imageThe same technology used to bring Godzilla to life in the movies and put Keannu Reaves in the virtual reality world of “The Matrix” also is being used to help surgeons in the operating room perform tasks such as placing new hips or reaching brain tumors.

As computers become faster and technology improves, operating in a 3D virtual reality environment will become increasingly more common.

Today, many image-guided surgeries utilize 2D or 3D preoperative images to plan and help surgeons navigate through the body. Cutting-edge hospitals are using real-time CT and MRI during surgery for even greater precision. Advances in navigational and robotic technology also are creating new opportunities to apply image guidance in the operating room.

Preoperative image guidance
“There’s an entire spectrum of image-guided surgery,” says Russell Taylor, Ph.D., computer science professor and director of the Engineering Research Center for Computer-Integrated Surgical Systems and Technology at Johns Hopkins University (Baltimore, Md.). “The basic theme is imaging in planning the surgery, in the localization of the plan to the patient, and then as feedback in actually doing the procedure. In each of these cases, you see a lot of potential for computing.”

Traditional image-guided surgery began with neurosurgery, primarily with brain tumors. The technique has expanded to other types of neurosurgery, such as placing devices in the brain to treat movement disorders. Some spine — most notably pedical screw placements — ear, nose and throat (ENT), and orthopedic procedures also use image guidance.

In many of these procedures, image guidance begins by creating a computer model of the patient made up of MRI or CT scans combined with an anatomical atlas. Using the model, surgeons plan and rehearse the procedure, such as mapping the course a needle should take through the brain or determining the size of device needed in a hip replacement. Those images then are brought into the operating room to help the surgeon more precisely perform the surgery. But first, the images must be matched to the patient in a process called registration or localization.

Frequently, registration is done with a 3D navigation or position-sensing device that uses anatomic markers to track the surgeon’s instruments in real-time and correlates the information to the computer model. Once the patient is registered, the surgeon uses the navigation device to track the instrument’s position relative to the computer model displayed on a monitor.

For Donlin Long, M.D., Ph.D., professor of neurosurgery and retired director of the neurosurgery department at The Johns Hopkins Hospital (Baltimore), increasing the ability to judge the surgery’s outcome — making sure the tumor was completely excised, for example — is the most important benefit of image-guided surgery.

Johns Hopkins Hospital owns four image-guided surgery (IGS) systems between its two hospitals. A longtime test site for the Surgical Navigational Network (SNN), a consortium of companies that support a common image-guided surgery platform, Johns Hopkins has systems from Surgical Navigation Specialists (SNS), a subsidiary of Cedara Software Corp. (Mississauga, Ontario, Canada), as well as components from other SNN companies. The hospital also recently acquired a Medtronic Surgical Navigation Technologies (Medtronic SNT of Louisville, Colo.) StealthStation treatment guidance system.

Although Johns Hopkins became involved in image guidance early on, Long says the practice is not yet universal. “We and other similar places use them routinely,” he says, “but it’s not widespread enough to say that it’s standard of care. I will say that it certainly improves things.”

Long, who specializes in brain tumors and complex spinal problems, says image guidance helps steer him to exactly the right position in the skull and allows him to reach structures deeper inside the brain than he could without the system, while at the same time limiting potential damage from unnecessary exploring.

Long cites brain tumor studies to demonstrate image guidance’s potential. Without it, surgeons, thinking they had removed the entire tumor, actually failed 20 percent to 50 percent of the time.

Please refer to the February 2001 issue for the complete story. For information on article reprints, contact Martin St. Denis