Jeffrey Thramann, M.D., a neurosurgeon at Boulder Community Hospital (Colo.), would not consider performing a brain tumor resection without his image-guidance system (IGS), particularly when the tumor is hard to differentiate from healthy tissue or is located near important structures. Today, about 80 percent of his colleagues nationwide agree. Cranial image guidance, particularly for tumor resections, is now considered standard-of-care.

The same cannot be said of spinal image guidance. Only 20 percent of those who perform spinal surgeries use IGS, and most of them are neurosurgeons already accustomed to using image guidance. Only about 5 percent of orthopedic surgeons perform IG-aided surgeries. But that number is growing, and as orthopedics increasingly take advantage of the technology, the number of applications in the spine and elsewhere using IGS will continue to increase.

Using optical dynamic referencing, image guidance allows surgeons to know exactly where the tip of their instruments are as they navigate through the body, an important aid when the surgeon cannot see the edge of a tumor or structural landmarks in the spine, for example. The technology also allows surgeons to make smaller and more precise incisions, expanding the field of minimally invasive surgeries. “It’s a technology whose time has come,” says Nadim Yared, vice president of Medtronic Inc. (Minneapolis) and general manager of Medtronic’s Surgical Navigation Technologies (Louisville, Colo.).

In the Crosshairs
Intercranial image guidance begins with a pre-operative magnetic resonance image (MRI). Patients are scanned with fiducials, or fixed reference points, placed on the head, which are used to orient the head in space to the MR image. Before the operation begins, the patient’s head is placed in a fixed frame and the surgeon “registers” the image by touching the IGS probe to the fiducials. The system uses the landmarks to orient the image on a monitor. Now, when the surgeon touches the patient’s head with the tip of an instrument, the precise location of the instrument relative to the tumor is visualized on the image.

Before they make an incision, surgeons can use the probe to plan the surgery by marking the boundaries of the tumor and the critical structures to avoid on the patient’s head. “Without navigational technology, you have to make a much bigger incision to encompass where you think [the tumor] is going to be when you get in there. Here, you can make very small incisions right over where the tumor is,” says Thramann. “Once you make the incision, the brain tends to herniate out at you. If you make your incision right over the tumor, the brain that herniates out is tumor. It’s much safer.”

Please refer to the March 2003 issue for the complete story. For information on article reprints, contact Martin St. Denis