Stelios Christofides

Gamma-ray measurements of naturally occurring radioactive samples from Cyprus characteristic geological rocks

Abstract Using high-resolution gamma-ray spectroscopy, the terrestrial gamma radiation in all the predominant types of geological rock formations appearing in Cyprus was measured. Soil samples were collected from each rock type, sealed in 1 l plastic Marinelli beakers, and measured in the laboratory for 24 h each. From the measured gamma-ray spectra, activity concentrations were determined for 232 Th (range from 1.3 to 52.8 Bq kg −1 ), 238 U (from 0.9 to 90.3 Bq kg −1 ) and 40 K (from 13 to 894 Bq kg −1 ). Elemental concentrations mean values of (2.8±0.7) ppm , (1.3±0.3) ppm and (0.6±0.1)% were extracted, for thorium, uranium and potassium, respectively. Absorbed dose rates in air outdoors were calculated to be in the range of 0.1– 50 nGy h −1 , depending on the geological features, with an overall mean value of (14.7±7.3) nGy h −1 . The corresponding effective dose rates per person outdoors were estimated to be between 0.1 and 61.4 μSv yr −1 , assuming a 20% occupancy factor.

Gamma radiation measurements and dose rates in commercially-used natural tiling rocks (granites).

The gamma radiation in samples of a variety of natural tiling rocks (granites) imported in Cyprus for use in the building industry was measured, employing high-resolution gamma-ray spectroscopy. The rock samples were pulverised, sealed in 1-l plastic Marinelli beakers, and measured in the laboratory with an accumulating time between 10 and 14 h each. From the measured gamma-ray spectra, activity concentrations were determined for (232)Th (range from 1 to 906 Bq kg(-1)), (238)U (from 1 to 588 Bq kg(-1)) and (40)K (from 50 to 1606 Bq kg(-1)). The total absorbed dose rates in air calculated from the concentrations of the three radionuclides ranged from 7 to 1209 nGy h(-1) for full utilization of the materials, from 4 to 605 nGy h(-1) for half utilization and from 2 to 302 nGy h(-1) for one quarter utilization. The total effective dose rates per person indoors were determined to be between 0.02 and 2.97 mSv y(-1) for half utilization of the materials. Applying dose criteria recently recommended by the EU for superficial materials, 25 of the samples meet the exemption dose limit of 0.3 mSv y(-1), two of them meet the upper dose limit of 1 mSv y(-1) and only one clearly exceeds this limit.

Indoor radon (222Rn) concentration measurements in Cyprus using high-sensitivity portable detectors

Using high-sensitivity radon ((222)Rn) portable detectors (passive electronic devices of the type RADIM3), the airborne (222)Rn concentration in the interior of various Cypriot buildings and dwellings was measured. For each preselected building and dwelling, a calibrated detector was put into a closed room, and the (222)Rn concentration was registered in sampling intervals of 2 to 4 h for a total counting time of typically 48 h. (222)Rn activity concentrations were found to be in the range of 6.2 to 102.8 Bq m(-3), with an overall arithmetic mean value of (19.3+/-14.7) Bq m(-3). This value is by a factor of two below the world average (population-weighted) value of 39 Bq m(-3). The total annual effective dose equivalent to the Cypriot population was calculated to be between 0.16 and 2.6 mSv with an overall arithmetic mean value of (0.49+/-0.37) mSv.

Staff dosimetry in interventional cardiology: survey on methods and level of exposure

In interventional cardiac procedures, staff operates near the patient in a non-uniformly scattered radiation field. Consequently, workers may receive, over a period, relatively high radiation doses. The measurement of individual doses to personnel becomes critical due to the use of protective devices and, as a consequence of the large number of methods proposed to assess the effective dose, great variability in monitoring programmes is expected among European countries. SENTINEL consortium has conducted a survey on staff dosimetry methods and on the level of staff exposure in 12 European cardiac centres demonstrating the urgent need to harmonise dosimetry methods. From the dosimetry survey, constraint annual effective dose of 1.4 mSv and Hp(0.07) over the protective apron of 14 mSv are proposed for the optimisation the exposure the most-exposed operator.

Airborne 222Rn concentration in Cypriot houses.

Studies from a pilot survey in 89 houses in Cyprus show that the arithmetic mean for the housing stock is about 7 Bq m-3 and the annual effective dose equivalent to the population from radon progeny is < 330 microSv y-1. Four houses have values > 30 Bq m-3, corresponding to two standard deviations from the mean value. The highest value recorded was 78 Bq m-3. These results are considerably lower than those of other countries reported in the literature. Radon concentrations in houses is correlated to the local geology. The highest concentrations are in houses built on Chalk formations with an average value of 9.29 Bq m-3 (standard deviation 19.69 Bq m-3). The lowest concentrations are in houses built on Olivine Basalt formations with an average value of 0.50 Bq m-3 (standard deviation 0.80 Bq m-3).

Curriculum for education and training of Medical Physicists in Nuclear Medicine: Recommendations from the EANM Physics Committee, the EANM Dosimetry Committee and EFOMP.

PURPOSE To provide a guideline curriculum covering theoretical and practical aspects of education and training for Medical Physicists in Nuclear Medicine within Europe. MATERIAL AND METHODS National training programmes of Medical Physics, Radiation Physics and Nuclear Medicine physics from a range of European countries and from North America were reviewed and elements of best practice identified. An independent panel of experts was used to achieve consensus regarding the content of the curriculum. RESULTS Guidelines have been developed for the specialist theoretical knowledge and practical experience required to practice as a Medical Physicist in Nuclear Medicine in Europe. It is assumed that the precondition for the beginning of the training is a good initial degree in Medical Physics at master level (or equivalent). The Learning Outcomes are categorised using the Knowledge, Skill and Competence approach along the lines recommended by the European Qualifications Framework. The minimum level expected in each topic in the theoretical knowledge and practical experience sections is intended to bring trainees up to the requirements expected of a Medical Physicist entering the field of Nuclear Medicine. CONCLUSIONS This new joint EANM/EFOMP European guideline curriculum is a further step to harmonise specialist training of Medical Physicists in Nuclear Medicine within Europe. It provides a common framework for national Medical Physics societies to develop or benchmark their own curricula. The responsibility for the implementation and accreditation of these standards and guidelines resides within national training and regulatory bodies.

Diagnostic sensitivity of SPECT myocardial perfusion imaging using a pumping cardiac phantom with inserted variable defects

BackgroundThe diagnostic sensitivity of various SPECT MPI procedures was assessed using a pumping cardiac phantom with variable defects inserted in the myocardial wall of the left ventricle.Methods and ResultsA diagnostic evaluation of 142 myocardial defects was performed. A diagnosis blinded to prior-known conditions was compared to the known defects severity (transmural, subendocardial) and defects position within the myocardial wall of the left ventricle (apical, anterior, inferior) for three body types (average male, large male, large female). Non-attenuation corrected, attenuation corrected and gated SPECT MPI were performed. The diagnostic sensitivity was improved when applying attenuation correction or gating techniques to identify subendocardial defects in the inferior, anterior and apical segments of the myocardial wall of the left ventricle for all three body types. Transmural defects could be identified without any attenuation correction or gating.ConclusionsThe diagnostic sensitivity was improved when applying AC or GSPECT techniques.

The Education and training of clinical medical physicists in 25 European, 2 North American and 2 Australasian countries: Similarities and differences

PURPOSE The clinical medical physicist is part of a team responsible for safe and competent provision of radiation-based diagnostic examinations and therapeutic practices. To ensure that the physicist can provide an adequate service, sufficient education and training is indispensable. The aim of this study is to provide a structured description of the present status of the clinical medical physicist education and training framework in 25 European, 2 North American and 2 Australasian countries. METHODS For this study, data collection was based on a questionnaire prepared by the European Federation of Organizations in Medical Physics (EFOMP) and filled-in either by the corresponding scientific societies-organizations or by the authors. RESULTS In the majority of cases, a qualified medical physicist should have an MSc in medical physics and 1-3 years of clinical experience. Education and training takes place in both universities and hospitals and the total duration of the programs ranges from 2.5 to 9 years. In 56% of all European countries, it is mandatory to hold a diploma or license to work as a medical physicist, the situation being similar in Australasian and 4 states of USA. Generally, there are national registers of medical physicists with inclusion on the register being voluntary. There are renewal mechanisms in the registers usually based on a Continuing Professional Development (CPD) system. CONCLUSIONS In conclusion, a common policy is followed in general, on topics concerning education and training as well as the practice of the medical physicist profession, notwithstanding the presence of a few differences.

Characterization of attenuation and respiratory motion artifacts and their influence on SPECT MP image evaluation using a dynamic phantom assembly with variable cardiac defects

BackgroundA phantom assembly that simulates the respiratory motion of the heart was used to investigate artifacts and their impact on defect detection.MethodsSPECT/CT images were acquired for phantoms with and without small and large cardiac defects during normal and deep breathing, and also at four static respiratory phases. Acquisitions were reconstructed with and without AC, and with misalignment of transmission and emission scans. A quantitative analysis was performed to assess artifacts. Two physicians reported on defect presence or absence and their results were evaluated.ResultsAll large defects were correctly reported. Attenuation reduced uptake in the basal LV walls, increasing FN physicians’ reports for small defects. Respiratory motion reduced uptake mainly in the anterior and inferior walls increasing FP and FN reports on images without and with small defects, respectively. Artifacts due to misalignment between CT and SPECT scans in normal breathing phantoms did not influence the physicians’ reports.ConclusionsAttenuation and respiratory motion correction should be applied to reduce artifacts before reporting on small defects in deep breathing conditions. Artifacts due to misalignment between CT and SPECT scans do not affect defect detection in normal breathing when the LV is co-registered in SPECT and CT images prior to AC.

Comparison of Lead-free and Conventional x-ray aprons for Diagnostic Radiology

Radiology personnel demand alternatives to lead x-ray aprons, as the weight of lead aprons often causes discomfort, fatigue and musculoskeletal problems. There is also a necessity to change the composition of x-ray protective aprons with environmentally friendly materials, as great concern exists worldwide, about health effects arising from lead exposure. Therefore, lead is being replaced by lightweight materials. The Medical Physics Department of Nicosia General Hospital, conducted a study to evaluate radiation transmission through commercially available lead-free aprons from different manufacturers. The study concluded that these aprons provide less lead equivalent thickness than what is stated on the lead aprons and their manufacturing certificates. This paper describes the methodology used and the results obtained.