DOI: 10.1148/radiol.2352040515
Measuring Coronary Calcium on CT Images Adjusted for Attenuation Differences1
Jennifer Clark Nelson, PhD,
Richard A. Kronmal, PhD,
J. Jeffrey Carr, MD, MS,
Michael F. McNitt-Gray, PhD,
Nathan D. Wong, PhD,
Catherine M. Loria, PhD,
Jonathan G. Goldin, MD, PhD,
O. Dale Williams, MPH, PhD and
Robert Detrano, MD, PhD
1 From the Ctr for Health Studies, Group Health Cooperative, Metropolitan Park East, Suite 1600, 1730 Minor Ave, Seattle, WA 98101 (J.C.N.); Dept of Biostatistics, Univ of Washington, Seattle, Wash (J.C.N., R.A.K.); Dept of Radiology, Wake Forest Univ School of Medicine, Winston-Salem, NC (J.J.C.); Dept of Radiology, David Geffen School of Medicine at UCLA, Los Angeles, Calif (M.F.M.G., J.G.G.); Heart Disease Prevention Program, Div of Cardiology, College of Medicine, Univ of California, Irvine, Calif (N.D.W.); Div of Epidemiology and Clinical Applications, National Heart, Lung, and Blood Institute, Bethesda, Md (C.M.L.); Dept of Medicine, Div of Preventive Medicine, Univ of Alabama at Birmingham, Birmingham, Ala (O.D.W.); and Harbor-UCLA Research and Education Inst, Div of Cardiology, Los Angeles, Calif (R.D.). Received Mar 18, 2004; revision requested May 27; revision received Jun 25; accepted Jul 27. Supported by NHLBI contracts N01-HC-95159 through N01-HC-95165, N01-HC-95169, N01-HC-95095, N01-HC-48047 through N01-HC-48050, and N01-HC-05187. Address correspondence to J.C.N. (e-mail: nelson.jl@ghc.org).
View larger version (164K):
[in a new window]
|
Figure 1. A calibration phantom is shown under a torso phantom in position for a periodic scanner quality-control check. The long axis of the calibration phantom is placed on and parallel to the long axis of the scanning table. One pair of phantoms (calibration and torso) was provided to each of the CARDIA and MESA scanning sites.
|
|
View larger version (138K):
[in a new window]
|
Figure 2. Transverse CT scan shows cross-section of study subject’s thorax and the calibration phantom under the thorax. Note the cross sections of the four phantom calibration rods, which are labeled according to their calcium hydroxyapatite concentrations. cc = cubic centimeter.
|
|
View larger version (19K):
[in a new window]
|
Figure 3. Graphs show means ( ) and 95% CIs (error bars) for quality-control torso phantom attenuation measurements (CT numbers in Hounsfield units) according to scanning site (top) and scanner type (bottom). Sites 1 and 2 used Siemens multi-detector row CT (MDT) scanners. Sites 3-6 used GE-Imatron electron-beam CT (EBT) scanners. Sites 7-8 used GE LightSpeed multi-detector row CT scanners. Means differed significantly across sites (P < .001) and scanner types (P < .001) and were lowest for Siemens multi-detector row CT scanners (at 140 kVp), followed by GE-Imatron electron-beam scanners (at 130 kVp) and GE LightSpeed multi-detector row scanners (at 120 kVp). Means also varied between sites that used the same type of scanner.
|
|
View larger version (53K):
[in a new window]
|
Figure 4. Scatterplots show Agatston score adjustments due to calibration plotted against unadjusted Agatston scores according to scanner type. Data are shown for 3326 participants with a nonzero Agatston score adjustment. Top: Data from sites that used Siemens multi-detector row CT scanners. Middle: Data from sites that used GE-Imatron electron-beam scanners. Bottom: Data from sites that used GE LightSpeed multi-detector row scanners. Left column: Scatterplots show all data points. Right column: Scatterplots show a restricted region that contains the majority of the data. The size of the Agatston score adjustment increased with unadjusted score, some adjustments were large, and the direction of the adjustment for different scanner types was consistent with expectations based on the torso and calibration phantom results.
|
|
Copyright © 2005 by the Radiological Society of North America.
