Gamma Knife (a registered trademark of Elekta Radiosurgery of Atlanta, GA)
Radiosurgery replaces the surgeon's scalpel with a single, high dose of gamma
radiation. Like the surgeon's scalpel, the Gamma Knife eradicates the diseased
area with a safe and effective approach. The patient wears a lightweight head
frame that attaches to a helmet, through which 201 beams of gamma radiation
precisely focus at a single target. Only the tissue being treated receives a
very strong dose of radiation while the surrounding tissue remains unharmed.
The painless, bloodless procedure is usually performed under local anesthesia
with mild sedation. Although the entire procedure takes several hours, the
actual treatment takes just 15 minutes to one hour, depending on the size of the
lesion being treated. If there are multiple tumors or if the tumor spreads to
another area, radiosurgery can be repeated.
There is no risk of surgical complications like infection, hemorrhage or leakage
of cerebral spinal fluid. Gamma knife radiosurgery has proven effective to over
200,000 candidates for brain surgery who have chosen this option over invasive
neurological procedures.
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Medical necessity can be determined by a neurosurgeon, radiation oncologist or
other medical specialist after evaluating a prospective patient's medical
condition. Treatment options are then determined and discussed with the patient
and family, so an informed decision can be made.
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Over 200,000 patients worldwide have chosen Gamma Knife Radiosurgery for
treatment of benign tumors such as acoustic neuromas, meningiomas, pituitary
adenomas, pineal tumors; malignant tumors like metastatic tumors, astrocytomas
and glioblastomas. The Gamma Knife has also been used to eradicate arteriovenous
malformations (AVM) and treatment protocols are under investigation for certain
functional disorders such as chronic pain, trigeminal neuralgia, and Parkinson's
disease.
Patients may be eligible for Gamma Knife Radiosurgery even if they have
previously had open brain surgery, radiation therapy, chemotherapy, or in the
case of AVM, embolization procedure. Results have proven to be superior or
comparable to conventional neurosurgery, depending on the specific condition
treated.
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Gamma Knife Radiosurgery is unique because no surgical incision is performed to
"expose" the lesion. Consequently, the risk of surgical complication is greatly
reduced. Patients are routinely administered a mild sedative, eliminating the
side effects of general anesthesia.
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 On the day of the treatment, the Gamma Knife patient will have a lightweight
frame attached to the head. Local anesthesia is used before the frame is secured
in place. The frame is used in conjunction with an imaging procedure to
accurately locate the diseased area.
With the frame in place, the patient has either an MRI or CT imaging study or,
in the case of arteriovenous malformations, angiography, in order to precisely
locate the diseased area to be treated.
 Data from the imaging study is transferred to the Gamma Knife computer system.
While the patient rests, the Gamma Knife Center team uses advanced software to
determine the treatment plan. This takes one or two hours to complete depending
on the complexity and location of the disease.
When the individualized treatment plan is completed, the patient is placed on
the Gamma Knife couch and is precisely positioned.
The patient is then moved
automatically, head first into the Gamma Knife and treatment begins. Treatment
typically lasts from 15 minutes to an hour, during which time the patient feels
nothing unusual. At the completion of the treatment the patient is automatically
moved out of the Gamma Knife and the head frame is removed. After a period of
rest the patient may be discharged or if medically necessary stay overnight in
the hospital for observation.
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After administering local anesthesia and intravenous sedation, a stereotactic
frame is attached to the patient's head. Next the head is imaged using a CT or
MRI scanner while the patient wears the stereotactic frame. For vascular
malformations, an angiogram is obtained as well.
The patient returns to the Gamma Knife Center while a treatment plan is made.
A treatment plan is developed by computer using the brain images. This is done
by the coordinated efforts of the neurosurgeon, radiation oncologist and
radiation physicist.
The completed plan outlines the gamma ray dose and location within the brain for
each treatment.
The patient lies on the treatment bed of the Gamma Knife unit while the frame is
affixed to the appropriate collimator which determines the size of the
treatment.
The treatment table is moved into the Gamma Knife where the patient rests for a
few minutes during each painless treatment.
Usually more than one treatment is given to completely cover the abnormal brain
tissue. Between each treatment the patient is moved out of the Gamma Knife so
minor adjustments in the stereotactic frame and collimator can be made.
After Gamma Knife surgery, the head frame is removed and after a period of rest,
the patient may be discharged or if medically necessary, stay overnight in the
hospital for observation.
Your physician will arrange periodic follow-up examinations and brain imaging to
follow the effects of treatment.
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The effects of Gamma Knife Radiosurgery occur over a period of time that can
range from days to several years, depending on the type of medical condition
treated. Some abnormalities dissolve gradually, eventually disappearing. Others
simply exhibit no further growth.
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Cost studies have shown Gamma Knife Radiosurgery to be less expensive than
conventional neurosurgery because it eliminates lengthy post-surgical hospital
stays, expensive medication and sometimes months of rehabilitation. Importantly,
there are virtually no post-surgical disability and convalescent costs with this
procedure. Gamma Knife Radiosurgery is reimbursed by most insurance companies,
PPO's, HMO's, and Medicare.
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- Tumors within the head from a primary site elsewhere in the body: metastatic
tumors.
- Tumors originating within the brain itself or its coverings: pituitary tumors,
acoustic neuromas, certain gliomas and meningiomas, etc.
- Abnormal blood vessels: arteriovenous malformations.
- Also specific centers within the brain can be destroyed to treat pain, tremors
and other functional disturbances.
- Trigeminal neuralgia
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The majority of brain tumors selected for treatment will disappear or stop
growing over time.
 |
 |
| Metastatic brain tumor before
treatment |
Metastatic brain tumor 2 months
after treatment |
(results vary from patient to patient) |
After one year 40% of arteriovenous malformations are cured increasing to 80%
two years after treatment. The risk of spontaneous bleeding during this time is
not more than untreated malformations.
 |
 |
| Arteriovenous malformation before
treatment |
After
treatment |
(results vary from patient to patient) |
Case treated by Ladislau Steiner MD PhD & Dheerendra Prasad MD, Lars Leksell
Center for Gamma Knife Radiosurgery, Charlottesville VA.
 |
 |
| Cavernous sinus meningioma before
treatment |
After treatment |
(results vary from patient to patient) |
Case treated by Ladislau Steiner MD PhD & Dheerendra Prasad MD, Lars Leksell
Center for Gamma Knife Radiosurgery, Charlottesville VA.
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- Gamma Knife surgery is different from conventional radiation therapy of the
brain because it is only directed to the target and spares unnecessary treatment
of adjacent, normal brain.
- It differs because only a one day treatment is required rather than many
treatments over several weeks and can be repeated if needed.
- It can be used in conjunction with conventional surgery as a boost and can be
used in previously inoperable cases.
- Gamma Knife surgery can replace brain surgery in some patients with brain tumors
and vascular malformations . . . ask your doctor about these options.
- An individual who would be at high risk for complications by conventional
surgery may be a candidate for Gamma Knife surgery. It can be used when prior
surgery or radiation therapy has failed to control the disease process.
- It can be used in conjunction with conventional surgery as a boost and can be
used in cases previously considered inoperable.
- Cost effective.
- Bloodless, virtually painless, no loss of hair with rapid return to activities
of every day living.
- Established effectiveness after 25 years of world wide experience with no
reported mortality and few complications.
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- Early complications
common
- local pain and swelling in the scalp
- headache
rare
- skin reddening and irritation
- nausea
- seizure
- Delayed complications
uncommon
- local loss of hair in superficial lesions
- local brain swelling in treatment site
- local necrosis in the treatment site
rare
- visual loss (dependent on diagnosis)
- deafness (dependent on diagnosis)
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In general the following kinds of radiation are evaluated for purposes of
radiation protection: alpha rays, beta rays, gamma rays, X-rays and neutrons.
Listed below are their definitions.
Gamma Ray
An electromagnetic wave, a gamma ray is similar to ordinary visible light but
differs in energy or wavelength. Sunlight consists of a mixture of
electromagnetic rays of various wavelengths, from the longest, infrared, through
red, orange, yellow, green, blue, indigo and violet, to the shortest in
wavelength, ultraviolet. A gamma ray's wavelength is far shorter than
ultraviolet (i.e. it is far higher in energy). Gamma rays are produced following
spontaneous decay of radioactive materials, such as cobalt-60 and cesium-137. A
cobalt-60 gamma ray can penetrate deeply into the human body, so it has been
widely used for cancer radiotherapy.
X-ray
X-rays have the same characteristics as gamma rays, although they are produced
differently. When high-speed electrons hit metals, electrons are stopped and
release energy in the form of an electromagnetic wave. Wilhelm Roentgen first
observed this in 1895, who considered it a mysterious ray, and thus called it an
X-ray. X-rays consist of mixture of different wavelengths, whereas gamma-ray
energy has a fixed value (or two) characteristic to the radioactive material.
Neutrons
Neutron particles are released following nuclear fission (splitting of an atomic
nucleus producing large amounts of energy) of uranium or plutonium. In fact, it
is neutrons that trigger the nuclear chain reaction to explode an atomic bomb.
However, the human body contains a large amount of hydrogen (a constituent of
water molecules that occupy 70% of the human body), and when neutrons hit the
nucleus of hydrogen, (i.e. a proton that is positively charged), the proton
causes ionizations in the body, leading to various types of damage. At
equivalent absorbed doses, neutrons can cause more severe damage to the body
than gamma rays.
Beta Rays
A particle ray consisting of a fast electron whose mass is nearly 1/2000 of the
mass of a proton or neutron; beta rays are produced following spontaneous decay
of certain radioactive materials, such as tritium (an isotope of hydrogen),
carbon-14, phosphrous-32, and strontium-90. Depending on its energy (or speed),
a beta ray can traverse different distances in water - less than 1 mm for
tritium to nearly 1 cm for phosphorous-32. As with alpha rays, the major concern
for health effects is after their ingestion (i.e. internal exposure).
Alpha Rays
A particle ray consisting of two protons and two neutrons (namely, a nucleus of
helium); alpha rays are produced following spontaneous decay of certain
radioactive atoms, such as radium, plutonium, uranium and radon. Because of its
large mass and positive charge, an alpha ray can usually pass only a short
distance - less than 1 mm - in water. A single piece of paper can stop an alpha
ray effectively. Therefore, health effects of alpha-ray exposures appear only
when alpha-emitting materials are ingested (i.e. internal exposure).
[Source: Idaho State University] |
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