Frameless Stereotactic Surgery

Instead of using an external frame as a reference
point, frameless stereotactic surgery uses tiny
markers, called fiducial markers, that are taped
or glued to the head before the brain is scanned.
The scan is then loaded into a planning and
navigation computer, producing a 3-dimensional
representation of the head, brain and tumor.
During surgery these markers are touched with
a pointing device, called a “Wand.” Identified
on the scan, the computer “knows” where the
surgical instrument is during the procedure in
relation to the brain and tumor.

Frame-Based Stereotactic Surgery

With frame-based stereotactic surgery, a lightweight
frame is attached to the skull at four points.
Local anesthesia is used to numb the places where
the pins contact the skull. Once the frame is
attached a CT, MRI or dye scan (angiography) is
done. Since the scan images both the tumor and
the frame, it is able to show the exact location of
the tumor in three dimensions in relation to the
head frame. The neurosurgeon takes these
coordinates and precisely inserts a probe through
a small incision in the skull to perform the biopsy
or other procedure.
It also has some limitations. The frame can
sometimes obstruct the neurosurgeon’s view of
the site; it can be time-consuming to manually
set the frame and read the scans; there is a
limited space to work within the radius of the
arc; and the scans and surgery usually need to
be performed the same day.

STEREOTACTIC SURGERY

The use of highly advanced computers to
locate and create a three-dimensional image of
a tumor is called stereotaxy. When used during
surgery, this technique is called stereotactic
surgery. Conventional x-rays can only measure
two dimensions: height and width.
Stereotaxyadds the third dimension of depth, which
enhances the neurosurgeon’s ability to precisely
map the location of the tumor and find the best
and safest pathway for removing it.
Stereotactic techniques may be used to prepare
for a surgery, during biopsy or tumor removal,
while implanting radiation pellets, or to provide
a navigation system during surgery. These
techniques are especially useful in locating and
removing tumors deep within the brain, such as
brain stem and thalamic tumors. Stereotactic
systems are used in operating rooms, enabling
surgeons to view images of the brain as surgery
is being performed.