"The CT scan saw something the stress test didn't find," Levi said.

And it was done within minutes, without surgery. Doctors injected Levi     with dye, made a 20-second X-ray scan with a CT and reaped dozens         of detailed, computerized images of his heart and vessels.

For years, doctors have relied heavily on the stress test and the      angiogram to find heart disease, the nation's top killer and the cause of      1.1 million heart attacks per year.

Stress tests use sound waves or radioactive dye to measure blood flow       to the heart while the patient is resting or exercising. If a problem is      found, patients usually get an angiogram. Doctors make an incision at         the groin, thread a thin tube through an artery, inject dye and examine     the blood vessels with an X-ray. They can see if the flow of blood is       being blocked in an artery narrowed by plaque, deposits of fat caused        by cholesterol.

But there's a hitch in this approach.

"Half of the people who have heart attacks never have narrowing of the   blood vessels. Something else is going on," said Dr. Claudio Smuclovisky, a CT specialist at South Florida Imaging in Boca Raton.

Doctors now know that plaque doesn't just bulge into the vessel, it       bulges out, undetectable to stress tests and angiograms. Plaque is    dangerous not just because it blocks the artery but because it         ruptures, prompting the body to form big clots that block the vessel.

Outward bulges are the more dangerous type. Studies show about 70    percent of those with outward bulges have heart attacks vs. 30 percent      of those with inward bulges. CT scans can see the outward bulges.

"If the stress test is negative, the doctor is going to tell you that you're    fine. Well, maybe not," Shen said. "With the CT, we can see the plaque.         We can be more aggressive in treating it."

CT scans have another advantage: They are not invasive. One percent       of angiograms, also called cardiac catheterizations, cause complications    such as stroke, internal bleeding, anesthesia reactions and in about 1 in    1,000 cases, death.

Stress tests will never fade away, some specialists say, because they    better measure the heart at work.

"You're never going to have any one test taking over the landscape,"    Martin said.

Even fans of CT heart scans say they expose patients to too much    radiation to be used as a routine screening test for healthy people. The    scan delivers 8 to 12 millisievert of radiation, about three times the       expose we get annually from nature. A stress test using nuclear dye is    about the same; an angiogram is a little less.

"The radiation risk from CT is significant," Shen said.

But proponents of heart CTs predict rapid growth of new uses and         wider acceptance. Most insurers cover CT heart scans if deemed       medically needed.

Cardiologists are using CTs to decide whether patients with borderline      heart problems need angiograms, about one-quarter of which find no       heart disease. Doctors said CT scans at $700 to $1,000 each can          spare thousands of people from the risk and expense of angiograms       costing $5,000 to $15,000.

A May study in the Journal of the American Medical Association found      heart CTs as accurate as angiograms, catching 87 to 99 percent of    blockages in German heart patients.

Cardiologist Seth Baum in Boca Raton is among a growing number using        CT scans to decide whether a patient needs cholesterol drugs, which        can damage the liver.

Scans have found patients deemed to be at low risk for heart disease       who have dangerous plaque and need to be on medication, Baum said, as    well as higher-risk patients who are free of plaque and can stick with      safer therapy such as niacin.

"If you're 40 and with elevated cholesterol but no heart disease on the CT, it might be wise to keep you off the medication and just put you on [a] diet     and exercise [regimen]," said radiologist Smuclovisky, who took himself       off cholesterol drugs after a clean CT.

Shen's team in Weston scanned 77 heart patients as part of a study        now being prepared. They found dangerous plaque in 48 percent of         those rated low risk based on family history, cholesterol and other       factors. About 20 percent of the patients had enough plaque to           justify starting medication, Shen said.

In some parts of the country, emergency room doctors use CT scans          to check patients with chest pain, hoping to quickly confirm or rule out     heart attacks, torn vessels or blood clots that could be fatal. A Mayo     Clinic study says hospitals waste $10 billion a year by admitting chest-      pain patients who prove to have no heart problems.

CT heart scans have found serious diseases by coincidence. Smuclovisky    said he has found cancer in lungs and livers. A University of Michigan study in May reported that CT heart scans found serious tumors, clots and    aneurysms in 43 of 98 scan patients.

Fort Lauderdale radiologist Charles Tate III went for a CT heart scan in August because he was feeling tired. The test proved his heart was fine,     he said, but found a potentially fatal blood clot in his left lung that            was removed immediately.

"In days gone people would have walked around with these things and     never have known it unless something happened," Tate said. "Now we       can know."