What’s the Difference Between a CT Scan and an MRI?

What’s the Difference Between a CT Scan and an MRI?

Although CT and MRI scans examine various areas of the body to diagnose injuries and internal pain, the technology behind each type of scan is different. Learn more about these key differences and how they impact patient care.

While both CT and MRI scans capture detailed images of the inside of the body, the technology used — and the details captured, are different. We visited the Department of Radiology at Keck Medicine of USC and spoke with Meng Law, MD, professor of radiology, neurology, neurological surgery, biomedical engineering and the director of neuroradiology, to learn more.

CT Scan

Computerized Axial Tomography (CT or CAT) X-rays bones, soft tissues and blood vessels in cross sections from different angles.

Your doctor might order a CT scan to evaluate:

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  • Brain and spine diseases
  • Trauma
  • Evaluation of the chest
  • Fractures or broken bones
  • Changes in soft tissue that can signal the spread of a disease
  • Fever or pain of unknown origin
  • Function of the heart, kidneys or liver

MRI Scan

Magnetic Resonance Imaging (MRI) uses magnets to capture detailed images of soft tissue in the body.

MRIs help diagnose or monitor treatment for:

  • Tumors and cysts
  • Disease of the liver, bile ducts, gallbladder and pancreas
  • Certain types of heart problems
  • Pelvic pain in women such as endometriosis
  • Diseases of the brain and spine

According to Dr. Law, MRIs pinpoint subtle differences in soft tissues. “This type of scan is especially helpful in diagnosing or monitoring conditions such as tumors, heart problems, blood vessel blockages and liver disease,” he says. “And because radiation is not used, MRI scans can be conducted more frequently.”

MRI Scan vs. CT Scan

Your injuries and the urgency of your condition dictate which type of scan is best for you. Personal preference may also play a role.

CT scans are quicker than MRIs, taking 5 to 10 minutes depending on the area being scanned. Because the imaging is faster, the scanner is less sensitive to a patient’s movements. A CT scanner is also quiet and open, making it an easier option for heavier people and those with claustrophobia. While CT scans are less expensive, they use radiation and therefore are not recommended for young children or pregnant women.

MRI scans vary from 10 minutes to an hour and even longer if an in-depth scan of a particular area is needed. Extremely sensitive, the scanner produces high quality images of specific areas. However, this means that patients must lie completely still during the procedure. Sometimes, patients are given a sedative to relax.

During an MRI, the patient lies still inside a tube-like scanner. The closed space can trigger claustrophobia in some patients. There are larger machines that accommodate more space. MRIs do not use radiation so they are safer for pregnant women and young children, but because the imaging is created with magnets, anyone who has metal implants should not get an MRI.

by Heidi Tyline King

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