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1.
J Radiol Prot ; 41(2)2021 06 01.
Article in English | MEDLINE | ID: mdl-33784644

ABSTRACT

The PODIUM project aims to provide real-time assessments of occupationally exposed workers by tracking their motion and combining this with a simulation of the radiation field. The present work describes the approach that would be taken in mixed neutron-gamma fields, and details the methods for generating and applying an effective dose rate map; the required fluence to effective dose conversion coefficients at intercardinal angles are also presented. A proof-of-concept of the approach is demonstrated using a simple simulated workplace field within a calibration laboratory, with corroborative comparisons made against survey instrument measurements generally confirming good agreement. Simulated tracking of an individual within the facility was performed, recording a 1.25µSv total effective dose and accounting for dose rates as low as 0.5 nSv h-1, which is much lower than anything that could be accurately measured by physical neutron dosemeters in such a field.


Subject(s)
Occupational Exposure , Radiation Monitoring , Radiation Protection , Calibration , Humans , Neutrons , Occupational Exposure/analysis , Radiation Dosage
4.
Radiat Prot Dosimetry ; 151(2): 323-43, 2012 Aug.
Article in English | MEDLINE | ID: mdl-22645386

ABSTRACT

The impact of depleted uranium (DU) on human health has been the subject of much conjecture. Both the chemical and radiological aspects of its behaviour in the human body have previously been investigated in detail, with the radiological impact being assumed to be linked to the alpha decay of uranium. More recently, it has been proposed that the accumulation in tissue of high-Z materials, such as DU, may give rise to enhanced local energy deposition in the presence of natural background photon radiation due to the high photoelectric interaction cross sections of high-Z atoms. It is speculated that, in addition to producing short-range photoelectrons, these events will be followed by intense Auger and Coster-Kronig electron emission, thereby causing levels of cell damage that are unaccounted for in conventional models of radiological risk. In this study, the physical and biological bases of these claims are investigated. The potential magnitudes of any effect are evaluated and discussed, and compared with the risks from other radiological or chemical hazards. Monte Carlo calculations are performed to estimate likely energy depositions due to the presence of uranium in human tissues in photon fields: whole body doses, organ doses in anthropomorphic phantoms and nano-/micro-dosimetric scenarios are each considered. The proposal is shown generally to be based on sound physics, but overall the impact on human health is expected to be negligible.


Subject(s)
Background Radiation , Photons , Radiation Dosage , Uranium , Computer Simulation , Electrons , Humans , Phantoms, Imaging , Risk Assessment , Whole Body Imaging
5.
Phys Med Biol ; 51(7): 1807-17, 2006 Apr 07.
Article in English | MEDLINE | ID: mdl-16552106

ABSTRACT

The nationwide breast cancer screening programme using mammography has been in full operation in The Netherlands since 1997. There is concern that the mean glandular doses due to mammography might be differing between different regions of the country due to differences in glandularity and compressed breast thickness. To investigate regional differences, glandularity, compressed breast thickness and mean glandular dose were determined for individual breasts during screening at mammography units at four locations in The Netherlands. Differences in glandularity were observed, which could be related qualitatively to differences in age of the participants at the different locations. Mean glandular dose depends on compressed breast thickness, glandularity and technical conditions of screening. The lowest average value of the mean glandular dose was found for the unit in Amsterdam. This is most likely due to the use of the Mo/Rh anode/filter combination at this unit, in addition to the Mo/Mo combination. At the other three units, almost exclusively the Mo/Mo anode/filter combination was used. Differences in mean glandular dose averaged per unit could be related mainly to differences in tube-current exposure-time product values. Consequently, it is concluded that differences in mean glandular dose at different units are marginal.


Subject(s)
Breast/anatomy & histology , Mammography , Mass Screening , Aged , Breast Neoplasms/prevention & control , Female , Humans , Middle Aged , Netherlands , Radiation Dosage
6.
Phys Med Biol ; 50(24): 5953-67, 2005 Dec 21.
Article in English | MEDLINE | ID: mdl-16333166

ABSTRACT

The nationwide breast cancer screening programme using mammography has been in full operation in the Netherlands since 1997. Quality control of the screening programme has been assigned to the National Expert and Training Centre for Breast Cancer Screening. Limits are set to the mean glandular dose and the centre monitors these for all facilities engaged in the screening programme. This procedure is restricted to the determination of the entrance dose on a 5 cm thick polymethylmethacrylate (PMMA) phantom. The mean glandular dose for a compressed breast is estimated from these data. Individual breasts may deviate largely from this 5 cm PMMA breast model. Not only may the compressed breast size vary from 2 to 10 cm, but breast composition varies also. The mean glandular dose is dependent on the fraction of glandular tissue (glandularity) of the breast. To estimate the risk related to individual mammograms requires the development of a method for determination of the glandularity of individual breasts. A method has been developed to derive the glandularity using the attenuation of mammography x-rays in the breast. The method was applied to a series of mammograms at a screening unit. The results, i.e., a glandularity of 93% within the range of 0 to 1, were comparable with data in the literature. The glandularity as a function of compressed breast thickness is similar to results from other investigators using differing methods.


Subject(s)
Mammography , Phantoms, Imaging , Breast/anatomy & histology , Female , Humans
7.
Radiat Prot Dosimetry ; 116(1-4 Pt 2): 428-32, 2005.
Article in English | MEDLINE | ID: mdl-16604673

ABSTRACT

A C3-dump is a facility for disposing of low activity natural radioactive waste containing the uranium series 238U, the thorium series 232Th and 40K. Only the external radiation owing to gamma rays, X-rays and annihilation photons is considered in this study. For two situations--the semi-infinite slab and the tourist geometry--the conversion coefficients from specific activity to air kerma rate at 1 m above the relevant level are calculated. In the first situation the waste material is in contact with the air but in the tourist geometry it is covered with a 1.35 m thick layer. For the calculations, the Monte Carlo radiation transport code MCNP is used. The yield and photon energy for each radionuclide are according to the database of Oak Ridge National Laboratory. For the tourist situation, the depth-dose distribution through the covering layer is calculated and extrapolated to determine the exit dose.


Subject(s)
Models, Statistical , Radiation Monitoring/methods , Radiation Protection/instrumentation , Radioactive Waste/analysis , Uranium/analysis , Waste Management/instrumentation , Computer Simulation , Equipment Design , Equipment Failure Analysis , Monte Carlo Method , Netherlands , Radiation Dosage , Radiation Monitoring/standards , Radiation Protection/methods , Scattering, Radiation , Waste Management/methods
8.
Radiat Prot Dosimetry ; 117(1-3): 277-82, 2005.
Article in English | MEDLINE | ID: mdl-16461518

ABSTRACT

Digital and interventional radiology are increasingly important areas of radiology. Quality control (QC) of such equipment is of particular importance to avoid unnecessary high doses and to help to achieve good image quality. Within the DIMOND III project, equipment requirements and specifications for digital and interventional radiology have been formulated. A protocol for QC tests has been drafted based on various national and international recommendations. Tests are included for various parts of the imaging chain, i.e. X-ray tube and generator, X-ray tube control system, laser printer and display station, and image quality and patient dose. Preliminary tolerance levels have been set for the various tests, after initial measurements. To check the suitability of QC tests and stated tolerance levels, measurements were made at the University Hospital Gasthuisberg in Leuven for equipment used for paediatric radiology and a unit used for chest examinations. The results of the various tests are reported.


Subject(s)
Radiographic Image Enhancement/methods , Radiology, Interventional/instrumentation , Radiology, Interventional/methods , Humans , Phantoms, Imaging , Quality Control , Radiation Protection , Radiographic Image Enhancement/instrumentation , Radiographic Image Interpretation, Computer-Assisted , Radiometry , Technology, Radiologic , X-Rays
9.
Radiat Prot Dosimetry ; 117(1-3): 269-73, 2005.
Article in English | MEDLINE | ID: mdl-16461526

ABSTRACT

Quality control in digital radiology can be time-consuming. Equipment self-tests may significantly decrease staff workload. The two most essential parameters for radiology systems are image quality and patient dose. Concerning patient dose, information on the dose-area product (DAP) values generally forms the basis for assessment of patient dose. DAP-values can be measured using a transmission ionisation chamber or calculated from equipment settings. In the present study, various image quality parameters were derived using a contrast-detail (C-D) phantom. The investigation included a computer-aided assessment of C-D images, which produced various parameters, and also parameters based upon scoring by human observers. In addition, another parameter was calculated from modulation transfer function (MTF) measurements. The automatically calculated parameters showed good correlation with human readings, although the number of X-ray systems studied is still limited. We propose a combined evaluation of DAP and automatically calculated C-D or MTF parameters for equipment self-tests.


Subject(s)
Radiographic Image Enhancement , Radiology/instrumentation , Radiology/methods , Computer-Aided Design , Equipment Design , Humans , Image Processing, Computer-Assisted , Models, Statistical , Phantoms, Imaging , Quality Control , Radiography, Interventional/methods , X-Rays
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