Mini MRI device could help diagnose knee injuries more quickly and accurately

Researchers at Imperial College London have developed a prototype mini MRI scanner that fits around a patient's leg.

The team say the device - which uses so-called 'magic angle' effect - could potentially help diagnose knee injuries more quickly, and more accurately.


The scientists say the device (which looks like a large metal ring through which a patient places their leg) could help diagnose conditions such as anterior cruciate ligament injuries - particularly common among footballers.


The research was funded by the National Institute forHealth Research.

Currently, key components of the knee joints such as ligaments and tendons are difficult to see in detail in the MRI scans, explains Dr Karyn Chappell, a researcher and radiographer from Imperial's MSK Lab: "Knee injuries affect millions of people - and MRI scans are crucial to diagnosing the problem, leading to quick and effective treatment. However we currently face two problems: connective tissue in the knee is unclear on MRI scans, and people are waiting a long time for a scan."

Dr Chappell added:



Following knee injury a doctor may refer a patient for a MRI scan to help establish which part of the joint is injured. MRI scans use a combination of radio waves and strong magnets to 'flip' water molecules in the body. The water molecules send out a signal, which creates an image.


"These structures are normally black on an MRI scan - they simply don't produce much signal that can be detected by the machine to create the image. This is because they are made mostly of the protein collagen, arranged as fibers. The collagen fibers hold water molecules in a tight configuration, and it is in fact water that is detected by the MRI. If you do see a signal it suggests there is more fluid in the area - which suggests damage, but it is very difficult for medical staff to conclusively say if there is injury."

To overcome this problem, Dr Chappell harnessed the power of a phenomenon called the 'magic angle': "The brightness of these tissues such as tendons and ligaments in MRI images strongly depends on the angle between the collagen fibers and the magnetic field of the scanner. If this angle is 55 degrees the image can be very bright, but for other angles it is usually very dark."



"Previously the magic angle phenomenon was thought of as a problem, as it could mean medical staff mistakenly thinking the knee is injured. However, I realized that if we took a number of scans around the knee, we could use the signal produced by the magic angle effect to build a clear picture of the knee structures," explained Dr Chappell.



In a new study, published in the journal Magnetic Resonance in Medicine, the multi-disciplinary team scanned the knee joints of six goats and ten dogs in a conventional MRI scanner.



The team say now they know magic angle scanning can be used to visualise the knee, combining this with the new prototype mini scanner could enable knees to be accurately scanned with this technology - and hope to progress to human trials of the 'mini' scanner within a year.

Dr Chappell explained: "Although this is an early-stage proof-of-concept study, it shows the technology could potentially be used to accurately detect knee injury. We now hope to enter human trials - and explore if this technology could be used for other joints such as ankles, wrists and elbows."


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