Exposure factor selection, exposure indicators and "Dose creep": Exploring knowledge, practices and experiences of...

The concept of 'dose creep' following the introduction of digital detectors is well established in the literature. Visual appearance of image features no longer directly correlates to patient radiation exposure but the use of dose indices, Exposure Index (EI) and Deviation Index (DI) for review and self-audit is not yet widespread. This paper explored the knowledge and clinical placement experiences of diagnostic radiography students regarding these dose indices and exposure factor selection.

A cross-sectional descriptive survey was undertaken, using a convenience sampling approach. The survey employed multiple choice, Likert scale and free text questions. Descriptive statistics were used for closed questions while associations were tested using Chi-square, Wilcoxon rank-sum test and Spearman's co-efficient of correlation where appropriate. Free text responses were thematically coded.

46 responses were received. 90.2% (37/41) of respondents stated they always or most of the time used pre-set exposure factors, whilst 65.9% (27/41) stated they rarely or never set their own exposure factors. Regarding how knowledge of appropriate selection of exposure factors was gained, 40.9% (27/66) responses mentioned informal teaching on clinical placement whilst only 13.6% (9/66) mentioned explicit instruction at university. Respondents also were unlikely to determine optimum exposure of images using exposure indicators as most (62.5%; n = 20/32) have not been taught either at university or on placement.

Minority of students gain their relevant knowledge via university teaching, with students not receiving sufficient training to have confidence in adjustment of exposure factors. This study also revealed students' lack of understanding of exposure indicators (EI and DI), and the concept of 'dose creep'. Universities should reinforce the use of EI and DI in managing patient radiation exposure.