Study on the uncertainty of passive area dosimetry systems for environmental radiation monitoring in the framework of the EMPIR "Preparedness" project

Abstract One of the objectives of the EMPIR project 16ENV04 "Preparedness" is the harmonization of methodologies for the measurement of doses with passive dosimetry systems for environmental radiation monitoring in the aftermath of a nuclear or radiological event. In such cases, measurements are often performed at low radiation dose rates, close to the detection limit of the passive systems. The parameters which may affect the dosimetric results of a passive dosimetry system are analyzed and four laboratories quantitatively evaluate the uncertainties of their passive dosimetry systems. Typical uncertainties of five dosimetric systems in four European countries are compared and the main sources of uncertainty are analyzed using the results of a questionnaire compiled for this specific purpose. To compute the characteristic limits of a passive dosimetry system according to standard ISO 11929, the study of the uncertainty of the system is the first step. In this work the uncertainty budget as well as the characteristic limits (decision thresholds and detection limits) are evaluated and the limitations and strengths of a complete analysis of all parameters are presented

The Radiation Issue in Cardiology: the time for action is now

The "radiation issue" is the need to consider possible deterministic effects (e.g., skin injuries) and long-term cancer risks due to ionizing radiation in the risk-benefit assessment of diagnostic or therapeutic testing. Although there are currently no data showing that high-dose medical studies have actually increased the incidence of cancer, the "linear-no threshold" model in radioprotection assumes that no safe dose exists; all doses add up in determining cancer risks; and the risk increases linearly with increasing radiation dose. The possibility of deterministic effects should also be considered when skin or lens doses may be over the threshold. Cardiologists have a special mission to avoid unjustified or non-optimized use of radiation, since they are responsible for 45% of the entire cumulative effective dose of 3.0 mSv (similar to the radiological risk of 150 chest x-rays) per head per year to the US population from all medical sources except radiotherapy. In addition, interventional cardiologists have an exposure per head per year two to three times higher than that of radiologists. The most active and experienced interventional cardiologists in high volume cath labs have an annual exposure equivalent to around 5 mSv per head and a professional lifetime attributable to excess cancer risk on the order of magnitude of 1 in 100. Cardiologists are the contemporary radiologists but sometimes imperfectly aware of the radiological dose of the examination they prescribe or practice, which can range from the equivalent of 1-60 mSv around a reference dose average of 10-15 mSv for a percutaneous coronary intervention, a cardiac radiofrequency ablation, a multi-detector coronary angiography, or a myocardial perfusion imaging scintigraphy. A good cardiologist cannot be afraid of life-saving radiation, but must be afraid of radiation unawareness and negligence

Occupational Exposure of the Eye Lens in Interventional Procedures: How to Assess and Manage Radiation Dose.

Occupational exposure from interventional x-ray procedures is one of the areas in which increased eye lens exposure may occur. Accurate dosimetry is an important element to investigate the correlation of observed radiation effects with radiation dose, to verify the compliance with regulatory dose limits, and to optimize radiation protection practice. The objective of this work is to review eye lens dose levels in clinical practice that may occur from the use of ionizing radiation. The use of a dedicated eye lens dosimeter is the recommended methodology; however, in practice it cannot always be easily implemented. Alternatively, the eye lens dose could be assessed from measurements of other dosimetric quantities or other indirect parameters, such as patient dose. The practical implementation of monitoring eye lens doses and the use of adequate protective equipment still remains a challenge. The use of lead glasses with a good fit to the face, appropriate lateral coverage, and/or ceiling-suspended screens is recommended in workplaces with potential high eye lens doses

Voxel model of a rabbit: assessment of absorbed doses in organs after CT examination performed by two different protocols

The objective of this work was to assess absorbed doses in organs and tissues of a rabbit, following computed tomography (CT) examinations, using a dedicated 3D voxel model. Absorbed doses in relevant organs were calculated using the MCNP5 Monte Carlo software. Calculations were perfomed for two standard CT protocols, using tube voltages of 110 kVp and 130 kVp. Absorbed doses were calculated in 11 organs and tissues, i.e., skin, bones, brain, muscles, heart, lungs, liver, spleen, kidney, testicles, and fat tissue. The doses ranged from 15.3 to 28.3 mGy, and from 40.2 to 74.3 mGy, in the two investigated protocols. The organs that received the highest dose were bones and kidneys. In contrast, brain and spleen were organs that received the smallest doses. Doses in organs which are stretched along the body did not change significantly with distance. On the other hand, doses in organs which are localized in the body showed maximums and minimums. Using the voxel model, it is possible to calculate the dose distribution in the rabbit’s body after CT scans, and study the potential biological effects of CT doses in certain organs. The voxel model presented in this work can be used to calculated doses in all radiation experiments in which rabbits are used as experimental animals

Comparison of pencil-type ionization chamber calibration results and methods between dosimetry laboratories

Puikkokammiota on käytetty vuosikymmeniä tietokonetomografian annosmittauksissa. Viime vuosina tietokonetomografian menetelmien kehittyessä myös dosimetrisiä menetelmiä on arvioitu uudelleen. Tässä julkaisussa kuvataan vertailumittaus, jossa puikkokammio kalibroitiin kahdeksassa eri kalibrointilaboratoriossa Euroopassa käyttäen kolmea eri menetelmää. Käytettävät menetelmät olivat: ”kokonaissäteilytys (total irradiation)”, ”osittaissäteilytys (partial irradiation)” ja ”keskiarvoinen osittaissäteiltys (average parital irradiation)”. Viimeisenä mainittua menetelmää käytettiin vain osassa laboratorioista. Kalibroitavina suureina käytettiin ilmakermaa (K) ja sen pituuden tuloa (PKL). Suurin osa mittausvertailun kalibrointituloksista vastasi hyvin referenssiarvoa (> 99%), yhden labora-torion (VINCA) arvot olivat jonkin verran korkeammat kuin muiden. STUKin tulokset olivat erinomai-set. Esimerkiksi STUK:n En-arvo (taulukko 5), jolla mitattiin kalibrointikertoimen eroa kokonainaise-pävarmuuteen oli pieni (0.03-0.22). Jos En-arvo on pienempi kuin yksi voidaan todeta, että mittaustu-los ja mittauksen referenssiarvo ovat hyvin linjassa vastaavien epävarmuuksien kanssa. STUK:ssa ka-librointi tehtiin kahdella eri menetelmällä (kokonais- ja osittaissäteilytys), joiden tulokset olivat lähellä toisiaan (kuva 7), myös ilmakerman ja sen pituuden tulon vertailu (kuva 6) osoittaa STUK:n onnis-tuneen hyvin kalibroinnissa. STUK:n ilmoittamat epävarmuudet ovat keskimääräisiä epävarmuuksia hieman isommat, mutta eivät kuitenkaan poikkea oleellisesti muiden vertailulaboratorioiden ilmoit-tamista epävarmuuksista. Kaiken kaikkiaan STUK:n kalibrointiprosessin voidaan todeta toimivan luotettavasti. Mittausvertailussa osittaissäteilytys todettiin parhaaksi menetelmäksi ja tämän menetelmän käyt-töönotto on myös mahdollista STUKin kalibrointilaboratoriossa