Cardiac CT for Calcium Scoring
Calcium scoring is a noninvasive way for physicians to get detailed images of your coronary arteries to help identify the presence, location and extent of calcified plaque. Calcified plaque occurs when fat and other substances build inside an artery, and can signal the presence of atherosclerosis, a disease of the vessel wall, also called coronary artery disease (CAD), leading to an increased risk for heart attack.
Over time, coronary artery disease can narrow the arteries, restricting or even blocking blood flow to the heart. The result may be chest pain, sometimes called angina, or a heart attack. Calcium can be an indication of CAD, so the amount of calcium detected on a calcium scoring scan is often a helpful prognostic tool and is expressed as a calcium score.
Calcium scoring is a quick and painless way to help detect coronary artery disease.
How does CT work?
CT scanning uses X-ray beams and a set of electronic X-ray detectors that rotate around your body while the examination table moves through the scanner. A computer processes this large volume of data to create two-dimensional cross-sectional images of your body, which can be displayed on a monitor. This technique is called helical or spiral CT.
CT imaging is sometimes compared to looking into a loaf of bread by cutting the loaf into thin slices. When a computer reassembles the image slices, the result is a very detailed multidimensional view of the body's interior.
Refinements in detector technology have allowed thinner slices to be obtained in a shorter period of time, resulting in more detailed images and the capability to get additional views. Modern scanners are so fast that they can scan through large sections of the body in just a few seconds. Such speed is beneficial for all patients but especially for children, the elderly and critically ill.
What are some common uses of calcium scoring?
Calcium scoring is often used to determine if coronary artery disease (CAD) is present and if it is, to what extent. Physicians may also order a calcium scoring screening for patients who are at risk for developing coronary artery disease, even if the patient has no signs of the disease. The major risk factors for CAD are:
- Abnormally high blood cholesterol levels
- A family history of heart disease
- High blood pressure
- History of cigarette smoking
- Being overweight or obese
- Being physically inactive
What will I experience during calcium scoring?
Calcium scoring scans are painless, fast and easy. Because they are noninvasive, you can usually resume your normal activities immediately. You will be alone in the exam room during the scan. However, the technologist will be able to see, hear and speak with you at all times.
When you enter the scanner, special lights may be used to ensure that you are properly positioned. With modern scanners, you will hear only slight buzzing, clicking and whirring sounds as the scanner revolves around you during the imaging process.
How is calcium scoring performed?
Radiologist reading scans
A technologist will help you position yourself on the examination table. In most cases, you'll be lying flat on your back, but sometimes patients are placed on their sides or stomach. Straps and pillows may be used to help you maintain the correct position without moving during the exam.
Electrodes (small, sticky discs) will be attached to your chest and to an electrocardiograph (ECG) machine that records the electrical activity of your heart. This makes it possible to record CT scans when the heart is not actively contracting.
The table will move quickly through the scanner to determine the correct starting position for the scans. After that, the table will move slowly through the machine as the scanning is performed. You'll be asked to hold your breath for 10 to 20 seconds while images are recorded.
When the examination is completed, a technologist will ask you to wait until he or she verifies that the scan has produced high quality images for accurate interpretation. The entire procedure can usually be completed within 10 minutes.
How are results interpreted and how do I get them?
After you have a calcium scoring scan, a radiologist who has expertise in supervising and interpreting radiology examinations, will analyze the images and send a signed report to your primary care physician or the physician who referred you for the exam. Your physician will discuss the results with you and recommend what, if anything, you should do to follow up.
A negative result from a calcium scoring scan shows there is no calcification within a patient's coronary arteries. That suggests that there is no coronary artery disease (CAD), or that it is so minimal a CT scan cannot see it.
A positive result means that coronary artery disease is present, whether or not the patient has experienced any signs or symptoms. The amount of calcification — expressed as the calcium score — may help to predict the likelihood of a myocardial infarction (heart attack) in the coming years and helps your doctor or cardiologist decide whether you may need to take preventive medicine or undertake other measures such as diet and exercise to lower the risk for heart attack.
The extent of CAD is graded according to calcium scores:
Calcium Scoring | Presence of CAD
- 0 | No evidence of CAD
- 1–10 | Minimal evidence of CAD
- 11–100 | Mild evidence of CAD
- 101–400 | Moderate evidence of CAD
- Over 400 | Extensive evidence of CAD
What are the benefits of calcium scoring? The risks?
- Calcium scoring is a convenient and noninvasive way to evaluate if you may be at increased risk for a heart attack.
- The exam takes little time, causes no pain and does not require an injection of contrast material.
- No radiation remains in a patient's body after an examination.
- X-rays used in calcium scoring scans usually have no side effects.
There is always a slight chance of cancer from excessive exposure to radiation. However, the benefit of an accurate diagnosis far outweighs the risk. The effective radiation dose from this procedure is about 2 millisieverts (mSv), which is about the same as the average person receives from background radiation in eight months. Newer scanners may even use less radiation.
- Are there any limitations to the test?
- A person who is very large may not fit into the opening of a conventional computed tomography (CT) scanner or may be over the weight limit for the moving table.
- CAD, particularly in people younger than 50 years of age can be present without calcium and may not be detected by this exam.
- Not all health insurance plans cover calcium scoring.
- A high heart rate may interfere with the test. If a patient's heart rate is 90 or more beats per minute, the exam may need to be rescheduled.