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Gamma Knife FAQ

Glossary

Acoustic Neuroma

A benign tumor of the eighth cranial nerve. It is sometimes called a vestibular schwannoma or neurinoma. This tumor grows slowly, and causes damage by pressing on nerves related to hearing and balance.

Adenoma

A usually benign tumor arising from a gland, such as a pituitary adenoma.

Adjunct or adjuvant treatment

One treatment given in addition to another. The treatments work together to make each more effective.

Aneurysm

A weak point in a blood vessel, such as an artery or vein, which may then blow up like a balloon. The danger is of the aneurysm bursting and bleeding into the brain, which causes a stroke.

Angiogram/Angiography

This procedure uses X-rays to produce pictures of arteries or veins by injecting a dye (contrast material) into the arteries or veins and "filming" it as it passes through the blood vessels.

Aphasia

Loss of ability to speak or write; loss of ability to understand speech or written words.

Arteriovenous malformation (AVMs)

A tangle of blood vessels in the brain.

Astrocytoma

A brain tumor arising in the supportive tissue of the brain. They are the most common primary CNS tumors, representing about half of all primary brain and spinal cord tumors.

Basal Ganglia

Masses of nerve cells deep within the brain at the base of cerebral hemispheres.

Benign

Not malignant, not cancerous.

Bilateral

Occurring on both sides of the body.

Blastoma

A tumor whose cells have embryonic characteristics, fast-growing and invasive.

Brachytherapy

In radiation therapy, the use of implants of radioactive material such as radium, iridium at the site or a short distance from the area being treated.

Brain Stem

The bottom-most portion of the brain connecting the cerebrum with the spinal cord. The midbrain, pons, medulla oblongata and reticular formation are all part of the brain stem.

Carcinoma

A malignant tumor that arises from skin or the lining of body organs. They often invade adjacent tissue and spread to distant organs, including the brain.

Central nervous system (CNS)

Pertaining to the brain, cranial nerves and spinal cord.

Cerebellopontine Angle

The angle between the cerebellum and the pons, a common site for the growth of acoustic neuromas (vestibular schwanomas).

Cerebellum

The second largest area of the brain, consisting of two hemispheres or halves and is connected to the brain stem.

Cerebral

Refers to the cerebrum or cerebral hemispheres.

Cerebral Edema

Swelling of the brain tissue due to an accumulation of fluid which may be caused by tumor, toxic chemicals or interaction.

Cerebrospinal Fluid

The clear fluid made in the ventricular cavities of the brain that bathes the brain and spinal cord.

Cerebrum

The largest area of the brain occupying the uppermost part of the skull. It consists of two halves called hemispheres. Each half of the cerebrum is further divided into four lobes: frontal, temporal, parietal, and occipital.

Chondroma

A rare, benign tumor arising at the base of the skull, especially in the area near the pituitary gland. It is very slow growing and might be present for a long time before causing any symptoms.

Chondrosarcoma

This very rare tumor arises from bone and is composed of cartilage. It is a locally invasive malignant tumor.

Chordoma

A rare, benign, slow growing tumor that occurs at the base of the skull in about 1/3 of patients or at the end of the spine.

Choroid Plexus

This is what produces spinal fluid, which flows through the ventricles and meninges surrounding the brain and spinal cord.

Circumscribed or encapsulated

Localized; having a border or being wholly confined to a specific area.

Conformal

Images in three dimensions to the shape of the tumor.

Congenital

Existing before or at birth.

Coronal

Circular In scans, an image from the top of a thin layer of the brain showing both the right and left sides.

Cranial Nerves

12 pairs of nerves having their origin in the brain.

Craniopharyngioma

A benign tumor arising from small nests of cells located near the pituitary stalk.

Craniotomy

Surgery involving the removal of skull bone to gain access to the brain and the bone is put back at the end of the operation.

CT

Computed Tomography. Also known as a "CAT scan". A sophisticated procedure using X-rays to produce computerized images through the body.

Cyst

A fluid-filled mass, usually enclosed by a membrane.

Diffuse

Lacking a distinct border, spread out, not localized.

Dosimetry

Measurement of doses.

Edema

Tissue swelling caused by the accumulation of fluid.

Efficacy

Able to achieve the desired results or produces beneficial results.

Encapsulated

Localized. Refers to a tumor that is wholly confined to a specific area, surrounded by a capsule.

Familial

Tending to occur repeatedly in family members, but is not genetic (inherited). Might indicate a susceptibility, or a common environmental influence.

Fractionated

The process of spreading the total required treatment dose over an extended period of time.

Focal

Limited to one specific area.

FSR or SRT (Fractionated Stereotactic Radiotherapy)

A moderately high dose radiation treatment usually received over three to eight sessions.

Ganglia

A mass of nerve tissue or a group of nerve cell bodies.

Glial Tissue/Cells

The supportive tissue of the brain. The most common cells are astrocytes and oligodendrocytes. Unlike nerves, glial can reproduce itself. Glial is the origin of the largest percentage of brain tumors.

Glioblastoma Multiforme (GBM)

A malignant tumor which commonly invades adjacent tissue and spreads throughout the CNS. This is usually a fast growing tumor containing a mixture of cell types.

Glioma

Any tumor arising from glial tissue of the brain, which provides energy, nutrients and other support for nerve cells in the brain.

Glomus Jugulare

A very rare, slow growing, benign tumor that invades the temporal bone.

Gy=Gray

A unit of absorbed radiation.

Hemangioblastoma

A benign tumor-like mass arising from blood vessels and is often cystic. It is often associated with von Hippel-Lindau disease.

Hemangiopericytoma

A rare tumor, grade II or grade III, different from the meningioma, although rising from the same cells.

Hemiparesis

Muscle weakness of one side of the body.

Hemiplegia

Complete paralysis of one side of the body.

Hereditary

Inherited or genetic; passed on from parent to child.

Hyperfractionation

An increased number of smaller dosage treatments of radiation therapy.

Hypothalamus

Part of the wall of the third ventricle and at the base of the optic chiasm.

Immunotherapy

Use of the body's immune system to fight tumors.

IMRT (Intensity Modulated Radiation Therapy)

The intensity of the radiation can be changed during treatment to spare adjoining normal tissue and increase the dose to the tumor.

Infiltrating

Penetrating normal, surrounding tissue.

Infratentorial

Below the tentorium, a flap of the membrane protecting the brain that separates the cerebral hemispheres from the brain structures in the posterior fossa.

Interstitial radiation

Implantation of radioactive seeds into a tumor.

Intracavity

Treatment delivered into the space created when the brain tumor was removed.

Intracerebral

Located within the cerebral hemispheres.

Intracranial

Within the skull.

Intraventricular

Injection into a ventricle. There are four ventricles or cavities in the brain, which are filled with cerebrospinal fluid and linked by ducts so the fluid can circulate.

Invasive

Refers to a tumor that invades healthy tissues; also called diffuse or infiltrating.

Irradiation

Radiation therapy; treatment by ionizing radiation.

Isodose

In radiation, to have equal doses of radiation in different areas.

Lesion

A change in tissue structure due to injury or disease.

Linac Radiosurgery

Radiosurgery given by a device producing powerful X-rays, which is normally used to give conventional radiotherapy. The unit is modified by bolting on a collimator which focuses the beam down to a few millimeters in width. Treatment with this equipment tends not to be as accurate as using the Gamma Knife, which is specifically designed for radiosurgery.

Lipoma

A rare, benign tumor composed of fat tissue, commonly located in the corpus callosum.

Local

In the area of the tumor; confined to one specific area.

Malignant

Cancerous or life-threatening, tending to become progressively worse.

Mass Effect

Damage to the brain due to the bulk of a tumor, the blockage of fluid, and/or excess accumulation of fluid within the skull.

Median Survival

Median means the middle value. An equal number of people live longer as die earlier than the median.

Medulloblastoma (MDL)

Fast-growing, invasive tumors located in the cerebellum that frequently spread to other parts of the central nervous system via the spinal fluid.

Membrane

Thin layer of tissue covering a surface, lining a body cavity, or dividing a space or organ.

Meninges

They are three, thin membranes that completely cover the brain and the spinal cord. Spinal fluid flows in the space between two of the membranes.

Meningioma

A brain tumor arising from the fibrous tissues that cover the brain's surface and spinal cord.

Metastasis

In cancer patients, the spreading of malignant cells.

Microsurgery

Delicate surgery involving the use of a special microscope and small instruments.

Morbidity

Complications directly resulting from treatment.

MRI Scan (Magnetic Resonance Imaging)

A scanning device that uses a magnetic field, radio waves, and a computer. Signals emitted by normal and diseased tissue during the scans are assembled into an image.

Necrosis

Dead cells.

Neoplasm

A tumor, either benign or malignant.

Nervous System

The entire integrated system of nerve tissue in the body: the brain, brain stem, spinal cord, nerves and ganglia.

Neuroectoderm

The region of the embryo that eventually develops into the nervous system.

Nuclear Medicine

The branch of medicine that deals with the use of radioisotopes in therapy and diagnosis.

Palliative Care

Caring for a patient by maintaining the best quality of remaining life.

Paresis

Weakness.

PET Scan (Positron Emission Tomography)

A special type of X-ray using a radioactive dye which shows areas of the brain that have a higher or lower metabolism than normal. It can sometimes be used when an MRI scan alone is inconclusive. This is a limited-use diagnostic tool.

Photodynamic Radiation Therapy (PRT)

A light sensitive drug is given through a vein and concentrates in the tumor. During a surgical procedure, a special light activates the drug which kills the tumor cells.

Pineal Gland

Lies below the corpus callosum that produces the hormone melatonin. Melatonin is believed to control the biological rhythms of the body.

Pituitary Gland

Composed of two lobes (anterior and posterior). Attached to and receives messages from the hypothalamus. Several hormones are produced by the pituitary including prolactin, corticotropin, and growth hormone.

Pons

Part of the brain stem, containing the origins of the 5th, 6th, 7th and 8th cranial nerves.

Primitive Neuroectodermal Tumor (PNET)

A tumor which appears identical under the microscope to the medulloblastoma, but occurs primarily in the cerebrum and most frequently occurs in very young children.

Protocol

An outline of care; a treatment plan.

Radiation Therapy

The use of radiation to destroy cancer or other abnormal cells in the body. During radiation therapy, a significant amount of healthy normal tissue is irradiated. To reduce the side effects caused by this, the radiation dose is split into a number of treatments, in theory enabling the normal healthy tissue to recover before the next treatment is given.

Radioresistant

Resistant to radiation therapy.

Radiosensitive

Responsive to radiation therapy.

Radiosurgery (stereotactic)

Use of a number of precisely aimed, highly focused beams of ionizing radiation to target a specific area.

Recurrence

The return of symptoms or the tumor itself.

Resection

Surgical removal of a tumor.

Residual tumor

Tumor remaining after surgery.

Sella

The saddle-shaped, hollowed extension of the sphenoid bone that contains the pituitary gland.

Sequela

The full disease process.

SRS (Stereotactic radiosurgery)

A one-session treatment with high dose focal radiation within the brain.

Stereotactic

A method of precisely locating areas in space utilizing 3-dimensional mapping, especially in the areas of the brain.

Steroids

Medications used to decrease swelling around tumors.

Tinnitus

Buzzing or ringing in the ear.

Trigeminal Neuralgia

An inflammatory or degenerative condition of the fifth cranial nerve characterized by severe pain in the face.

Toxoplasmosis

A generalized infection of the central nervous system caused by a small parasite.

Tumor

An abnormal growth.

Vascular

Relating to blood vessels.

Vascularity

The blood supply of a tumor.

Vertigo

Dizziness.

Vestibular Schwannoma

(also known as an acoustic tumor or neuromas) a benign tumor of the eighth cranial nerve, which supplies the ear.

XRT (Conventional external beam radiation therapy)

Small amounts of external beam radiation therapy given over an area to eliminate stray cells and future growth.

 

Frequently Asked Questions

The Gamma Knife is not a knife, but a sophisticated technology that can in some situations replace the surgeon's scalpel with a single, high dose of gamma radiation. It consists of a lightweight head frame; a helmet called a collimator, and the radiation unit itself.
Through advanced imaging and three-dimensional planning techniques, Gamma Knife Radiosurgery delivers multiple, very narrow beams of gamma radiation to small targets inside the brain. It does so by sending radiation beams through 196 holes in a device called a collimator helmet. Only at the point where all 192 beams converge at a single, finely focused point is enough radiation delivered to treat the diseased tissue while nearby healthy tissue is spared.
The Gamma Knife replaces the surgeon's scalpel with a single, high dose of radiation. Like the surgeon's scalpel, the radiation eradicates the diseased area with a safe and effective approach. The patient wears a light weight head frame that attaches to a helmet, through which radiation is precisely focused 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 minimal risk of surgical complications like infection, hemorrhage or leakage of cerebral spinal fluid.
  • 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 tissue.
  • It differs because only a one day treatment is required rather than daily treatments over several weeks from whole brain radiation.
  • 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.
  • An individual who would be at 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.
  • Gamma Knife treatment is 30-70% less than the cost of alternate treatment modalities, including traditional open skull surgery.
  • It is bloodless, virtually painless, no loss of hair with rapid return to activities of every day living.
  • Excellent, well-documented clinical outcomes.
Gamma Knife radiosurgery is especially valuable for patients whose neurologic disorders require a difficult surgical approach or may be impossible by conventional neurosurgical techniques. Patients of advanced age or in poor medical condition can be at an unacceptably high risk for anesthesia and conventional surgery, making Gamma Knife treatment an ideal solution. Gamma Knife technology also is highly beneficial for patients whose lesions are situated in an inaccessible or functionally critical area within the brain. In addition, the treatment can be used as an adjunct to the care of a patient who has undergone brain surgery, interventional neuroradiology, or conventional radiation therapy or chemotherapy.

Potential candidates are reviewed by a multi-disciplinary panel of professionals for the following:

  • Medical history
  • Clinical examinations
  • Imaging studies
  • Previous surgeries and treatments

Conditions for which the Gamma Knife is considered are include benign tumors:

  • meningiomas
  • acoustic neuromas
  • pituitary tumors
  • low grade glioma and skull based tumors
  • Gamma Knife is also considered for malignant tumors such as:

    • metastases and malignant gliomas

    It can be an effective treatment for vascular malformations such as arteriovenous malformations cavernous angiomas And it can treat functional disorders such as trigeminal neuralgia, parkinsons disease and essential tremors.

    Most patients are referred by their doctors to the Gamma Knife program. Many patients make self-referrals. The Gamma Knife team meets and looks at each patient's records to determine if Gamma Knife treatment would be advantageous to the needs of the patient.
    • Medical and Surgical History
    • Clinical Examinations
    • Imaging Studies, such as MRI and CT and PET scans
    • Function Studies
    The success rate of the Gamma Knife is impressive. Supported by two decades of clinical research, this neurosurgical tool has meet with unprecedented results. Clinical applications continue to grow, and its many benefits as a non-invasive treatment modality continue to make it the treatment of choice in certain clinical conditions.
    On the day of treatment, the 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 either has an MRI or CT imaging study or, in the case of an arteriovenous malformation (AVM), angiography, in order to precisely locate the diseased area to be treated. Data from the imaging study is transferred into the treatment planning computer. While the patient rests, the treatment team (which consists of a neurosurgeon, radiation oncologist and physicist) 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 individual treatment plan is completed, the patient is placed on the Gamma Knife couch and precisely positioned. The patient is then moved automatically, head first into the machine, 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 machine, and the head frame is removed. The patient may remain in the hospital overnight for observation.
    There is a slight discomfort from the local anesthetic used prior to frame placement. Patients have reported that they feel pressure when the pins are inserted but no pain. The pressure can be a little uncomfortable but id does not last for long. Anesthetic is used so the patient will have very little discomfort. The patient does not see or feel the radiation during treatment.
    The patient remains conscious throughout the entire procedure, and may communicate with the treatment team.
    No, the head is not shaved, in rare cases, the treatment may cause some hair loss.
    When the treatment session is finished, the head frame will be removed. Sometimes there is a little bleeding from where the pins were attached to the head. Gauze and pressure will be applied to stop the bleeding and keep the area clean. A small Band-Aid is placed over the pin locations. It is recommended that the patient take it easy over the next 12-24 hours. Normal activities can be resumed within a few days.
    The Gamma Knife allows non-invasive brain surgery to be performed with extreme precision while sparing healthy tissues surrounding the targeted treatment area. Also, because surgical incision is not required, the risks usually involved with open brain surgery, such as hemorrhage or infection, may be reduced. Hospitalization and recovery time are minimal. While individual patient outcomes may vary, patients may resume their normal pre-surgery lifestyle within a few days.
    The effects of Gamma Knife radiosurgery occur over a period of time that can range from several days to several years, depending on the type of medical condition treated. The radiation alters the DNA of the tumor or lesion being treated so that the cells no longer reproduce, eventually rendering the lesion inert. Some abnormalities dissolve gradually, eventually disappearing. Others simply exhibit no further growth. The effectiveness of the treatment is monitored by MRI scans at regular intervals. The goal of radiosurgery is tumor control, which is defined as stable tumor size or tumor shrinkage.
    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, PPOs, HMOs and Medicare.
    Within a few days. The only restrictions you will have are the same you had prior to your treatment.
    Gamma Knife radiosurgery is reimbursed by most insurance companies, PPOs, HMOs and Medicare.
    There is a slight discomfort from the local anesthetic used prior to frame placement. Patients have reported that they feel pressure when the pins are inserted but no pain. The pressure can be a little uncomfortable but it does not last for long. Anesthetic is used so the patient will have very little discomfort. The patient does not see or feel the radiation during treatment.