How Coronary Calcium Scoring is Performed
Coronary artery calcium scoring is performed using an electrocardiogram-gated multidetector CT scan that acquires images in just a few heartbeats, with approximately 1 minute of actual scan time and 10 minutes total patient time. 1
Technical Acquisition
The scan uses ECG-gated multidetector CT to capture images during mid-diastole, when cardiac motion is minimal, ensuring optimal image quality 1. The number of detector rows determines how quickly data can be acquired—modern scanners complete the acquisition in just a few heartbeats 1.
Radiation Exposure
Modern CT technology with dose-reduction techniques delivers minimal radiation exposure of 0.37 ± 0.16 mSv 1, which is actually lower than screening mammography (0.44–0.56 mSv) 1. This addresses historical concerns about radiation, as earlier protocols used higher doses that are no longer relevant 2.
Scoring Methodology
The Agatston Score
The Agatston score is the most widely used and extensively validated scoring system in both clinical practice and research 1. The algorithm works as follows:
- Identifies calcific lesions with CT density >130 Hounsfield units and area >1 mm² 1
- Assigns a weighting factor of 1–4 based on CT density of at least three contiguous imaging pixels 1
- Calculates individual lesion scores by multiplying the lesion area by the weighting factor 1
- Sums all calcified lesions across all coronary arteries to generate the total score 1
The score can be expressed as an absolute number or as a percentile adjusted for sex and race (white, Chinese, black, Hispanic) 1, and can be calculated for each individual coronary artery 1.
Alternative Scoring Methods
While Volume score and Mass score exist 3, the Agatston score remains the gold standard due to its extensive validation in clinical outcomes studies 3.
Practical Considerations
Time and Cost
- Total patient time: ~10 minutes
- Actual scan time: ~1 minute 2
- Cost: $75–250 cash price where not covered by insurance 2
Insurance Coverage
Coverage has expanded since 2018 guidelines incorporated CAC into care algorithms. Anthem, UnitedHealthcare, and Aetna have favorable coverage decisions, and Medicare covers the test in certain states. Texas mandates coverage by state law. However, many HMOs and some carriers still classify it as experimental and do not provide coverage 2.
Important Caveats
CAC measures atherosclerotic burden, not stenosis severity. The calcified area represents only 20% of total atherosclerosis burden, as not all plaques contain calcium 1. Vascular remodeling often preserves lumen patency, so there is limited correlation between calcium burden and degree of stenosis 1. Therefore, CAC should be interpreted as a marker of overall plaque burden and cardiovascular risk, not as an indicator of flow-limiting disease.
The test requires no contrast administration and no patient preparation beyond the ability to lie still and hold breath briefly during image acquisition 1.