A question commonly asked at Fairfield Physiotherapy is, “What’s the difference between an MRI and an X-Ray or CT (Computerised Tomography)?”
Physiotherapists are part of the primary healthcare sector working in conjunction with GPs, so the decision about which scan is optimal is typically taken in communication with your GP. Sometimes the rebate you receive for your scan is higher if the referral is from your GP, so your physio can communicate with your GP to ensure you get the best care possible.
There are several different scans you could get for a musculoskeletal injury, and each will give different information. Deciding which scan is most suited to your particular injury will take these different factors into account.
What do they stand for?
MRI stands for Magnetic Resonance Imaging and works using magnetic fields to see a variety of tissues inside the body, including bone and soft tissue. Given that the magnetic field will pass through the body (it will not harm you), it can also see the deeper areas.
X-Ray is the scan with which most people will be familiar. It is primarily used to diagnose issues with bones as that is what x-rays image; however, it can also indicate some other issues. For example, the spaces between the vertebrae appear blank, but we know it is filled with a disc. If this space is reduced, it could indicate an issue with the disc.
CT (Computerised Tomography) is a series of X-Rays used to create a more 3D image of the body part being scanned. Getting more angles and compiling the images to create a clearer picture can help identify the problem.
Ultrasound scans are used to image soft tissues and are often superficial (closer to the skin). An ultrasound typically views 1-4 cm through the skin and can lose definition in deeper structures as it cannot see through bone or other tissue.
Why might I need a scan?
While many diagnoses can be made clinically (with a physical assessment) and do not always need a scan, sometimes it will be recommended by your physiotherapist or doctor. Scanning simply to prove a diagnosis is correct is typically not recommended. However, a scan is often useful if the physical assessment is unclear or the management/treatment could change depending on the result. Scans can help give a conclusive diagnosis and more accurate expectations on healing timeframes and direct whether referral to a specialist is warranted.
How do I know which one I need?
All of the details about which scan type is suitable for your injury will be explained by your physio or GP so you obtain the best recommendation for your circumstances.
If there is concern about a fracture or bone injury, including bone spurring or arthritis, then an X-ray will typically be used. X-rays may also be used as a screening tool to see your spine and to see if the vertebrae spacing is uniform or if the curvatures are normal.
It will be used if the structure in question is soft tissue and in a joint well suited to ultrasound (shoulder, ankle, wrist, lateral hip). This scan will show tears or inflammation in the soft tissues, such as tendons and ligaments, which helps confirm a diagnosis, give indications of expected healing time frames and direct the best treatment.
A CT is usually ordered when there are possibly more complex bone issues around joints or in the spine. While the scan is essentially a number of X-rays from different angles because it gives a 3D representation of the area, CT helps diagnose finer details. It will still be used primarily for bone issues, but it can be helpful to see some simple detail of discs and other tissues.
Finally, the MRI is often considered the “gold standard” of scans as it can see everything in terms of different tissue types and deeper tissues, along with superficial tissues. An MRI is used for deeper joint injuries, such as in the knee, to check for meniscus, ACL tears, or disc prolapses in the spine. It is not always necessary to get an MRI as a number of diagnoses can be made accurately with other types of scans, but sometimes an MRI can be ordered to see more detail and confirm a diagnosis.
This blog covers the basics of imaging scans and their purpose within the diagnosis and treatment of Musculoskeletal injuries. If you have an injury and are wondering whether a scan is necessary or will be useful in your case, feel free to discuss your options with one of our physiotherapists at Fairfield Physiotherapy & Sports Injuries Centre on 94897744.