A study of chest radiography with mobile X-ray units.

A survey of radiographic technique and estimated entrance surface dose has been carried out for 364 chest radiographs performed with mobile X-ray equipment in the Intensive Therapy Unit (ITU) and 30 wards at Aberdeen Royal Infirmary. Data for these two types of location were compared, as were those for two film/screen systems used on the wards. Image quality assessments were made on sets of radiographs for two patients. Entrance skin doses for chest radiographs performed in the ITU were 50% greater than on the wards with the same film/screen system. The main technique difference was the use of shorter focus-to-skin distances (FSDs) in ITU. Doses with the Kodak Insight system were 20% higher than those using Du Pont Quanta III in similar locations. No correlation was found between image quality and entrance surface dose (ESD). Results from the survey were used to recommend exposure factors for shorter FSDs. A follow-up study revealed a 35-45% reduction in ESD for Kodak Insight and a 20% reduction for Quanta III.

Dose-area product measurements in paediatric radiography.

The dose-area product (DAP) could provide a useful quantity for monitoring doses for paediatric radiography, because it is a sensitive parameter, which is simple to record. A study of DAP measurements has been carried out for single radiographic projections for paediatric patients and comparisons made with measurements of entrance dose. The technique has been used to investigate doses for examinations performed with and without a grid. There is a linear relationship between DAP and entrance dose, with a variation of +/- 20% for pelvis, abdomen, spine and skull radiographs, but data for chests are more scattered. Logarithm of the DAP is linearly related to an equivalent patient diameter and reference levels could be set in terms of DAP either by patient age range or size. Effective doses determined from DAPs were 0.1-0.3 mSv for abdomen, pelvis and spine anteroposterior radiographs for 5-15 year olds, and less than 0.03 mSv for 0 and 1 year olds. Doses for examinations performed without a grid were only 20% of those for which a grid was used in the X-ray room studied. Significant reductions in doses for paediatric radiology can be achieved, where the use of grids can be avoided.

Implementation of a programme for reduction of radiographic doses and results achieved through increases in tube potential.

Experiences in implementation of a programme to reduce doses to patients from radiographic examinations are described. A preliminary survey of entrance doses for selected examinations, calculated from mean exposure factors, identified equipment and examinations requiring attention. Subsequently more detailed studies were carried out with thermoluminescent dosimeters (TLDs). Results were coordinated with the aid of a database, which was used to monitor the agreement between dose calculations and TLD measurements. Surveys highlighted that doses from lumbar and thoracic spine examinations were high throughout the region. Reductions of 26-36% in entrance dose and 20-25% in effective dose were achieved by raising tube potentials for these examinations. This gave a reduction in annual collective dose of 4 man-Sv with no cost implication. In some departments dose charts were used to support the purchase of new screens. Surveys revealed a wide range in other factors such as transmission of X-ray table tops and results are being used in planning replacement of equipment.