Variation of the Coronary Calcium Score Depending on Image Reconstruction Interval and Scoring Algorithm ANDREAS H. MAHNKEN,* JOACHIM E. WILDBERGER,* ANIL M. SINHA,† THOMAS FLOHR,‡ HUU T. TRUONG,* GABRIELE A. KROMBACH,* AND ROLF W. GÜNTHER* Mahnken A, Wildberger J, Sinha A, et al. Variation of the coronary calcium score depending on image reconstruction inter- val and scoring algorithm. Invest Radiol 2002;37:496 –502. RATIONALE AND OBJECTIVES. To evaluate the reconstruction interval dependent bandwidth of the coronary calcium score, considering different methods of image reconstruction and quantification of coronary calcifications MATERIALS AND METHODS. Seventy-five patients underwent coronary calcium scoring by use of retrospectively ECG-gated multislice spiral CT. In all patients overlapping and nonover- lapping image reconstruction was performed every 10% of the RR-interval. Coronary calcium score was calculated for every reconstructed image series using the Agatston score and a volumetric scoring method. In 25 patients the analysis was performed twice to determine the reconstruction interval de- pendent intraobserver variability. RESULTS. For nonoverlapping image reconstruction the me- dian of the calcium score determined by the Agatston method ranged from 125.8 to 216.2 and from 166.9 to 211.7 for the volumetric scoring method. For overlapping image reconstruc- tion the corresponding values ranged from 91.6 to 160.5 for the Agatston score and 128.3 to 175.3 for the volumetric calcium score. Reconstruction interval dependent median (mean) vari- ation of the coronary calcium score ranged from 24.1 (45.5)% for nonoverlapping image reconstruction using the Agatston score to 17.5 (25.2)% utilizing a volumetric calcium score with overlapping image reconstruction. There was no statistical significant (P < 0.05) difference between the different meth- ods. Intraobserver variability for the different image recon- struction intervals ranged from 0.78% to 21.51%. The least intraobserver variability was found for overlapping image reconstruction during the diastole using the volumetric scoring method. CONCLUSIONS. Diastolic image reconstruction at 50% or 60% of the RR-interval is recommendable for retrospectively ECG-gated multislice spiral CT. Volumetric calcium scoring and overlapping image reconstruction are beneficial to reduce the variation of the coronary calcium score. KEY WORDS. Multislice spiral CT; coronary calcium score; coronary vessels; coronary artery disease. A S CORONARY calcifications are a constituent of arterio- sclerosis, quantification of coronary calcifications be- came a diagnostic tool to determine the presence of coro- nary heart disease and to monitor drug therapy. 1,2 Electron beam tomography (EBT) is widely accepted as gold stan- dard for the evaluation of coronary artery calcification. A good correlation for quantification of coronary calcifications was found between EBT and single-slice spiral CT and multislice spiral CT (MSCT), 3-5 although systematic differ- ences were reported for single slice spiral CT. 6 One major drawback of all methods is the limited reproducibility of the coronary calcium score with a mean (median) interscan variability ranging from 14.4% to 20.1% (5.7% to 7.8%). 7–9 Measuring method, motion artifacts, signal-to-noise ratio, partial volume effects, trigger errors, point of image acqui- sition, and varying analysis tools proved as potential source of error. 10 For the first time MSCT scanners acquiring four or more slices per rotation and a rotation time of 500 ms or less permit an overlapping spiral CT scan of the entire heart with reasonable slice width within a single breath hold. In com- parison with sequential CT scanning with prospective ECG triggering this technique allows gapless retrospectively ECG-gated image reconstruction with individual adaptation From the *Department of Diagnostic Radiology, and the †Medical Clinic I, University of Technology, Aachen, Germany. ‡From Siemens Medical Solutions, Computed Tomography, Forchheim, Germany. Reprint requests to: Andreas H. Mahnken, Department of Diagnostic Radiology, University Hospital, University of Technology Aachen, Pau- welsstrasse 30, D-52074 Aachen, Germany; E-mail: mahnken@rad.rwth- aachen.de Received March 2, 2002, and accepted for publication, after revision, May 5, 2002. INVESTIGATIVE RADIOLOGY Volume 37, Number 9, 496 –502 ©2002, Lippincott Williams & Wilkins, Inc. 496