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What is Diagnostic Imaging?

September 6, 2023
Learn the difference between the most common types of diagnostic imaging and how they are interpreted in your overall treatment plan.
Healthcare Provider examining diagnostic image

By Susie Reiner, PhD, CSCS, EP-C

When you seek treatment for an injury, your healthcare provider may request standard diagnostic imaging to understand your body’s underlying structure and determine what might be causing you pain and discomfort. Diagnostic imaging includes X-ray, magnetic resonance imaging (MRI), computed tomography (CT) scan, or ultrasound. 

An invaluable tool in the diagnosis process, targeted treatment planning, and progress monitoring—each technique is different in its capabilities and information provided. Each intervention may carry inherent risk, or added cost. Here, you’ll learn about diagnostic imaging techniques and how they are interpreted in your overall treatment plan.

Different Imaging Techniques:


X-ray imaging is a widely available, affordable technique in which the machine sends brief electromagnetic waves (low levels of radiation) through your body, creating a film of the internal structure. An X-ray is used to assess bone tissue health—denser tissue will absorb the light and appear bright on the film, and softer tissue, like muscle and skin, will appear darker. However, it only gives flat images, and you may require further imaging to pinpoint a problem. An X-ray would show smooth bone surfaces, joint alignment, and tissue degeneration, like arthritis. Getting an X-ray done is a quick and pain-free process. You are exposed to a small amount of radiation, but you may be given protective equipment to mitigate this risk. 

X-ray image of foot on tablet device
X-Ray: Widely accessible technique for bone tissue and joint imaging

Magnetic Resonance Imaging (MRI):

MRI produces high-quality images of bone and soft tissue by observing the magnetic pull of the atoms in your body. When you lie still in an MRI machine, it creates a magnetic field around you and pulses radio waves to measure the rate at which your tissues resonate or vibrate. The data creates precise high-resolution images of underlying tissues. It can help diagnose soft tissue injuries such as ACL tears, rotator cuff tears, herniated discs, and low back injuries. MRI is a noninvasive imaging technique that does not emit radiation found in X-ray and CT imaging. However, the strong magnetic pull may be dangerous for those with any medical implants with metal in them. It can also be uncomfortable for those sensitive to loud noises or claustrophobia, and can last up to 60 minutes. 

healthcare provider looking at MRI on computer screen
MRI: Radiation-free high-resolution images of soft tissue

Computer Tomography (CT) Scan:

A CT scan is primarily used to gain detailed information on bones and joints, with some applications in soft tissue when MRI is not possible. While you lie still, a cylindrical CT scanner rotates around you, taking X-ray images from different angles. The computer then combines the X-rays to produce a multi-dimensional snapshot of the area. A healthy scan would show smooth bone tissue with no signs of fracture or deformity, joint alignment and a smooth articular surface (the cartilage that covers the ends of your bones and articulates with other bones at a joint), and no sign of inflammation or edema in your soft tissues. A CT scan is more costly and time-intensive than a regular X-ray but provides a more detailed view of the area of interest. It is not widely available in smaller facilities, and as with a standard X-ray, you are exposed to small amounts of radiation during a CT scan. 

CT-scan: A two-dimensional X-ray for deeper look at bone tissue and joints.


Ultrasound imaging is a non-invasive technique that uses high-frequency sound waves through the ultrasound probe. The probe emits the waves to create images of the underlying structures on the screen. You’ll see real-time images of muscles, tendons, ligaments, and nerves. Your healthcare provider can also compare damaged tissue to healthy tissues on the uninjured side for a more accurate diagnosis, and measure progress from your program by observing muscle thickness over time. Ultrasound technology is significantly less expensive and more portable than other imaging modalities, meaning there’s a better chance you don’t need a referral for another office visit for imaging

Ultrasound: Non-invasive technique to see underlying structures in real-time

Interpretation of Imaging

Your healthcare professional can provide individualized and timely care with precise imaging in the case of an emergency, or to confirm a clear diagnosis. However, while the hope is that diagnostic imaging can find the cause of your pain and discomfort, imaging is not always warranted, and may be overused

One review found that when imaging asymptomatic patients, a bulging disc or degenerative disc disease was apparent in up to 97 percent of patients, without any pain or movement dysfunction. Imaging was once routine in a treatment plan for patients with non-specific low back pain, but new research is showing only 5 to 10 percent of all low back pain is due to a specific cause you might see on a diagnostic image. 

Seeing natural age-related changes on a diagnostic image or waiting to hear back about results from a scan can cause you undue stress as well. Healthcare professionals go through rigorous training to understand when to strategically refer patients for further imaging. Thorough assessments of pain, function, mobility, and strength provide ample information to inform most diagnoses. 

The bottom line: Diagnostic imaging, alongside functional assessments and pain indexes, is a powerful tool in providing care for an injury. Each technique differs in its level of detail, the tissue it targets, time, expense, and level of risk. Your healthcare provider will consider your specific condition, health history, and other risk factors before recommending imaging ensuring you follow a targeted treatment plan to help you get back on your feet.