From the Guidelines
The procedure for performing a coronary artery calcium scan to determine a calcium score involves using an electrocardiogram-gated multidetector CT scan, which quantifies calcium deposits in the coronary arteries and calculates the Agatston score 1. The patient lies on a table that slides into a donut-shaped CT scanner, wearing a hospital gown and removing metal objects. No special preparation is typically required—no fasting or medication adjustments are needed. During the 10-15 minute procedure, the patient holds their breath briefly (about 10 seconds) while the scanner takes multiple images of the heart. ECG leads are attached to synchronize imaging with the heartbeat. The scan uses low radiation doses (0.37 ± 0.16 mSv) and doesn't require contrast dye, as stated in the study by 1. The images are analyzed by software that calculates the Agatston score, which quantifies calcium deposits on a scale from zero (no detectable plaque) to over 400 (extensive plaque). This score helps assess cardiovascular risk by detecting atherosclerosis before symptoms develop, as calcium indicates hardened plaque in arteries. Some key points to consider when performing a CAC scan include:
- The best-quality data are acquired during mid-diastole, when the cardiac cycle is most quiescent 1.
- The Agatston score is the most widely used CACS scoring system in clinical practice and research 1.
- The scan should be performed with prospective triggering to minimize radiation dose, as recommended by 1.
- Patient selection is an important consideration, and CT scanning should generally not be done in men under 40 years old and women under 50 years old due to the low prevalence of detectable calcium in these age groups 1. The procedure is particularly useful for asymptomatic patients with intermediate cardiovascular risk to guide preventive treatment decisions, as supported by studies such as 1.
From the Research
Procedure for Performing a Coronary Artery Calcium Scan
To determine a calcium score, a coronary artery calcium scan is performed using a noncontrast computed tomography (CT) scan or a contrast-enhanced coronary CT angiography (CTA) scan. The procedure involves:
- Acquiring a noncontrast scan before contrast-enhanced coronary CTA, if a separate noncontrast scan is required 2
- Measuring the coronary calcium volume on coronary CTA using an automated standardized method with scan-specific calcium thresholds 2
- Calculating the coronary calcium score (CCS) from the coronary CTA using a conversion factor between calcium scores measured in noncontrast CT and the calcium volume measured on coronary CTA 2
- Alternatively, using a non-gated chest CT scan to obtain a coronary artery calcium score, which can be used to assess the risk of arteriosclerotic cardiovascular disease (ASCVD) 3
Interpretation of Calcium Scores
The interpretation of calcium scores is crucial in determining the risk of coronary artery disease. The scores are categorized into different ranges, including:
- 0: indicating no calcium present
- 1-10: indicating minimal calcium present
- 11-100: indicating mild calcium present
- 101-400: indicating moderate calcium present
400: indicating extensive calcium present 4
- A score of 300 or higher may be used as a cutoff for recommending statin therapy 3
Diagnostic Accuracy of Coronary Artery Calcium Scoring
Coronary artery calcium scoring has been shown to have high diagnostic accuracy for detecting non-obstructive and obstructive coronary artery disease. Studies have compared the diagnostic accuracy of coronary artery calcium scoring with computed tomography coronary angiography (CTCA) and conventional coronary angiography (CAG) 5. The results indicate that CTCA has higher diagnostic accuracy than coronary artery calcium scoring for detecting non-obstructive and obstructive coronary artery disease 5.
Quantification of Coronary Artery Calcium
Ultrafast computed tomography can be used to detect and quantify coronary artery calcium levels. The total calcium score is calculated based on the number, areas, and peak Hounsfield computed tomographic numbers of the calcific lesions detected 6. The sensitivity, specificity, and predictive values of clinical coronary artery disease can be calculated for several total calcium scores in each decade of life 6.