Author + information
- Christoph Gräni,
- Jan Vontobel,
- Dominik Benz,
- Sara Bacanovic,
- Beatrice Hirt Moch,
- Michael Messerli,
- Marvin Grossmann,
- Cathérine Gebhard,
- Aju Paul Pazhenkottil,
- Oliver Gaemperli,
- Philipp Kaufmann and
- Ronny Buechel
Background: Coronary artery calcium scoring (CACS) by cardiac computed tomography (CT) is a well-established predictor of coronary heart disease events. There have been several recent technical advancements that allow for significant radiation dose reduction in CACS. In this study we are assessing an adapted tube voltage protocol for CACS evaluation in order to further decrease radiation dose.
Methods: We prospectively included 103 patients referred for clinically indicated CACS scanning on a latest generation 256-slice CT scanner. Besides the standard protocol with 120kV, two additional scans with 80kV and 70kV were acquired. Using attenuation coefficients derived from The National Institute of Standards and Technology XCOM photon cross-sections database, we defined novel attenuation-based thresholds for calculating Agatston scores for each tube voltage. CACS derived from 70kV and 80kV scans using the adapted thresholds were compared to standard 120kV scans using intraclass correlation (ICC) and Bland-Altman analysis. Risk class (CACS 0, 1-99, 100-399, ≥ 400) changes between different kV were assessed.
Results: Mean age was 69±10 years and 68% were male. Mean BMI was 28.0±5.1kg/m2. Median CACS was 212.0 (IQR 24.5 – 900.5), and 10 (9.7%) patients had a CACS of 0. Using the novel adapted thresholds, CACS derived from 80kV scans showed an excellent correlation (r=0.994, p<0.001) compared with standard 120kV scans with Bland-Altman analysis revealing a mean difference of −31.0 and limits of agreement of −135 to 73. Similarly, for Agatston scores derived from 70kV scan, correlation was excellent (r=0.972, p<0.001) but with increased underestimation and broader limits of agreement (-103 and −294 to 87, respectively). A change in risk classes was observed in 3 (2.9%) patients and in 10 (9.7%) after obtaining CACS from the 80kV and the 70kV scans, respectively. Mean effective radiation dose was 0.58±0.07mSv, 0.19±0.02mSv, and 0.12±0.01mSv for the 120kV, the 80kV, and the 70kV scans, respectively.
Conclusions: CACS scanning with reduced tube voltage offers substantial radiation dose reduction and is feasible and accurate if adapted thresholds for calculation of Agatston scores are applied.
Poster Hall, Hall C
Saturday, March 18, 2017, 9:45 a.m.-10:30 a.m.
Session Title: Non Invasive Imaging: Coronary Calcium Scoring and CV Risk Assessment
Abstract Category: 27. Non Invasive Imaging: CT/Multimodality, Angiography, and Non-CT Angiography
Presentation Number: 1198-241
- 2017 American College of Cardiology Foundation