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Glossary of terms

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An element used in contrast media for magnetic resonance imaging.

A pear-shaped receptacle that is located along the anterior and inferior surfaces of the liver just beneath the lower rib cage; it stores bile produced by the liver and releases it into the small intestine to aid in the digestion of fats.

Small stone-like objects made of cholesterol or other substances that form in the gallbladder or bile ducts. For more information see the Gallstones page.

gamma camera
A camera that records the distribution of radiation emitted from a chemical containing a radionuclide that is attracted to a specific organ or tissue of interest.

Gamma Knife
A cobalt-60 based radiation therapy machine used to treat brain tumors and abnormalities. The Gamma Knife delivers 201 beams of highly focused gamma rays to the treatment site. See the Gamma Knife page for additional information.

gamma radiation
(Also called gamma rays.) A very high frequency form of electromagnetic radiation that consists of photons emitted by radioactive elements. Gamma rays can injure and destroy body cells and tissue, especially cell nuclei.

gamma ray
See gamma radiation.

Necrosis (death of one or more cells, or of a portion of tissue or organ) due to obstruction, loss, or diminution of blood supply; it may be localized to a small area or involve an entire extremity or organ (such as the bowel), and may be wet or dry.

A frame housing the x-ray tube, collimators, and detectors in a CT or radiation therapy machine, with a large opening into which the patient is inserted; a mechanical support for mounting a device to be moved in a circular path.

gastroesophageal junction
The point at which the esophagus and the stomach join.

Gastroesophageal reflux disease (GERD)
A condition in which stomach acid leaks into the esophagus. Heartburn is the most common symptom. Left untreated, the disease can cause changes to the tissue lining the esophagus and increase the risk of esophageal cancer.

gastrointestinal (GI)
Relating to the stomach and intestines.

A disease or any condition that affects the stomach.

Establishment of a new opening into the stomach.

The use of an electronic signal from the pumping of the heart to obtain images of heart contractions.

gene therapy
Treatment based on alteration of genetic material.

general anesthesia
The use of medications (intravenous or gases), called anesthetics, that cause unconsciousness and help patients tolerate a medical or surgical procedure. General anesthetics are always administered under the care of an anesthesiologist or nurse anesthetist.

genetic marker
A specific gene or other identifiable portion of DNA that can be used to identify an individual disease or trait.

genetically engineered tumor vaccines
A DNA molecule that is broken into fragments and then rearranged to create an altered microorganism that when administered, induces immunity.

A group of cells that secrete a substance needed by the body.

Of or relating to elated to a gland, a group of cells that secrete a substance needed by the body.

glenoid labrum
A rim of fibrocartilaginous tissue attached to the scapula, or shoulder blade, that provides a deeper socket for the head of the humerus, or upper arm bone. The labrum is a common site of injuries: it can be damaged in falls and from repetitive use, as in throwing and weightlifting.

glial cells
The most abundant cell type in the central nervous system; glial cells surround and support neurons.

A category of brain and spinal cord tumors that begin in glial cells.

Glucophage® (Metformin)
Medication prescribed for diabetics to help the body respond better to its own insulin and decrease glucose production by the liver, ultimately helping to control a patient's blood sugar level. Bristol-Myers Squibb, the manufacturer of Glucophage, recommends that:

  • Glucophage should be stopped at the time of or prior to the procedure.
  • Glucophage should then be withheld for 48 hours after the procedure.
  • Once renal function is found to be normal, Glucophage therapy can be started again.

A major source of energy for human function. During the digestive process, carbohydrates break down into this sugar. It is then carried through the bloodstream to the body’s cells where it is converted to energy or stored.

gluten intolerance
See Celiac disease .

An enlarged thyroid gland, usually evident as a pronounced swelling in the neck.

A patented commercial product known as a waterproof laminate that has multiple uses, including as a material for surgical implants.


  1. Any free (unattached) tissue or organ for transplantation.
  2. To transplant an organ or unattached tissue.
  3. An artificial blood vessel connection used to facilitate kidney dialysis.

grand mal seizure
Also known as tonic–clonic seizure.
A type of seizure or convulsion often associated with epilepsy in which the patient shakes violently and loses consciousness.

Graves' disease
A condition, also called hyperthyroidism, in which the thyroid gland produces more thyroid hormone than the body needs. Symptoms include an enlarged thyroid gland, rapid heart rate, and high blood pressure.

great saphenous vein
The longest vein in the body extending from the foot up the inner thigh to the groin.

guide wire
A thin wire used to guide the placement of a catheter within the body during a minimally invasive procedure.

Guillain-Barre syndrome
An autoimmune illness, often occurring after a viral infection, that causes severe nerve damage.

A physician who specializes in functions and conditions of the female reproductive system.