Pictures. Images.
A lot of patients ask me if I need an xray or MRI before I treat, and the honest answer is most of the time, no I don’t. I screen for red flags with every patient, and only if something is present that warrants an image, we go for a safe trail of conservative care first. If a red flag shows up later or the progression isn’t happening the way we want, then I typically will begin the process of imaging with an xray.
Why is this my approach? A clean film can be from a patient in awful debilitating pain, and a mess of an image can be for a patient that feels just mild soreness. And not only that, we do not want unnecessary exposure to radiation or to overburden the system with images that aren't necessarily needed.
Education on images and what they tell is is key.
On the note of education, let's talk about what kind of images your doctor might send you for, and what they are good for seeing!
Radiographs:
AKA, xrays, these are high energy radiation waves that penetrate most substances at varying degrees. In low doses, we can use these waves to see tissue and form a diagnosis. At higher does it is used to treat cancer with radiation therapy. For xrays, the patient is positioned specific ways to get pictures that are requested by the doctor, it can get pretty funny some of the positions we need to get into for these, but it's all about the beam hitting the tissue the right way!
Tissues absorb and block xrays at different levels, which gives us the classic multiple versions of grey image we know as an xray. Metal is white, bone is almost white, fat/muscle/fluids are shades of gray and air/gas appear as black.
Xrays are what I call the “gateway” image, as they are the easiest to access, however they don’t always show us what we are looking for. It is great for bony concerns most of the time, with a CT being more detailed, and can also show is things like Pneumonia and blocks in the GI tract.
Computed Tomography:
Commonly referred to as a CT scan. Xrays are also used for these images, but instead of the patient being positioned, they typically lay down and the scanners rotate around the patient. This gives us reading from many different angles, and these readings are sent to a computer that converts it into a 2D slice image. We can also get 3D images.
Sometimes you may need a contrast agent injected to aid in the imaging.
CT is highly detailed, and gives us more detail regarding location and density when compared with plain xrays. It provides enough detail that we can differentiate between organs, and it can commonly be used to the brain, head, neck, chest and abdomen.
Magnetic Resonance Imaging
MRI's use strong magnets and radio waves to give us incredibly detailed images. Like a CT, MRI imaging is done with the patient laying down, and moved into the scanner. Most of these are small, narrow doughnut like machines, but open MRI's do exist as well. How does a magnet gives us pictures? The protons in tissue are usually just randomly floating around, but when a magnet shows up, they line up along the magnetic field. Then we use the radio waves to knock them out of line, energy gets released, and the signal gets read by a computer and converted to imagines. Cool, right? Contrast is sometimes used for MRI's similar to CT scans.
When we are looking for detailed soft tissue (muscles, nerves, organs), MRI is the preferred method. It doesn't use xrays, and gives us great detail.
Positron Emission Tomography (PET)
For these scans, radionuclide (a radioactive form of an element) is used. A substance that we metabolize like glucose or oxygen gets tagged by this element, and together they form what we call a tracer. This tracer will collect in specific tissues, that the scanner then reads. This gives us information about tissue function. We don't see anatomy detail with this type of scan.
For a PET scan, the radionuclide is injected, then the patient lays on a table while the PET scanner does its thing.
We use PET scans to look at heart and brain function as well as to detect cancers.
Ultrasound
After Xrays, this is the most common and easily accessed type if imaging. It uses high frequency sound waves to give us images of organs and sift tissues. These waves bounce off of body structs and get reflected back to the wand (transducer), which then converts it to an electrical signal and gives us a picture.
Most people think of pregnancy when it comes to ultrasound, but it can be used in a musculoskeletal context, looking at muscles, tendons and ligaments. Sometimes we can detect tears, and even inflammation on ultrasounds. It can also help with any growths that need to be assessed.
Those are some of the most common types of images we see the in the MSK world. There are definitely more, and subtypes of the above as well, but this should help give a general idea about what kind of testing is best for certain situations, and will help you advocate for yourself with your healthcare practitioner!