3/10/2010

A reader emailed, asking me to comment on how technology has changed neurosurgery. The glib answer is, “Tremendously.” When I started training we had limited ways of imaging the brain and diagnosed tumors by seeing normal structures distorted by mass. Development of the CT scan allowed us, for the first time, to see changes in the brain substance well before any distortion to surrounding structures developed. Not only has CT scanning improved over the years but MRI provides additional ways to see changes in brain down to the level of the insulation coating nerve cells.

High speed, high capacity chips now provide enough computing power to give surgeons 3-dimentional real-time visualization of tumors and blood vessel abnormalities during surgery, a process called Image-Guided Surgery. Immediately prior to surgery, the patient is taken to an MRI scanner and images made of their brain. These are sent via fiber optic cables to a computer in the operating room. The patient is put to sleep and their head locked into a fixed position on the operating table. Using a special pointer that is sensed by the computer, boney landmarks on the patient’s head (bridge of the nose, the outer corners of the eyes, etc.) are touched while the cross hairs on the computer are moved to exactly the corresponding spot on the MRI image and locked into place on the computer. By correlating 7 reliable skull landmarks in this way the computer can now reinterpret the MRI into a 3 dimensional view from the surgeon’s perspective. In other words, as the surgeon moves the probe over the patient’s head he can see its relative location on the MRI image. This is extremely valuable for planning the shortest, safest approach to a deep tumor as well as providing important feedback during the actual tumor removal.

Before image guided surgery, surgeons had to plan an approach to a tumor by estimating 3 dimensional space from 2 dimensional images, such as X-Rays. The accuracy of doing this was sometimes less than perfect. Now, with the help of image guided surgery, smaller openings can be more accurately placed with the surgeon knowing exactly where the tumor is in relation to the special probe. Although the technology was originally developed for treatment of brain tumors it’s commonly used for to surgery of the sinuses, where it helps avoid damage to brain and nervous system.

Image guided systems are extremely expensive and require trained personnel to operate them so not all hospitals have them. The Medtronic Stealth Station is the most widely used navigation system on the market, and utilizes both electromagnetic and optical tracking technology.