What is diagnostic imaging testing and when is it needed?
When dealing with pain of any sort, physical therapists and medical doctors have a number of tools at their disposal to help determine the cause and what needs to be done to address it. A thorough physical examination that involves a variety of objective and subjective assessments of strength, flexibility, balance, and other variables is always the first and most important step of reaching an accurate diagnosis. But in some cases, additional testing may also be performed.
If your doctor is still uncertain of what is causing your pain or if a severe injury was sustained, she may recommend having a diagnostic imaging test to obtain more information. These non–invasive techniques let the doctor see inside your body to get a clearer picture of your bones, muscles, tendons, and ligaments. This can help to determine if any of these structures look damaged and are possibly contributing to your pain. Diagnostic imaging tests include x–rays, computed tomography (CT) scans, and magnetic resonance imaging (MRI) scans, which all use slightly different methods to produce images of the internal structures of the body.
- The most commonly used diagnostic test; readily available in many doctor’s offices
- Sends a type of electromagnetic radiation called X–rays through the body
- Bones and other dense matter appear white or light because they absorb the radiation, while less dense soft tissues (like ligaments and tendons) and bone fractures look darker because they let radiation pass–through
- X–rays do not show as much detail as more sophisticated tests but are often used as a starting point
- You are exposed to radiation which can, in some cases, cause harmful effects to cells of the body
- CT scan
- Combines X–rays with computer technology to produce a more detailed image that includes the size, shape, and position of structures deep in the body
- During the test, an X–ray tube will rotate slowly around you and take several pictures from all directions, which are displayed on a computer screen
- May be needed for problems with small, bony structures or severe trauma
- You are exposed to a much higher dose of radiation than with an x–ray, which in some cases, can cause harmful effects to cells of the body
- Costs more and takes more time than regular X–rays
- Uses magnetic fields and computerized technology instead of radiation to take high–resolution pictures of bones and soft tissue
- Involves lying on a table that slides into the MRI scanner. MRIs employ powerful magnets which produce a strong magnetic field that forces protons in the body to align with that field. When a radiofrequency current is then pulsed through the patient, the protons are stimulated, and spin out of equilibrium, straining against the pull of the magnetic field; a computer records how these tissues respond to these radio pulses and then translates the data into a detailed picture
- May be used in helping to diagnose torn ligaments and cartilage, torn rotator cuffs, herniated disks, osteonecrosis, bone tumors, and other problems
- Ultrasound: is a radiation–free technique that uses high–frequency sound waves that echo off body structures to diagnose a variety of conditions
- Bone scan: shows bone activity throughout the body by injecting a small amount of radioactive material into a vein, which is absorbed by areas forming new bone (like fractures and bone tumors) and can be identified by a scan of the body several hours later
Each of these techniques can serve a unique and important role in the diagnosis of many conditions, but there are only certain situations in which they should be used. In our next newsletter, we’ll look into why diagnostic imaging tests are being overused and the downsides of this ongoing trend.