Orthopedics & Sports Medicine

MRI: The Magic Behind the Machine

What is MRI and what is it used for?

Magnetic resonance imaging (MRI) is an imaging technique which uses a strong magnetic field and radio waves to create detailed, computer-generated pictures of your body’s organs and tissues. MRI has a wide range of scientific and medical applications, and is commonly used by physicians to diagnose disease or injury to a specific part of the body.

What is the difference between MRI and X-ray?

X-rays are typically used to examine skeletal structure and are helpful in detecting conditions such as fractures, bone spurs (osteophytes), and joint degeneration associated with osteoarthritis. X-rays do not provide pictures of soft tissue, however, and are less useful when attempting to identify damage to muscles, tendons, and ligaments. In these instances, MRI is used instead and allows for visualization of soft tissue injury or disease.

How does MRI work?

As humans, our bodies are primarily composed of water molecules. Each molecule contains one oxygen atom and two hydrogen atoms. In their normal state, these hydrogen atoms are randomly oriented in space. Because each hydrogen atom carries a positive charge, they can be re-oriented using a magnetic field. MRI technology takes advantage of this fact; each MRI scanner contains two powerful magnets which reorient your body’s hydrogen atoms by using magnetic pulses. The time it takes each hydrogen atom to return to its normal randomized state differs between body tissues of different densities. This is called relaxation time. These differences in relaxation time can be detected by the MRI scanner and used to distinguish tissues such as bone from tissues such as muscle or fat.

Is MRI safe?

MRI is considered a safe imaging technique. Unlike X-rays, MRI does not use ionizing radiation and is therefore not associated with an increased risk of cancer development. However, because MRI utilizes strong magnetic fields, you should inform your physician if you have any metal-based devices before having an MRI performed, as these devices may interfere with the test. 

*Post written by Pre-Medical Intern Jason Strawbridge