuclide sources at PTB is necessary based on these new definitions. In this work, a numerical estimation of the conversion coefficients of moderated and unmoderated 252Cf and 241Am-Be neutron sources based on ICRU57 and ICRU95 reports and using spectrum data available in the ISO 8529-1 standard and at PTB are discussed. Two numerical approaches are used for this estimation to ensure the reliability of the calculated values: a direct calculation using MCNP6, and cubic interpolation of conversion coefficients datasets written in Python. The results show large differences between the spectrum-averaged operational quantities for the current and new conversion coefficients of up to 23%. The choice of spectrum data affects conversion coefficient values by 6-8%.

Моделирование конверсионных коэффициентов фракций фитомассы для определения биологической продуктивности древостоев

The purpose of the research is to develop a multidimensional model of conversion coefficients of phytomass fractions for pine forests of the coniferous-deciduous forests of the European part of the Russian Federation. The approved standards are the values of the coefficients averaged over the age groups of stands related to different forest-forming species growing in the three natural and climatic zones of Russia. In contrast to the simplified approach to determining the biological productivity of stands by the values of conversion coefficients averaged in age groups, the most scientifically sound approach based on methods of statistical modeling of the relationship of phytomass fractions with inventory indicators of stands is shown. The obtained regression models, interconnected with the data of regional tables of the growth course of different authors, made it possible to obtain multidimensional models, and as a result, the most accurate standards for conversion coefficients. The differences between the two methodological approaches are confirmed by the example of pine stands. The results of assessing the accuracy of determining conversion coefficients indicate a significant advantage of an approach that takes into account, along with age, the average height of stands. At the same time, it should be pointed out that the age itself, and even more so the age group, which is the basis of the first approach, is not able to reliably characterize the accuracy of obtaining the values of conversion coefficients (R2 = 0.908) with an error ES = ± 35.4%. As for the influence of the average height of stands on the conversion coefficients, it is more reliable (R2 = 0.990) with an error ES = ± 11.5%. The specified accuracy of the first two models is significantly inferior to the combined influence of the predictors indicated in them (R2 = from 0.998 to 0.999) with an error ES = ± 1.76% for trunks, ES = ± 1.34% for roots, ES = ± 2.03% for branches, ES = ± 3.7% for needles, ES = ± 1.19% for bark.

Моделирование биологической продуктивности сосняков по группам возраста субъектов ЦФО РФ

The purpose of the research was to develop a model for the digitalization of the biological productivity standards for forest stands based on conversion coefficients (cav) averaged by age groups. At the present stage of forestry, one of the priority areas of research is the assessment of the biological productivity of forest stands by individual fractions of phytomass (biomass of trunks, branches, bark, needles (foliage), roots), the determination of their bioenergy potential, the accumulation of carbon by forest elements in all the diversity of species, age and spatial structure of plantations. Studies of the climate-regulating function of forests, and first of all, the assessment of their absorption of carbon dioxide and carbon sequestration, are recognized as relevant. To solve this problem on a large scale, it is recommended to use conversion coefficients of wood stock into phytomass, taking into account the latitudinal strip of the terrain and age groups of stands. As a result, using the example of pine forests of the Central Federal District, a multidimensional model of changes in phytomass fractions in 17 constituent entities of the Russian Federation depending on the completeness, share of pine in the composition, average height and age group of stands was obtained. The resulting model is functional, characterized by a coeffi cient of determination R2 = 1.0 and a standard error ES = ± 0.2%, and only a tool for digitalization of biomass standards for individual fractions of phytomass. However, the use of the standard model a priori cannot exceed the accuracy of determining the average values of conversion coefficients obtained in the context of age groups.

Influence of the irradiation geometry on the severity of acute radiation damage

The aim of this study was to demonstrate how the severity of radiation damage in the case of bone marrow syndrome due to acute irradiation depends on the non-uniform irradiation of the body. We used the calculation method that involves the evaluation of organism mortality as a function of bone marrow cells colony survival vs dose for different radiation profiles. It was presumed that the probability of the death for the organism is the same for the same value of survival level of the bone marrow cells regardless of the dose distribution by mass of the organ. The dose of uniform irradiation that is equivalent to the dose for the L-th case of non-uniform irradiation is calculate based on the survival level of the total marrow cells. After that the probability of the death of the organism is estimated according to the dose response curve. Dose distribution in bone marrow of computational MIRD-5-type stylized model adult man for different geometries of exposure by point source of 137Cs was evaluated. Larger non-uniformity of the dose distribution in the bone marrow at the same dose in free air in the site of human location causes a greater probability of survival due to a greater proportion of bone marrow cells that have preserved the possibility of reproduction. The values of mean 50% lethal dose for cases of approximately uniform irradiation of the body surface (point source at a distance 10m) and sharply non-uniform irradiation (point source at a distance of 0.5 m) differ approximately by the factor of 1.7 – 2.5 depending on direction of irradiation. Additionally the values of conversion coefficients from the reading of an individual dosimeter to the value of an effective dose for various geometries of irradiation of emergency workers from the 137Cs point source were calculated. The average value of the conversion coefficient from personal dose to effective dose for the considered exposure situations is 0.7 Sv Cy-1 and the 90% confidence interval is 0.49 – 0.99 Sv Gy-1.

Study on the conversion coefficient between ACH50 and ACH in typical zones of public buildings

• Analyzed the conversion coefficient (CC) between ACH 50 and ACH of public buildings. • CC is strongly affected by meteorological conditions and varies in a wide range. • Recommended value of CC was given, as well as the applicable condition. The air infiltration of buildings is closely related to its indoor and outdoor environment and energy consumption. However, measuring air infiltration of a building under natural conditions is time-consuming, easily affected and expensive, so it's often inferred based on building airtightness in practical engineering. Empirical models can nevertheless make a rapid prediction without building parameters, which are widely applied in practical engineering. At present, most of the existing empirical models take residential buildings as objects, therefore they are difficult to be applied to public buildings. Hence, it is imperative to build an empirical model applicable to public buildings. In this study, the conversion coefficients between the airtightness (air change rate under the pressure difference of 50Pa) and the air infiltration rates under natural conditions of four typical zones of public buildings were analyzed. Firstly, the airtightness of four zones of public buildings in the cold region of China was measured. Secondly, their air infiltration rates under 1800 combined conditions of wind pressure and stack effect pressure were simulated based on the airtightness measured results. Finally, calculation and statistical analysis of the conversion coefficient were carried out based on the measured and simulated results, and the recommended value of conversion coefficient was proposed. Analysis results show that the CC of each zone is significantly affected by outdoor meteorological conditions and varies in a wide range (1# zone: 3.21 to 188.44). It is advised to ignore the extreme data and take the mean value of the CC corresponding to 95% of the data volume as the recommended value (22.2). This study can provide theoretical basis for the formulation of standards for the performance evaluation of building airtightness.

Разработка математической модели интерферометрической системы определения доплеровского сдвига частоты.

This work presents the result of the received signal measuring system for processing Doppler frequency theoretical research. In the researching device means of controlling laser frequency whose amplitude is proportional to the Doppler frequency shift of the received RF signal is realized. The coherent laser beam is divided in two forming interference pattern. In this case, one of the beams passes through the delay line, which leads to a phase shift in the optical wave. The rate of this phase shift is proportional to the laser frequency, changes in which cause corresponding changes in the interference pattern. Changes in the interference pattern in center analysis makes it possible to determine the changes of the laser frequency, which depends on Doppler frequency shift of the received RF signal. In this work opposition of the requirements for the Doppler frequency shift determination interferometric system parameters (the coefficient of proportionality to conversion Doppler frequency shift of the received RF signal in laser frequency and time delay) is discovered: large dynamic measurement range and high Doppler frequency shift measurement resolution. The processing the received RF signal method is proposed. This method take into consideration these requirements. The proposed measurement algorithm implements the multiscale principle. It is pointed that the proposed processing the measurements results method can be implemented both the parallel processing in channels with different values of conversion coefficients, and sequential – with their iterative change.

Monte Carlo study of patient and medical staff radiation exposures during interventional cardiology.

The aim of this study is to assess the radiation exposure of the patient and the medical staff during interventional cardiology procedures. Realistic exposure scenarios were developed using the adult reference anthropomorphic phantoms adopted by the International Commission on Radiological Protection (ICRP110Male and ICRP110Female), and the radiation transport code Geant4 (version 10.3). The calculated equivalent and effective doses were normalised by the simulated Kerma-Area Product (KAP), resulting in two conversion coefficients HT/KAP and E/KAP. To properly evaluate the risk of exposure, several dose-dependent parameters have been investigated, namely: radiological parameters (tube kilovoltage peak (kVp), type of projection, field size (FOV)), and operator positions. Four projections (AP,PA,LAO25° and RAO25°) were simulated for three X-ray energy spectra (80,100 and 120 kVp) with four different values of FOV (15×15cm2,20×20cm2,25×25cm2 and 30×30cm2). The results showed that the conversion coefficients values increase with increasing tube voltage as well as the FOV size. Recommended projection during the interventional cardiology procedures, whenever possible, should be the PA projection rather than AP projection. The most critical projection for the patient and the main operator is the RAO25° projection and the LAO25° projection respectively. The comparison of our results with the literature data showed good agreement allowing their use in the dosimetric characterization of interventional cardiology procedures.

Микросистемы с высоким коэффициентом преобразования слабого магнитного поля на основе магниторезистивных наноструктур

The magnetoresistive transducers of magnetic field have been claimed both for direct and indirect applications in various areas of industry, transport and special equipment. In the paper the special features of used terminology and dimensions in the main parameters of magnetic field magnetoresistive transformers have been revealed. The main results of experimental studies on the developed thin-film magnetoresistive nanostructures (TMN) with even and odd transfer characteristics have been presented. The TMN design on an anisotropic magnetoresistive effect has an odd transfer characteristic and conversion coefficient at the level of 8 mV/V/E. The TMN design based on a giant magnetoresistive effect has an even transfer characteristic and a conversion coefficient at the level of 27 mV/V/E. The results of promising design and technological solutions allowing reaching the values of conversion coefficient of TMN at the level exceeding 100 mV/V/E have been shown. The results of the study of the test spin-tunnel magnetoresistive nanostructure (spin-tunnel TMN) with giant magnetoresistive effect, exceeding 100% have been presented. The novelty of the obtained results has been reflected and the perspective of using highly sensitive TMN and creating the non-volatile MRAM on the basis of thin-film magnetoresistive structure with the spin-tunnel magnetoresistive effect have been determined.

Technical Note: Patient-weight dependence of the effective dose conversion coefficients for diagnostic x-ray imaging procedures.

The aim of this study was to provide a method and reference data for the evaluation of the weight dependence of the conversion coefficients from air collision kerma integrated over beam area to the effective dose for patients undergoing diagnostic x-ray examinations. A simple physics-based analytical model was developed in order to calculate the weight dependence of the effective dose conversion coefficients based on existing values of the conversion coefficients between patient effective dose and air collision kerma integrated over beam area calculated by the Monte Carlo method on the base of computational MIRD-5-type stylized models. The analytical expressions that make possible taking into account a patient's weight when assessing the effective dose were presented. The following categories of diagnostic x-ray examinations are considered: CT; plain radiography; cardiac angiography; fluoroscopy. The results indicate that the weight dependence of the effective dose conversion coefficients for different categories of diagnostic x-ray examinations has the same form. Correction factor for evaluation of the new value of the effective dose conversion coefficient for a patient with weight Wpa. when we know its value for a standard patient with weight Wst. depends on the ratios of their weights (Wst. /Wpat. ) and fractions of the incident energy which is imparted to a patient. The paper presents an approach and necessary data for the estimation of the weight dependence of the effective dose conversion coefficients for patients undergoing different diagnostic x-ray examinations.

Broadband Vibrational Energy Harvesting with a Spherical Piezoelectric Transducer Devoted to Underwater Wireless Sensor Networks

A new sensing node container based on a spherical piezoelectric transducer is proposed. This device provides broadband vibrational energy harvesting and sensing facilities intended for underwater wireless sensor networks. The transducer is composed of two acrylic glass (PMMA) half-spherical shells and a Pz26 piezoelectric ring clamped between the two shells. A simulation model of vibrational energy harvesting has been developed with electromechanical circuits for thickness and radial vibrational modes. This approach was validated by a finite element simulation. As a result, optimal power harvesting conditions and estimated harvested voltage were defined. A prototype of 2.2 cm in diameter was realized and characterized. Analysis in air environment reveals several structural resonance modes in the 20–80 kHz frequency range. The directivity patterns corresponding to these modes was obtained using laser Doppler vibrometry. The measurements for the underwater environment show that the structural resonance modes shift down in frequency to the 10–60 kHz range, and exhibiting low directivity dependence. Power harvesting performances was measured and quantified relative to acoustical pres- sure measurements using a hydrophone. The average conversion coefficient value was found to be in the order of 3 V/MPa. In broadband excitation mode, and for an acoustic pressure of 10 kPa, the amount of harvested power out of 5 main resonance modes is 3.3 μW.

Conversion Coefficients of equivalent and effective doses in terms of air kerma for computational scenarios of Total Body Irradiation in lying-down patients

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.

OA202] Recent update of typical effective doses received by patients at diagnostic and interventional radiology procedures and its impact on assessment of collective effective dose to population in bulgaria

Purpose Performance of regular national patient dose surveys is required by European and International Basic Safety Standards and by National law. Third national patient dose survey (TNS) was conducted in 2016–2017 with aim of updating information on radiation exposure to patients at different diagnostic and interventional radiology (DIR) procedures. The purpose of this work is to assess and update typical effective doses received by patients at various diagnostic and interventional radiology procedures (DIR) and to find its impact on assessment of collective effective dose to population. Methods Values of typical patient doses (TPD) are based on data obtained during TNS. Typical effective dose (TED) for each procedure was calculated using conversion coefficients (CC) from TPD to effective dose (E) with dimensions: (mSv. Gy - 1 . cm - 2 ) for radiography, fluoroscopy and interventional procedures; and (mSv. mGy - 1 . cm - 1 ) for Computed tomography procedures respectively. Values of CCs are based on UNSCEAR recommendations, as for Chest radiography an own CC assessment is made based on kerma area product values and respective E values calculated using PCXMC software. Total collective effective dose to Bulgarian population ( S E ) and the effective dose per capita were calculated based on the number of the most frequent DIR procedures and the TED per procedure. Results TED are updated for 16 of most common DIR procedures of which: 5 are radiography; 4 – fluoroscopy; 4 – computed tomography; 2 – interventional cardiology and one is for mammography respectively. For year 2016 SE is assessed to 5868 man.Sv which relates to mean effective dose of 0.82 mSv per capita. It is 16.8% higher than its relevant assessment based on older information for not updated typical patient doses obtained during previous national survey performed in 2007. An increase of 84% in S E is observed for the period of 2007 to 2016 year, as dynamics of collective effective doses is analysed and discussed. Conclusions Updated assessments of TEDs and SE due to DIR procedures are elaborated. Regular patient dose surveys are important for update of National Diagnostic Reference Levels (NDRLs) as well as for obtaining more realistic and precise assessment of collective effective dose to population due to diagnostic radiology procedures.

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.

Conversion Coefficients for Proton Beams using Standing and Sitting Male Hybrid Computational Phantom Calculated in Idealized Irradiation Geometries.

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.

CAN HALF VALUE LAYER MEASUREMENTS BE USED TOGETHER WITH THE EFFECTIVE ENERGY TO OBTAIN CONVERSION COEFFICIENTS FOR X-RAY SPECTRA?

Conversion coefficients are a substantial vehicle in practical radiation protection to determine the dose (rate) of a given radiation field. According to ICRU report 57, their values shall be obtained by means of spectrometry. This is, however, a time-consuming complicated procedure that cannot be performed by all dosimetry laboratories. Therefore, it is desired to find acceptable alternative methods to replace spectrometry. One possibility is to set up the X-ray facility in accordance with international standard ISO 4037-1:1997 and use the tabulated values from that standard. However, this needs to be considered during the construction phase of the X-ray facility. In this work, the combined usage of half-value layer measurements and the effective energy (both with respect to air kerma) to determine the conversion coefficients is investigated and compared with the values obtained by spectrometry. The investigations utilise all combinations of the H-, W-, N- and L-series, reference distances of 1 and 2.5 m and aluminium and copper as attenuation materials. We find that for most of the radiation qualities, the investigated method results in conversion coefficients that show an unacceptable deviation from the conventionally true values. However, the values of conversion coefficients of selected N- and L-qualities could be reproduced with high accuracy (within ±1 %).

Evaluation of the medical and occupational shielding in cerebral angiography using Monte Carlo simulations and virtual anthropomorphic phantoms

Abstract 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.