A medical technology known for its 360-degree approach to cancer treatment is finally coming full circle.

In December, the University of Wisconsin System Board of Regents authorized the construction of a $3.5 million addition to the UW School of Veterinary Medicine. The addition will house a TomoTherapy unit, a radiation therapy system developed at UW.

“It’s going to be the first TomoTherapy Unit of any veterinary school or veterinary application in the world,” said Dr. Mark Markel, chair of Medical Science at the School of Vet Med.

Now used all over the country and overseas to treat human patients, the first TomoTherapy units were tested on dogs with nasal tumors in 2001, with help from Dr. Lisa Forrest, an assistant professor of radiology and veterinary oncology at UW.

What makes TomoTherapy unique is its ability to supply radiation solely to a tumor without damaging the healthy tissues next to it. For dogs with nasal tumors, traditional treatment can eliminate tumors, but often renders them blind.

“We treated 32 dogs using the TomoTherapy unit and we were able to deliver (radiation) to the tumor and spare the eyes,” Forrest said. “In veterinary medicine, it’s going to be revolutionary.”

A TomoTherapy unit is a radiation machine mounted on a helical, or circular, CT scanner. A 360-degree CT scan of the patient is taken, taking pictures from all angles. The resulting 3-D image is then aligned with a patient’s original CT scan to adjust the patient’s exact position within the unit. Radiation is then delivered to the tumor in the same rotating 360-degree pattern.

Delicate tungsten “leaves” adjust in front of the radiation beam, blocking or opening to provide a higher dose of radiation when the tumor is fully exposed and a smaller dose when healthy tissues are exposed.

Markel said the TomoTherapy is a much-needed addition to the School of Veterinary Medicine, replacing the antiquated Cobalt radiation system currently in use.

“Right now, we are nationally known as one of the leaders in veterinary oncology in the world,” Markel said, adding the program has principally focused on chemotherapy and immune modulation treatment. “One of the things that’s prevented us from developing an equivalent program in radiation therapy, one funded by the National Institutes of Health, is that we don’t have a state-of the-art radiation facility.” TomoTherapy, Markel said, will fill the void in the radiation program. He added construction on the addition to the School of Veterinary Medicine is set to begin in the late summer or early fall of 2009, with full occupancy in mid-to-late 2010.

The unit will treat primarily dogs and cats. Private citizens around the state who are referred by their veterinarian to the program will have potential access to the treatment, once an animal’s case is officially diagnosed and approved by the school’s oncology group.

For Forrest, the long journey from the development of TomoTherapy in the 1990s and the test rounds in 2001 to this point has been worth the wait.

“I am just so thrilled and excited,” she said. “I have lots of other colleagues at other universities, and they all have linear accelerators and some of them have even more advanced equipment. Now, I will have the most advanced equipment out there.”