Environmental protection: researches in National Institute of Radiological Sciences

Some studies for radiological protection of the environment have been made at the National Institute of Radiological Sciences (NIRS). Transfer of radionuclides and related elements has been investigated for dose estimation of non-human biota. A parameter database and radionuclide transfer models have been also developed for the Japanese environments. Dose (rate)-effect relationships for survival, growth and reproduction have been investigated in conifers, Arabidopsis, fungi, earthworms, springtails, algae, duckweeds, daphnia and medaka. Also genome-wide gene expression analysis has been carried out by high coverage expression profiling (HiCEP). Effects on aquatic microbial communities have been studied in experimental ecosystem models, i.e., microcosms. Some effects were detected at a dose rate of 1 Gy day(-1) and were likely to arise from interspecies interactions. The results obtained at NIRS have been used in development of frameworks for environmental protection by some international bodies, and will contribute to environmental protection in Japan and other Asian countries.

Radiation dose reduction in CT coronary angiography

During recent years, technologic advancements in computed tomography (CT) have allowed robust cardiac and coronary imaging. Small, mobile cardiac structures such as the coronary arteries can now be imaged directly and noninvasively with high precision. Given the fact that coronary CT angiography (CCTA) can detect preclinical calcified and noncalcified atherosclerosis, there is potential to revolutionize the management of ischemic heart disease by refining risk stratification and improving outcomes in various clinical settings. However, despite this progress, CT has come under scrutiny as concerns about the level and risk of the radiation exposure of the population grow. Although there are no data to support a direct association between CT imaging and risk of future cancer, health care practitioners should make every effort to minimize radiation exposure to their patients. The purpose of this article is to describe techniques that can reduce radiation dose to patients during CCTA but maintain diagnostic image quality.

Evidence of confounding by smoking of associations between radiation and lung cancer mortality among workers at the Savannah River Site

BACKGROUND

This study investigates confounding by cigarette smoking of associations between occupational exposure to ionizing radiation and lung cancer mortality among workers at the Savannah River Site (SRS).

METHODS

Thirteen thousand two hundred sixty-five white males hired at SRS between 1950 and 1986 were followed through 2002 to ascertain causes of death. Estimates of radiation doses from external sources and internal tritium uptakes were derived from dosimetry records. Logistic regression methods were used to derive discrete-time estimates of rate ratios. An indirect approach to control for unmeasured confounding by smoking was employed that involves joint modeling of lung cancer and chronic obstructive pulmonary disease (COPD) mortality.

RESULTS

Prior to indirect adjustment for smoking, there was minimal evidence of association between lung cancer mortality and cumulative radiation dose under a 10-year lag assumption (RR at 100 mSv = 0.90; 90% CI: 0.80-1.01). Subsequent to indirect adjustment for smoking, the association between lung cancer mortality and cumulative radiation dose under a 10-year lag was positive (RR at 100 mSv = 1.33; 90% CI: 1.01-1.77).

CONCLUSIONS

In this cohort, there is evidence of negative confounding of radiation dose–lung cancer mortality associations by cigarette smoking.

Effective dose: practice, purpose and pitfalls for nuclear medicine

Effective dose (E) is the only comparatively simple dose quantity that is related to health detriment for stochastic effects from exposure to ionising radiation. As such, E has found wide application for medical exposures, as it allows comparisons with doses from different examinations and other sources. E is derived from the weighted sum of doses to tissues known to be sensitive to radiation from epidemiological studies and contains inherent approximations. Thus it is not a scientific quantity, but a practical one that the International Commission on Radiological Protection (ICRP) has created for use in the calculation of reference doses for protection purposes. In the application of E to medical exposures, there has been a tendency to attribute a greater accuracy to values of E than is justified by its derivation. Recognising that E is strictly not subject to uncertainties, an analysis has been undertaken of potential uncertainties in E for different nuclear medicine examinations to enable users to judge its reliability as a comparator of relative risk. Assessments have been based on the considered accuracy of the component parts and indicate that the uncertainties in the values of E as a relative indicator of harm for nuclear medicine procedures for a reference patient are about ± 50%. These are larger than those for radiology procedures, because of the tendency for doses to single organs, especially the bladder, to form a substantial part of E for some procedures. Revision of the tissue weighting factors in 2007 produced a 10% decrease in the mean value of E for nuclear medicine examinations. Estimations of cancer risk based on E for an individual could vary by one or two orders of magnitude. E fulfils an important role as a health-related dose quantity that can be used in justification of nuclear medicine examinations, but physicians should be aware of its limitations. General terminology should be used in conveying risks to patients and medical professionals.

[The influence of spa and resort-based therapy on the incorporated cesium elimination rate in children presenting with environmental disadaptation syndrome]

A total of 50 children presenting with environmental disadaptation syndrome have been treated based at N.K. Krupskaya health resort (Zheleznovodsk). The therapy included the consumption of mineral water with low salt content from the Slavyansky spring at a dose of 3-5 cub.ml per 1 kg b.w. 30 min before meal, thrice daily. Its influence on the radionuclide elimination rate from the organism of the patients previously exposed to enhanced levels of background radiation was estimated from the results of spectrometric and radiochemical analysis of their urine. It was shown that introduction of drinking mineral water into the program of combined spa and resort-based therapy causes a 2-3-fold increase in the cesium excretion rate and thereby reduces the internal radiation load.

A Note on Irradiated Heparin: Some Biological and Chemical Properties

The effect of gamma radiation and high energy electrons on the anticoagulant and antilipaemic properties of heparin has been investigated. There was a fall in both activities, but the anticoagulant was reduced more readily than the antilipaemic. After electron bombardment the anticoagulant activities of two different batches of heparin were reduced almost identically, an unexpected finding since such a high degree of reproducibility is not possible with chemical degradation.

An Investigation into the Effects of Gamma-Rays on Aqueous Solutions of p-Aminobenzoic Acid

Aqueous solutions of p-aminobenzoic acid (0·3 per cent) were irradiated with gamma-rays under both oxygen-saturated and oxygen-free conditions. By means of paper chromatography, p-nitrobenzoic acid has been isolated from the irradiated, oxygenated aqueous solution and 4-amino-3-hydroxybenzoic acid isolated from the irradiated, oxygen-free aqueous solution.

These products were probably produced by indirect action of the Co-60 gamma-rays.

Radiation-protection of Serratia marcescens by a thiolsulphonate related to cysteamine

A thiolsulphonate, 2-aminoethyl 2-aminoethanethiolsulphonate (also known as cystamine disulphoxide) affords significant protection to the micro-organism Serratia marcescens against the lethal effects of X-rays. The thiolsulphonate breaks down extensively at pH7, but the degree of protection given by it is much greater than can be accounted for by the action of decomposition products and is considered to be characteristic of the compound itself.

Gamma-irradiation of spores of Bacillus subtilis

Freeze-drying from a 5% aqueous solution of glucose produced a marked protection of spores of Bacillus subtilis subjected to spent fuel gamma-irradiation over the range 2·5–12·5 × 105 rads. Freeze-drying from aqueous suspension produced no protection. Irradiation in 5% aqueous glucose and in aqueous suspension gave log % survivor/dose regressions with similar slopes.

Effect of radiation-induced charge accumulation on build-up cap on the signal current from an ionisation chamber

The signal current from a thimble ionisation chamber with a build-up cap made of an insulator decreases by about 0.41 % after being irradiated for 17 h at an air kerma rate of 41 Gy h(-1) by a collimated (60)Co gamma-ray beam in air. In contrast, the signal current remains constant when the thimble ionisation chamber is irradiated in a water phantom. During irradiation, positive charge is considered to accumulate near the outer surface of the build-up cap where electron equilibrium is not achieved. Secondary electrons travelling in the build-up cap and the chamber wall toward the ionisation volume are decelerated by the electric field generated by the positive charge. Consequently, the signal current decreases with increasing charge accumulation because some secondary electrons are prevented from entering the ionisation volume. In the water phantom, electron equilibrium is established in and around the ionisation chamber and charge does not accumulate. To confirm this hypothesis, the signal current was measured for an ionisation chamber in air with a build-up cap wrapped with Al foil and covered with PMMA tubes. Electron equilibrium was established over the build-up cap because the tubes were thicker than the secondary electron range. The signal current decreased with increasing positive voltage applied to the Al foil. It was estimated from the results that positive charges equivalent to a voltage of over 6 kV applied to the Al foil accumulated during irradiation. The signal current was also measured for an ionisation chamber with a metal build-up cap and for an ionisation chamber with a wall and build-up cap made of conductive plastic.

Factors that impact susceptibility to fiber-induced health effects

Asbestos and related fibers are associated with a number of adverse health effects, including malignant mesothelioma (MM), an aggressive cancer that generally develops in the surface serosal cells of the pleural, pericardial, and peritoneal cavities. Although approximately 80% of individuals with MM are exposed to asbestos, fewer than 5% of asbestos workers develop MM. In addition to asbestos, other mineralogical, environmental, genetic, and possibly viral factors might contribute to MM susceptibility. Given this complex etiology of MM, understanding susceptibility to MM needs to be a priority for investigators in order to reduce exposure of those most at risk to known environmental carcinogens. In this review, the current body of literature related to fiber-associated disease susceptibility including age, sex, nutrition, genetics, asbestos, and other mineral exposure is addressed with a focus on MM, and critical areas for further study are recommended.

The impact of exposure to radio frequency electromagnetic fields on chronic well-being in young people--a cross-sectional study based on personal dosimetry

A possible influence of radio frequency electromagnetic field (RF EMF) exposure on health outcomes was investigated in various studies. The main problem of previous studies was exposure assessment. The aim of our study was the investigation of a possible association between RF EMF and chronic well-being in young persons using personal dosimetry. 3022 children and adolescents were randomly selected from the population registries of four Bavarian cities in Germany (participation 52%). Personal interview data on chronic symptoms, socio-demographic characteristics and potential confounders were collected. A 24-h radio frequency exposure profile was generated using a personal dosimeter. Exposure levels over waking hours were expressed as mean percentage of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) reference level. Half of the children and nearly every adolescent owned a mobile phone which was used only for short durations per day. Measured exposure was far below the current ICNIRP reference levels. The most reported chronic symptom in children and adolescents was fatigue. No statistically significant association between measured exposure and chronic symptoms was observed. Our results do not indicate an association between measured exposure to RF EMF and chronic well-being in children and adolescents. Prospective studies investigating potential long-term effects of RF EMF are necessary to confirm our results.

Benefits and challenges in bowel MR imaging at 3.0 T

Abdominal imaging at 3.0 T has shown to be challenging because of a number of artifacts and effects related to the physics at higher field strength. For bowel imaging at 3.0 T, artifacts due to magnetic field inhomogeneities, standing waves, increased susceptibility, and greater chemical shift effects are of particular concern because they are likely to affect the assessment of relevant structures and counterbalance the benefits of higher signal-to-noise ratio. Regarding small- and large-bowel magnetic resonance imaging, the benefits of higher field strengths translate mainly in better contrast-to-noise ratio of contrast-enhanced T1-weighted gradient echo and T2-weighted imaging, whereas steady-state free precession sequences seem to suffer from serious degradation of image quality. The present article summarizes the technical challenges in bowel imaging at 3.0 T, provides an overview of performance compared with 1.5 T in small- and large-bowel diseases including the rectum, and revises the current literature.

Abdominal magnetic resonance imaging at 3 T: oncological applications

The gain in signal-to-noise ratio at 3 T magnetic resonance (MR) imaging produces many benefits for abdominal imaging applications, including the capability to reduce acquisition times and/or improve spatial resolution for a variety of pulse sequences, the potential for broader application of parallel imaging techniques, and an increased sensitivity to gadolinium-based contrast media. These advances have the potential of improving the accuracy of MR imaging in the detection, staging, treatment planning, and follow-up of patients with abdominal tumors. At the same time, because certain high-field-strength-related drawbacks could not be compensated for, abdominal 3 T MR imaging should be clinically implemented with caution in some patients (eg, patients with massive ascites).