Submillisievert Median Radiation Dose for Coronary Angiography with a Second-Generation 320–Detector Row CT Scanner in 107 Consecutive Patients

© RSNA, 2013



Appendix E1

Retrospective CT Parameters

The retrospective portion of the study was performed with a first-generation 320 × 0.5-mm detector row CT unit (Aquilion ONE, Toshiba Medical Systems) with a gantry rotation time of 350 msec. Image acquisition was similar to that with the second-generation CT scanner; however, iterative reconstruction and automated exposure control were not available. Tube potential and tube current were determined by the supervising cardiovascular imaging physician and based on body mass index charts. Contrast-enhanced images were triggered within 4 seconds of reaching a bolus-tracking threshold of 180 HU. Contrast material was delivered at a rate of 5 mL/sec with a triphasic protocol of, in general, 54 mL of contrast material followed by 30 mL of a 30% contrast material-70% saline mixture, and 50 mL of saline.

 

Supplemental Figures

 

Fig E1

Figure E1: Chart shows distribution of body sizes for the 107 patients evaluated with the new second-generation CT scanner. Most patients (66.4%, 71 of 107 patients) were overweight (body mass index, 25-30 kg/m2), obese (body mass index, 30-40 kg/m2), or morbidly obese (body mass index, >40 kg/m2).

 

Fig E2

Figure E2: Box and whisker plot of distribution of heart rates during coronary CT of 107 consecutive patients who underwent imaging with the second-generation 320-detector row CT unit. A heart rate threshold of 75 beats per minute or lower enabled single-heartbeat scanning in 95.3% of cases (102 of 107 patients). The first-generation 320=detector row unit could have permitted single-heartbeat scanning below a threshold of 65 beats per minute in 78.5% of cases (84 of 107 patients), depicted with the light gray shading. The improvement in temporal resolution of this second-generation scanner with a gantry rotation time of 275 msec enables single-heartbeat acquisitions in an additional 17% of cases (18 of 107 patients), depicted in dark gray shading, owing to inclusion of patients with a heart rate between 65 and 75 beats per minute (P < .0001 vs the proportion of patients with a heart rate of <65 beats per minute). The horizontal line within the box represents the median. Box length represents interquartile range, and whiskers represent 2 standard deviation range.

 

Fig E3

Figure E3: Chart shows distribution of estimated effective dose in 107 patients imaged with the new second-generation CT scanner. The median estimated effective dose was 0.93 mSv (interquartile range, 0.58-1.74 mSv). Overall, the radiation dose was less than 1 mSv in 54% of the CT angiography examinations (including 22% of which were <0.5 mSv) and less than 4 mSv in 96%.

 

Fig E4

Figure E4: Normal coronary CT angiogram in a 42-year-old man (height, 175 cm; weight, 61.9 kg; body mass index, 20.2 kg/m2; effective diameter, 28.0 cm; heart rate, 47 beats per minute). Image was obtained with a single-heartbeat prospective ECG-triggered wide-volume acquisition. The estimated effective dose was 0.27 mSv (dose-length product, 19.3 mGy · cm; CTDIvol, 1.5 mGy; SSDE, 1.97 mGy).

 

Fig E5a

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Fig E5b

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Fig E5c

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Fig E5d

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Figure E5: Images in a 72-year-old woman (height, 160 cm; weight, 72.6 kg; body mass index, 28.3 kg/m2; effective diameter, 33.9 cm) with a heart rate of 87 beats per minute. (a) Three-dimensional surface rendering of heart and coronary arteries. (b) ECG shows frequent premature ventricular contractions. Images were segmented between two heartbeats from diastole (yellow bars). (c, d) Nonobstructive coronary CT angiograms. Despite the elevated heart rate and arrhythmia during CT acquisition, the right coronary artery (c) and left circumflex coronary artery (d) were free of motion artifact. The estimated effective radiation dose was 9.6 mSv (dose-length product, 687.5 mGy · cm; CTDIvol, 57.3 mGy; SSDE, 60.5 mGy).

 

Fig E6a

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Fig E6b

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Fig E6c

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Figure E6: (a, b) Scout images and (c) nonobstructive coronary CT angiogram of left anterior descending artery in a 70-year-old morbidly obese woman (body mass index, 44.9 kg/m2; height,152 cm; weight, 104.5 kg; effective diameter, 46.1 cm) who was unable to raise her right arm due to arthritis. Despite substantial attenuation from the patient's large body habitus compounded by her inability to move her arm outside the scan field of view, the coronary CT angiogram was diagnostic to exclude significant coronary artery disease as a cause of heart failure. The estimated effective radiation dose was 3.2 mSv (dose-length product, 226.7 mGy · cm; CTDIvol, 18.9 mGy; SSDE, 12.7 mGy).

 

Fig E7

Figure E7: Curved multiplanar reformations (top row) and corresponding axial images (bottom row) of right coronary artery from all available phases (69%-79%) of the R-R interval from the prospectively triggered coronary CT angiogram in a patient with a heart rate of 59 beats per minute. Patients with a low heart rate can sometimes manifest coronary motion artifacts (arrows), especially from the right coronary artery. Volume acquisition from a 320-detector row CT scanner allows reconstruction from several different cardiac phases and selection of the best phase for minimizing coronary motion artifact (red box, 76%).