After a couple of shots of a sedative to the jugular, Mr. Bojangles wasn't the spunky young gelding he usually is. Sharp tugs on his tail were required to get him to drag his hooves across the padded floor of the oversize exam room at the Marion duPont Scott Equine Medical Center in Leesburg. Several pushes finally got him into a stall, where MRI equipment was wrapped around a hoof, and his soft, squishy mouth rested on a headboard, frozen in a gummy pink smile.

"It's like a four-martini lunch," said the horse's owner, Joseph Keusch of Middleburg, referring to the near-instantaneous effects of the sedative, which was administered to prepare Mr. Bojangles for a magnetic resonance imaging of his front right leg.

The duPont center, a referral-based hospital operated by the Virginia-Maryland Regional College of Veterinary Medicine at Virginia Tech, recently leased one of the country's first MRI machines designed for horses. The machine is used only for hooves and fetlocks (ankles) and has greatly increased the center's ability to accurately diagnose the causes of lameness.

"Before, we just knew it was painful in the foot," said Kenneth Sullins, a professor of surgery at the center. "Now, we know exactly what we're treating."

The MRI, which lasts one to two hours, captures a 3-D black-and-white image and allows veterinarians to see cross sections from virtually any angle. It detects hydrocarbons -- water or fat -- so blood, fluid, muscle and soft tissue appear white, while bones or air in the lungs appear black. An injury usually appears bright white because fluid collects there as a result of inflammation.

Previously, the duPont center veterinarians had to rely on two-dimensional images of soft tissue and guess-and-check approaches to relieving symptoms -- not the problem itself.

Mr. Bojangles started limping about three months ago. At first, the Keusches thought their 8-year-old horse just needed new shoes, but soon they realized he needed medical attention. Lameness can be difficult to diagnose because there are many causes, ranging from a pebble stuck in the hoof to shoulder sprains to a bump on the head.

Their local vet, using X-rays and ultrasound, guessed Mr. Bojangles's problem was a small tear to the deep digital flexor tendon.

Humans have 20 flexor tendons, which allow them to bend their fingers and toes. Horses have one such tendon in each of their spindly legs. Because each leg is like a "finger" that supports a giant body, the deep digital flexor tendon is highly prone to injury.

Mr. Bojangles was referred to the duPont center, where he became the 51st MRI patient since the center began using the equipment in April.

The drowsy, 1,000-pound horse was not a willing patient. Much coaxing was required to get him to step into a contraption shaped like a loose bracelet and a boxy, foot-high horseshoe. The horseshoe contains two magnets that cause living tissue to produce faint radio waves, which are detected by the bracelet. Computer software converts the data into black-and-white images that digitally dissect the hoof at different angles. Depending on the angle of the scan, veterinarians can visualize razor-thin cross sections of the hoof in the form of a tower of pancakes or a loaf of bread.

In the MRI room at the duPont center, Dani Keusch, 13, and her father, joint master of the Fairfax Hunt, held Mr. Bojangles's head during the procedure. She kissed her very first horse between the ears, murmuring "Bobo" every now and then.

Mr. Bojangles's MRI, which took about two hours, confirmed the vet's diagnosis. He will have to wear special shoes that support the heel to take pressure off the injured tendon; take anti-inflammatory drugs; and remain confined in his stable for a month.

The horse already demonstrated distaste for that lifestyle when he kicked through his black plastic feed bucket when he was locked in his stall two days before the MRI appointment and cut his hind right leg.

"He's like an adolescent kid," Keusch said. "He is not happy being in [when] his friends are out. But he gets used to staying in the stall, like a prison. He just puts up with it."

A handful of veterinarians elsewhere in the country use human MRIs for horses. In such cases, the horses must be placed under anesthetic and lie on a large gurney or other contraption. The practice was popularized by Washington State University's College of Veterinary Medicine in Pullman in the mid-1990s, which for many years after was the only clinic capable of imaging an adult horse. Even now, the images are limited to the head and lower leg.

Washington State performs 150 to 200 horse imaging procedures a year using human MRI equipment at a cost of $500 per MRI plus $500 for general anesthesia, said university spokesman Charles Powell.

The special horse MRI leased by the duPont center allows horses to remain standing throughout the procedure. That equipment works best for the hoof or ankle area of the horse, which remain relatively stable, even when a drugged horse sways. An MRI at the duPont center costs about $1,200.

The hospital pays $4,600 a month to lease the equipment from Hallmarq Veterinary Imaging, a British company that is the only manufacturer of equine-specific MRIs, and an additional $460 per patient. The center also had to spend about $50,000 to build a special room with copper in the floor and steel in the walls and ceiling to screen out ambient radio waves.

Mr. Bojangles has horse health insurance, which covered the procedure. And the Keusches are glad he is going to recover.

"He thinks he is a dog," Keusch said. "He always plays and snuggles up to you, and if you don't pay attention, he puts his nose up under your elbow. . . . He's not like an average horse. He's like a family member."

Some veterinarians in the United States have agreements with their regional hospitals to perform MRIs on smaller pets. Iams Co., which manufactures food and pet care products for cats and dogs, opened an MRI center for small pets in Vienna in spring 2002. It plans to open a second facility this month at N.C. State University in Raleigh. That center will be able to accommodate sleeping horses, said Iams spokesman Kurt Iverson.

Joseph and Dani Keusch comfort their horse Mr. Bojangles as radiology technician Carolyn Smith, left, and vet Christina Hewes, sitting by the horse's right leg, begin the procedure. The images of his hoof, above, are 3-D. Mr. Bojangles's metal harness must be removed before the MRI.