Neuroradiologist Offers Insight on MRI Scans

February 16, 2022, by Kendall Morgan, NCI-CONNECT Contributor

In magnetic resonance imaging (MRI), a powerful magnet and radio waves are used to take pictures of your body in many slices. These slices, when put together, are useful for capturing detailed 3D images of the inside of your body—particularly the brain and spinal cord—to see both healthy and unhealthy tissue. A single MRI scan is useful for diagnosing a tumor, but your doctors will use multiple MRI scans over time to see if and how your tumor is changing.

“A lot of radiology starts off like what you learn on Sesame Street,” says Neuroradiologist John Butman, M.D., Ph.D., of NIH. Doctors will have multiple MRI scans from the same individual, and the fundamental question is: Which ones are different? Or, are they all the same? The first scan provides an initial diagnosis and a baseline. After an initial diagnosis, the task is to determine whether subsequent images differ or not, and—if so—what it means.

The difference between MRI interpretation and Sesame Street is the level of difficulty, Dr. Butman explains. If the MRI slices don't appear to match, it might be because the underlying tumor has changed, however slightly. It’s also possible that they appear different because the images were captured at a slightly different angle or taken on different scanners.

“In the past, we would often spend 15 minutes or more arguing about whether something had changed on the MRI or not,” Dr. Butman says. In the end, there were sometimes differences of opinion.

A Better Way to Interpret Brain MRI Scans

To address this issue and make their work easier and more reproducible, Dr. Butman and colleagues developed a more foolproof way to interpret brain tumor MRI scans. This resource, called the Registration Engine, is unique to the NIH Clinical Center and allows neuroradiologists to accurately evaluate the progression or treatment response of a brain tumor within minutes. The Registration Engine facilitates both clinical trial evaluation as well as research into tumor biology and treatment response.

When Dr. Butman first started at NIH, he knew based on his background in neuroscience, math, and radiology that mathematical algorithms had been used to evaluate high resolution brain scans for years. "Why not integrate them into clinical systems?" he asked.

When it was first developed at NIH, the approach required advanced computers. Now, due to advances in computing across the board, it can be done in a couple of minutes on a standard computer. "The computer moves the brain images relative to each other to get the best match between the two," Dr. Butman says.

Once those images are optimally aligned based on a sophisticated mathematical algorithm, the neuroradiologist or neuro-oncologist can easily determine whether the MRI has changed. “It's really simple,” Dr. Butman says.

There is still the challenge of interpreting whether a change means tumor growth or an effect of therapy, he says, but at least the basic question of change or no change is taken out of the equation. Over the years, they’ve added bells and whistles to handle it when, for example, a person moves a lot in the scanner. They can also use the system to align MRI and positron emission tomography (PET) scans to determine where the activity they see on the PET scan is located on the MRI.

“This approach isn’t widely used in many other places,” says Dr. Butman. “But it is very useful for us at NIH because of the large volume of brain scans we process.”

Expert Advice

“No matter where you’re getting your scans done to start, it’s a good idea to request a 3D T1 sequence,” says Dr. Butman. This sequence is higher resolution based on taking many thinner slices through the brain. It can be done on any scanner, but isn’t standard for brain MRIs at many places. Often, this type of scan is reserved for pre-surgical or radiation planning.

“To evaluate scans taken elsewhere at NIH, it’s necessary to have these higher quality scans,” says Dr. Butman. But that doesn’t mean you have to have your scans done at NIH, he adds, noting there are many high-quality imaging centers all around the country using scanners from the same manufacturers. The NIH system is also built to handle outside scans.

“Convenience and timing are actually really important,” says Dr. Butman. “If you must wait an extra couple weeks to get a scan, that’s something to keep in mind. A lot of practical issues supersede in many cases.”

If you’re following a tumor over time to look for subtle changes, it’s generally a good idea to have your scans done on the same scanner every time. "There can be slight difference among scanners that may make it more difficult to reliably detect subtle changes,” says Dr. Butman.

“Imagine you have a scale you’re weighing yourself on and it’s off a couple pounds, and you’re trying to decide whether you’re gaining weight,” he explains. If you use the same scale every time, you can still detect changes reliably. But, if you use a different scale, you’ll no longer be able to tell for sure how or if your weight is changing.

MRI images taken on different scanners may have slight variations based on settings, techniques, and other factors. If you’re following a small glioma, for instance, it’s best to have repeat scans done on the same scanner. However, if that means waiting an extra week and it delays therapy, it may be better to go ahead on a different scanner. “A scan can always be repeated elsewhere, if needed,” says Dr. Butman.

What to Expect

Dr. Butman says that imaging frequency varies depending on the diagnosis, biology of the disease, therapy needed, and the individual. Benign tumors may be scanned once a year. More aggressive tumors may be scanned every one to three months. If a patient is in the hospital, scans could be every day.

The amount of time in the scanner per session can also vary. If you’re visiting NIH for imaging, you might expect longer scan sessions to get more imaging done at once. Imaging to diagnose a tumor can also take longer. “When doing diagnostics, we need to cover all our bases,” Dr. Butman says. Imaging a tumor that’s already been diagnosed can be completed faster, because the imaging is more focused.

Neuroradiologists can now image the total spine—including the cervical, thoracic, and lumbar spine—in a little over an hour. For brain tumors, it’s similar. If both are needed, NIH radiologists may bring you in for two sessions so that you’re not in the scanner for too long at one time. “The pace and nature of imaging is tailored to the biology of the disease,” Dr. Butman says. Ask your doctors about your specific imaging plan, so you know what you can expect and prepare for.