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CT Calcium Score vs CT Coronary Angiogram: Which Heart Scan Is Right For You?

August 28, 2026

Summary:

A CT calcium score measures the amount of calcium within the heart arteries and estimates your future risk of heart disease.
A CT coronary angiogram (CTCA) directly visualises the coronary arteries to detect narrowing or blockages.
A calcium score is mainly used in people without symptoms to assess cardiovascular risk.
A CT coronary angiogram is usually preferred in patients with chest pain or suspected coronary artery disease.
These heart scans complement each other—they are not interchangeable.

Many people searching for a “heart scan” are surprised to learn that there are actually two very different CT scans used to assess heart disease— a CT Calcium Score (Coronary Artery Calcium Score or CAC Score) and a CT Coronary Angiogram (CTCA).

Although both scans use CT technology to examine the coronary arteries (or the blood vessels supplying our heart muscle), they answer very different clinical questions. Choosing the wrong test may lead to unnecessary anxiety, additional investigations, or even a false sense of reassurance.

In this article, we’ll explain the differences between these two heart scans, who should undergo each test, and how cardiologists decide which investigation is most appropriate.

What Is the Difference Between a CT Calcium Score and a CT Coronary Angiogram?

Although both scans use CT imaging, they provide very different information.

CT Calcium Score	CT Coronary Angiogram
No contrast injection	Requires intravenous contrast
No heart-rate-lowering medications required	Heart rate-lowering medications often required
Measures calcium within coronary arteries	Directly visualises plaque and stenosis within coronary arteries
Estimates future cardiovascular risk	Detects coronary artery disease
Best for people without symptoms	Best for patients with chest pain or suspected heart disease
Scan takes only a few minutes	Appointment usually lasts 30–60 minutes
Lower radiation dose	Higher radiation dose

Think of it this way:

A CT calcium score tells us whether, and how much, calcified plaque has developed within our heart arteries. It estimates future cardiovascular risk but does not tell us the severity of narrowing caused by these plaques.
A CT coronary angiogram reveals the location and degree of narrowing within the coronary arteries and can identify significant coronary artery disease.

What is a CT Calcium Score?

A CT calcium score is a quick non-invasive CT scan that measures the amount of calcium within the coronary arteries.

As cholesterol plaque ages, calcium is deposited within it. The scan detects the presence of these calcium deposits and calculates a Coronary Artery Calcium (CAC) Score, often called an Agatston score. In general, a higher calcium score indicates a greater burden of calcified coronary plaque and a higher future cardiovascular risk.^1,2

Unlike a CT coronary angiogram, a CT calcium score does not measure the percentage of narrowing in the artery. It is also possible to have non-calcified plaques which can cause significant stenosis. Nevertheless, a higher calcium score tends to correlate with the severity of underlying coronary atherosclerosis.

Coronary artery calcium (red arrows) detected on a CT calcium score

Calculation of calcium score

What is a CT Coronary Angiogram?

A CT coronary angiogram (CTCA) is a specialised CT scan that uses X-rays, intravenous contrast dye, and advanced computer technology to produce detailed 3-dimensional images of the coronary arteries— the blood vessels supplying oxygen to the heart muscle.

A CT coronary angiogram frequently includes a calcium score, but the administration of intravenous contrast dye allows for visualisation of the degree of narrowing in each coronary artery.

Severe stenosis seen in the proximal LAD on CTCA (left panel) and coronary angiogram (right panel). Calcium deposits at the proximal LAD appear on CTCA as bright spots.

Post-stenting of the severe stenosis

Not sure what happens during a CT coronary angiogram? Read our complete guide here.

Why Is a CT Calcium Score Important?

Coronary artery disease usually develops silently over decades before symptoms appear. Many people who eventually suffer a heart attack have no warning symptoms.

A CT calcium score helps identify subclinical coronary artery disease, allowing treatment to begin before a heart attack occurs.

A calcium score can also help guide decisions regarding:

Starting cholesterol-lowering medication (statins)
Intensifying cardiovascular risk factor management
Encouraging lifestyle modification
Improving patient motivation and adherence to treatment

Large population studies, including the Multi-Ethnic Study of Atherosclerosis (MESA), have consistently shown that coronary calcium scoring is one of the strongest predictors of future cardiovascular events.³

Who Should Get a CT Calcium Score?

A CT calcium score may be useful in people without symptoms when the result could help refine their cardiovascular risk or guide decisions about preventive treatment.^1,2

It may be useful if you:

Are aged approximately 40–75 years
Have cardiovascular risk factors such as diabetes, high cholesterol, or high blood pressure
Smoke or previously smoked
Have a strong family history of premature heart disease
Have elevated Lipoprotein(a) [Lp(a)]
Have an intermediate estimated cardiovascular risk where treatment decisions are uncertain

A calcium score is particularly helpful when deciding whether long-term cholesterol-lowering medication is likely to provide meaningful benefit.

Who Should Not Have a CT Calcium Score?

A calcium score is generally not the appropriate stand-alone test if you have:

Symptoms suggestive of coronary artery disease such as chest pain or breathlessness
An abnormal stress test
Established coronary artery disease detected on previous cardiac investigations

In some of these situations, a CT coronary angiogram is usually much more informative because it directly assesses whether there are significant coronary artery blockages.⁴ Using a calcium score alone in patients with symptoms may delay the correct diagnosis.

How Accurate Is a CT Calcium Score?

Coronary calcium scoring is highly reproducible and has been extensively validated.

A score of zero is associated with a very low short-term risk of heart attack in asymptomatic individuals.^2,3 However, a calcium score of zero does not completely exclude coronary artery disease or totally eliminate the possibility of a cardiac event.

Some younger patients, smokers, and individuals with diabetes may have soft (non-calcified) plaque, which cannot be detected by calcium scoring.⁵ This is one of the main reasons why CT coronary angiography is preferred in patients with symptoms.

Severe stenosis in the proximal RCA with minimal calcium.

Understanding Your CT Calcium Score

Calcium Score = 0

No detectable coronary calcium.
Very low short-term cardiovascular risk.
However, healthy lifestyle habits remain important as a score of zero does not mean you have zero cardiovascular risk.

Calcium Score 1–99

Mild atherosclerotic plaque.
Lifestyle modification is recommended.
Depending on your age and overall cardiovascular risk, cholesterol-lowering medication is reasonable.

Calcium Score 100–399

Moderate atherosclerotic plaque.
The risk of future heart attack is significantly increased.
More intensive cholesterol-lowering treatment and risk factor management is usually recommended.

Calcium Score ≥400

Extensive atherosclerotic plaque.
This indicates a high burden of atherosclerosis and a substantially increased cardiovascular risk.
Further assessment, including CT coronary angiography or functional testing, may be recommended depending on your symptoms and overall clinical assessment.

The calcium score is then used to determine the calcium percentile, which compares your calcium score with those of people of the same age and sex. In addition to the calcium score and percentile, your age, sex, overall cardiovascular risk, family history, and other risk factors are also important when interpreting your score and deciding on treatment.^1,2

Example of a young patient with an extremely high calcium score of 1508, putting him in the 90-100^th percentile.

What Are the Limitations of a CT Calcium Score?

Calcium scoring cannot:

Detect soft (non-calcified) plaque
Determine whether an artery is severely narrowed
Diagnose angina
Assess blood flow to the heart
Replace CT coronary angiography in symptomatic patients

A person can have a calcium score of zero and still have coronary plaque, particularly at a younger age. Conversely, a high calcium score also does not necessarily mean a patient has severe arterial blockages.

What Are the Risks of a CT Calcium Score?

A CT calcium score is one of the safest cardiac imaging tests available.

Potential risks include:

Low-dose radiation
Radiation exposure is typically very low, often around of below 1 mSv with modern low-dose protocols and CT scanners.5

Incidental findings
Occasionally, the scan identifies unrelated abnormalities in the lungs or chest that require further assessment.

Unlike CT coronary angiography, calcium scoring does not require iodinated contrast dye, so there is no risk of an allergic-like reaction or kidney injury related to contrast administration.

How Should I Prepare for a CT Calcium Score Test?

Preparation is simple.
Usually no fasting is required.
Continue your usual medications unless instructed otherwise.
Avoid wearing clothing containing metal around the chest.

What Happens During a CT Calcium Score Test?

The scan usually takes only a few minutes.
ECG leads are attached to your chest.
You lie on the CT scanner while images are obtained during a brief breath-hold.
No injections are required.
No contrast dye is used.

What Happens After a CT Calcium Score Test?

There is no recovery period.
You can return to your usual activities immediately.

Get Advice On Heart CT Scan in Singapore

A CT calcium score and a CT coronary angiogram are complementary tests, but they are designed for different purposes.

If you have no symptoms but want to understand your future risk of heart disease, a CT calcium score may be the most appropriate investigation.

If you have chest pain, breathlessness, or suspected coronary artery disease, a CT coronary angiogram usually provides far more useful information.

Choosing the right test is just as important as performing the test itself. Discuss your symptoms and risk factors with your cardiologist to determine which heart scan is best suited to your individual circumstances.

FAQs on Heart CT Scan in Singapore

Is a CT calcium score better than a CT coronary angiogram?

Neither test is better as they answer different clinical questions. A calcium score test estimates cardiovascular risk in people without symptoms, whereas CT coronary angiogram diagnoses coronary artery disease in patients with suspected heart disease.

Can I do both heart scans?

Yes. A calcium score is often obtained as part of the CT coronary angiography examination, before contrast is administered. The calcium score helps quantify plaque burden, while CT coronary angiography determines whether significant narrowing is present.

What is a good calcium score?

A calcium score of zero is generally considered reassuring, particularly in an asymptomatic person. However, a score of zero does not mean that you have zero cardiovascular risk or completely normal coronary arteries. Your age, sex and other cardiovascular risk factors also need to be considered.

If my calcium score is zero, can I still have a heart attack?

Yes, although the risk is low. Some heart attacks occur because of rupture of soft, non-calcified plaque that cannot be detected by calcium scoring.

Can a calcium score of zero rule out blocked arteries?

No. A calcium score of zero means that no calcified plaque was detected, but it cannot exclude non-calcified plaque. This is particularly relevant in younger patients and people with symptoms. If coronary artery disease is suspected, a CT coronary angiogram may provide more information.

Can a high calcium score be reversed?

No. Calcium deposits usually remain visible even after aggressive cholesterol treatment. However, appropriate treatment can stabilise plaques and substantially reduce the risk of heart attack.

References

Blumenthal RS, Morris PB, Gaudino M, et al. 2026 ACC/AHA/AACVPR/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Dyslipidemia: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Journal of the American College of Cardiology. 2026;87(19):2624–2757. doi:10.1016/j.jacc.2025.11.016.
Arnett DK, Blumenthal RS, Albert MA, et al. 2019 ACC/AHA Guideline on the Primary Prevention of Cardiovascular Disease: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Circulation. 2019;140:e596–e646. doi:10.1161/CIR.0000000000000678.
Budoff MJ, Nasir K, McClelland RL, et al. Coronary Calcium Predicts Events Better With Absolute Calcium Scores Than Age-Sex-Race/Ethnicity Percentiles: MESA (Multi-Ethnic Study of Atherosclerosis). Journal of the American College of Cardiology. 2009;53(4):345–351. doi:10.1016/j.jacc.2008.11.008.
Vrints C, Andreotti F, Koskinas KC, et al.; ESC Scientific Document Group. 2024 ESC Guidelines for the management of chronic coronary syndromes. European Heart Journal. 2024;45(36):3415–3537. doi:10.1093/eurheartj/ehae177.
Hecht HS, Blaha MJ, Berman DS, et al. Clinical indications for coronary artery calcium scoring in asymptomatic patients: Expert consensus statement from the Society of Cardiovascular Computed Tomography. Journal of Cardiovascular Computed Tomography. 2017;11(2):157–168. doi:10.1016/j.jcct.2017.02.001.