The national dose register in Finland.

The Finnish Dose Register includes exposure data for all workers engaged in radiation work. These data already cover a period of almost 50 y. The earliest data in the register apply to workers in health care, research and industry. Data on nuclear power plant workers have been recorded since 1977 and data on aircrews since 2001. The Dose Register is an extensive national register with doses currently recorded for more than 15,000 workers annually. This paper presents the content and structure of the register, together with recently completed and forthcoming reforms. It also describes how the recorded data are used in the regulatory control of radiation practices.

Covalent binding of three epoxyalkyl xylosides to the active site of endo-1,4-xylanase II from Trichoderma reesei.

The three-dimensional structures of endo-1,4-xylanase II (XYNII) from Trichoderma reesei complexed with 4,5-epoxypentyl beta-D-xyloside (X-O-C5),3,4-epoxybutyl beta-D-xyloside (X-O-C4), and 2,3-epoxypropyl beta-D-xyloside (X-O-C3) were determined by X-ray crystallography. High-resolution measurement revealed clear electron densities for each ligand. Both X-O-C5 and X-O-C3 were found to form a covalent bond with the putative nucleophile Glu86. Unexpectedly, X-O-C4 was found to bind to the putative acid/base catalyst Glu177. In all three complexes, clear conformational changes were found in XYNII compared to the native structure. These changes were largest in the X-O-C3 complex structure.

Patient dose and image quality in five standard x-ray examinations.

Patient doses and image quality in five standard x-ray examination projections (22-36 measurements per each projection) have been measured, using homogeneous phantoms. The means and range of variation for the entrance skin air kerma values were: abdomen AP 5.2 mGy (1.1-21 mGy), chest PA 0.27 mGy (0.035-0.84 mGy), lumbar spine AP 8.4 mGy (2.9-28 mGy), skull LAT 3.1 mGy (1.1-7.7 mGy), and thoracic spine AP 7.9 mGy (1.3-22 mGy). Considerable variation was found in image quality parameters: film optical densities, image contrasts, and resolutions as well as in exposure values, tube voltages, exposure times, and in half-value thicknesses. The study indicated the need to standardize medical x-ray examination techniques in different x-ray departments. The measuring method can be used for comparing the patient dose and image quality of an individual x-ray unit to the doses and image quality in general use. The results can be used as the reference values for quality control of x-ray equipment.

Radiation exposure during percutaneous nephrostomy.

Radiation doses of radiologists, assistants and patients during 21 percutaneous nephrostomies (PN) (including 11 unilateral and 5 bilateral procedures) were measured using an area-exposure meter and thermoluminescent dosimeters. The mean fluoroscopy time per PN was 12 min and the mean product of air kerma and the cross-sectional area of the fluoroscopic beam was 8.0 (range 0.41-24) Gycm2. Doses to the radiologists and assistants were generally modest, and the yearly dose limits of ICRP will not be exceeded in practice. The doses to the radiologist's fingers were found to be the most restrictive in this study. Regarding the mean dose to the radiologist's fingers (190 muGy), the yearly dose limit of 500 mSv would be exceeded after about 2600 PNs provided that his fingers are not otherwise exposed. With the maximal finger dose of 1100 muGy, this would occur after about 450 yearly PNs.

Survey of dental radiographic equipment and radiation doses in Finland.

The radiation dose exposure, and the faults in about 1,700 dental units inspected at dental surgeries by the Finnish Centre for Radiation and Nuclear Safety in 1981-1985, were analysed. The mean value of skin doses in the bite-wing projection was about 6.2 mGy, the range 0.5 to 151 mGy. The mean energy imparted per bite-wing examination was estimated as 0.68 mJ and that per panoramic examination as 1.2 mJ. That gives a total imparted energy of about 600 J per year for conventional dental examinations and about 420 J per year for panoramic examinations. This gives a total of 0.13 mJ from conventional and 0.089 mJ from panoramic examinations per inhabitant per year. The collective effective dose equivalent was calculated as about 9 manSv for conventional dental examinations and about 6 manSv for panoramic examinations. Twenty per cent of units had some fault which was capable of decreasing radiation safety. Forty per cent of units were served reparation orders or other remarks were made in inspection documents. Large doses were usually accounted for by incorrect film processing and malfunction of the exposure timer.

Characteristic curves of dental x-ray film.

The characteristic curves of the dental x-ray films Ultra-Speed, Ekta-Speed, Defilux, Dentus, and Phil-X30, all of which are used in Finland, and the absorption of radiation in the films with their protective wrappers were determined at the x-ray laboratory of the Institute of Radiation Protection. The most sensitive film (Ekta-Speed) was found to be almost three times more sensitive than the least sensitive film (Defilux). In the usable optical density range, the gradient of the characteristic curve obtained with the three most sensitive film types--Ekta-Speed, Dentus and Ultra-Speed--was roughly the same, whereas Phil-X30 was far more gentle. All film types gave a resolution better than 10 lp/mm. The grain size used in the most sensitive film was slightly larger than that used in the less sensitive films. The films provided with lead backing foil transmitted 10% to 20% of the radiation, whereas the film type without lead backing foil (Phil-X30) transmitted 70% to 80%.