PATIENT GUIDE TO THE GAMMA KNIFE
WHAT IS A GAMMA KNIFE?
The Gamma Knife is a machine that focuses a very large amount of
radiation on a small part of the brain in order to shrink or destroy
that area. This is not surgery in the usual sense of the word. There
are no incisions and it is, in a sense, surgery of a lesion without
HOW DOES THE GAMMA
The best way to understand the Gamma Knife is to imagine an
entertainer on a stage in Las Vegas. When the entertainer first
comes on stage, the room is entirely dark. Then the spotlights are
turned on, and all intersect on the entertainer. He or she is brightly
illuminated, and all around is extremely dark and can barely be
seen. The Gamma Knife works on a similar principle except instead
of spotlights, there are 201 pencil-thin "spotlights"
of radiation. The spotlights are between 4 and 18 millimeters in
diameter, and all intersect precisely where we want in the brain
with a precision of less than 1 mm. The intent is to have these
beams intersect at the lesion in your brain that we want to treat;
the normal brain structures around the lesion receive an insignificant
amount of radiation.
PREPARATION FOR THE
There is little you need to do to prepare for the Gamma Knife.
A few days before the treatment, you are invited to come to the
Gamma Knife Center at which time you will be given a tour of the
unit. They will familiarize you with the surroundings so that on
the day treatment, all will go as comfortably and smoothly as possible.
THE DAY OF THE GAMMA
We usually ask that you arrive at 6 AM on the day of treatment
so that you can be admitted to the hospital, and fill out the usual
forms. You should eat nothing the day of the Gamma Knife, but please
take all your usual medications with a sip of water on leaving for
then are taken to the Gamma Knife unit. Beverly Ponte and one of
the doctors will put a metal device on your head. This takes about
5 minutes, and is called a Leksell frame. It allows us to control
the motion of your head so that the area we wish to treat can be
precisely moved to where all the beams in the Gamma Knife intersect.
The Leksell frame attaches to your head with one-inch metal posts.
We start by injecting the scalp in the forehead and behind the ears
with Novocaine. We may put a small gauze pad over your eyes to prevent
any irritation should the Novocaine drip into them.
These metal posts advance to those anesthetized areas, and put pressure
against the scalp and head. Putting the Novocaine in is unpleasant,
but this only lasts for a few seconds. When the Leksell frame is
securely in position, you can expect to feel pressure for about
15 minutes, and then it should be comfortable and cause you little
discomfort. You will wheel over to the MRI unit that is just down
the corridor from the Gamma Knife Center.
The MRI study often takes as long as an hour, so sometimes we will
give you some sedation to enable you to sleep through it. After
this, you go to your room where you can read, watch television,
or take a nap.
PREPARATION OF THE
In the next several hours, the images from the studies are transferred
through the communications network to the Gamma Knife planning computer.
Dr. Saris and the physicist then make the treatment plan.
Once the treatment plan
has been finalized, we will ask that the transportation people bring
you to the Gamma Knife unit. You'll lie on the treatment table and
the gamma knife frame is used to maneuver your head into what is
called the Gamma Knife helmet. It is securely attached and everyone
except you will leave the room. You have a microphone and can talk
to us at all times. There is music playing to help pass the time.
You may bring your own music, and we will be glad to play it for
For each gamma knife
treatment, the bed you are on will slide into the Gamma Knife unit
itself, and your entire body and head move up a foot or so to engage
with the radiation part of the unit. Undergoing the gamma treatment
is very much like undergoing an MRI. The table moves you about,
but nothing appears to be happening otherwise. The radiation is
odorless and colorless, and you will feel nothing at all as you
are treated. Each treatment lasts for a few minutes as the radiation
is directed to different parts of your lesion, but occasionally
will last longer. We will tell you what to expect for each one.
The typical treatment
takes between 30 minutes and two hours. When the last treatment
has been done, the Leksell frame is removed. The areas where the
metal rods posts have come in contact with the skin can be little
tender, but once they are removed should cause only a mild to moderate
ache. We will put Band-Aids on those areas, and may put a small
ACE wrap on your head for an hour or so.
When this has been completed,
you'll go back to your room for overnight observation. You can have
something to eat in evening. Then, if all goes well, you'll go home
at your convenience the next day.
My office will call you in regard to being seen again, and we will
arrange more MRIs as needed. In general, the first MRI is either
two or six months after the treatment. If you have any questions
or problems, please do not hesitate to call my office at (401) 453-3545.
A helpful Web site to
look at is www.elekta.com. This
is the company that makes the Gamma Knife. It will give you helpful
links to many other sites.
Stephen Saris M.D.