Increasing source to image distance for AP pelvis imaging – impact on radiation dose and image quality

Tugwell, e; Everton, c; Kingma, a; Hogg, P

Abstract

Aim: A quantative primary study to determine whether increasing source to image distance (SID), with
and without the use of automatic exposure control (AEC) for antero-posterior (AP) pelvis imaging, reduces
dose whilst still producing an image of diagnostic quality.
Methods: Using a computed radiography (CR) system, an anthropomorphic pelvic phantom was positioned
for an AP examination using the table bucky. SID was initially set at 110 cm, with tube potential set
at a constant 75 kVp, with two outer chambers selected and a fine focal spot of 0.6 mm. SID was then
varied from 90 cm to 140 cm with two exposures made at each 5 cm interval, one using the AEC and
another with a constant 16 mAs derived from the initial exposure. Effective dose (E) and entrance surface
dose (ESD) were calculated for each acquisition. Seven experienced observers blindly graded image
quality using a 5-point Likert scale and 2 Alternative Forced Choice software. Signal-to-Noise Ratio (SNR)
was calculated for comparison. For each acquisition, femoral head diameter was also measured for
magnification indication.
Results: Results demonstrated that when increasing SID from 110 cm to 140 cm, both E and ESD reduced
by 3.7% and 17.3% respectively when using AEC and 50.13% and 41.79% respectively, when the constant
mAs was used. No significant statistical (T-test) difference (p ¼ 0.967) between image quality was
detected when increasing SID, with an intra-observer correlation of 0.77 (95% confidence level). SNR
reduced slightly for both AEC (38%) and no AEC (36%) with increasing SID.
Conclusion: For CR, increasing SID significantly reduces both E and ESD for AP pelvis imaging without
adversely affecting image quality.

Citation

Tugwell, E., Everton, C., Kingma, A., & Hogg, P. (2014). Increasing source to image distance for AP pelvis imaging – impact on radiation dose and image quality. Radiography, 20(4), 351-355. https://doi.org/10.1016/j.radi.2014.05.012

• Journal Article Type: Article
• Acceptance Date: May 28, 2014
• Online Publication Date: Jun 21, 2014
• Publication Date: Nov 1, 2014
• Deposit Date: Jan 23, 2015
• Publicly Available Date: Apr 5, 2016
• Journal: Radiography
• Print ISSN: 1078-8174
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 20
• Issue: 4
• Pages: 351-355
• DOI: https://doi.org/10.1016/j.radi.2014.05.012
• Publisher URL: http://dx.doi.org/10.1016/j.radi.2014.05.012
• Related Public URLs: http://www.sciencedirect.com/science/journal/10788174/20/4