4D heart imaging could have far-reaching effects for patients

By Tannith Cattermole

4D images show blood flow, direction and velocity and are markedly different in healthy volunteers when compared to patients with heart problems (Image: University of Wisconsin School of Medicine and Public Health)

Heart disease is the number one killer in the U.S, and congenital heart disease is the most common birth defect around the world. About five million people in the U.S. have heart failure, and it kills 300,000 people a year. Current lengthy MRI heart imaging technology has led to long waiting lists but remarkable new imaging technology can not only show the heart in 3D showing blood flow, direction, and velocity but can also show them relating to a fourth dimension - time. The procedure is fast, and requires no invasive procedures, no contrast agent or general anesthesia and could have significant consequences for patients at risk of cardiac problems.

Until now physicians have measured blood velocity with MRIs that require a patient to be completely still for up to 90 minutes in order to capture the 20 to 30 slices needed to scan the entire heart. Ultrasound is also sometimes used but other anatomy can make it difficult to see some areas of the heart. Furthermore the images from both are typically 2D, though sometimes 3D.

With the new technology the MRI scan takes only ten minutes, and while wriggly children might need to be sedated patients don't need to be absolutely still for long periods. From a short procedure scientists can produce remarkable images to measure how fast blood is flowing through various places in the heart and the major arteries around it. Blood flowing through the heart is seen as a bundle of long filaments color-coded to indicate the speed of the flow at various locations in the heart. Blue threads represent a relaxed heart with relatively slow flow such as when sleeping or at rest, while green threads indicate blood flowing faster during contraction. Red and yellow threads show abnormally fast blood flow in patients with heart problems.

In addition to this, direction of blood is depicted and the effect of any obstructions or deviations on blood flow. Scientists hope that the new technology could be adapted to analyze blood vessel walls as well by identifying weak areas or areas under increased stress that could lead to aneurysms or build-up of damaging plaque. This would have far-reaching effects for any patients with heart defects or at risk of cardiac problems.

The new imaging technology, developed by researchers at the University of Wisconsin School of Medicine and Public Health (SMPH) is known as Phase Contrast Vastly undersampled Isotropic Projection Reconstruction (PC VIPR). Dr. Oliver Wieben, a School of Medicine and Public Health medical physicist who has been working on the technology for several years, and Dr. Christopher Francois, a radiologist at the medical school who specializes in heart imaging have demonstrated their technology on hundreds of volunteers and patients, and the images have created a stir among amazed physicians and peers.

"In designing this, we threw out all the old rules of radiology and came up with a new way to acquire data that allows us to do the imaging much faster while still getting excellent quality," Wieben says. "We're also developing new ways to display the complex flow data on a 2-D monitor."

"This is a new paradigm in cardiac imaging," says Francois. "It will allow physicians to see things they haven't seen before in all their complexity."

This new development could soon have significant implications for those people born with heart defects or at risk of heart problems if it is available in hospitals in only three or four years from now.

Other similar research into 4D brain imaging has been positive but is still in study phase.