Magnetic Resonance Imaging or MRI

MRI is the most sensitive of the structural tests. MRI, as its name indicates, utilizes magnetic fields to image the brain’s tissue, as opposed to the X-ray radiation of the CT scan. The patient lies wholly within a magnetic tunnel, as opposed to the more open CT scan.

When protons are placed in a magnetic field, they receive and transmit electromagnetic energy. The strength of the transmitted energy is proportional to the number of protons in the tissue. Signal strength is modified by properties of each proton’s microenvironment, such as its mobility and the local homogeneity of the magnetic field. MR signal can be “weighted” to accentuate some properties and not others.

When an additional magnetic field is superimposed, one which is carefully varied in strength at different points in space, each point in space has a unique radio frequency at which the signal is received and transmitted. This makes constructing an image possible. It represents the spatial encoding of frequency, just like a piano.

Pros:

• MRI has better resolution than CT.
• MRI is better for Parenchymal Lesions.
• MR has some value in post acute evaluations.
• MRI has no ionizing radiation, ala, CT and X-ray.
• MRI sagital images (side view) have superior resolution to CT.

Contra:

• MRI is a structural test.
• MRI can’t be used if patient has IV lines and ventilation equipment or pacemakers, because of its magnetic field.
• Patients find MRI more difficult to tolerate as the test is conducted in a much more confined space and takes substantially longer to complete.
• MRI has a longer scanning time.

Recommendation:

• Make sure that the facility has a 1.5 Tesla Strength magnet in the MRI it is using, and uses a technique for seeing petechial hemorrhages, called Gradient Echo Imaging.
• Consider medication with claustrophobic patients.
• No Open MRI – Resolution is insufficient to identify brain injury.

Magnetic Resonance Angiogram -
MRA can be an extremely useful diagnostic tool if blood flow issues are involved.

NEXT: EEG.

Understanding Subtle Brain Injury

The concussions that disable, are almost always more symptomatic at 24 hours, than at the 2-4 hour time frame when injured persons are evaluated in the emergency room. Brain injury symptoms escalate over the first 24 hours, because brain injury involves a cascade of events. It is critical that if you are still symptomatic the day after your injury, go back to the same Emergency Room, don’t wait for a doctors appointment. It is critical that the Emergency Room personnel see that the symptoms still persist or have gotten worse.

View Our Video Series on Concussions