Magnetic resonance imaging protocols used in veterinary medicine are more simplified compared to human medicine. However, current protocols are adequate in assessing for the majority of diseases of concern.

 

Anesthesia

Use either an MRI-safe anesthetic machine or constant rate IV anesthesia protocols (See CPG 16). Patient monitoring presents challenges in the MR gantry due to increased noise, greater chance of hypothermia, and overall decreased patient accessibility.

 

MRI Technician Assistance

It is very important for the Veterinary Corps Officer to be present during image acquisition (if available) to help determine the beginning and end points (range) of the study in each plane, due to anatomic differences between humans and dogs (humans have five lumbar vertebrae compared to seven in dogs, for instance). Beginning and end points for the study should be based on neurolocalization.

 

MRI Contrast Administration

Paramagnetic contrast agents are commonly used during MRI. Contrast agent administration is always required when imaging the brain, and may be necessary for other exams dependent on the case. For example, if neoplasia or diskospondylitis of the spine is suspected, then administration of contrast during a spinal exam is warranted. All pre-contrast sequences must be performed prior to contrast bolus administration. The contrast agent most often used in MWDs for MRI is gadolinium-based, and the dose for IV bolus use in the dog is 0.1 mmol/kg (0.2mL/kg). As a quick rule of thumb, 1 mL per 10 pounds body weight is the appropriate dose.