CT Calcium Scoring for Cardiovascular Risk Assessment

Introduction to CT Calcium Scoring

CT calcium scoring is a non-invasive imaging technique that quantifies coronary artery calcification to assess atherosclerotic burden and predict cardiovascular risk, serving as one of the strongest independent predictors of future cardiovascular events 1, 2
The American College of Cardiology recommends CT calcium scoring as a reasonable guide for shared decision-making in adults aged 40-75 years with intermediate ASCVD risk 3

CT calcium scoring uses electrocardiogram-gated multidetector computed tomography (CT) to detect and quantify calcium deposits in coronary arteries, which serve as a reliable marker of coronary atherosclerosis and vascular age 1
The scan is performed using a prospectively ECG-triggered scanning mode with 2.5-3.0 mm thick axial images obtained through the heart 4
The radiation dose is relatively low (approximately 0.37-1.5 mSv), comparable to or slightly lower than screening mammography (0.44-0.56 mSv) 1, 5

CAC is a robust marker for risk assessment and prediction of future atherosclerotic cardiovascular disease (ASCVD) events in asymptomatic patients without known coronary artery disease 1, 2
The degree of CAC represents atherosclerotic burden, with cardiovascular risk increasing as calcium scores increase, especially when scores exceed 300-400 1
A calcium score of zero (CAC=0) indicates excellent prognosis with very low risk (<1% annually) for cardiac death or myocardial infarction 1

CT calcium scoring is particularly valuable for risk stratification in patients with intermediate (7.5-20%) or borderline (5-7.5%) 10-year ASCVD risk 1, 4
The American College of Cardiology/American Heart Association recommends screening for clinically silent ischemia when calcium scores exceed 400 1
Patients with intermediate risk but no coronary calcification can be reclassified into a lower-risk group, potentially avoiding statin therapy 1

CT calcium scoring should be seen primarily as a marker of atherosclerosis and not of degree of stenosis 1
Due to radiation exposure and low prevalence of calcification in younger individuals, calcium scoring is generally not recommended for men under 40 and women under 50 years of age 4, 5

The American College of Radiology recommends using the Agatston method to quantify calcified plaque, providing a numerical score that reflects the burden of calcified atherosclerotic plaque 6
A calcium score of zero indicates absence of calcified plaque in the coronary tree, but this does NOT rule out the presence of non-calcified plaque, as stated by the American College of Radiology and JACC: Cardiovascular Imaging 7, 8, 9

The American College of Radiology suggests that calcium score should not be used in isolation and should be combined with at least a qualitative assessment of total plaque burden to ensure non-calcified plaque is accounted for 6

Coronary calcium scoring CT quantifies only calcified plaque (Agatston score) and does not provide systematic assessment of non‑calcified atherosclerotic plaque. 10
A calcium score of zero does not exclude the presence of non‑calcified plaque; this limitation is acknowledged by the American College of Cardiology and the American College of Radiology. 10
Coronary CT angiography (CCTA) with intravenous contrast is the sole non‑invasive modality that can evaluate both calcified and non‑calcified plaque and visualize resultant coronary stenosis. 11
CCTA can differentiate plaque composition by CT density (Hounsfield units): the lowest densities correspond to lipid‑rich plaque, intermediate densities to fibrous plaque, although overlap limits precise discrimination between fibrous and soft plaques. 12

The American College of Radiology advises that calcium scoring should not be used in isolation; it must be combined with at least a qualitative assessment of total plaque burden (calcified + non‑calcified). 10
The American Heart Association highlights CCTA’s high negative predictive value: when no calcified or non‑calcified plaque is identified, it is highly unlikely that a patient’s symptoms are due to atherosclerotic coronary disease. 13

Calcium scoring markedly underestimates total plaque burden because it cannot quantify non‑calcified plaque, which may represent more vulnerable, rupture‑prone lesions. 12
The spatial resolution of non‑contrast CT (≈ 750 µm) is insufficient to detect thin fibrous caps (~ 70 µm) that characterize vulnerable plaques, as noted by the American Heart Association. 12

For cardiovascular risk stratification in asymptomatic adults aged 40‑75 with intermediate ASCVD risk, calcium scoring is appropriate and sufficient when the purpose is risk assessment only (no symptom evaluation). 11
CCTA is not recommended for routine screening of truly asymptomatic individuals, because the clinical benefit of detecting non‑calcified plaque in this population remains unclear. [11][14]

In situations where identification of non‑calcified plaque is essential, clinicians should proceed directly to contrast‑enhanced CCTA rather than rely on calcium scoring alone. [13][11]
CCTA offers a comprehensive evaluation of total plaque burden, stenosis severity, and plaque characteristics, supporting more informed management decisions. [15][10]16

Calcium scoring provides anatomical information about plaque burden but does not deliver functional or physiological assessment of myocardial ischemia. 13