Diagnostic Imaging: Beam Me Up Dr. McCoy

We're not quite at the Star Trek level yet with imaging technology, but recent advances are fine-tuning your medical care.

From the WebMD Archives

Recent advances in imaging technology -- like CT scans, MRIs, PET scans, and other techniques -- have had a huge impact on the diagnosis and treatment of disease.

"Advances in imaging over the last five years have revolutionized almost every aspect of medicine," says Jonathan Lewin, MD, chairman of the department of radiology at Johns Hopkins School of Medicine in Baltimore.

More detailed imaging is allowing doctors to see things in new ways. Imaging can provide early and more accurate diagnoses. In some cases, it might even lead to better and more successful treatment.

"Just about every field of medicine is using imaging more than they used to," says William Eversman, MD, chairman of radiology at the Mayo Clinic in Scottsdale, Ariz. "I'm not saying that the physical exam is a dying art. But doctors are coming to see just how valuable and accurate these tests can be."

Four Big Advances in Imaging

There have been many improvements to imaging technology in recent years. Here are a few that experts singled out as especially significant. While these are becoming more common, keep in mind that the newest technology may not be available yet at your local hospital.

  • Computed Tomography (CT) Angiography

    "CT angiography is one of the greatest advances in imaging," says Lewin.

    Just a few years ago, an angiography -- an examination of the blood vessels -- could only be done by inserting a catheter into an artery. In the procedure, contrast material -- a substance that makes it easier to see tissue in an X-ray -- is injected through the catheter. Then an X-ray is taken of the area to look for blockages, internal bleeding, or other problems. Catheter angiography can take up to several hours. It often requires sedatives and sometimes a night in the hospital. It also has risks, like a small chance of blood clots or bleeding.

    "The newest CT scans allow a completely noninvasive way to get the same information as an invasive catheter angiography," says Lewin.

    In a CT angiography, the doctor just injects the contrast material into the arm and takes a CT scan. The arteries in the lungs, kidneys, brain and legs can then be examined. The whole process takes just 10-25 minutes. It's safer, faster, and cheaper than the traditional way.

    CT angiography hasn't completely replaced the old technique. For example, traditional angiography is still commonly used to evaluate heart arteries for blockages.

  • Imaging Tests Instead of Exploratory Surgery

    One of the biggest changes in the use of imaging, says Hillman, is that it has largely replaced exploratory surgery.

    "In the past, we had to do surgery just to see what was going on inside the body," says Hillman. "But CT scans, MR scans, and ultrasound have become so good that they have largely done away with the need for the surgical approach."

  • PET/CT Scans for Cancer

    PET (positron emission tomography) scanning is not new. But it has become increasingly important in recent years, particularly since it was combined with CT scanning in one device.

    "PET scanning has been around for a long time," says Hillman, who is also a professor of radiology at the University of Virginia. "But for years no one was sure just what to do with it."

    PET scans are a type of "nuclear medicine." The name is unnerving. But "nuclear" refers to the small dose of radioactive material that you are injected with before the test. The amount of radiation exposure is similar to what you would get from a standard X-ray.

    Unlike many other imaging technologies, PET scans aren't designed to look at organs or tissue. Instead, they can image biological functions, like blood flow or glucose metabolism. "PET is able to pick up the metabolic changes associated with cancer much earlier than you could see tumors or other physical changes in the organs," says Lewin.

    PET/CT scans give a doctor a broader view of a person's condition.

    "By fusing PET and CT," says Lewin, "you get to see both the metabolic information of PET and the anatomic detail of CT at once. It's a big advance."

  • Digital Mammography

    "Digital mammography for breast cancer screening is a significant leap forward," says Lewin. "It gives us a much higher level of detail than older technology."

    Digital mammograms produce similar results to traditional mammograms, which use X-rays and film. But the digital approach has several advantages. Bruce J. Hillman, MD, chairman of the American College of Radiology Imaging Network, notes that digital mammograms are easier and faster to perform. And since they are digital, it's very easy for a doctor to send the images instantly to other experts or medical centers.

    Early studies showed that digital mammography worked as well as traditional mammography in detecting breast cancer. A 2005 study published in The New England Journal of Medicine found digital mammography was actually more accurate for some women. This includes women who were under 50, women with dense breast tissue, premenopausal women, and women who were around the age of menopause.

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Easier, Faster Imaging Exams Yield Better Information

It's not just the quality and detail of the images that has improved. Some advances have made the actual experience of having an imaging exam easier.

For one thing, they are a lot faster. "When I was doing my training 20 years ago, a CT exam might take half an hour," says Lewin. "We can now literally get the same amount of information in less than two seconds."

The full length of an exam varies depending on the person and the type of imaging. But Hillman estimates that an MRI (magnetic resonance imaging) takes between 20 to 40 minutes. However, the imaging itself only takes up a few seconds or minutes of that time. (The rest is taken up by the technicians preparing the exam.) Because the exams are quicker, fewer people need sedation or pain medicine to lie still, says Lewin.

Open MRIs Ease Claustrophobia

Other modifications are helping too. For many people, MRIs have traditionally been an unpleasant experience. In standard MRI exams, a person slides into a narrow tube and has to stay there for the length of the exam. People with claustrophobia can find it unbearable.

"It can feel like being in a coffin," says Lewin.

There have been "open MR" imagers for years. They are not enclosed on the sides and are less restrictive. But experts also say they may be less accurate.

"In the past, there were trade-offs between the openness of an MRI and the image quality," says Hillman. "But we're seeing the gaps being narrowed."

New MRI machines are available that are just as accurate as traditional ones, but much shorter, so that they never fully enclose the person.

Another problem with some older imaging devices is that they couldn't accommodate heavy people. That has been at least partially resolved.

"With new machines, we can give exams to people who are 350-400 pounds," says Hillman. But he says that because of image degradation, imaging tests for the obese are often less accurate in general than for people of average weight.

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Using Imaging for Routine Screening -- the Pros and Cons

A topic that's spurred interest -- and debate -- is screening apparently healthy people for cancer, heart disease, and other problems. Sophisticated imaging tests can sometimes detect disease in very early stages, long before a person shows any other symptoms.

So given the obvious benefits, why isn't everyone in America being screened? It turns out that there are some real drawbacks to routine screening.

First of all, imaging has risks. Many tests involve exposure to small amounts of radiation or radioactive material. While the odds that this could cause harm are low, they still exist, says Eversman.

The other problem is that screening can detect abnormalities that don't actually need any treatment. But once the doctor sees them, further tests must be ordered to make sure that these abnormalities are harmless. So people may need a number of tests or even surgery -- and suffer a lot of anxiety - only to discover that they didn't need treatment!

"There are a lot of nonspecific abnormalities," says Hillman. "For instance, an enormous number of people have nodules in their chests. But only a fraction of them actually turn out to be cancer." Universal screening could lead to a lot of unnecessary and risky tests and procedures.

Even in apparently healthy people who really do have a disease, screening may not always help.

"Catching the disease early and stopping it would be great," says Hillman. "But lots of times, that doesn't happen. You find the disease earlier, you treat it earlier, but the outcome is the same and the person dies anyway." Early detection helps many people, of course. But it doesn't always make a difference. For those who aren't helped, it leads to tests, treatments, and intense distress much earlier than someone who wasn't screened.

Smarter Use of Imaging for Screening

As for now, no one recommends routine high-tech screening for everyone.

"The American College of Radiology does not endorse whole body screening of healthy people," says Eversman. "It probably shouldn't be done, since there's no proof that it saves lives or even improves them."

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"I think it's fair to say that at this point, the only cancer screening that we know to work in reducing the death rate is mammography," Hillman tells WebMD. "Everything else is undergoing testing or completely unproven."

But experts are trying to figure out how to use screening as a tool for people at higher risk of certain diseases. Lewin also says that as imaging exams become safer and more accurate, the pros of screening may outweigh the cons.

"As MR screening continues to improve, and as we lower the dose of radiation with CT, routine screening will make sense for a bigger and bigger proportion of people," he tells WebMD.

Imaging Moved Into the Operating Room

Soon, imaging tests may not only be used to diagnose disease. They may also become a key part of some medical procedures. During minimally invasive surgery, imaging will allow surgeons to see inside the body better, to improve treatment -- and minimize complications.

"Minimally invasive surgery and new imaging technologies are developing hand in hand," says Lewin.

"MRI in particular -- but also other technologies, like ultrasound -- may have the ability to monitor a surgery in real time," says Hillman. "They could potentially detect when all of a tumor was removed, or when a surgeon was accidentally beginning to harm normal tissue."

Lewin says that using MRI during brain surgery is already helping. "The studies are still being done," he says. "But I've seen that combining the surgeon's eyes with MR improves the operation. Because the human eye, even with a microscope, just can't see what an MR can see."

Eversman says that CT scans are starting to be used to create computer-generated models of the heart for use during surgery. "During the operation, the 3D model is shown on a screen, and it moves and rotates to show where the surgeon currently is in the heart," he tells WebMD. "It's a great innovation."

Experts say that imaging will become even more detailed and focused in the future.

"In the next 20 years, imaging technology is going to focus on the molecular and cellular levels," says Hillman. "Instead of only seeing the gross anatomy like we do now, we're going to be looking at metabolism and physiology." He says that PET scanning is the first step in this direction.

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In general, imaging technology is certain to become faster and more accurate. More combination devices -- like the CT/PET scan -- are inevitable. "There are some prototype PET/MR scanners now," says Hillman. "And people are talking about CT/MR scanners." Fusing different imaging techniques will allow doctors to get a much fuller understanding of a person's condition.

"In our lifetimes, I don't think that we will reach the technology of Star Trek, where you can wave a wand over someone and instantly diagnose them," says Eversman. "But step by step, we're getting there."

WebMD Feature Reviewed by Michael W. Smith, MD on February 23, 2006

Sources

SOURCES: William Eversman, MD, chairman of radiology, Mayo Clinic, Scottsdale/Phoenix, Ariz. Bruce J. Hillman MD, Theodore E. Keats Professor of Radiology, University of Virginia, Charlottesville, Va.; chairman of the American College of Radiology Imaging Network. Jonathan Lewin, MD, professor and chairman, department of radiology, Johns Hopkins School of Medicine, Baltimore. Pisano E, et al, New England Journal of Medicine, Oct. 27, 2005; vol 353: pp 1773-1783. RadiologyInfo web site: "Catheter angiography," "Positron Emission Tomography (PET Imaging)," "General Nuclear Medicine," "Computed Tomography Angiography," "MR Imaging (Body)."

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