Advanced Imaging

Last time we talked about x-rays, today we’ll look at two other common types of imaging, referred to as “advanced” imaging, that is CT and MRI. Both of these give us nice views from the side at various tissue depths as well as cross-sectional views. This allows us to look at your insides, slice by slice, both horizontally and vertically which means we get a very clear picture of the region being investigated. In some cases, doctors may request that the image be performed with contrast dye. This special dye can enhance some structures and is either injected into the joint being assessed or given by IV just prior the scan. Most of the time the scans are done without the dye and both of these advanced imaging technologies are non invasive and give us great detail. 

CT scans, short for Computed Tomography scans, use radiation just like x-rays, but rather than taking a couple single shots the scan is comprised of a series of many many x-rays together, from different angles creating a cross-sectional image. When put together, these generate a much clearer, more detailed picture of your insides than plain x-ray does. CT is the gold standard imaging technique for investigating changes to the bone as it gives the most detail on bony structures (remember plain single x-rays needed at least 30% bone loss before being detected, this is not so for a CT scan!) It also gives a good amount of detail on soft tissue structures so can also be used to visualize organs, vessels, and spinal discs. We can also sometimes use special technology with CT images to generate 360 degree views of a given body region - like what may be required for some surgeries. CT scans are often used to check for any metastasis (spread of cancer) in the body or to keep tabs on changes in tumour size or number as part of the monitoring process. As with all medical procedures and tests, there are a few down sides to CT. The biggest draw back is that there is a fairly large radiation dose with a CT, it can be thought of as dozens or perhaps hundreds of x-rays. That being said, medical radiology has advanced and is considered to be safer now than in the past. CT scans are fairly quick to perform and don’t require the patient to be placed into a “tube” like an MRI scan does. Finally, though CT can show us a lot more detail on the soft tissues and vessels, there are some small details that aren’t quite as well visualized, leaving the gold standard for soft tissue imaging to be MRI. 

MRI stands for Magnetic Resonance Imaging. This involves sliding the patient into a large machine that looks like a tube. As would be suspected by its name, MRI using strong magnets (and radio waves) to generate the picture of your insides. A big plus here is that there is no radiation exposure to the patient in MRI. Because of the strong magnets we have to be careful that there is no chance that the patient may have shards of metal in the body as you can imagine that might create a problem once the magnets are turned on! This is why you have to fill out a more detailed form prior to going in the machine (usually metals used for surgery like pins and plates are ok, but always double check when booking). People who are claustrophobic may also have trouble in here as it can often take10-30 minutes to complete the scan. You’ll be in the tube the whole time and won’t be able to move during the active cycles of imaging, however there is a speaker in the there so the tech can give you instructions and you’re given a button to push in case you need to stop. The machine is also quite loud and requires patients to wear hearing protection while having the scan done. Perhaps the biggest draw-back to getting an MRI is the wait time. Because each scan takes awhile, and the machines take up a lot of space (and are very expensive), access to them is limited. That being said, the soft tissue detail of MRI is second to none and can provide very good images of the soft tissue structures and nerves. Small tears that could not be seen with other types of imaging are often captured by MRI.  

One potential draw back to both machines that should be mentioned is that the patient is lying still when the scan is performed. This is needed to get a clear image, but we also must remember that we humans are moving, dynamic beings! Sometimes what we “look like” on a still image leaves out part of the picture - primarily, the biomechanics! Pictures show us anatomical structures only - nothing about how they move and how each structure is functioning. For example, in the spine world, that small disc bulge that we see on an image generated while you are lying down might actually be more than a small bulge when you are loading your spine as you would be when standing and bending forward. So in some cases, although they provide great detailed images, we must take the image with a little grain of salt on the side - especially when assessing musculoskeletal and spinal concerns or when the patient seems to be having more symptoms than what their pictures might imply. 

Depending on what we’re looking for, what kinds of imaging you have already had done and if the results are likely to change your treatment plan, your doctor will advise on which type of imaging (if any) is best for your individual circumstances. At the end of the day, while these advanced imaging techniques can be an invaluable tool, they must be used appropriately and not in isolation - in essence, they allow us to form just one part of your overall clinical picture!