Unsolved or unsolvable problems with diagnostic reference levels.

Diagnostic reference levels (DRLs) for X-ray examinations have been introduced in many countries, among others in most European countries, as a consequence of the Directive on Medical Exposures from 1997. The concept seems to be straight forward, but when implementing it into practice a number of problems arise. The results are dependent on how the dose data are measured and assessed. The interpretation of the results must be performed with great care giving due consideration to the fact that X-ray examinations are very complex and hence not very well characterised by a single figure. In this presentation the various parameters influencing the patient dose are discussed and suggestions are given on how these are managed so as to get the best outcome. When these intentions are followed diagnostic reference levels will be a powerful tool for the optimisation process.

In search of optimum chest radiography techniques.

A nation-wide study of chest radiography in Sweden had previously revealed a large variation in the physical and technical factors involved, in particular the radiation dose. In this study the image quality could not be assessed unambiguously. The aim of the present study was to try to establish a correlation between visual grading of radiographs and physical and technical factors in order to find the optimum chest X-ray system. The physical and technical performance of 24 chest units was evaluated. Radiographs were taken of an anthropomorphic chest phantom supplied with test structures simulating various pathologies. Image quality was assessed by visual grading analysis of the radiographs. The physical and technical parameters of the units rated best were used to exemplify good radiographic practice. The results were in agreement with the recommendations issued by the Commission of the European Communities (CEC). It was also shown that low radiation dose is compatible with high-quality radiographic imaging of the chest.

Assessment and comparison of chest radiography techniques in the United States and Sweden.

The United States Center for Devices and Radiological Health and the Swedish National Institute of Radiation Protection started a collaborative project in 1983. The purpose of the project was to test the adequacy and practicability of the United States (US) Nationwide Evaluation of X-ray Trends (NEXT) programme in Sweden. The NEXT protocol for the postero-anterior chest projection was modified and expanded to make it both "statistical" and "investigational" (in the US, NEXT gives mainly "statistical" information). All chest X-ray units in Sweden were surveyed in 1986-87. The project showed that the NEXT programme is applicable to countries other than the United States and provides a standardized protocol that enables intercomparison of the radiological techniques. This paper presents the comparison of the radiological techniques used in Sweden and the United States. The results of the investigational modifications made to the protocol used in Sweden are discussed. Recommendations concerning expansion of the NEXT protocol to include these valuable tools for investigational surveys are presented.

Guidance levels in the Nordic countries: a preliminary report for selected interventional procedures.

The Nordic radiation protection authorities have already published recommended guidance levels for patient doses for six conventional radiological examinations. Over the past two years a similar protocol has been in progress for three interventional procedures. Measurements have been performed in 22 different hospitals in the Nordic countries on patients in the weight range 40-100 kg. The selected procedures are percutaneous transluminal coronary angioplasty (PTCA), percutaneous transluminal angioplasty (PTA) and endoscopic retrograde cholangio- and pancreatio-graphy (ERCP). A total of 281 PTCA procedures, 304 PTA procedures and 147 ERCP procedures are included in the study. The results from this survey are presented as a first attempt to set guidance levels.

Mass screening for breast cancer: benefits, risks, costs.

In general, mass screening for health is of doubtful value, but specific programmes like breast cancer screening could be beneficial. Breast cancer is the major cause of death in middle-aged women in many countries. Experience in Sweden shows that properly designed and performed mammography screening can reduce mortality by one-third, and lead to a better quality of life for treated cancer patients. However, if radiation causes damage proportional to the dose even at low doses, these benefits could be offset by radiogenic cancers in younger age groups (particularly under 40 yr of age). In Sweden, the direct cost of screening equals about 15 pounds sterling. Swedish authorities consider well designed screening justified. Optimization is necessary and involves design, technique, staff competence and organization. An optimized program should save one life in 100 in the screened cohort, while perhaps one life in 10,000 might be lost due to radiogenic cancers (with conventional radiation risk assumptions).

Radiation risk and mammographic screening of women from 40 to 49 years of age: effect on breast cancer rates and years of life.

The aim of this study was to evaluate the carcinogenic risks associated with radiation in mass mammographic screening. Assessment was in terms of breast cancer mortality and years of life for a hypothetical cohort of 100 000 women. Data were obtained on incidence, mortality and life expectancy for the female population of Stockholm. With a screening interval of 18 months at ages 40-49 years, a total absorbed dose to the breast of 13 mGy per invited woman; and an annual breast cancer reduction of 25% per year 7 years from screening start, the net number of years gained was at least 2800. However, using the highest absorbed dose reported in routine mammographic screening in Sweden (approximately 3 mGy per view), and the highest reported radiation risk in the literature, a programme entailing annual screening with 2 views would require at least a 20% annual reduction in breast cancer mortality to give a net benefit in both the number of years of life gained and number of breast cancer deaths avoided. This observation supports the conclusion that exposures with low absorbed dose are essential when performing mass screening with mammography among young women.

A Nordic survey of patient doses in diagnostic radiology.

The aim of this study was to test the applicability of the guidance levels for patient doses cooperatively set by the radiation protection authorities in the five Nordic countries. The kerma-area product (KAP) for five conventional radiological examination types was obtained from several hospitals in each of the Nordic countries. The number of radiographic images and fluoroscopy time were also registered, and the mean values for each examination type and hospital were established based on a representative number of patients (40-100 kg). The results indicate that the situation is very similar in the five Nordic countries, even though some differences were identified. Most of the hospitals demonstrated lower doses than the proposed guidance levels for chest, probably explained by use of faster film/screen combinations during the past decade. An increased use of fluoroscopy for positioning was observed for radiographic examinations of lumbar spine and urography. Large variations in patient doses were found for barium enema depending on the use of fluorospot or 100-mm camera vs full-format film, the range in fluoroscopy times, dose rate, and field size. The guidance levels for lumbar spine (10 Gy x cm2), pelvis (4 Gy x cm2), urography (20 Gy x cm2), and barium enema (50 Gy x cm2) seem to reflect the present quality of X-ray equipment and examination techniques in the Nordic countries. The guidance levels for chest (1 Gy x cm2) should be lowered to 0.6 Gy x cm2.