Keywords:
Radiographers, Paediatric, Radioprotection / Radiation dose, Digital radiography, Experimental investigations, Technology assessment, Physics, Dosimetric comparison
Authors:
K. Matthews, J. Creedon; Dublin/IE
DOI:
10.26044/ecr2019/C-3462
Results
During the phantom study,
21 sets of three exposures were made: 18 with AEC and nine without.
Mean DAP values were taken from each set of three images and only one image in each set was further analysed i.e.
21 images.
During the specimen study,
21 additional exposures were made to match the phantom exposures,
all of which were subject to analysis.
The phantom exposures and values recorded are summarised in Table 2.
DAP values demonstrate broadly linear reduction with each decrease in DCC for each phantom.
Predictably,
SDNR values demonstrate a similar linear reduction indicating that as doses were reduced,
SDNR values also decreased and noise levels rose.
An example for exposures on the ten year old phantom is given in Fig. 5. The apparent conclusion is that patient doses cannot be reduced without detriment to image quality.
However,
consideration of noise levels in isolation does not account whether or not image quality remained diagnostic.
Consideration of VGA scores showed that an approximate SDNR reduction of 17% was tolerated before this detriment became noticeable to the observer.
VGA scores remained constant and equated to that of the baseline image (at 3.0),
until a DCC setting lower than -2 was reached (See Fig. 6).
Diagnostic image quality was thus maintained to this point,
permitting potential DAP reductions of 22.22% to 26.67% with respect to the neutral AEC setting.
This suggests that the dose constant may be reduced by similar proportions,
from the current 2.2µGy to somewhere in the range of 1.61 - 1.71µGy.
VGA scores also indicate potential dose reductions of up to 40.54% with respect to prevailing clinical exposures.
This leads to the refined conclusion that quite considerable dose reduction is possible without loss of diagnostic image quality.