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Updated: Aug 7, 2026
Identifying Coronary Artery Calcification on Non-gated Computed Tomography Scans
Published on: August 28, 2018
Variability of repeated coronary artery calcium measurements on low-dose ECG-gated 16-MDCT
Jun Horiguchi1, Hideya Yamamoto, Nobuhiko Hirai
1Department of Clinical Radiology, Hiroshima University Hospital, 1-2-3, Kasumi-cho, Minami-ku, Hiroshima 734-8551, Japan. horiguch@hiroshima-u.ac.jp
Insights
Low-dose retrospective ECG-gated CT offers reliable coronary artery calcium (CAC) scoring with minimal variability. This approach enables effective monitoring of coronary atherosclerosis progression while reducing radiation exposure.
Area of Science:
- Cardiovascular Imaging
- Radiology
- Medical Physics
Background:
- Reproducible coronary artery calcium (CAC) scoring is crucial for monitoring atherosclerosis progression.
- Retrospective ECG-gated helical CT provides superior CAC measurement reproducibility compared to prospective gating.
- However, retrospective gating involves higher radiation doses.
Purpose of the Study:
- To compare low-dose and standard-dose protocols for retrospective ECG-gated helical CT in CAC measurements.
- To evaluate the variability in CAC scores and assess image quality.
- To determine the feasibility of low-dose protocols for monitoring coronary atherosclerosis.
Main Methods:
- Eighty-six patients with CAC underwent CT scans using two tube current settings: 100 mA and a weight-equivalent setting.
- Coronary artery calcium (CAC) scores (Agatston and volume) and interscan variability were assessed.
- Image quality was evaluated by measuring CT attenuation values in the aorta.
Main Results:
- A high correlation (r=0.998) was found between sequential helical CT scans for log(10) (Agatston score + 1).
- Interscan variability in CAC measurements was low, ranging from 11% to 12% for both Agatston and volume scores.
- The weight-equivalent tube current setting achieved diagnostic image quality, with a mean + 2 x SD CT attenuation value not exceeding 130 HU.
Conclusions:
- Low-dose retrospective ECG-gated helical CT is feasible for CAC measurements.
- This protocol yields low variability and sufficient image quality for monitoring coronary atherosclerosis.
- It offers a viable alternative for reducing radiation exposure in CAC scoring.
Objective:
High reproducibility on coronary artery calcium (CAC) scoring is a key requirement in monitoring the progression of coronary atherosclerosis. Retrospective ECG-gated helical CT has been shown to be superior to prospective gating helical CT in the reproducibility of CAC measurements. However, it brings with it a high level of radiation exposure. The purpose of this study was to compare low- and standard-dose protocols in the variability of CAC scores and in image quality, thereby assessing the feasibility of low-dose retrospective ECG-gated helical CT in CAC measurements.
Subjects And Methods:
Eighty-six patients with CAC were scanned using a tube current setting of 100 mA once and then a tube current setting equivalent to the patient's body weight twice. CAC scores (Agatston and volume) and interscan variability were evaluated. The mean and SD of the CT attenuation values in regions of interest in the aorta were measured, and the value (mean + 2 x SD) was obtained.
Results:
A high correlation of log(10) (Agatston score + 1) was observed between sequential helical CT scans (r = 0.998). The variability in CAC measurements ranged from 11% to 12% for both the Agatston and volume scores. With the tube current equivalent to body weight, the value (mean + 2 x SD) did not exceed a CT attenuation value of 130 H.
Conclusion:
Low-dose retrospective ECG-gated helical CT-yielding low variability and achieving the level of image quality needed to measure CAC-can be used to monitor patients with coronary atherosclerosis.
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