Pets finally get their own magnetic resonance (MRI) machine
at Cornell's veterinary hospital, and a Persian cat gets good news
FOR RELEASE: November 23, 2004
The cat in the center of the gleaming machine has a blissful look on her 10-year-old Persian face, but the Cornell Hospital for Animals veterinarians at the controls of the newly installed medical-imaging device seem deeply concerned. Will their magnetic resonance (MR) scans of the cat's head find a brain tumor - perhaps the cause of seizures their patient is experiencing?
"CT (computed tomography) actually shows better detail in bone, but MR is best for soft tissue, and that's what we're looking at today," explains Dr. Peter Scrivani, a board-certified radiologist at the hospital in the Cornell University College of Veterinary Medicine. Of all the medical imaging technologies available at leading veterinary hospitals like Cornell's - from radiography (X-rays), ultrasonography and nuclear medicine to echocardiography and scintigraphy - he has chosen magnetic resonance imaging.
Luckily for the cat in question, the Cornell Hospital for Animals has just installed North America's first permanent-, open-magnet MRI system specifically designed for companion animals - dogs, cats and other small pets. Before that, imaging veterinary cases had to share humans' MR facilities, either after hours in medical centers or in people-sized machines at veterinary clinics.
"This machine is here 24/7 just for the animals," says Scrivani of the Vet-MR instrument built by the Italian company, Esaote, and previously available only in a few veterinary hospitals in Europe. The Cornell instrument was bought and installed with a grant from the Maurice and Corinne Greenberg Foundation.
"This is an open MRI, not a closed tunnel that the patient disappears into," explains Dr. Nathan Dykes, the hospital's imaging chief of section as he displays a doughnut-shaped coil that fits loosely around the part of the animal being imaged - in this case, the head and neck. "Not that dogs and cats care much about claustrophobia, but the open MRI seems to make the pet owners more comfortable."
The same reason pets undergoing MR scans are not claustrophobic also accounts for the blissful expression on this Persian patient: Pets get to snooze. They are anaesthetized so they can remain nearly motionless during the 30- to 45-minute series of MR scans.
An anesthesiologist monitors the flow of gases in and out of the cat's lungs. Flexible tubes for air and anaesthetic gas run through one wall of the of Vet-MR enclosure - which looks something like a metal-screened gazebo and shields the instrument from radio-frequency interference - to the anesthesiologist's console in one corner of the room.
In the other corner sits Scrivani with a large computer monitor and controls for the Vet-MR. Just as he begins to list other uses of MR in veterinary medicine (soft-tissue diagnoses of musculo-skeletal disorders and brain disease such as cancer, as well as a teaching tool for veterinary students of anatomy) and explains the principle behind MR (computer-controlled radio waves measure the response of body cells to temporary magnetic fields created by power electro-magnets), the first images of the Persian cat's head begin to appear.
"Looks like a little nasal disease - fluid in the sinuses - and something's going on in the middle ear, but so far I'm not seeing any evidence of tumors," Scrivani says. "Just to be sure, let's try another scan at a different plane."
Each additional scan takes five to ten minutes, and the MR operator can order scans of different planes (orientations), adjust the machine's parameters to optimize imaging of body materials (fluids or various parts of the anatomy, for example) or order the injection of paramagnetic compounds that react in the magnetic field to highlight particular areas of the body.
If he does find cancer, the tumor might be removed by surgery - if it is safely accessible - or possibly reduced in size with radiation therapy.
Results of the next scan begin to scroll down the computer monitor and Scrivani falls silent. The only sounds in the room are the "whoosh-whoosh" of the ventilator that is breathing for the cat and a muffled machine-gun noise as the MR's magnetic gradient coils switch on and off.
"This is beautiful! This is so much better than radiography or CT," Scrivani exclaims. What he sees is pretty good news for the cat and for its human companions, too.
True, there's still some evidence of ear and nose disease, but not enough to cause seizures, he says. Previous tests have ruled out metabolic causes of siezures, such as hypoglycemia, and Scrivani is not seeing too much cerebral edema that can produce pressure on the brain. "Of course there could be a tumor so small we can't detect it," he says, "but I'm considering a diagnosis of inflammatory disease or idiopathic epilepsy as more likely."
Idiopathic means the doctors don't know the cause, but at least epileptic seizures - in cats as well as in people - usually can be controlled with medicine. Scrivani wants the referring veterinarian to monitor the cat's progress under epilepsy medication. If seizures continue, the Persian may have to return in a few months to see if some undetectable tumor has grown in size.
And now, soon after the anesthesia gas is turned off, the cat begins to stir. Cradled in the arms of a veterinary technician, she is carried to the recovery room.
Standard feline attitude makes all cats think they're special, and Persians know they're more special than most. Still this lucky kitty seems to have no idea of her place in North American veterinary medical history - as one of the first to be scanned in an MRI that pets can call their own.