SU‐G‐206‐07: Dual‐Energy CT Inter‐ and Intra‐Scanner Variability Within One Make and Model

Abstract

Purpose:It can be logistically quite difficult to scan patients on the same exact device for their repeat visits in multi‐scanner facilities. The reliability between dual‐energy CT scanners’ quantitative results is not known, nor is their individual repeatability. Therefore, we evaluated inter‐ and intra‐scanner variability with respect to several key clinical quantitative metrics specific to dual‐energy CT.Methods:Eleven identical GE HD‐750 CT scanners in a busy clinical environment were used to perform dual‐energy (DE) CT scans of a large elliptical quality control (QC) phantom (Gammex, Inc.; Middleton, WI) which contains many standard insert materials. The DE‐QC phantom was scanned bi‐weekly during 2016; 3 to 4 scans were obtained from each scanner (a total of 35 data sets were used for analysis). Iodine accuracy for the 2mg/ml, 5mg/ml and 15mg/ml rods (from the Iodine(Water) image set) and soft tissue HU (40 HU based on NIST constants) from the 50keV data set were used to assess inter‐ and intra‐scanner variability (standard deviation).Results:Intra‐scanner variability average for 2mg/ml Iodine was 0.10 mg/ml (range 0.05–0.15 mg/ml), for 5mg/ml Iodine was 0.12 mg/ml (range 0.07–0.16 mg/ml), for 15 mg/ml Iodine was 0.25 mg/ml (range 0.16–0.37 mg/ml), and for the soft tissue inserts was 2.1 HU (range 1.8–2.6 HU). Inter‐scanner variability average for 2mg/ml Iodine was 0.16 mg/ml (range 0.11–0.19 mg/ml), for 5mg/ml Iodine was 0.18 mg/ml (range 0.11–0.22 mg/ml), for 15 mg/ml Iodine was 0.35 mg/ml (range 0.23–0.44 mg/ml), and for the soft tissue inserts was 3.8 HU (range 3.1–4.5 HU).Conclusion:Intra‐scanner variability for the iodine and soft tissue inserts averaged 3.1% and 5.2% respectively, and inter‐scanner variability for these regions analyzed averaged 5.0% and 9.5%, respectively. Future work will include determination of smallest measurable change and acceptable limits for DE‐CT scanner variability over longer time intervals.This research has been supported by funds from Dr. William Murphy, Jr., the John S. Dunn, Sr. Distinguished Chair in Diagnostic Imaging at MD Anderson Cancer Center.