What is MRI

 

MRI has for many years been the imaging method of choice in human medicine making it the gold standard for diagnosing pathology.

MRI images closely reflect true anatomy whereas x-rays show bone only and ultrasound shows soft tissues only. This is demonstrated in the three images below.

Section through a horses hoof at post mortem Foot X-ray - side view Foot MRI - side view

How does it work?

When tissue is placed in a strong magnetic field and a short pulse of radio waves is applied, a weak signal echoes back and is used to create an image

The tissue examined must be completely inside the magnet, limiting MRI in the horse to limbs (standing) and heads (under anaesthesia).

Because MRI transmits and receives radio signals, scanning must take place in a screened room MRI.

MRI does not use ionising radiation (as used in X-rays) and has no known hazardous biological effects

The images appear as black-and-white slices through the tissue. The position of the slice is chosen by the scanner operator.