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

Tugwell, e, Everton, c, Kingma, a and Hogg, P 2014, 'Increasing source to image distance for AP pelvis imaging – impact on radiation dose and image quality' , Radiography, 20 (4) , pp. 351-355.

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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.

Item Type: Article
Themes: Health and Wellbeing
Schools: Schools > School of Health Sciences > Centre for Health Sciences Research
Journal or Publication Title: Radiography
Publisher: Elsevier
Refereed: Yes
ISSN: 1078-8174
Related URLs:
Funders: Erasmus
Depositing User: P Hogg
Date Deposited: 23 Jan 2015 13:32
Last Modified: 01 Dec 2015 01:38

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