Improvement of in-stent lumen measurement accuracy with new High-Definition CT in a phantom model: comparison with conventional 64-detector row CT

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Abstract
The purpose of this study was to evaluate improvement of measurement accuracy of in-stent lumen using coronary stent phantoms on new high-definition CT (HDCT) compared with conventional 64 detector-row CT (MDCT). To estimate the spatial resolution, a high-resolution insert of CATPHAN (The Phantom Laboratory, NY, USA) was scanned by both HDCT (Discovery CT750 HD) and MDCT (LightSpeed VCT). Also, we developed six types of stent phantom, which have 2.5- and 3.0-mm-diameter with three different types of stents (Velocity: Johnson & Johnson, Driver: Medtronic, Multilink-Rx: Guidant). A 50% stenotic segment made of acrylic resin was built at the center inside the stent. Those coronary vessel phantoms were made of acrylic resin and filled with diluted Iodine (350 HU in 120 kVp), and each stent was fixed inside of those vessels. Those phantoms in water-filled tank were scanned on both HDCT and MDCT. The luminal diameter obtained using digital calipers at five different points and the mean luminal diameter (MLD) were calculated. The underestimate ratio (UR) and △UR was defined as follows: UR = [True diameter of stent-MLD]/True diameter of stent; △UR = [MLD at HDCT-MLD at MDCT]/True diameter of stent. The spatial resolution was estimated to be 0.71 mm on MDCT and 0.50 mm on HDCT. At the non-stenotic segments, the △URs were 11.6% (Velocity), 16.4% (Driver) and 7.2% (Multilink) for the 2.5-mm stents, and 14.0% (Velocity), 16.3% (Driver) and 13.3% (Multilink) for the 3.0-mm stents. At the stenotic segment, the △URs were 23.2% (Velocity), 8.0% (Driver) and 13.6% (Multilink) for the 2.5-mm stents, and 20.0% (Velocity), 14.7% (Driver) and 15.3% (Multilink) for the 3.0-mm stents. Superior spatial resolution of HDCT could be promising for more accurate measurement of in-stent diameter.

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