Piercing the body with precision  pg. 3

Guiding the scalpel

Registration already is an integral part of stereotactic surgery and radiosurgery, the precise guidance of scalpels and radiation beams to remove abnormalities, including tumors, with minimal damage to surrounding tissue.

New techniques developed by Vanderbilt engineers and computer scientists are extending the reach of the neurosurgeon and radiation oncologist even further. Their contributions are proving to be invaluable, especially for treatment of aggressive, infiltrating glioblastomas of the brain.

“The visual cues we have at surgery are really poor,” explains Reid C. Thompson, M.D., director of Neurosurgical Oncology at Vanderbilt. “There isn’t often a discrete edge… maybe there’s a slight discoloration… maybe the tumor just feels a little different.”

As a result, he says, “you either don’t take out enough tumor in the brain, and we know that’s probably not good in terms of prognosis, or you take out too much, which is an obvious problem.”

To further define the margins of the tumor during surgery, Anita Mahadevan-Jansen, Ph.D., and her colleagues in the Department of Biomedical Engineering have developed an optical probe that within 30 seconds can differentiate between normal and abnormal brain tissue based on the spectra of light bounced off of them.

A recent clinical study concluded that the instrument can achieve what amounts to an “optical biopsy” with “near-instantaneous feedback,” improving the percentage of tumor that is removed during surgery and reducing operating time and expense.

Michael I. Miga, Ph.D., assistant professor of Biomedical Engineering and director of the Biomedical Modeling Laboratory, has harnessed a widely used commercial technique, laser range scanning, to adjust for changes in the surface of the brain as the surgeon cuts into it.

By repeatedly sweeping a laser beam across the brain surface, the scanner produces “point clouds” or sets of three-dimensional points that—in clinical studies—have accurately predicted the changing locations of the tumor as well as nearby blood vessels and other delicate structures during the operation.

The development of these techniques owes much to the rich, longtime collaboration between Vanderbilt engineers, computer scientists and neurosurgeons.

Leaders in this effort include J. Michael Fitzpatrick, Ph.D., and Benoit M. Dawant, Ph.D., professors in the Department of Electrical Engineering & Computer Science; Robert L. Galloway, Ph.D., professor of Biomedical Engineering; and Neurosurgery Department chair George S. Allen, M.D., Ph.D.

During the past 15 years, Vanderbilt researchers have improved the registration of preoperative images with anatomical information collected by an optical probe during surgery. The combined image, projected onto a computer screen in the operating room, helps the surgeon hold a true course through tissue topography that changes with each the touch of the scalpel.

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