What scan is that
Imaging can assist with determining a clearer diagnosis, prognosis, intervention and assessment of your injury or dysfunction – but why would we suggest a particular scan?
When you visit our Physiotherapists our assessment primarily includes what you tell us about your injury or condition and the assessment of physical movements that stimulate your symptoms. From this we develop ideas of potential causes influencing your injury or condition.
In some cases during the course of management we may request you seek a scan to assess your internal structures to confirm or deny these theories.
The image is formed by exposing the target area to electromagnetic radiation called X-Rays. The X-Rays pass through the body and leave a shadow of bony tissue as they cannot pass through the dense structure of bone and is often used to look at the hard structures within the body. The denser materials tend to absorb the rays, causing them to appear white on the X-ray film. X-Ray is useful for diagnosing dislocation or fracture of bones, they are often used as a first step to rule out serious injury which may require surgical intervention.
X-rays are also used to help indicate how much space there is between joints, but will not clearly show the structures (cartilage, ligaments) of the joints. Hence, they can provide an idea of ‘wear-and-tear’, compression and arthritic changes, as well as fractures or deformities that may be present. X-rays can also be used in a number of other situations, such with as detecting bone cancer, lung infections or foreign objects.
Ultrasound is produced by introducing a sound wave to the structures immediately beneath the skin. The soundwave produces an image of the structures beneath the skin. This image assists in identifying breaks in normal tissues and or swelling in the affected area and works best for soft tissues such as ligaments and tendons. However it is not as accurate as other forms of images.
CT scans are a 3D representation of multiple X-Ray scans. The machine performs multiple X-Rays around the affected area in a circular fashion to produce a 3D image on a computer. The images are shown as cross sectional “slices” that show different tissues in different shades of grey. CT’s are useful at showing small fractures in bone tissue and changes in soft tissue consistency identifying damage to tissue. These images can look at bones, joints, blood vessels, nerves and soft tissues.
CT scan images provide more detailed insight than plain X-rays, but less detailed than MRI scans. CT is often used as an alternative to MRI as there is no magnetic field produced by the machine and its operation.
Magnetic Resonance Imaging uses a magnetic field, along with radio waves to create much more detailed images of the internal structures, tissues and organs of the body. An MRI machine can create 3-D images that are able to be viewed from many different angles resulting in better image quality and more accurate diagnosis than other forms of medical imaging.
Patients are required to lay still as they are introduced to a narrow tube containing the scanning equipment which highlights the water and fat molecules within the body. These molecules in different proportions represent separate tissues within the body. Damage and injury can be observed as disruptions to the consistency of these tissues.
Bone scans are used to help detect very specific problems and work by the patient being injected with a radioactive material into their bloodstream. This radioactive material moves with normal blood and increases in areas of bone repair and remodelling. Bone damage can be identified by the amount of repair that the body is conducting, but may also be identified by a lack of normal bone synthesis.
Take Home Points
It is important to understand that there may be contraindications, or reasons that prevent an individual from being able to safely receive a certain type of scan.
It is also necessary to realise that there are limitations to what scans can show. In certain situations, scans may not show any indication of a cause for pain or dysfunction –For example, scans will show tears in the muscle, but not muscular tightness or imbalances.
Just because something shows on your scan, it doesn’t mean that this is the cause of your pain. Studies have showed 25-50% of patients without low back pain had some form of hypointense disc signal, annular tears, high intensity zones, disc protrusions, endplate changes, zygapophyseal joint degeneration, asymmetry, and foraminal stenosis. Importantly they have also found that disc herniation and nerve root compromise were not consistently associated with lower back pain.