A Glimpse of the Heart

UT-Houston Physicians are Making Advances in
Imaging to Detect Heart and Vascular Defects at
Their Earliest Stages (continued)

By Meredith Raine

A Word of Caution

Cardiac imaging is rapidly evolving, and those technological advances are designed to improve diagnostic capabilities and patient care. However, there is still room for error.

In a recent study, K. Lance Gould, M.D., professor in the Division of Cardiology, discovered that PET-CT scanners with standard commercial software designed to provide images of the heart were falsely indicating coronary artery disease in as many as 40 percent of patients.

Dr. Gould, who published findings in the Journal of Nuclear Medicine, discovered the abnormalities upon his initial use of cardiac PET-CT scanners in the Weatherhead P.E.T. Center For Preventing and Reversing Atherosclerosis at Memorial Hermann.

Positron emission tomography, or PET, is nuclear cardiac imaging for optimally assessing blood flow in the heart. When paired with CT, the PET-CT scanners should be an accurate, noninvasive tool for detecting or assessing severity of heart disease, says Dr. Gould, executive director of the Weatherhead P.E.T. Center. However, he says, an erroneous basic concept in the software functions made the PET-CT scanners prone to generating false-positive results.

Dr. Gould developed a solution to the software problem with Tinsu Pan, Ph.D., associate professor in the Department of Imaging Physics at The University of Texas M. D. Anderson Cancer Center.

“When done properly, PET-CT produces absolutely perfect images of blood flow in the heart muscle,” Dr. Gould says. “It’s the best way to assess and direct management of heart disease.”

The Future of Cardiac and Vascular Imaging

While Drs. Hamilton, Coogan, and Gould are seeing patients in UT clinics, the Memorial Hermann Heart & Vascular Institute – Texas Medical Center and the Weatherhead P.E.T. Center, Jay Conyers, Ph.D., is working on ways to further advance their imaging capabilities.

At the Office of Biotechnology at The University of Texas Health Science Center at Houston, Dr. Conyers is working on what he calls “the holy grail of cardiac imaging,” a diagnostic tool for detecting vulnerable plaques before they become rupture-prone and well before the onset of a heart patient’s symptoms.

Vulnerable plaques are pools of lipid and cellular debris within the arterial wall that can become highly inflamed and rupture, leading to a sudden heart attack or stroke. Because vulnerable plaques don’t always produce significant stenosis, detecting them with CT is currently not possible.

“We want to develop angiographic dyes that can specifically detect the lipid building behind the arterial wall, where these vulnerable plaques are growing,” Dr. Conyers says. “We want to target the disease site at the earliest possible stage, improving on current contrast agents that don’t have the capability of honing in on the rupture-prone lesions.”

To do this, Dr. Conyers, assistant professor and director of the Office of Biotechnology, is researching how nanovectors can be utilized to carry the angiographic dyes directly to the site of vulnerable plaques. The nanovectors used in Dr. Conyers’ laboratory are comprised of single-walled carbon nanotubes, liposomes, or C-60 buckyballs that entrap high quantities of contrast agent and can be labeled with plaque-specific recognition molecules. Researchers in the lab also are exploring ways of loading drug molecules within the nanovectors – a strategy that may afford the opportunity to combine detection and treatment.

“The imaging agent and drug agent would be released at the same time,” Dr. Conyers said. “Then we could monitor disease regression.”

The continued advancement of cardiac imaging will help physicians, including cardiologist James T. Willerson, M.D., president of the UT Health Science Center at Houston, provide the best treatment to their patients.

“Dr. Willerson is committed to making sure we are leaders in cardiac imaging in early detection,” Dr. Conyers says.