Influence of dose reduction recommendations on changes in chest radiography techniques

A previous dosimetric study on chest radiography identified ways to reduce patient entrance surface dose (ESD). This present study was designed to monitor changes that had occurred in the use of applied potential and film-screen sensitivity, after a series of recommendations were issued. The study falls into two parts: (1) an assessment of the impact of the recommendations and (2) what factors were responsible for change. Where changes had occurred, exposure factors were collected for 30 patients per tube and the mean ESD was calculated for each tube. Intercomparison (r = 0.93, p < 0.001) was made between calculated and measured (TLDs) values of mean ESD for 10 X-ray units, to ensure that the calculated values provided accurate estimates of the new mean ESDs. 89% of units previously monitored for patient ESD now use average applied potentials greater than 90 kVp and 51% are using film-screen sensitivities of 400. The mean ESD has been reduced on average by 47%, from 0.15 mGy to 0.08 mGy. It has been estimated that the annual collective dose from diagnostic radiology procedures in 30 hospitals in the West Midlands has been reduced by a value in excess of 40 man Sv. Reasons for change could be attributed to some of the following factors: (a) a knowledge of dose levels in comparison with other centres; (b) personal contact with departments; (c) feedback in terms of results and dose savings and (d) positive encouragement to make changes.