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PubMed2005

Artificial neural networks in neutron dosimetry.

An artificial neural network (ANN) has been designed to obtain neutron doses using only the count rates of a Bonner spheres spectrometer (BSS). Ambient, personal and effective neutron doses were included. One hundred and eighty-one neutron spectra were utilised to calculate the Bonner count rates and the neutron doses. The spectra were transformed from lethargy to energy distribution and were re-binned to 31 energy groups using the MCNP 4C code. Re-binned spectra, UTA4 response matrix and fluence-to-dose coefficients were used to calculate the count rates in the BSS and the doses. Count rates were used as input and the respective doses were used as output during neural network training. Training and testing were carried out in the MATLAB environment. The impact of uncertainties in BSS count rates upon the dose quantities calculated with the ANN was investigated by modifying by +/-5% the BSS count rates used in the training set. The use of ANNs in neutron dosimetry is an alternative procedure that overcomes the drawbacks associated with this ill-conditioned problem.

Algorithms↗
PubMed2006

Dose constraints and guidance for exposure of individuals knowingly and willingly helping in the support and comfort of individuals undergoing medical exposure.

The council of the European Union (EU) has adopted directive 97/43/EURATOM that states that Member States shall ensure that dose constraints are established for exposure of those individuals (voluntary helpers) knowingly and willingly helping patients undergoing medical diagnosis or treatment. This study investigates for which medical diagnoses and treatments voluntary helpers are active. It provides a rough estimation of the effective dose to the voluntary helper for various applications. It summarises the dose constraints established in various EU Member States. Voluntary helpers are especially active in paediatric radiology and in nuclear medicine for both diagnostic and for therapeutic purposes. No voluntary helpers are active during radiotherapy. Voluntary helpers are commonly one of the parents, relatives or friends of the patient. In The Netherlands, the highest effective dose to voluntary helpers of approximately 2.3 mSv is found for therapy of patients younger than 1 y with metaiodobenzylguanidine labelled with 131I. Effective doses to voluntary helpers in paediatric radiology are, generally, quite small, i.e. lower than several tens of microSv at maximum without wearing protective clothing.

Body Burden↗
PubMed2005

Radon concentration measurements in the Amasra coal mine, Turkey.

In this study, the results of atmospheric radon measurements that were performed for the Amasra underground coal mine in Zonguldak bituminous coal basin (Turkey) are presented. The radon measurements were performed for 40 days between November 2004 and December 2004 using passive nuclear etched track detectors. The radon concentrations vary from a minimum value 49 Bq m(-3) in a site located at +40 m to a maximum value 223 Bq m(-3) in a site located at -100 m. Mean concentration is 117 (Bq m(-3)). This value is well below the action level of 500-1,500 Bq m(-3) recommended by the International Commission on Radiological Protection (ICRP) (1993). The mean effective dose value for workers of this mine of 3.4 microSv per day was obtained. This result shows that protection against radiological hazards would not be necessary for workers of this mine((2)).

Air Pollutants, Occupational↗
PubMed2006

Fluence-to-absorbed dose conversion coefficients for use in radiological protection of embryo and foetus against external exposure to protons from 100 MeV to 100 GeV.

In the literature, no conversion coefficients are available for use in radiological protection of embryo and foetus against external exposure to protons. This study used the Monte Carlo code MCNPX to determine mean absorbed doses to the embryo and foetus when the mother is exposed to proton fields. Monoenergetic protons ranging from 100 MeV to 100 GeV were considered. The irradiation geometries include antero-posterior (AP), postero-anterior (PA), lateral (LAT), rotational (ROT) and isotropic (ISO). At each of these standard irradiation geometries, absorbed doses to the foetal brain and body were calculated for the embryo of 8 weeks and the foetus of 3, 6 or 9 months. Proton fluence-to-absorbed dose conversion coefficients were derived for the four prenatal ages.

Body Burden↗
PubMed2006

Neutron scattering in concrete and wood.

In this work, the energy spectra of photoneutrons, scattered by ordinary, high-density concrete and wood barriers, have been evaluated using the MCNP4B code. These spectra were calculated for different scattering angles, and for incident neutron energies varying between 0.1 and 10 MeV. The results presented are required to simulate typical photoneutron fluence, produced by medical accelerators, which is scattered by the room walls and reaches the door. It was found that the mean energy of the scattered neutrons does not depend on the scattering angle. Furthermore, it was found that the scattered neutron energies are lower in wood and baryte concrete, which indicates that these materials can be used for lining the maze walls in order to reduce neutron dose at the room door. These data will help to estimate the personal dose received by the patient and staff in radiotherapy facilities.

Air Pollution, Indoor↗
PubMed2006

In vivo EPR dosimetry to quantify exposures to clinically significant doses of ionising radiation.

As a result of terrorism, accident or war, populations potentially can be exposed to doses of ionising radiation that could cause direct clinical effects within days or weeks. There is a critical need to determine the magnitude of the exposure to individuals so that those with significant risk can have appropriate procedures initiated immediately, while those without a significant probability of acute effects can be reassured and removed from the need for further consideration in the medical/emergency system. It is extremely unlikely that adequate dosemeters will be worn by the potential victims, and it also will be unlikely that prompt and accurate dose reconstruction at the level of individuals will be possible. Therefore, there is a critical need for a method to measure the dose from radiation-induced effects that occur within the individual. In vivo EPR measurements of radiation-induced changes in the enamel of teeth is a method, perhaps the only such method, which can differentiate among doses sufficiently to classify individuals into categories for treatment with sufficient accuracy to facilitate decisions on medical treatment. In its current state, the in vivo EPR dosemeter can provide estimates of absorbed dose of +/- 0.5 Gy in the range from 1 to >10 Gy. The lower limit and the precision are expected to improve, with improvements in the resonator and the algorithm for acquiring and calculating the dose. In its current state of development, the method is already sufficient for decision-making action for individuals with regard to acute effects from exposure to ionising radiation for most applications related to terrorism, accidents or nuclear warfare.

Body Burden↗
PubMed2006

ICRP special radiation protection issues in interventional radiology, digital and cardiac imaging.

The International Commission on Radiological Protection (ICRP) has published two reports giving recommendations dealing with the avoidance of deterministic injuries in interventional radiology and the management of patient dose in digital radiology in 2001 and 2004, respectively. Another document, on radiation protection for cardiologists performing fluoroscopically guided procedures, will be produced during 2005. This paper highlights some of the topics of the published reports, their relevance to European legislation on medical exposures and the importance of radiation protection research in underpinning the ICRP task groups' work in to producing these documents. It is also anticipated that the results, obtained in the cardiology work package of the European research project, will be used in the new document on radiation protection for cardiologists.

Heart↗
PubMed2006

Evaluation of methods to estimate the patient dose in interventional radiology.

Dosimetric methods used for interventional and diagnostic radiology are reviewed and evaluated, including terms, quantities, equipment, calibration and measurements. Measurement of local skin dose and estimation of maximum local skin dose are emphasised. Aspects related to dosimetry in computed tomography and to methods of determining organ and tissue doses are not considered.

Calibration↗
PubMed2006

Does digital imaging decrease patient dose? A pilot study and review of the literature.

The potential for decreasing patient dose is one of the main arguments for the justification of the cost of digital imaging equipment. However, the literature review with respect to patient doses using digital imaging modalities, presents conflicting results. During this study, patients' entrance surface doses were measured for three simple radiographic examinations, in European centres equipped with a computed radiography digital system. Results showed that doses between centres varied from 30% for chest LAT to 250% for chest PA examination. With the digital image quality criteria still under discussion, and with the post-processing parameters and/or image documentations varying, any dose comparisons between conventional/digital systems, as well as dose comparisons between different centre using digital units, are difficult. Clinical trials are required in order to define reference levels associated with quality of digital image necessary to address specific clinical requirements.

Humans↗
PubMed2006

Bulgarian experience in the establishment of reference dose levels and implementation of a quality control system in diagnostic radiology.

Results from a Bulgarian patient dose survey in diagnostic radiology are presented. Reference levels for entrance surface dose (ESD) were 0.9 mGy for chest radiography (PA), 30 mGy for lumbar spine (Lat), 10 mGy for pelvis, 5 mGy for skull (AP), 3 mGy for skull (Lat) and 13 mGy for mammography. Quality control (QC) programmes were proposed for various areas of diagnostic radiology. Film processing QC warranted special attention. Proposed QC programmes included parameters to be tested, level of expertise needed and two action levels: remedial and suspension. Programmes were tested under clinical conditions to assess initial results and draw conclusions for further QC system development. On the basis of international experience, measurement protocols were developed for all parameters tested. QC equipment was provided as part of the PHARE project. A future problem for QC programme implementation may be the small number of medical physics experts in diagnostic radiology.

Bulgaria↗
PubMed2006

Patient and staff doses in radiology and cardiology in Estonia.

This paper presents a short description of the Estonian radiological facilities and the doses to staff in radiology and cardiology. For each major work practice, the annual (2002) average effective doses are listed: X-ray diagnostics (radiologists: 1.11 mSv; radiographers: 1.03 mSv), interventional radiology (doctors in cardioangiography: 6.04 mSv; radiologist in angiography: 2.71 mSv), nuclear medicine (radiologists: 0.91 mSv; technicians: 2.41 mSv) and radiotherapy (radiologists: 1.00 mSv; technicians: 1.04 mSv). This paper also presents the first results of adult patient dose measurements in diagnostic X-ray departments in Estonia. The average entrance skin dose for chest PA examinations was 0.3 mGy, for chest LAT 0.9 mGy, for lumbar spine AP 6.4 mGy, for lumbar spine LAT 10.7 mGy and for pelvis AP 3.9 mGy.

Cardiology↗
PubMed2006

Implementation of QA and QC standards in radiology in Slovakia.

The Slovak government organizes the radiation protection policy through its regulatory authorities within the Ministry of Health, on a central level. The health protection regulations are compatible with international standards and recommendations of the ICRP and the EC. The general requirements on quality assurance (QA) and quality control (QC) (acceptance, constancy and routine tests), the guidance levels for various types of radiological examinations and the instructions for optimisation procedures are supported by Slovak technical standards, compatible with European standards. But the QA/QC process, as well as the training of the staff, needs improvement. The Slovak Medical University participates in the QA implementation through organising and managing national audits for control of the QA programme. In this paper, we present results of patient dose measurement studies carried out in the Slovak Republic, in the framework of activities of the Slovak Commission of QA established by the Slovak Ministry of Health.

Embryo, Mammalian↗
PubMed2006

Investigation of occupational radiation exposure during interventional cardiac catheterisations performed via radial artery.

The purpose of this study was to determine the thyroid, sternum and hand radiation doses of radiologists who perform angiographies and angioplasties via the radial artery. Staff radiation dose was estimated for 21 cardiac interventional catheterisations. Thermoluminescence dosemeters (TLDs) were used to determine radiation dose for each procedure at the right and left wrist, at the sternum and the thyroid. A dose area product (DAP) meter was also attached to give a direct value in Gy cm2 for each procedure. Staff radiation doses varied between 34 and 235 microGy per procedure at the left wrist, 28 and 172 microGy at the right wrist, 16 and 106 microGy at the level of the thyroid and 16 and 154 microGy at the level of the sternum. The DAP values varied between 25 and 167 Gy cm2. Radiation doses in this study are comparable to those reported in previous studies. Moreover, good correlation was found between the DAP values and the occupational dose measured with TLDs.

Angioplasty↗
PubMed2006

Dose to cardiologists in haemodynamic and electrophysiology cardiac interventional procedures.

Interventional cardiac procedures can be complex and involve extensive use of low dose rate fluoroscopy and high dose rate in image acquisition mode; hence, staff may receive significant radiation exposure. Radiation exposure to operators was assessed in 173 procedures. Fluoroscopy time, number of acquired images and dose-area product were recorded and occupational dose assessed with thermoluminescence dosemeters. The effective dose to the operator was compared with relevant literature data: values found were generally lower than those reported for other interventional cardiology laboratories. This is probably because of the strict radiation protection policy in our centre. Higher effective doses were found for defibrillator implantation and percutaneous transluminal coronary angiography procedures; for other cardiac procedures, effective dose was lower. Yearly extrapolated occupational doses to cardiologists are lower than the regulatory dose limit and in the lower band of doses reported in the literature.

Algorithms↗
PubMed2006

Comparison of the distribution of doses summarised over different periods of time.

Track dosemeters are very useful devices for dose assessment. The low cost and relatively simple procedures of dose calculation allow the mass distribution of track dosemeters in the population of exposed people. Because of the large number of measurements, observations may be made that would not be possible if the number of measurements were low. One such observation is the unexpected difference between the parameters of the annual dose distribution and the distribution of short-term doses. This difference may have a strong impact on lifetime dose or risk calculations. Much epidemiological data are based on the extrapolation of the distribution of short-term doses into the distribution of the lifetime dose. How the distribution of lifetime doses is spread is more complicated. The answer depends on the period of the single measurement.

Data Interpretation, Statistical↗
PubMed2006

Experiences with area specific spectrum stripping of NaI(Tl) gamma spectra.

Processing of airborne and carborne gamma-ray spectra (AGS and CGS) often includes the stripping (elimination) of the signals from natural radioactivity. Hereby the net result becomes the signals from man-made radioactivity or other radiation anomalies. The parameters needed for spectrum stripping are dependent on detector size and quality as well as on the energy windows. In addition they depend on the environmental geometry including the vehicle carrying the detector. For AGS the altitude also influences the parameters. In general the stripping parameters are determined from tedious laboratory or field measurements with known sources of natural radioactivity. Stripping parameters may, however, often be calculated from the actual survey data or from data from a similar area. Both post-processing and real-time processing are possible. The technique is useful for gamma source search, for detection of radiation anomalies and for mapping of contamination levels. The use of the technique is illustrated with field exercise data.

Air Pollution, Radioactive↗
PubMed2006

Estimating effective dose for a cardiac catheterisation procedure with single or double personal dosemeters.

In most countries of the European Union legislation requires individual determination and registration of the dose to radiological workers exposed to ionising radiation to check whether dose limits are exceeded. To assess stochastic risk, ideally effective dose (E) should be known. In practice, personal dose equivalent [H(P)(10)] is used as it can be measured with a personal dosemeter. The dosemeter reading may provide a reasonable assessment of H(P)(10), but it may deviate strongly from E, in particular in radiology procedures for medical diagnosis or intervention when protective clothing like lead-equivalent apron and thyroid collar is worn. In the literature various correction factors and algorithms to convert readings of single or dual dosemeters to an estimate of E can be found. An illustrative example of a cardiac catheterisation procedure, in which dose calculations are made by Monte Carlo simulation of radiation transport, shows that such corrections may still yield considerable overestimation.

Cardiac Catheterization↗