by Erin Looney, DPT
Do I need an MRI? This is one of the most common questions I am asked on a daily basis. X-rays and MRIs are probably 2 of the most familiar to the public and most common diagnostic tests used in orthopedics. While the intention of this blog is not to discuss if and when they should be ordered, it is my hope to clarify what some of the most common tests are used for and what they may reveal.
These are the most common diagnostic imaging tests out there – in part, because they are by far the “cheapest” option. A doctor will use an x-ray to look for/at some of the following:
- Presence of a fracture
- Osteonecrosis (bone cell death)
- Joint dislocation
- Joint space
- Rule out tumors
These tests are like a snapshot taken in a certain position. Several x-rays from different angles are common. The doctor may or may not have you drink or be injected with contrast dye. The test will likely take 10 minutes to complete.
This test is a series of X-ray images taken after a contrast dye has been injected. Fluoroscopy or ultrasound is used to help guide the needle containing the contrast dye to the correct place in the joint. Several x-rays are then taken from different angles. This is used to help diagnose the cause of unexplained joint pain. The patient may be asked to move the joint in various positions while the images are being taken
CT Scan (computed tomography):
This can be equated to a “high tech” x-ray. It combines x-rays with the use of a computer to produce more detailed cross-sectional (like “slices of bread”) images of your body. It is often used to look for/at some of the following:
- Suspected tumor
- Fracture that isn’t showing up well on plain X-ray
- Following trauma to look at internal organs/structures
This produces a series of “slices” that are more detailed than a plain X-ray. Some technology now allows for 3D imaging. Contrast dye may be used in conjunction to improve the visibility of suspected structures. You will be asked to lie still on a table that slides into a tube. Those with claustrophobia often have difficulty with this test.
This is not the same ultrasound that we use in PT. This is a diagnostic ultrasound that produces an image. A gel (yes, sometimes cold) will be placed on your skin closest to the area. An ultrasound wand that moves against the skin over the area to be tested will send high-frequency sound waves through your body. These waves echo off various structures in the body and produce an image. The test is usually 20-30 minutes and does not produce discomfort. It is mostly used to look at:
- The heart
- Abdomen (including pregnancy)
- Detect the presence of blood clots (DVTs)
- Swelling and cysts
MRI (magnetic resonance image):
This test uses strong magnets and magnetic fields, coupled with the use of computers to take high resolution pictures. Similar to the CT Scan, it also takes cross-sectional (slice) images of your body. People that are claustrophobic often have difficulty with this test, as you must lie still on a table that is slid into a tube. Some MRI centers now have an “open MRI scanner”, which may be better tolerated for those with severe claustrophobia. This test will be used to look at the following:
- Herniated discs
- Other soft tissue
This test can last anywhere from 30 to 90 minutes and can be noisy, however it is not painful. Patients with implanted metal or metal that cannot be removed from the body cannot undergo this form of testing.
This is used to look at the electrical activity in your muscles and the functioning of nerves if diminished or absent neural conductivity is suspected. Thin needles are placed in specific muscles to measure the electrical activity. With the needle in the muscle, the doctor will ask you to both relax and contract the muscle. The electrical activity between the resting and active state will be measured as compared to look at its overall function. This test is generally uncomfortable.
When considering if/what test should be ordered, your doctor will generally consider whether the potential information gained from this test will change or dictate the course of treatment. X-rays are usually ordered regularly, since they are fairly inexpensive when compared to other forms of testing. In situations that are not emergent, doctors will often have a patient try more “conservative” options before ordering more expensive testing. These conservative options may include some of the following:
- Physical therapy
- Ice or heatNSAIDs (ibuprofen, advil, muscle relaxors)
Testing that is purely informational or “good to know” is often not covered by third party payers (insurance) and therefore is not usually ordered until conservative options are exhausted.