What is a computer-assisted image-guided craniotomy?
Computer-assisted craniotomy is a craniotomy that is guided by computers. The computers are used by the surgeons to gather, store, and reformat images from the patient's MRI or CT scan. These are rendered in three dimensional volumetric information that allow definition of an intracranial lesion with respect to the surgical field. Most importantly, this information is displayed to the surgeon intraoperatively and scaled to the actual size and location of the surgical field.
With this technique, a surgeon can plan and simulate the surgical procedure beforehand, reach deep-seated or centrally located brain tumors employing the safest and least invasive route possible. Figure 1 shows reformatted and three-dimensional images of a patient with a brain tumor.
What are the disadvantages of conventional craniotomy?
The most common disadvantages of craniotomy for resection of brain tumor include, but are not limited to:
A large skin and bone opening is necessary.
A surgeon can get lost attempting to find the tumor. Normal brain tissue can be damaged unnecessarily. This can result in neurologic deficit and prolonged stay in the hospital.
In most cases it is difficult to tell where tumor ends and normal brain tissue begins. Thus, there is risk that the surgeon can resect normal brain tissue along with the tumor. In important brain areas, this will also result in neurologic deficit.
A surgeon performs a subtotal removal of the tumor. The consequence is only partial tumor resection that will result in a faster recurrence of the tumor and neurological symptoms.
Who is a candidate for computer-assisted craniotomy?
Anybody who needs brain surgery and wants a precise and minimally invasive operation is a candidate, The conditions include brain tumors, vascular malformations, infections, surgery for Parkinson's disease, and other movement disorders.
What are the advantages of computer-assisted craniotomy?
Computer-assisted craniotomy provides the following major advantages to the surgeon in the management of intra-axial brain lesions:
It allows a small skin and bone opening.
It allows locating the lesion promptly.
It allows removal of the tumor respecting the normal brain and vascular anatomy.
The surgeon is guided by the computer and thus knows exactly where tumor ends and normal brain begins. This allows a more complete tumor removal with much less risk to surrounding brain tissue.
"Inoperable" tumors (inoperable by conventional surgical techniques) can be resected with computer-assisted procedures. Frequently, these are deep seated-relatively benign tumors in children and young adults or elderly patients. Many of these tumors can be cured with computer-assisted craniotomy.
Neurologic results are better; fewer patients require rehabilitation programs and return to work sooner.
How does image-guided computer-assisted technology work?
The entire image-guided surgery process can easily be correlated or compared to location and directional tracking systems used for cars and ships today. The image-guided surgery system camera performs much like the satellite that detects signals from vehicles that are equipped with special tracking devices. As the vehicle moves, the satellite calculates its position and transfers the information to the vehicle computer.
This computer shows the direction the vehicle is moving and when programmed will give specific directions as to how to proceed. A CT or MR scan is essential to an image-guided surgery procedure. Special markers or "fiducials" may be placed on your head prior to a cranial scan. This scan will be loaded into a computer and your surgeon can build a three-dimensional (3-D) model of your head or spine to be viewed on a computer monitor. Viewing the model and scan information, surgeons can plan, in advance, their surgical path and identify the surrounding anatomy.
Your scan will be displayed on the computer screen and the surgeon will conduct a "registration" process, matching your physical anatomy to the computer scan information. As it begins, the surgeon will touch the center of the "fiducials" or markers that were placed on your head, or he will touch specific anatomical points on the spine or cranium with an image-guided instrument. The camera for the image-guided surgery system will see the light emitting diodes on the instrument and on the arc and will transfer a signal to the computer to "register" the specific location being touched. By matching the scan to the real anatomy, the surgeon can now track instrumentation as it proceeds into the operative field as well as view its relative position and trajectory.
