The MRI is being used by the Vet community. It can be used on brain scans, but also to see different types of tissue. That will help with tissue repairs.
Ultrasounds can do a lot of the same things as MRI's, but ultrasounds are cheaper. With the MRI's you have to sedate the animals to keep them still. Which would tack on more cost then what already is being spent. That's why most people are turning towards Ultrasounds.
The procedures use a small camera and light source that can be inserted into the abdominal or thoracic cavity to see inside the body. Before this came about it was very hard to see the inside of the body.
"The Newest Advances in Veterinary Technology." Carrington. 20 Dec. 2016. Web. 26 Jan. 2017.