A heart CT scan for calcium scoring, also known as a coronary artery calcium (CAC) scan, uses a very low dose of radiation, typically around **1 to 1.5 millisieverts (mSv)**. This amount is considered quite low in the context of medical imaging and is comparable to or even less than some common screening tests like mammography, which is about 0.8 mSv. For perspective, the average person is naturally exposed to about 3 mSv of background radiation annually from the environment.
The purpose of this scan is to detect calcified plaque in the coronary arteries, which is an early sign of atherosclerosis—a buildup of fatty deposits that can lead to heart disease. The scan is noninvasive, painless, and quick, usually taking about 10 minutes. It does not require any contrast dye injection, which further reduces risk and complexity.
Radiation exposure in medical imaging is measured in millisieverts, which quantifies the risk of radiation-induced harm. The 1 to 1.5 mSv dose from a calcium scoring CT is considered low because it delivers just enough radiation to produce clear images of the coronary arteries without unnecessary excess. This low dose is achieved through specialized CT protocols designed specifically for calcium scoring, which focus on capturing the calcium deposits rather than detailed soft tissue images.
To put this into context:
– **Natural background radiation:** About 3 mSv per year from cosmic rays, radon, and other sources.
– **Chest X-ray:** Approximately 0.1 mSv.
– **Mammogram:** Around 0.8 mSv.
– **Calcium scoring CT:** Approximately 1 to 1.5 mSv.
– **Standard chest CT:** Around 7 mSv or more, depending on the protocol.
Because the radiation dose is low, the risk associated with the scan is minimal, especially when weighed against the benefit of early detection of coronary artery disease. Early detection can guide preventive measures, lifestyle changes, and treatments that reduce the risk of heart attacks and other serious cardiovascular events.
The scan is generally recommended for adults over 40 or 50 years old who have risk factors for heart disease, such as high blood pressure, high cholesterol, smoking, diabetes, or a family history of heart disease. It is usually not recommended for younger individuals because the likelihood of significant calcium buildup is low, and the radiation exposure, while small, is best avoided unless clearly justified.
Technological advances continue to reduce radiation doses further. Some newer CT scanners and imaging techniques can lower the dose below 1 mSv by optimizing scan parameters and using advanced image reconstruction algorithms. These improvements maintain image quality while minimizing radiation exposure.
In summary, a heart CT for calcium scoring involves a low radiation dose, roughly equivalent to a few months of natural background radiation or a bit more than a mammogram. This low dose is carefully balanced to provide valuable information about coronary artery health with minimal risk, making it a useful tool in cardiovascular risk assessment and prevention.
