Abstract
Purpose To develop and evaluate a triple arterial phase CT liver protocol with a similar radiation dose to that of standard single arterial phase CT in study subjects suspected of having hepatocellular carcinoma (HCC). Materials and Methods The study consisted of a retrospective part A for protocol development (n = 15) and a prospective part B to evaluate diagnostic accuracy (n = 38). All 53 participants underwent perfusion CT with 50 mL contrast material between August 2013 and September 2014. Group B underwent an additional standard multiphasic liver CT examination with 120 mL of contrast material (range, 70-143 mL). Image sets from triple arterial phase imaging were reconstructed from perfusion CT by fusing images from three dedicated arterial time points. Triple arterial phase CT and standard single arterial phase CT were compared by two readers, who assessed subjective image quality and HCC detection rate. A third reader served as reference reader and assessed objective image quality. The paired Student t test, Wilcoxon signed rank test, jackknife alternative free-response receiver operating characteristic (JAFROC), and JAFROC curve were applied. Results The mean volume CT dose index was 11.6 mGy for triple arterial phase CT and 11.9 mGy for standard single arterial phase CT (P = .73). Triple arterial phase CT showed lower image noise and better contrast-to-noise ratio compared with standard single arterial phase CT (P < .001 and P = .032, respectively); however, there was no significant difference in lesion-to-liver-contrast ratio (P = .31). Subjective image quality was good for both protocols. The detection rate of the 65 HCC lesions was 82% for reader 1 and 83% for reader 2 at triple arterial phase CT and 80% for reader 1 and 77% for reader 2 at standard single arterial phase CT (P = .4). Conclusion Triple arterial phase imaging is feasible at the same radiation dose as that used for standard single arterial phase CT. Triple arterial phase imaging provides equivalent to superior image quality and equal HCC detection rate despite the use of less than half the contrast material dose used at standard single arterial phase CT. © RSNA, 2018.
Highlights
The triple arterial phase maximum intensity projection (MIP) protocol is feasible at the same radiation dose as that used with a standard single arterial phase protocol by using a new postprocessing technique
Triple arterial phase MIP provides equivalent-to-superior image quality and an equal hepatocellular carcinoma detection rate despite using less than half the contrast material dose used at standard single arterial phase CT
Our study demonstrated that triple arterial phase MIP imaging with a radiation dose equivalent to that of standard single arterial phase CT is feasible
Summary
Triple arterial phase CT and standard single arterial phase CT were compared by two readers, who assessed subjective image quality and HCC detection rate. The paired Student t test, Wilcoxon signed rank test, jackknife alternative free-response receiver operating characteristic (JAFROC), and JAFROC curve were applied. Triple arterial phase time-resolved MIP images were prospectively simulated and compared with late arterial phase (single arterial phase) images from standard CT for evaluation. Confidence ratings (of the Likert Scale) were analyzed by using the jackknife alternative free-response receiver operating characteristic (JAFROC) as described by Chakraborty [18]. The performance of triple arterial phase MIP and single arterial phase CT was estimated by using the area under the JAFROC curve, including 95% confidence intervals
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