An Initial Report on the Investigation of High Patient Doses for the Lateral Lumbosacral Projection in the Lumbar Spine Examination

Abstract

Lumbar spine investigations in our diagnostic imaging department were included in a recent European study of patient dose and image quality. On average, for views other than the lateral projection of the lumbosacral junction, the study found a relatively good image quality at a reasonable average patient dose. For the lumbosacral view the average dose was high and the spread of doses involved was broader than expected. As this is a relatively high dose examination (approx. 40 mGy to skin) a formal investigation of the methodology involved in this projection was undertaken. A reject analysis for this projection revealed that it was discarded with a high frequency, given the extent to which it is performed and the fact that automatic exposure control (AEC) devices are commonly used for it. This paper presents results for (a) a survey of the pattern of use of AEC and pre-programmed exposure control facilities by radiographers for the lumbosacral view and (b) the aforementioned reject analysis of lumbosacral junction and related projections. From the survey of radiographers and related studies, the following are identified as possibly being of importance: (i) use of AEC and related devices for this view, (ii) the occasions on which such devices are or are not used, and (iii) the reasons why such systems are often not trusted. In the case of the reject analysis, the relatively high reject rate for the projection and the impact and significance of such a rate are highlighted.