Imaging the Heart: The New Frontier
MRI Heart Scans
Cardiac MRI "provides the gold standard of cardiac function and anatomy
unsurpassed image quality in evaluating heart structure and function in
3-D-quality moving images," Levine tells WebMD.
And cardiac MRI "shows us more than echocardiography or an exercise
stress test," Steiner adds. "Those tests have benefits, but MRI shows
more in terms of the heart's shape, size, volume, function. We can see if there
is valve disease, heart abnormalities, heart tumors, clots in the heart --
anything to do with anatomy and function. All the other tests can show parts of
that, but MRI potentially shows it all."
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
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."