Abstract
Extensive coronary artery calcium (CAC) diminishes the accuracy of coronary computed tomography angiography (CCTA). Many imagers adjust CCTA acquisition parameters depending on a preCCTA Agatston CAC score to optimize diagnostic accuracy. Typical preCCTA CAC imaging adds considerably to radiation exposure, partially attributable to imaging beyond the area known for highest CAC, the proximal coronary arteries. We aimed to determine whether a z-axis reduced scan length (RSL) would identify the majority of CAC and provide adequate information to computed tomography angiography providers relative to a standard full-scan length (FSL) preCCTA noncontrast CT. We retrospectively examined 200 subjects. The mean CAC scores detected in RSL and FSL were 77.4 (95% CI 50.6 to 104.3) and 93.9 (95% CI 57.3 to 130.5), respectively. RSL detected 81% of the FSL CAC. Among false negatives, with no CAC detected in RSL, FSL CAC severity was minimal (mean score 2.8). There was high concordance, averaging 88%, between CCTA imaging parameter adjustment decisions made by 2 experienced imagers based on either RSL or FSL. CAC detected and decision concordance decreased with increasing CAC burden. CAC detected was lower, and false negatives were more common in the right coronary artery owing to its anatomic course, placing larger segments outside RSL. Axial scan length and effective dose decreased 59% from FSL (∼14.5 cm/∼1.1 mSv) to RSL (∼5.9 cm/∼0.45 mSv). This retrospective study suggests that RSL identifies most CAC, results in similar CCTA acquisition parameter modifications, and reduces radiation exposure. Our colleagues corroborated these results in a recently published prospective study.
Highlights
Coronary computed tomography angiography (CCTA) is a wellestablished noninvasive method to evaluate coronary pathology; the accuracy of CCTA varies depending on the amount and location of calcified plaques in the coronary arteries [1]
A stratified analysis showed that reduced scan length (RSL) detected 98.4% of full-scan length (FSL) CAC in the left coronary artery
In this study, we retrospectively examined the clinical feasibility of using a pre-CCTA CAC score with RSL in the z-axis with the intention of reducing patient radiation exposure
Summary
Coronary computed tomography angiography (CCTA) is a wellestablished noninvasive method to evaluate coronary pathology; the accuracy of CCTA varies depending on the amount and location of calcified plaques in the coronary arteries [1]. A high coronary artery calcium (CAC) score is often associated with a nondiagnostic CCTA [2, 3]. Beam hardening in densely calcified coronary arteries causes decreased sensitivity and specificity of CCTA in patients with high CAC. One meta-analysis suggests that careful pre-CCTA planning is crucial in patients with CAC score !400 to ensure diagnostic accuracy [7]. Radiation doses of a standard pre-CCTA CAC scoring, covering the entire heart, are typically 1–3 mSv [8, 9], whereas the radiation dose of CCTA is typically 2–8 mSv [10]. Performing a standard pre-CCTA CAC scoring exposes patients who are undergoing CCTA to considerable radiation. The majority of coronary artery calcifications occurs in the proximal to mid portions of the coronary
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