AP pelvis x-ray imaging on a trolley: the impact of trolley design, mattress design and radiographer practices on image quality and radiation dose

Tugwell, JR

Abstract

Background: Major physical and technical differences exist between imaging a patient on an x-ray tabletop and imaging a patient on a trolley. The aim of this thesis was to evaluate the impact of trolley design, mattress design and radiographer practice on image quality and radiation dose for AP pelvis imaging on a trolley in order to optimise this imaging examination. AP pelvis was chosen as the focus of this thesis due to the frequency of this examination on a trolley and the dose implication associated with it.
Materials and Method: An anthropomorphic pelvis phantom was imaged on a commercially available trolley under various imaging conditions using computed radiography (CR). Variables explored were two different mattresses, two different image receptor holder positions, three source to image distances (SIDs) and four mAs increments. Image quality was visually evaluated using a 2 alternative forced choice (2AFC) method with a reference image acquired on the x-ray tabletop using 75kVp, the AEC, broad focus, 110cm SID and 3.2mmAl. Contrast to noise ratio (CNR) was also calculated. Effective dose was established by using Monte Carlo simulation software. Optimisation scores were derived as a figure of merit by dividing effective dose with visual image quality scores.
Results: Visual image quality significantly reduced by an average of 13 % (p<0.05) whilst effective dose significantly increased on average by 56% (p<0.05) for the images acquired on the trolley with identical acquisition parameters to the image acquired on the x-ray tabletop. For all experimental trolley images, mean image quality scores ranged from 47.4 to 33.2 (45 being the reference image score) and effective dose ranged from 0.08mSv to 0.33mSv (reference effective dose being 0.09mSv). The image with the highest figure of merit (optimisation score) from all trolley images was acquired at 130cm SID, with 20mAs, using the standard mattress and platform not elevated. Magnification variation was also evident on the trolley images with a 12.8mm difference between the image with the lowest and highest magnification level (18%).
Conclusion: From the results it is clear that acquisition parameters used for AP pelvis on the x-ray tabletop are not transferable to trolley imaging and further work needs to be conducted in order to develop a separate exposure chart specifically for trolley imaging.

• Thesis Type: Dissertation
• Deposit Date: Dec 8, 2016
• Publicly Available Date: Dec 8, 2016