Figure 1a:
Obstructive noncalcified stenosis (arrow) of proximal left anterior descending artery in 42-year-old overweight man with atypical chest pain and a heart rate of 70 beats per minute (height, 175 cm; weight,100 kg; body mass index, 32.7 kg/m2; effective diameter, 35.4 cm). Two-heartbeat acquisition was selected because this case was early in our experience with prototype scanner. (a, b) Quality of image reconstructed from data obtained with only one heartbeat (a) is nearly indistinguishable from that of image reconstructed with data segmented between two heartbeats (b). (c) Three-dimensional surface rendering of heart and coronary arteries. Estimated effective radiation dose for two-heartbeat scan was 4.0 mSv (dose-length product, 284.5 mGy ⋅ cm; CTDIvol, 28.4 mGy; SSDE, 28.4 mGy). However, radiation dose could have been halved if only a single-heartbeat acquisition was selected. On the basis of similar initial experience, a prospectively acquired single-heartbeat scan can be obtained for heart rates slower than approximately 75 beats per minute.