Aims and objectives
Accurate centring carries a number of implications,
including accurate projection of radiographic anatomy,
consistent function of automatic exposure control (AEC) and accurate and optimal collimation [1].
The use of explicit centring points is taught and encouraged by authoritative texts.
However,
it is reported that the teaching of certain centring points differs in clinical practice and may introduce a level of confusion to students [2].
Beyond any differences in teaching,
centring points may also vary for other reasons.
Centring points may be changedpurposely by radiographers in...
Methods and materials
Focus groups
Focus groups were used initially to discover what variations in centring points are taught to students in clinical practice.
Twelve final year undergraduate Radiography students volunteered to participate and were divided randomly into four groups.
Using a set of trigger questions,
the groups identified four projections with most noticeable variations in taught centring points: lateral lumbar spine,
lateral knee,
antero posterior (AP) shoulder and oblique lateral hip projections.
Details of the centring points reported by the focus groups were recorded,
along with the...
Results
Location of centring points in clinical practice
The varying centring points reported by the focus groups are visually represented inFig. 1,
Fig. 2, Fig. 3 andFig. 4.
The degree ofvariation between centring points
For each reported centring point,
the distance from the published centring point was estimated (Table 6).
Effect of centring on image quality score
Fig.
5toFig.
8summarise the image quality score (IQS) for each image qualitycriterion at each centring point.
Fig. 5shows that anatomical distortion was scored as non-diagnostic for centring points L3...
Conclusion
The purpose of this study was to investigate the effect of various centring points on the image quality of a radiograph.
The conclusions are:
Centring points used and taught in clinical practice can vary from those published in authoritative texts.
Subjective centring points can adversely affect the visualisation of radiographic anatomy,
as the greater distance from thepublished centring point can lead to distortion of important structures.
Subjective centring points appear to be in close enough proximity to the published centring points for the adequate operation...
Personal information
K.
McNally,
2018 Graduate,
Radiography and Diagnostic Imaging,
School of Medicine,
University College Dublin,
Belfield,
Dublin 4,
Ireland.
K.
Matthews,
Associate Professor,
Radiography and Diagnostic Imaging,
School of Medicine,
University College Dublin,
Belfield,
Dublin 4,
Ireland.
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Prevalence rates and comparisons...