There's a lot you can do in 30 minutes. Watch your favourite TV show. Cook a nice meal. But let's be honest: lying in a noisy, narrow tube at the behest of your doctor is probably not high on the list. However, the half an hour (give or take) that an MRI scan usually takes is really important for both diagnosing and monitoring MS, providing information that helps doctors monitor disease activity and track how the condition develops.
If you've been diagnosed with MS, you've likely had at least one MRI scan already. MRI stands for "magnetic resonance imaging," and the technique was first developed way back in the 1930s. It wasn't until the 1980s, however, that it started being used in hospitals. Today it's a key tool for clinicians, particularly when it comes to diseases like MS that affect the central nervous system. The structural details of the brain and spinal cord are seen much more clearly with MRI than with X-rays and computed tomography (CT) scans and, unlike X-rays and CT, MRI doesn't involve radiation.
MRI scanners are pretty complex bits of kit, but here's the big picture...
How MRI works
Scanners use a strong magnet, radio waves, and a computer to produce detailed images of soft tissues (like the brain). They do this by showing the amount of water in the tissue. Damaged areas of the brain (lesions) show up because they have higher water content than healthy brain tissue.
Types of MRI scans
Two main types of scans are frequently used in MS - you may have heard your doctor or radiologist talking about T1 and T2. In T1-weighted images, white matter in the brain shows up as darker than grey matter, whereas in T2-weighted images, it is brighter. In T1 scans, a contrast agent called gadolinium (abbreviated to Gd or gad) is injected into the body beforehand to help make the images clearer.
The two types of scans can show different elements of disease activity in the brain. A Gd-enhanced T1-weighted MRI scan will highlight areas of acute inflammation. Hypointense T1-weighted MRI scans will show "black holes," which are considered to be areas of permanent damage. T2-weighted images are used to assess the total amount of damage, or lesion load. You might also hear this referred to as "disease burden."
Diagnosing MS with MRI
The physical signs of MS are really only part of the story. MS often impacts the brain in ways that don't show externally, particularly early on in the disease. So to confirm a diagnosis of MS, neurologists use MRI scans to look beneath the surface. In fact, detecting early changes with MRI has transformed the way MS is managed by neurologists, with the emphasis shifting from managing physical symptoms to preventing damage in the brain in the first place.
Monitoring changes with MRI
MRI is also a really important part of your neurologist's toolkit for monitoring the progression of MS as it can provide information about disease activity. MRIs provide valuable information and it is recommended that a follow-up MRI is done 6 - 12 months after starting a new treatment to monitor condition activity. Monitoring the level of MS activity inside your brain can reveal how quickly the disease is progressing, and how well a particular treatment strategy is working.
What's next in MRI technology?
Technology never stands still and as with so much else, MRI technology is improving all the time. For example, recent research suggests that a technique called whole-body diffusion-weighted MRI scanning can track the spread of blood cancers in the body which were previously extremely difficult to monitor.
In neurology, scientists have been carrying out research into how our brains change over time by comparing scans of healthy people of all ages - work which may lead to a better understanding of the changes in the brain seen in diseases like MS.
Increasingly, new MRI techniques are being used for research purposes. While conventional MRI highlights the presence of lesions, emerging techniques (which can sound like they've come straight from a sci-fi film) offer scientists an increasingly clear picture of what's actually going on in damaged tissue, as well as elsewhere in the brain.
A technique called magnetization transfer ratio, for example, zeroes in on damaged areas and allows researchers to calculate the extent of tissue damage in specific lesions, while magnetic resonance spectroscopy (MRS) measures important chemical changes that take place as brain cells are damaged. Another cutting-edge technique, diffusion tensor imaging, zooms in on individual nerve fibres to reveal brain changes on a cellular level.
These new-fangled machines are of course incredibly expensive to develop and run, which is why they're confined to the laboratory for now. But it's only a matter of time before one of them reaches a hospital near you. In the meantime, it's encouraging to know these advances in MRI are helping researchers to better understand MS.
Brings a whole new meaning to the question "what's in your head," doesn't it?
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