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Coronary Artery Calcium Quantification at Multi–Detector Row CT: Influence of Heart Rate and Measurement Methods on Interacquisition Variability—Initial Experience¹

¹ From the Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 S Kingshighway Blvd, CB 8131, St Louis, MO 63110. Received June 7, 2002; revision requested August 9; final revision received November 18; accepted November 20. Address correspondence to K.T.B. (e-mail: baet@mir.wustl.edu).

View larger version (32K): [in a new window]   Figure 1. Scatterplot illustrates relationship between interacquisition (Interscan) variability and the heart rate of subjects. There is a clear tendency for interacquisition variability to increase as heart rate increases for volume (r = 0.55, P < .001), score (r = 0.63, P < .001), and mass (r = 0.67, P < .001) calcium quantification methods. Gray dots = score, white dots = volume, black dots = mass.

View larger version (23K): [in a new window]   Figure 2. Bar graph illustrates interacquisition variability in the group of subjects with heart rates of 70 bpm or lower and in the group of subjects with heart rates higher than 70 bpm. For all measurement methods, interacquisition variability was considerably larger in the high heart rate group than in the low heart rate group (P < .002). Interacquisition variability was relatively small and uniform in all measurement methods in the group with heart rates of 70 bpm or lower; a statistically significant difference was seen only between score and mass measurement methods (P = .03, paired t test). In contrast, interacquisition variability was larger and more variable among the measurement methods when heart rates were higher than 70 bpm; statistically significant differences were observed among all measurement methods (P ≤ .01, paired t tests). Gray bar = score, white bar = volume, black bar = mass. Error bars represent 95% CIs.

View larger version (63K): [in a new window]   Figure 3a. Coronary artery calcium quantification with serial multi-detector row CT acquisitions in (a) a 47-year-old man with a mean heart rate of 43 bpm and (b) a 65-year-old man with a mean heart rate of 84 bpm. In a, a calcified plaque (arrows) in the proximal portion of the LAD artery is shown on two consecutive transverse images. The images are free of misregistration or motion artifact. Calcium measurements for the plaque with each of the two scans were very similar: score, volume, and mass measurements, respectively, were 76.3, 25.3 mm3, and 4.8 mg with the left image and 78.8, 25.8 mm3, and 4.8 mg with the right image. In b, two calcified plaques (arrows) in the proximal portion of the middle of the RCA are shown on two consecutive transverse images. The images are degraded by motion artifacts, and calcium measurements for the plaques with each of the two scans differed considerably: score, volume, and mass measurements, respectively, were 333.7, 313.4 mm3, and 57.4 mg with the left image and 445.8, 410.2 mm3, and 69.8 mg with the right image. Note that variation was least with mass measurement in both cases.

View larger version (75K): [in a new window]   Figure 3b. Coronary artery calcium quantification with serial multi-detector row CT acquisitions in (a) a 47-year-old man with a mean heart rate of 43 bpm and (b) a 65-year-old man with a mean heart rate of 84 bpm. In a, a calcified plaque (arrows) in the proximal portion of the LAD artery is shown on two consecutive transverse images. The images are free of misregistration or motion artifact. Calcium measurements for the plaque with each of the two scans were very similar: score, volume, and mass measurements, respectively, were 76.3, 25.3 mm3, and 4.8 mg with the left image and 78.8, 25.8 mm3, and 4.8 mg with the right image. In b, two calcified plaques (arrows) in the proximal portion of the middle of the RCA are shown on two consecutive transverse images. The images are degraded by motion artifacts, and calcium measurements for the plaques with each of the two scans differed considerably: score, volume, and mass measurements, respectively, were 333.7, 313.4 mm3, and 57.4 mg with the left image and 445.8, 410.2 mm3, and 69.8 mg with the right image. Note that variation was least with mass measurement in both cases.