Gamma Knife Glossary 2017-01-28T09:41:35+00:00

Gamma Knife Glossary

See the FAQs and the health library for more detailed information about the Gamma Knife.

A – BCD – H I – L M – N P – RS – X

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
Usually a 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 an aneurysm bursting and bleeding into the brain, which causes a stroke.

Angiogram/angiography
A procedure that 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 abnormal blood vessels in the brain.

Astrocytoma
A brain tumor arising from the supportive cells (astrocytes) of the brain. They are the most common primary central nervous system tumors, representing about half of all primary brain and spinal cord tumors.

Benign
Not malignant, not cancerous, usually grows slowly.

Bilateral
Occurring on both sides of the body.

Blastoma
A tumor whose cells have embryonic characteristics (usually fast-growing and invasive).

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.

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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.

Cerebellum
The second largest area of the brain, connected behind the brain stem. This part of the brain controls coordination.

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.

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 one-third of patients) or at the end of the spine.

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

Computed tomography (CT; also known as a “CAT scan.”)
A sophisticated procedure using x-rays to produce computerized images of the body.

Conformal
A three-dimensional image that conforms to the shape of the tumor.

Cranial Nerves
The 12 pairs of nerves that originate 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. The bone is put back at the end of the operation.

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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.

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

Focal
Limited to one specific area.

Fractionated Stereotactic Radiotherapy (FSR or SRT)
A moderately high-dose radiation treatment usually received over three to eight sessions.

Glioblastoma Multiforme (GBM )
A malignant tumor which commonly invades adjacent tissue and spreads throughout the central nervous system. This is usually a fast growing tumor containing a mixture of cell types.

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

Gy=Gray
A unit of absorbed radiation.

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.

Hypothalamus
Part of the brain that forms the wall of the third ventricle that controls hormonal function, appetite and body temperature.

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Immunotherapy
Use of the body’s immune system to fight tumors.


Penetrating normal, surrounding tissue.

Intracranial
Within the skull.

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 performed by a device (linear accelerator) producing powerful x-rays, normally used for conventional radiotherapy. The unit is modified by bolting on a collimator which focuses the beam down to a few millimeters in width.

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

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Magnetic Resonance Imaging (MRI Scan)
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.

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

Median Survival
The middle survival value. (An equal number of people live longer as die earlier than the median.)

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

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.

Necrosis
Dead cells.

Neoplasm
A tumor, either benign or malignant.

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

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Paresis
Weakness.

Pituitary Gland
An endocrine gland composed of two lobes (anterior and posterior) that is attached to and receives messages from the hypothalamus. Several hormones are produced by the pituitary including prolactin, corticotropin, growth hormone and antidiuretic hormone or ADH.

Pituitary tumor
Usually benign tumors arising from pituitary cells. Pituitary tumors can cause elevation of hormone levels and may grow to compress the optic chiasm and effect vision.

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

Positron Emission Tomography (PET Scan)
A special type of x-ray using a radioactive dye that shows areas of the brain with a higher or lower metabolism than normal. It can sometimes be used when an MRI scan alone is inconclusive, and may be useful in detecting tumors.

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 single precisely aimed, highly focused beam 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.

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Sequela
The full disease process.

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

SRS (Stereotactic radiosurgery)
A one-session treatment with high dose focal radiation within the brain.

Stereotactic radiosurgery (SRS)
A one-session treatment with high-dose focal radiation within the brain.

Steroids
Medications used to decrease swelling around tumors.

Tinnitus
Buzzing or ringing in the ear.

Trigeminal Neuralgia
A condition of the fifth cranial nerve characterized by severe “electric like” pain in the face.

Tumor
An abnormal growth.

Vascular
Relating to blood vessels.

Vertigo
Dizziness.

Vestibular schwannoma (also known as an acoustic tumor or acoustic neuroma)
A benign tumor of the eighth cranial nerve, which is involved in balance and hearing. Patients frequently present with loss of hearing.

XRT (conventional external beam radiation therapy)
Small amounts of external beam radiation given over many sessions to control tumor growth.

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For more information or to find out if this treatment option is right for you, please call our Gamma Knife Center at 501-603-1800.

If you have a patient with trigeminal neuralgia and wish a consult, please call 501-603-1800.