The upper slicing system is the main components of the optical system in MSCT. This paper focuses on the design of upper slicing system and its accuracy analysis to improve the accuracy of imaging. The error of slice thickness and ray center by bearings, screw and control system were analyzed and tested. In fact, the accumulated error measured is less than 1 microm, absolute error measured is less than 10 microm. Improving the accuracy of the upper slicing system contributes to the appropriate treatment methods and success rate of treatment.
Computer Simulation ; Equipment Design ; Tomography, Spiral Computed ; instrumentation ; methods

BACKGROUND: Dysfunction of endothelial cells is independently associated with coronary atherosclerotic heart disease. Correlation of dysfunction of endothelial cells to restenosis after stent implantation is not yet clearly determined.OBJECTIVE: To evaluate the correlation of vascular endothelial dysfunction to restenosis after stent implantation. DESIGN, TIME AND SETTING: A case control study was performed at the Department of Cardiology and Department of Heart Ultrasound, Sichuan People's Hospital from March 2005 to January 2007.PARTICIPANTS: After review, coronary angiography showed that 11 patients who occurred restenosis at the lesion region after stent implantation were included in a restenosis group, and an additional 15 patients who did not develop in-stent restenosis were included in a control group. Patients in the following conditions were excluded: over 70 years old, histories of long-term smoking, diabetes mellitus, multivessel disease, long coronary lesion and chronic total occlusion, heart failure (Killip's class Ⅲ or above), severe hepatic and/or renal insufficiency.METHODS: High-resolution ultrasound was used to assess the percentage of flow-mediated dilatation of brachial artery. Differences in endothelial function were compared between both groups.MAIN OUTCOME MEASURES: Ultrasound parameter of the brachial artery in both groups; Partial correlation analysis on control variable including sex, age, blood lipid level, diseased region and stent type.RESULTS: No significant difference was found in basic diameter of brachial artery in both groups. During reactive hyperemia, inner diameter and its absolute variation of brachial artery were smaller in the restenosis group than in the control group (P<0.01). The percentage of brachial artery flow-mediated dilatation was lower in the restenosis group compared with the control group (P=0.013). The partial correlation coefficient between the percentage of flow-mediated dilatation of brachial artery and in-stent restenosis was 0.47 (P=0.04).CONCLUSION: The endothelial dysfunction significantly decreases in patients with restenosis compared with controls following stent implantation. There is a correlation between endothelial dysfunction and restenosis.