Medical Imaging – How CT and MRI Procedures Affect the Body

by | May 14, 2021 | CT

Reading Time: 3 minutes

Technological advancements in medical imaging have made it possible for physicians and radiologists to take a good look at internal organ systems and diagnose serious health issues based on these images. Diagnostic images can help analyze simple arm fractures, brain tumors, and everything in between.

Every year, over 75 million CT scans and over 40 million MRI procedures are performed in health facilities across the US. As helpful as these diagnostic images are, these complex medical imaging procedures come with inherent risks.  


How CT scans affect the body

When you undergo a computed tomography (CT) scan, you lie on a table that takes you through a scanning ring. The CT scanner uses X-rays to take cross-sectional images of the area of interest, and the software combines all the data into a 3-dimensional image that your physician can use for diagnosis or health check.

Each CT scan exposes you to some amount of ionizing radiation that’s powerful enough to pass through your body. This mechanism creates clear images, but it can also increase your risk for cancer if you are exposed to high amounts.

Humans are exposed to small doses of radiation every day, mainly from the sun, at an average of 3 millisieverts (mSv) per year. In comparison, here are the average radiation doses for some of the most common CT scan procedures:

Head CT – 2 mSv

Spinal and pelvic CT – 6 mSv

Chest CT – 7 mSv

Colonoscopy CT – 10 mSv

Angiogram CT – 16 mSv

Decades of research have shown that even multiple CT scans don’t boost the risk for cancer in any way. The medical benefits of a CT scan still greatly outweigh the minuscule risk.


How MRI procedures affect the body

The magnetic resonance imaging (MRI) procedure is similar to a CT scan in that patients also lie on a table and go through a large scanning rig. MRI machines use very large magnets to blast the body with radio waves that make the protons in the body spin from their natural alignment. When the magnets are turned off, the photons travel back to equilibrium, and the MRI sensors detect the energy they release.

The resulting images are used to identify disorders in the bones, joints, ligaments, and tendons. Through these scans, physicians can evaluate and examine organs, soft tissues, and internal structures.

MRI machines emit no radiation, and the imaging procedure poses no threat to healthy individuals. The only concern is for patients with metal structures such as pacemakers, hearing aids, or metallic plates implanted in their bodies. The strong magnets of the MRI machine will pull on these devices and cause severe damage on the surrounding tissues and blood vessels.

MRI procedures can last anywhere between 30 to 60 minutes. In closed MRI systems, the patient has to lie very still in a very narrow tunnel. Throughout the procedure, the machine occasionally emits a loud noise. The combination of the enclosed space and noise can cause anxiety and claustrophobia in some patients.


Can you be scanned too many times?

Despite the radiation used in CT scan procedures, there is no upper limit to the number of scans any person can undergo within a year or their lifetime. Some conditions such as kidney stones or Crohn’s disease require multiple CT scans for management, but specialists have not set any limit for those patients.



Medical imaging procedures have made it possible for doctors to diagnose and manage complex diseases for millions of patients. These machines and procedures are incredibly valuable and will continue to bring many more benefits than risks in decades to come.

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