BALTIMORE—Down the hall from the hospital waiting room where patients await their turn to get medical scans, a middle-aged patient was undergoing an MRI of her lower back. That she had arrived at the hospital in a cage is only the first clue this was no ordinary MRI procedure. There’s the pulse-reading clip normally affixed to a finger that instead was clamped to her tongue. And the disposable bubble wrap tucked under her front paws to keep her warm.

Having our furry friends like eight-year-old Glacier, a Boxer, undergo a pricey medical scan may come as no surprise to devoted pet owners. But with few exceptions most veterinary centers lack the expensive scanners, so four-legged patients must use the ones originally meant for two-legged ones. The new animal medical-imaging center at The Johns Hopkins Hospital, which debuted last September, should lead to faster diagnoses and more effective treatment. Moreover, it could serve as a model for other hospitals seeking a new revenue stream, because pet owners tend to pay in cash, often up front, rather than rely on insurance.

Animals and humans have quietly shared such machines for decades. Yet animal care has historically been sidelined to nights and weekends, when human patients are not scheduled to use the machines. Such deferred late-night veterinary services were not just a matter of convenience for human patients. It was also about aesthetics. People may get “upset” when they hear that the patient on the exam table before them was a cat or dog, says Dara Kraitchman, one of the two veterinarians overseeing the Center for Image-Guided Animal Therapy. The long-standing late-night setup has not created a health issue for people, she says, because the same procedures are used to sanitize the room and examination table between patient sessions—animal or human. Moreover, relatively few maladies can be transmitted from pets to people. Still, even today at Hopkins people may feel uncomfortable sharing a space with animals, so veterinary patients come in for care through a separate door and are largely kept out of sight, she says.

The real strength of Hopkins’s center is that it offers the latest medical imaging for animals during typical work hours. That is more critical than it might seem. In the late-1980s Larry Gainsburg, the veterinarian who brought in Glacier for a scan, remembers having to bring animals in at 3 A.M. for imaging with machines owned by Duke University. And before Hopkins launched this new service he was taking animals for scans at a medical facility after it finished serving human patients in the evening. That schedule made for “long workdays,” he says. At Hopkins, he says, “one of the nicest things about this is I can do it during the day.” At $2,000, a typical scan is still expensive (roughly $500 less than one for a person), but many people do not think twice about passing up on medical care for their pets, says Rebecca Krimins, co-director of the center. Despite the cost, roughly 70 percent of owners still choose to get scans when Gainsburg recommends them, he says of his practice. Still, it’s a balancing act to consider costs, risks and benefit.

The market for animal scans appears to have grown in recent years, according to the American Veterinary Medical Association (AVMA), citing anecdotal evidence. As with humans, the field of veterinary medicine has evolved to include more expensive and complex care options for companion cats and dogs. Of the $55 billion spent on U.S. pet care in 2013 (almost half of which was spent on food), $14.37 billion was spent on veterinary care, according to the American Pet Products Association. The AVMA puts the pet care price tag even higher in their last annual report: $28 billion on pet veterinary care.

Just how much is spent on scans is not known. No clear estimates exist for how many pet scans take place each year or even how many facilities offer on-site imaging. Some veterinarians have their patient scanned at large academic institutions where machines are primarily used for research not veterinary care, but such places are not always conveniently accessible. Still others go to veterinary schools or to the handful of stand-alone veterinary imaging centers across the country. Few veterinary offices own their own multimillion-dollar imaging equipment.

Currently the Hopkins center scans about 10 four-legged patients a week (it has yet to market its services widely), which often leaves about half of each day open. In that spare time the scanners are also tapped for other uses, such as taking human patients. Krimins hopes to eventually use the scanners for research on the animals they scan. One common problem in their sights: service dogs such as German Shepherds often develop a malady that causes lower back pain and hind limb weakness. The disorder, called lumbosacral (LS) disease, often forces the animals into early retirement. If healthy dogs and those with LS disease received additional advanced imaging analysis when they came in for care, Krimins remarks, the team could start to look for patterns in nerve degradation that could provide clues about the disorder.

As for Glacier, the scans revealed two large masses on her spleen—a surprising finding because the team was hunting for spinal cord disease. The masses may help explain why the dog was anemic and had other blood-work issues. Next up, she will have her spleen removed and go in for further exams. Glacier’s testing and treatment is not all that different from one a human patient would expect. After all, to her owners, Glacier is a member of the family.