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Imaging the Heart: The New Frontier

MRI Heart Scans continued...

No radiation is used with MRI; however, powerful magnets are used to create images -- so certain people cannot have an MRI, like those who wear a pacemaker or defibrillator. The contrast medium is not iodine-based, so there are no allergy problems.

The MRI scan requires that the patient lay on a cushioned table inside the MRI tube, which gives some people claustrophobia (a sedative can help with this). Open MRI scanners were developed to solve the claustrophobia problem, but it's not an option for heart procedures, says Steiner.

"We can't use open MRI with the heart, because there is motion. If patients are claustrophobic, they can have the other tests - echocardiography, nuclear stress tests, or CTA," Steiner says.

PET/CT Heart Scans

Positron emission tomography (PET) scanning -- combined with CTA -- "is the future," Steiner tells WebMD. "We will have the combined advantages of PET and CTA, either in one composite image or side-by-side images."

PET scans are a form of nuclear medicine -- "nuclear" being the small dose of radioactive material you are injected with before the test (the radiation exposure is similar to that of a standard X-ray). As with CTA, PET involves a doughnut-like scanning device that takes the images.

With PET, the cardiologist and radiologist can examine biological functions, like blood flow or glucose metabolism of the heart, Steiner explains. "However, PET does not show the heart's shape or volume," he adds. "CTA and MRI show us that."

There is a debate among cardiologists whether PET/CTA is appropriate for heart diagnosis, Garcia says. "PET has been very useful in cancer diagnosis. PET tells whether the tumor is active or not, whether it is consuming a lot of blood. CTA tells where the tumor is. But we don't deal with cancers in the heart that often."

In cardiology, Garcia believes that PET/CTA may help "in very specific circumstances, like when we know there is a blockage but are uncertain how severe it is. But in the majority of cases, the other tests can tell us this."

Garcia is also concerned about safety. "There are arguments that we're giving too much radiation when we're doing both [tests] at the same time," he says.

PET/CTA "is in evolution," Levine tells WebMD. "It has the potential to assess both heart anatomy and function, and can be a diagnostic tool when the two are combined. But right now, only a minority of hospitals has the capability to use it."

Medicare is now paying for PET/CTA, Steiner adds. "Each of these tools has advantages and disadvantages. We want to do the right thing for each patient decide the best approach."

Garcia remarks that older tests may in time be used less, or in different ways. "We're still learning about the potential of this new technology," he says.


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