Magnetic resonance imaging (MRI) is a technique that uses a magnetic field to create images of the internal structures of the body. The body is composed largely of water, which is a combination of hydrogen atoms and oxygen atoms. The center, or nucleus, of the hydrogen atoms contains proton particles. When these protons are exposed to a strong magnetic field (like that of an MRI scanner), they align in a uniform direction. A low-frequency radio wave is then directed at the target area, causing the protons to relax and return to their original positions. As the protons relax, they emit radiofrequency signals. The radiofrequency signals vary according to the density and depth of the tissue. The radio signals from the protons are picked up by special receiver coils in the MRI unit. A computer analyzes the information and uses the data to construct images.

MRI can be a very useful tool for imaging of the heart. It can determine the health of the heart muscle (whether alive, impaired or dead), strength of pumping action and measurement of the amount of blood released with each heart beat. Cardiac MRI is also useful to detect tumors in the heart, blood clots, health of the aorta (the main blood vessel from the heart to the body) and function and health of the heart valves. In children, cardiac MRI is an excellent tool for evaluating congenital heart disease.

Analyzing the Images: CardioVue

Traditionally, when an MRI is performed, the images are taken by a technologist, stored in computer files and later read by a radiologist. Researchers at Wake Forest University Baptist Medical Center have developed technology that enables cardiologists to review images directly from the MRI, in real-time.

CardioVue is a workstation that's added on to the standard MRI equipment. It displays the images of the beating heart as soon as they are processed. The cardiologist can examine the images as they appear. The program also allows doctors to sort through a compilation of images and select certain ones for comparison. Doctors can view the heart from different angles for a more thorough analysis. They can also detect abnormalities in the movement of the wall of the heart, which may be an indication of damage from a heart attack.

CardioVue enables cardiologists to detect a problem and make a diagnosis very rapidly. Doctors can administer medications to perform stress testing during the MRI to diagnose coronary artery disease. In addition, as soon as the imaging procedure is finished, the images can be sent to the referring physician via the Internet. CardioVue was approved by the FDA in May 2006.

The website for the company is currently under construction at http://www.provaimages.com.

For general information about cardiac MRI:

American Heart Association

Radiological Society of North America, public site