Influence of gantry rotation time and scan mode on image quality in ultra-high-resolution CT system

Publication date: Available online 4 April 2018
Source:European Journal of Radiology
Author(s): Osamu Honda, Masahiro Yanagawa, Akinori Hata, Noriko Kikuchi, Tomo Miyata, Shinsuke Tsukagoshi, Ayumi Uranishi, Noriyuki Tomiyama
ObjectivesTo investigate the image quality of helical scan (HS) mode and non-helical scan (non-HS) mode on ultra-high-resolution CT in different gantry rotation time.Methods Ultra-high resolution CT scanned eleven cadaveric lungs with the following rotation time with tube current of 200 mA and 0.25 mm collimation: HS with 1.5 s/rot (HS200 mA/1.5 s), non-HS with 1.5 s/rot (non-HS200 mA/1.5s), non-HS with 0.75s/rot (non-HS200 mA/0.75 s), non-HS with 0.35 s/rot (non-HS200 mA/0.35 s). Three observers compared each non-HS image with HS image, and scored non-HS images by using 3-point scale, paying attention to normal findings, abnormal findings, noise, streak artifact, and overall image quality. Statistical analysis was performed with Steel-Dwass test.ResultsOverall image quality (score: 2.45) and noise (score: 2.42) of non-HS 200 mA/1.5s was statistically best (p < 0.0005). Overall Image quality and noise of non-HS200 mA/0.75 s (score: 2.0) was comparable to that of HS200 mA/1.5 s. CTDIvol of HS200 mA/1.5 s is 23.2 mGy. CTDIvol of non-HS200 mA/1.5 s, non-HS200 mA/0.75 s, non-HS200 mA/0.35 s is 19.2 mGy, 9.8 mGy, 4.7 mGy.ConclusionOverall image quality and noise of non-helical scan is better than that of helical scan in the same rotation time. Overall Image quality of non-HS200 mA/0.75 s is comparable to that of HS200 mA/1.5 s, though the radiation dose of non-HS200 mA/0.75 s is lower than that of HS200 mA/1.5 s.



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