COMPUTED-TOMOGRAPHY PRACTICE IN SWEDEN - QUALITY-CONTROL, TECHNIQUES AND PATIENT DOSE

A survey on computed tomography (CT) practice was carried out in Swede n. The items investigated were the examination frequency, the age/sex distribution and the techniques used for all types of examination, inc luding the assessment of the patient dose. The radiation doses were an alysed and discussed with respect to individual values, to the variati on with different techniques and different types of equipment, to the collective impact for the whole country, and to the level of quality c ontrol measures applied. Examination statistics and techniques were de rived from protocols recorded for every patient examination performed in one week, containing all relevant patient and exposure data. The do se assessment was based on measurements with a pencil-shaped ionisatio n chamber in cylindrical standard phantoms and free in air. All but on e of the 90 CT scanners installed in Sweden at the time of this invest igation participated. The examination statistics are similar to those reported from other countries, especially with regard to the age and s ex distribution and to the type of examinations. The patient dose was strongly correlated with the type of equipment, was moderated slightly with differences in the choice of exposure settings, and showed no co rrelation at all with the extent of QC activities. The annual frequenc y is 24 CT examinations per 1000 inhabitants, leading to a collective effective dose of 840 man.Sv or approximately 0.1 mSv per inhabitant. Examinations of the trunk region give the largest contributions, follo wed by examinations of the brain and the spine.