Evaluation of Attenuation-Based Tube Current Control in Coronary Artery Calcium Scoring on Prospective ECG-triggered 64-detector CT

Horiguchi, Jun; Matsuura, Noriaki; Yamamoto, Hideya; Kitagawa, Toshiro; Sato, Kenichi; Kihara, Yasuki; Ito, Katsuhide

doi:10.1016/j.acra.2009.04.008

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Volume 16, Issue 10 , Pages 1231-1240, October 2009

Evaluation of Attenuation-Based Tube Current Control in Coronary Artery Calcium Scoring on Prospective ECG-triggered 64-detector CT

Jun Horiguchi, MD
- Department of Clinical Radiology, Hiroshima University Hospital, 1-2-3, Kasumi-cho, Minami-ku, Hiroshima, 734-8551, Japan
- Address correspondence to: J.H..
Noriaki Matsuura, MD
- Department of Radiology, Division of Medical Intelligence and Informatics, Programs for Applied Biomedicine, Graduate School of Biomedical Sciences, Hiroshima University, Minami-ku, Japan
Hideya Yamamoto, MD
- Department of Cardiovascular Medicine, Hiroshima University Graduate School of Biomedical Sciences & Hiroshima University Hospital, Programs for Applied Biomedicine, Graduate School of Biomedical Sciences, Hiroshima University, Minami-ku, Japan
Toshiro Kitagawa, MD
- Department of Cardiovascular Medicine, Hiroshima University Graduate School of Biomedical Sciences & Hiroshima University Hospital, Programs for Applied Biomedicine, Graduate School of Biomedical Sciences, Hiroshima University, Minami-ku, Japan
Kenichi Sato, PhD
- Department of Environmetrics and Biometrics, Research Institute for Radiation Biology and Medicine, Hiroshima University, Minami-ku, Japan
Yasuki Kihara, MD
- Department of Cardiovascular Medicine, Hiroshima University Graduate School of Biomedical Sciences & Hiroshima University Hospital, Programs for Applied Biomedicine, Graduate School of Biomedical Sciences, Hiroshima University, Minami-ku, Japan
Katsuhide Ito, MD
- Department of Radiology, Division of Medical Intelligence and Informatics, Programs for Applied Biomedicine, Graduate School of Biomedical Sciences, Hiroshima University, Minami-ku, Japan

Received 25 March 2009; accepted 9 April 2009. published online 10 June 2009.

Rationale and Objectives

The aims of this study were to investigate image noise (standard deviation of computed tomographic value) and to assess variability in repeated coronary artery calcium (CAC) scoring on prospective electrocardiographically triggered 64-detctor computed tomography.

Materials and Methods

Patients (n = 428) suspected of having coronary artery disease were scanned twice using three protocols: with tube current modified by body mass index (BMI; group A), by BMI and body height (group B), and by attenuation at the maximal heart diameter (group C). Image noise was plotted against BMI. Interscan variability of CAC scores was determined. The effective dose was estimated by computed tomographic dose index.

Results

The mean effective dose and image noise, respectively, were 0.9 ± 0.2 mSv (range, 0.6–1.5 mSv) and 19 ± 4 Hounsfield units (HU) (range, 10–32 HU) for group A; 0.8 ± 0.2 mSv (range, 0.5–1.4 mSv) and 18 ± 4 HU (range, 10–31 HU) for group B; and 0.8 ± 0.4 mSv (range, 0.3–2.2 mSv) and 20 ± 2 HU (range, 16–26 HU) for group C. Group C used a wide dose range and controlled noise within a small range. The positive slopes of image noise versus BMI, 0.81 HU/(kg/m²) in group A and 0.62 HU/(kg/m²) in group B, suggested insufficient control of the tube current. In contrast, the nearly flat slope in group C, 0.091 HU/(kg/m²), indicated optimal control. The interscan variability for Agatston score, volume, and mass in patients with CAC (n = 300) was 13% (median, 8%), 12% (median, 7%), and 11% (median, 6%), respectively.

Conclusions

CAC scoring on prospective electrocardiographically triggered 64-detector computed tomography using attenuation-based tube current control has the potential to favorably control image noise with low dose and low interscan variability.

Key Words: Coronary artery, calcium, tube current, attenuation, variability