Eyeglass lenses for personal radon dosimetry

Eyeglass lenses are commonly composed of allyl-diglycol carbonate (CR-39), an alpha-particle detecting plastic, thus making such lenses personal radon dosimeters. Samples of such lenses have been etched to reveal that radon and radon progeny alpha tracks can be seen in abundance, and sensitivities have been calibrated in radon chambers as a primary calibration and with a uranium-based source of alpha particles as a convenient secondary standard. Natural, environmental (fossil) track densities ranged from 3,000 to 25,000 cm(-2) for eyeglasses that had been worn for various times from 1 to nearly 5 y. Average radon concentrations to which the wearers were exposed are inferred to be in the range 20 to 130 Bq m(-3) (0.5 to 3.5 pCi L(-1)). Procedures for consistent, meaningful readout are described.     

An instrument for measuring equilibrium-equivalent 222Rn and 220Rn concentrations with etched track detectors.

To simultaneously measure both 222Rn and 220Rn progeny concentrations, a new type of portable integrating monitor with allyl diglycol carbonate (CR-39) plastic detectors was developed. The monitor gives the average equilibrium-equivalent 222Rn and 220Rn concentrations (EEC(RN) and EEC(Tn)) during sampling intervals. The detection efficiencies of the alpha particles were calculated by Monte Carlo method. The lower limits of detection for EEC(Rn) and EEC(Tn) are estimated to be 0.57 Bq m(-3) and 0.07 Bq m(-3) for 24 h continuously sampling at a flow rate of 0.8 L min(-1). The measuring results with the new type monitors were confirmed through intercomparison experiments. In a small survey, a rather high 220Rn progeny concentration with an average of 1.73 Bq m(-3) was observed in traditional Japanese dwellings with soil/mud plastered walls. On the other hand, a very high 232Th concentration in soil was reported in China. They suggested that there is a possibility of high 220Rn progeny concentration in both Japan and China.     

Calculating the calibration coefficient for radon measurements with the bare LR 115-II track detector.

Model calculations were performed to determine the calibration coefficient for radon measurements using a bare LR 115-II track detector. Calculations were based on an expression for stopping power for heavily charged particles, as well as on the Monte Carlo method. The sensitivity of the LR 115-II detector depends on equilibrium factor F, and it has been calculated for various values of F. For equilibrium factor F = 1, the calibration coefficient in this calculation was 89 m-1 (10.3 Bq d m-3 per tracks cm-2) for the removed layer, which was 5.5 microns thick.     

Practical IMRT QA dosimetry using Gafchromic film: a quick start guide

This work outlines a method for using Gafchromic film for dosimetry purposes, by scanning it with currently available commercial scanners. The scanners used were: Epson V800, Epson V700, Epson V37 series, specifically a V370 and a Canon multi-function office printer/scanner. The Epson scanners have 16 bit RGB resolution, the Canon has 8 bit RGB (Red Green Blue) resolution, and the V800 and V700 allow scanning in transmission mode. The V700 uses an Epson White Cold Cathode Florescent Lamp; the recently released V800 uses an Epson light emitting diode (LED) light source, while the V37 series uses a reflective mode and the Epson LED light source. The Epson V37 series scanners are designed for non-professional use so the cost has been kept at a low “entry level” point, so they would be a suitable option for a department wanting to use Gafchromic film or with limited needs that did not justify a more sophisticated and expensive unit. Note that the V800 or V700 scanners are not expensive in context, costing approximately the same as a 25 sheet box of Gafchromic film. The Canon was included to demonstrate that a scanner with 8 bit RGB resolution can be used for dosimetry. These general multi-function units are available in most departments, and they would allow Gafchromic film to be evaluated as a dosimetry tool without a significant investment. Furthermore, they are generally capable of scanning large format film (425 × 350 mm) in one part. Although this is not necessary for dosimetry, it is often useful for machine QA, where dividing the film into two parts to ensure accurate measurements is not practical. Moreover, this analytical method uses software that is freely or commonly available, particularly the image processing package ImageJ. Note ImageJ v1.48 was the version used. The results demonstrate that this method used with the scanners evaluated is a practical method of using Gafchromic film as a dosimeter for IMRT QA.     

Modeling the distribution and dosimetry of internal emitters: a review of mathematical procedures using matrix methods.

This paper reviews the mathematical procedures for an analytical representation of linear compartmental systems and the radiation dosimetry of internal organs in terms of matrices and vectors. The features characteristic for internal dosimetry, such as the various forms of intakes, subsystems (e.g., lung, gastro-intestinal tract), and decay products are also discussed. The ICRP concept of internal dose calculation is translated into matrix notation and its application demonstrated by calculating the radiation doses from the ingestion of 40K.     

Site characterization for radon supply potential: a progress review.

"Radon-resistant" house foundations were developed by 1981, but additional construction costs made it undesirable to require them unless necessary. The survey methods used then were labor-intensive and cost so much that it was impractical to identify "radon-prone" areas by nationwide surveys. A cheaper method was required to show where radon-resistant foundations were needed. Information available in 1981 suggested that unusual soil conditions were needed to produce high radon concentrations in houses. If these conditions could be identified, elevated radon concentration levels could be predicted from soil measurements at a lower cost than a radon-in-housing survey. Recent radon surveys show that near-surface bedrock or clay soils, which cover most of the continent, are radon-prone. The measurement methods cannot be used in these soils. The cost of radon surveys has been greatly reduced over the past 10 y. Radon-prone areas can now be identified by radon surveys at a lower cost than soil measurements, and the cost of radon-resistant foundations has been reduced. These developments have removed most of the financial incentive for developing soil-based site classification methods. The priority task now is to encourage the adoption of radon-resistant foundations in radon-prone areas.     

Field and laboratory tests of etched track detectors for 222Rn: summer-vs-winter variations and tightness effects in Maine houses

Effects of tightness of homes and of bedrock character on indoor 222Rn concentrations were sought in 70 homes in the state of Maine by means of four 6- to 8-month-long surveys over a 1.5-yr period. Laboratory experiments were also performed that document the reliability of the track etching system used for the measurements. In this survey the Rn in tight homes was on the average 3.5 times that in drafty ones, and areas with granitic bedrock led to homes having 2.3 times the Rn as for homes on chlorite-biotite-rich bedrock. Winter-to-summer ratios ranged from 0.5-7, and averaged 1.5, implying that surveys of individual homes require a full year of monitoring.     

An optical method for three-dimensional dosimetry.

Accurate determination of the spatial distribution of the absorbed dose of ionising radiation plays an important role in radiotherapy, industrial radiation processing and many other applications. Computer calculations have frequently been used to estimate three-dimensional (3D) dose distributions in complex geometries and it becomes important to validate these by accurate 3D measurements. For this purpose we have been investigating the use of gelatin gels loaded with a modified Fricke solution which are pale orange in appearance and which, upon irradiation, become increasingly purple when viewed in normal light. This ferrous sulphate xylenol orange in gelatin gel (FXG) system displays very good properties, such as sensitivity, linearity and dynamic range, that make it suitable for 3D dosimetry applications. A high-speed optical tomography readout technique has been developed enabling two-dimensional projections of optical absorption data to be recorded rapidly. From these data the 3D absorbed dose distribution can quickly be derived with minimal degradation due to ion diffusion.     

HSE performance tests for dosimetry services.

In the United Kingdom a dosimetry service that measures and assesses whole-body or part-body doses arising from external radiation must successfully complete a performance test. Results of the performance tests for routine whole-body, routine extremity/skin and special accident dosimetry, carried out over the past six years by the AEA Technology Calibration Service at Winfrith, and DRaStaC, the AWE Calibration Service at Aldermaston, are presented. The test involves irradiating groups of dosemeters to known doses of gamma radiation and determining the bias and relative standard deviations for each dose group. The results are compared with the pass criteria specified by the UK Health and Safety Executive. For routine whole-body dosimetry, both the film badge and thermoluminescent dosemeter (TLD) perform adequately for irradiations between 0.6 and 30 mSv. For higher doses up to 250 mSv, where the slow emulsion of the film is used, the film badge shows poorer performance with a tendency to overestimate the dose. For routine extremity/skin dosimetry there is a wider spread of relative standard deviation results than is seen for routine whole-body dosimetry. This is to be expected since the results will include dosemeters that are based on 'disposable' TLDs and ones based on lithium fluoride powder in sachets. For special accident dosimetry the dosemeters are tested between 0.26 and 6 Gy. For the highest dose group the film badge invariably underestimates the true dose, whereas the TLD has a tendency to overestimate it.     

现行门急诊服务流程民意调查

通过对医院门急诊病人进行问卷调查,获得病人对现行门急诊服务流程的评价。其中就医流程单方面满意度评价最低．仅为59．3％,提示无效就医环节多、无效排队等待时间多的现行门急诊服务流程在一定程度上影响了病人满意度,并就改进就医流程进行了探讨。     

Elevation correction factors for E-PERM radon monitors.

E-PERM radon monitors are based on the principle of electret ion chambers and are usually calibrated in a standard radon chamber located at sea level. Corrections are needed if the monitors are used at elevations other than sea level. These were experimentally determined for three models of commercially available electret ion chambers (E-PERM) as functions of elevation above sea level. These corrections are minor and should be applied for obtaining more accurate results.