Background: Coronary artery calcium (CAC) scanning is commonly performed before coronary CT angiography (CTA) based partly on its potential to influence CTA scan parameters. Encompassing the whole heart and performed at high tube potential (120 kVp), standard (Agatston) CAC scanning adds to patient radiation exposure. Most CAC exists in the proximal and mid coronary segments and is easily visualized at low kVp.
Methods: We tested the impact of a modified calcium scan on coronary CTA acquisition decision-making and image quality in a randomized clinical trial. Providers documented planned CTA acquisition parameters prior to CAC scanning in a blinded manner. Standard Agatston CAC scans proceeded in typical fashion whereas modified scans utilized 80 kVp and reduced z-axis length focused on the proximal-to-mid coronary arteries. CTA providers reviewed the CAC burden then documented final acquisition parameters.
Results: The study included 172 patients (48% female; mean age 59 ± 6.7). As planned, the calcium scan effective dose was significantly lower in the modified CAC scan group (0.14 vs. 0.74 mSv using a 0.014 k-factor or 0.26 vs. 1.38 mSv using a 0.026 k-factor; both p < 0.001). Initially selected CTA parameters were changed at an identical rate following visual CAC assessment (59%). There was no significant difference in coronary CTA image quality (median quality score = 4 in both groups, p = 0.26), noise (31.0 vs 31.4 HU; p = 0.81), or signal/noise ratio (17.9 vs 16.8; p = 0.26).
Conclusions: A low-kVp scan with focused field-of-view provides actionable information regarding the presence and severity of CAC prior to coronary CTA. Coronary CTA parameters based on patient variables are frequently modified after assessing CAC burden in the CTA suite. CLINICALTRIALS.
Gov registration number: NCT02972242.
Keywords: Coronary CT angiography; Coronary artery calcium; Coronary artery disease.
Published by Elsevier Inc.