Atherosclerosis is a disease in which fatty deposits consisting of fat, cholesterol and other substances collect along the walls of arteries. It is sometimes referred to as hardening of the arteries, arteriosclerosis and coronary artery disease.
As the fatty material hardens, it forms calcium deposits called plaques. The build-up of plaque makes a blood vessel narrow and less flexible and eventually, may block blood flow. Reduced blood flow in the coronary arteries may cause chest pain (angina), shortness of breath, a heart attack and other symptoms.
Small pieces of plaque (called unstable atherosclerotic plaque) may break away and lodge in smaller blood vessels, blocking blood flow. This blockage, called an embolization, is a common cause of heart attack and stroke. Blood clots can also form around a tear in the plaque leading to a blockage. A blood clot that moves into an artery in the heart, lungs, or brain can cause a stroke, heart attack, or pulmonary embolism. Plaque may also weaken the wall of an artery leading to an aneurysm.
Today, many patients are evaluated for atherosclerosis by invasive tests such as angiography, which involves inserting a catheter into the body and threading it into the aorta. Molecular and nuclear imaging offer the opportunity to assess blood flow noninvasively–without making a surgical incision or inserting a medical instrument into the body.
Myocardial perfusion imaging (MPI) and PET use radiotracers and a special camera or similar device to produce images of the coronary arteries. MPI visualizes blood flow to the heart while patients are at rest and immediately following stress. PET imaging with a radiotracer called FDG is also used to examine blood vessels in the heart for signs of inflammation.
Clinical trials are currently underway to evaluate the use of molecular and nuclear imaging as the primary method of assessing patients with suspected atherosclerosis. Scientists are also exploring molecular approaches to detecting unstable atherosclerotic plaque before it causes damage.