Aims and objectives
It is widely accepted best practice to use automatic exposure control (AEC) devices where applicable [1].
AEC use has aided radiographers in reducing patient dose whilst maintaining diagnostic image quality [2].
However,
literature has suggested that when an AEC device is first installed,
the manufacturer will set the dose constant of the device to demonstrate the detector's optimal performance,
with less consideration of patient dose [3].
The overall aims of AEC are to facilitate consistent imaging exposures,
thus reducing repeated exposures and patient dose [4]....
Methods and materials
Design
An anthropomorphic PIXY phantom [6] was exposed for AP lumbar spine and pelvis examinations using a digital radiography system.
AP pelvis and lumbar spine projections are amongst the most frequently performed projection radiography examinations where AEC is used [7].
Investigation of these two projections allowed all three AEC chambers to be incorporated into the research [8].
Exposure Conditions
Source to image distance (SID),
centring and collimation were optimal [9] and consistent throughout.
A stationary,
transparent,
115cmgrid was used as per clinical routine.DAP was recorded...
Results
24 of the 45 pelvis and 23 of the 45 lumbar spine projections had DAP and mAs values less than or equal to the values from images taken with the AEC set as in current practice.
The quality of these 47 images was analysed,
whilst the 43 images with DAP values exceeding those in clinical practice were discarded.
Influence of Altering AEC Settings on the Dose Constant
The effects on DAP of altering the DS and ECF settings on the AEC controls are shown inFig....
Conclusion
This undergraduate experimental study was conducted in a single hospital to allow findings to be implemented into clinical practice.
The study found that the ECF and DS controls are consistently set up to achieve proportionate change in exposure for each step of each control,
and thus can be effectively applied to produce predictable change in exposure,
and therefore in DAP.
Some experimental limitations existed in that indicative noise values were gathered from post processed images rather than images without processing such as grayscale transformations and...
Personal information
E.
Higgins,
Radiography and Diagnostic Imaging,
School of Medicine,
University College Dublin,
Belfield,
Dublin 4,
Ireland.
K.
Matthews,
Radiography and Diagnostic Imaging,
School of Medicine,
University College Dublin,
Belfield,
Dublin 4,
Ireland.
References
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(1988) “Automatic Exposure Control: A Primer”,
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