Do I Need a Scan? And, What’s the Difference Between Them
Most of us have had a scan at some point of our lives. There are lots of different types of scans and they all have certain strengths and weaknesses. The type of scan relevant for you will depend on a number of factors – the type of tissue we want further information about being the big factor.
First, let’s take a look at the different types of scans we often refer to as physiotherapists, as well as the pro’s and cons of the different imaging.
An x-ray is a quick beam of radiation that produces a still film or picture of the given area. As varying body tissues absorb x-rays differently, we get a ‘black and white’ picture which highlights bones and hard structures (see below).
Pro’s: Relatively cheap, accurate at identifying most fractures, less radiation than other techniques, only takes minutes
Cons: Doesn’t show soft tissue accurately, doesn’t reliably show small fractures, even though there is less exposure than other techniques you are still exposed to radiation
A computer tomography scan, or CT scan, is a combination of lots of X-ray films taken in a number of directions. A dye is used to highlight different structures, and the films are automatically ‘joined’ together to make a 3D image of the area including bone, organs, brain and even blood vessels.
Pro’s: Quick (10-20 mins), fast results, shows smaller fractures, more detailed than x-ray – picks up soft tissue, mostly non-invasive
Con’s: Costly, large amount of radiation compared with x-ray, possible allergic reaction to dye
Magnetic Resonance Imaging, or MRI, is similar to a CT scan in that there are lots of thin cross-sectional strips of images that are compiled together to get an accurate picture of the area that has been scanned. The scanner is a small tube that you lie down in which uses really strong magnets and radio waves to develop a very detailed image of the area. Similar to a CT scan, it will show bone, brain, organs and soft tissue.
Pro’s: Detailed images, no radiation so can be used by those who are pregnant, non-invasive and painless
Con’s: Costly, tube can exacerbate claustrophobia, can take 15-90 mins, very noisy during scan, unable to have scan if you have metal in your body (e.g. pacemaker – due to strong magnets)
Ultrasound uses high frequency sound waves to get real time images of soft tissue. Commonly used to image the unborn baby when pregnant, we can use this type of imaging in physiotherapy to assess muscles and tendons.
Pro’s: Can be as short as 10 min, minimal side effects, real time images
Con’s: Few – possible allergic reaction to latex
So these are the more common scans you may be referred for by your physio or GP. As you can see, there are risks involved with every scan and as such we want to make sure that it is necessary for you to be exposed to these risks before recommending that you have a scan. This is always judged on a case by case basis depending on your history and symptoms.
So do I need a scan??
Most often, the answer is no. Very few people who come in to see us at the BeFit clinic will be sent off for a scan at all, let alone in the first session. Suspected fractures and more serious injuries will be sent straight away, however if there is nothing sinister suspected then we usually don’t need to scan at all.
Although scans can definitely play a role in our clinical picture, it’s only part of the assessment and it’s important not to be too reliant on the scan results alone. Many scans will show ‘radiographic findings’ which are normal age related changes and may not necessarily be relevant to the issue at hand. Below is an infographic showing the percentage of ‘radiographic findings or abnormalities’ that are seen in people who are asymptomatic, or in other words have no pain at all.
As you can see, a large amount of people will have imaging findings despite not having any pain. The chance of asymptomatic findings like these also increase with age – so as we talked about before, the scan is only part of the picture and needs to be combined with a thorough physical examination in order to aid in diagnosis.
But what’s the harm in a scan?
Potential harm can come from the aforementioned risks, including high costs and exposure to radiation. Having scans also leaves us susceptible to focusing on those ‘abnormal findings’ that may not be the cause of any pain, which can have serious negative effects long term. A good example of this is if someone came into the clinic with back pain as a result of a strained muscle – then was quickly referred for an MRI – they may come back with results that show disc bulging and disc degeneration that are normal for someone their age and are not causing their symptoms. The effect of being told you have a bulging disc can be extremely negative. That person may then stop lifting things, stop going to the gym, playing sport etc. which will decondition the body and can also have a significant effect on the mental health of the person.
As you can see, it’s not as easy as having a scan and it’ll tell us what’s wrong. There are important pro’s and con’s with any imaging and they are always considered when deciding whether it is appropriate for you to have a scan.