Patient dose optimization in plain radiography based on standard exposure factors

A computational technique for assessing patient dose in plain radiography is described allowing a large number of examinations to be assessed and enabling dose optimization to be promoted. Entrance surface dose (ESD) was calculated for more than 1500 standard exposure settings in an initial dose assessment. Validation of the technique showed good agreement with thermoluminescent dosimetry and showed broad agreement between the standard exposures and the exposure settings used in practice. The dose assessment was repeated 18 months later using the same techniques for almost 2000 standard exposure settings. In both cases, calculated doses showed good compliance with national diagnostic reference levels where available. Suggested investigation levels were established and set at twice the mean dose for each of 47 examinations. Radiology departments were encouraged to review and optimize doses exceeding these levels. The computed mean ESD in the review study was less than the corresponding value in the initial study in 37 of the 47 examinations. The dose reduction was attributable partly to equipment replacement, but primarily to optimization of exposure settings. The technique employed here provides a valid and cost effective method of complying with statutory requirements for the assessment of representative patient dose and is useful in assisting the ongoing process of dose optimization.