A calcium score test is a quick, noninvasive CT scan that takes about 10 to 15 minutes from start to finish, with the actual scanning portion lasting only a few seconds. There are no needles, no contrast dye, and no sedation involved. The scan detects calcium deposits in the arteries that supply your heart, which are an early sign of plaque buildup.
What Happens During the Test
When you arrive, you’ll change into a hospital gown and remove any jewelry. A technologist will clean three small areas on your chest, possibly shaving them, and attach small sticky electrode patches. These electrodes connect to a heart monitor that tracks your heartbeat throughout the scan.
You’ll lie on your back on a narrow table that slides into the center of a large, doughnut-shaped scanner. The opening is short and wide, so most people don’t feel claustrophobic. You can talk to and hear the technologist operating the machine from another part of the room the entire time. You may notice light lines projected onto your body as the scanner positions itself.
During the scan, the machine captures multiple X-ray images of your heart. You’ll be asked to hold your breath for about 10 to 20 seconds while the images are taken. This keeps your chest still so the pictures come out clear. That’s essentially the entire experience. The table slides back out, the patches come off, and you’re done. There’s no recovery time and no restrictions on what you can do afterward.
How the Scanner Gets Clear Images
Your heart is constantly moving, which would normally blur a CT image. To solve this, the scanner synchronizes its X-ray pulses with your heartbeat using the electrode patches on your chest. It times each burst of imaging to the moment between heartbeats when your heart is briefly still. This technique, called ECG gating, eliminates most of the motion blur and produces sharp cross-sectional images of your coronary arteries.
There are two ways scanners do this. Some trigger the X-rays only during the resting phase of each heartbeat. Others scan continuously and use software to sort the useful frames afterward. Either way, the result is a detailed picture of the calcium in your artery walls.
How to Prepare
Preparation is minimal. Wear loose, comfortable clothing, or expect to change into a gown. Leave jewelry at home. Some facilities ask you to avoid caffeine for a few hours beforehand, since a slower heart rate produces clearer images. No fasting is required, and you won’t receive any contrast dye or injections.
What the Test Can and Cannot Detect
The scan is highly accurate at finding calcified plaque, the hard, calcium-containing deposits that form in artery walls over years. Studies comparing CT scans to direct imaging inside arteries found that the test picks up calcified plaque with about 94% accuracy.
What it cannot reliably detect is soft, noncalcified plaque. This is the fatty, cholesterol-rich buildup that hasn’t yet hardened. When arteries contain only soft plaque and no calcium, the scan catches it only about 53% of the time. This matters because soft plaque can also rupture and cause heart attacks. A score of zero is reassuring, but it doesn’t guarantee completely clean arteries.
How Your Score Is Calculated
A radiologist reviews the images and assigns a number called an Agatston score, which reflects how much calcium was detected across all your coronary arteries. The higher the number, the more plaque has accumulated.
- Score of 0: No calcium detected. This suggests a low chance of heart attack in the coming years.
- Score of 1 to 99: Mild plaque deposits. Some buildup is present but the risk is still relatively low.
- Score of 100 to 300: Moderate plaque deposits, associated with a relatively high risk of heart attack or other heart disease over the next three to five years.
- Score above 300: More extensive disease with a higher heart attack risk.
Your results are typically also compared to other people of the same age and sex, giving you a percentile ranking. Someone with a score of 50 might be at the 90th percentile for a 40-year-old but only the 30th percentile for a 70-year-old, which changes how the result is interpreted.
Radiation Exposure
The scan exposes you to about 1 to 2 millisieverts of radiation. For context, that’s roughly the amount of background radiation you absorb naturally over six months of everyday life, or about the same as a mammogram. It’s a fraction of what a full diagnostic chest CT delivers. For a one-time screening test, the dose is considered very low.
Cost and Coverage
A calcium score test typically costs around $150. Most insurance plans, including Medicare, do not cover it as a screening test. It’s often paid out of pocket. Some hospitals and imaging centers offer it at a reduced rate as a self-pay option, so it’s worth calling ahead to compare prices in your area.
The test is most useful for people at intermediate risk of heart disease, meaning those who have some risk factors like high cholesterol, family history, or high blood pressure but haven’t yet had a heart attack or been diagnosed with heart disease. For people already known to be at high risk or very low risk, the scan is less likely to change the treatment plan enough to justify the cost and radiation.