Understanding X-rays, vs CT Scans, vs MRIs, vs Ultrasounds
Medical imaging can be very useful in diagnosing and treating musculoskeletal injuries but what are they really looking at.
Plain film radiograph (X-RAY)
X-rays look at bony anatomy. A beam of radiation passes through your tissues and gives off different shades of grey on the film.
The shading all depends on the density of the tissues. Bones are dense and are white on an X-ray film whereas subcutaneous tissue (fat) and other structures like skin, and muscle are grey to black in colour on an X-ray film.
Computer tomography (CT scan)
CT scans are many slices of X-rays that are enhanced by a computer to make clearer. The 3D image can be taken in many different planes, meaning we can look at the tissues from all different sides and angles.
Like an X-ray, a CT scan primarily looks at bony anatomy and gives us a better look at the bony structures however CT scans can be used to look at other structures like muscles, tendons and an intervertebral disc (but not as well as an MRI).
Magnetic Resonance Imaging (MRI)
A MRI uses magnetic fields to generate a image instead of radiation (remember X-ray and CT Scans uses radiation to make an image).
MRIs are a great way to look at structures such as muscles, tendon and ligaments. Saying that it is possible also view bony anatomy on an MRI.
This type of investigation uses high frequency sound waves to make an image. Mostly looking at muscles, tendons and ligaments. It does not provide as much detail as an MRI however it’s quicker/cheaper and can give enough detail to aid in proper diagnosis and treat.
Hopefully now when your doctor refers you for any imaging you will now understand the differences between the four main types of investigations and specifically what structures they are looking at in order to aid in diagnosis and treatment of a musculoskeletal injury.
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Written by Christina Brownlowis
Masters of Physiotherapy