Increased CT Dose due to Miscentering with use of Automated Tube Voltage Selection: Phantom and Patient Study

Publication date: Available online 15 December 2015
Source:Current Problems in Diagnostic Radiology
Author(s): Peter D. Filev, Pardeep K. Mittal, Xiangyang Tang, Phuong-Anh Duong, Xiaojing Wang, William C. Small, Kimberly Applegate, Courtney C. Moreno
PurposeTo determine if miscentering impacted dose with use of automated tube voltage selection software.MethodsAn anthropomorphic phantom was imaged at different table heights (centered in the CT gantry, and – 6cm, – 3cm, + 3cm, and + 5.7cm relative to the centered position). Topogram magnification, tube voltage selection, and dose were assessed. Impact of table height on dose also was assessed retrospectively in human subjects (n=50).ResultsWhen the CT table was positioned closer to the x-ray source, subjects appeared up to 33% magnified in topogram images. When subjects appeared magnified in topogram images, automated software selected higher tube potentials and tube currents which were based on the magnified size of the subject rather than the subject's true size. Table height strongly correlated with CTDIvol (r=0.98, p<0.05) and DLP (r=0.98, p<0.05) in the phantom study. Transverse dimension in the topogram highly correlated with dose in human subjects (r=0.75-0.87, p<0.05).ConclusionMiscentering results in increased dose due to topogram magnification with automated voltage selection software.

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