MRI vs. CT Scan in Determining Brain Injuries

by Steve Holder on June 25, 2008

When a traumatic head injury occurs, one of the first questions is “How bad is it?” Doctors have a variety of tests and evaluation methods for assessing the extent of brain injury, including CT scans and MRIs.

CT Scans

If the doctor’s initial evaluations indicate a skull fracture or intracranial bleeding, a CT (or CAT) scan is usually ordered. CT stands for Computerized Tomography. CAT stands for Computerized Axial Tomography. They’re both essentially the same thing, a way to obtain detailed X-ray pictures of cross-sections through the body.

A CT scan is preferred over standard X-rays because of its greater detail. Testing is fast and results are quick; making it exceptionally valuable when prompt diagnosis and treatment are critical. Unlike some other scanning methods, the CT scan can be taken while the patient is hooked up to IV’s or other medical equipment.

Though the CT scanner uses ordinary X-rays, the rays are focused from many different angles to yield a picture of a very narrow “slice” of the body. The scanner’s computer assembles the X-ray data into the final image or “tomogram.” A series of tomograms provide a detailed picture of internal body structures.

The CT scans can reveal hematomas, hemorrhages, and skull fractures giving the neurologist exactly the information necessary for deciding if emergency treatment is needed and precisely where.


MRI Scan

Magnetic Resonance Imaging (”MRI”) is not often used in acute head injury cases. After the acute phase has passed, the doctor may want an MRI to evaluate the location and extent of brain injury to determine further treatment and rehabilitation options.

Although MRI images yield finer detail than CT scans, MRI’s drawbacks include:

  • Longer to perform
  • Not as readily available as a CT scanner in most hospitals
  • Is not practical for patients hooked up to medical equipment
  • Cannot be used if patient has metal embedded anywhere in the body
  • Is not tolerated well by some patients because of the confined space inside the MRI machine

MRI uses powerful magnetic fields and the magnetic reaction of the body’s cells to construct cross-sectional images similar to CT scans. Because it doesn’t use X-rays, it can be safer than CT if multiple imaging sessions are expected.

Variations of MRI technology can also examine brain functioning and identify injuries not visible in CT scans. But even the detail available using MRI cannot detect mild concussions.

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