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Glossary of terms

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B cell
A type of white blood cell (called a lymphocyte) that is an essential component of the immune system. Non Hodgkin B cell lymphoma begins in B cells.

balloon angioplasty
An image-guided procedure in which a balloon-tipped catheter, a long thin, hollow plastic tube, is guided into an artery and advanced to a blockage or narrowing in a blood vessel. The balloon is then inflated to open the vessel, deflated and removed.

balloon assistance
A vascular treatment technique that uses catheter-guided balloons to open narrowed blood vessels.

barium (Ba)
A naturally occurring metal that is used in barium sulfate, a contrast material. Barium is most commonly used for studying the gastrointestinal (GI) tract.

barium sulfate
A white insoluble radiopaque powder that is used as a contrast material to make certain body parts more visible in x-ray images. Radiopaque substances limit the penetration of x-rays and other forms of radiation.

barium swallow
Also called an esophagram.
An x-ray examination that uses a barium sulfate contrast material to assess both the pharynx and esophagus in the upper gastrointestinal tract.

Barrett’s esophagus
A condition in which the cells lining the esophagus undergo change due to damage from repeated exposure to stomach acid. These changes increase the risk of esophageal cancer. Treatments include antacids, proton pump inhibitors, dietary changes and surgery.


becquerel (Bq)
The SI unit of measurement of radioactivity, equal to 1 disintegration per second;;
1 Bq = 0.027 × 10-9 Ci.

Not cancerous. May also be defined as non-malignant. Benign is also used to describe medical conditions that have a mild course.

benign prostatic hyperplasia (BPH)
An enlarged prostate gland, a common problem among older men. See the Benign Prostatic Hyperplasia page for additional information.

beta blocker
A type of medicine used to lower blood pressure, treat chest pain and heart failure, and to prevent a heart attack.

beta-amyloid plaque
Thick deposits of proteins in the brain considered one of the hallmarks of Alzheimer’s disease (AD).

An iodine-131 agent used in radioimmuniotherapy to treat non-Hodgkin lymphoma.

A greenish-yellow fluid secreted by the liver, stored in the gallbladder and released through tubular passageways called bile ducts into the bowel to help digest fat and carry away waste.

bile ducts
Tubular structures that course through the liver and carry bile – a greenish-yellow fluid – to the gallbladder and small intestine where it is used to help digest fat.

biliary atresia
A condition present at birth in which there is a blockage in the ducts that carry bile from the liver to the gallbladder.

biliary system
See biliary tract.

biliary tract
Also called the biliary system.
Includes the gallbladder and tubular structures called ducts that course through the liver. Bile, a greenish-yellow fluid secreted by the liver, is stored in the gallbladder and released into the bowel through bile ducts to help the small intestine digest fat and carry away waste.

biologic therapy
Also called biotherapy
A treatment that involves natural or laboratory-made substances designed to boost, direct or restore the body's natural defenses against cancer.

biologically active coils
A type of coil, made of soft platinum wire smaller than a strand of hair and available in different diameters and lengths, used in a procedure called a detachable coil embolization to treat an aneurysm (a bulge) or a blood vessel malformation called a fistula (a false passageway) that occurs in the brain and other parts of the body. Using image guidance, the coils are placed at the site of a bulge or passageway, where it helps block the flow of blood and prevents a rupture of the vessel.

Biometrics requires a user to provide a unique identifier, such as a fingerprint or voice sample, which is compared to a stored record before the user can gain access to the computer.


  1. Process of removing tissue from living patients for diagnostic examination.
  2. A specimen obtained by biopsy.

See the Biopsies page for additional information.

Also called biologic therapy
A treatment that involves natural or laboratory-made substances designed to boost, direct or restore the body's natural defenses against cancer.

A balloon-like organ where urine is stored before being passed from the body.

bleeding disorder
A condition in which the body's blood clotting mechanism, which turns blood from a free-flowing liquid to a thickened state, is defective.

blood clot
A thickened mass of blood. For additional information see the Blood Clots page.

blood clotting
See blood coagulation.

blood coagulation
Also called blood clotting.
A process in which blood changes from a free-flowing liquid to a semi-solid gel.

blood oxygenation
The level of oxygen in the blood.

blood thinning agents
Also known as blood thinners. Medicine used to prevent blood clots from forming or getting larger.

bone marrow
The soft tissue that fills the cavities of bones in which blood cells are produced.

bone scan
An imaging test in which a radiotracer called technetium-99m is injected into a vein and travels to the bone where it is detected by a special camera.

The center of the cylindrical shaped magnet (often referred to as a doughnut) within an magnetic resonance imaging (MRI) scanner.

The part of the digestive system distal to the stomach, consisting of the small and large intestines, that digest and eliminate food.

bowel cancer
See colorectal cancer.

Also called internal radiation therapy.
A type of radiation therapy used to treat cancer, involving the placement of a radioactive material, either temporarily or permanently, directly inside the body. For more information please refer to the Brachytherapy page.

brain herniation
An often fatal condition that results when brain tissue, fluid or blood vessels are pushed outside the skull.

brain mapping
A medical imaging study of the brain's surface using small electrodes to stimulate a nerve so its electrical response can be measured. By determining the role of specific nerves in a patient, this technique helps surgeons avoid damage to sensitive areas while operating on the brain.

The base of the brain consisting of stems connected to the spinal cord.

BRCA1 and BRCA 2
Human genes that belong to a class of genes known as tumor suppressors. A mutation of these genes has been linked to hereditary breast and ovarian cancers.

breast coil
A wire coil placed around the breast that sends and receives radio waves within the magnetic field of an MRI unit to create images.

breast density
A measure of the proportions of fat, connective tissue and breast tissue within the breast. A dense breast has a greater amount of ducts, glands, fibrous tissue and less fat. When mammography is performed, many cancers can be difficult to see in patients with dense breast.

brentuximab vedotin
See Adcetris®.

The large air passages that lead from the trachea (windpipe) to the lungs.

bronchial tubes
Tubes that carry air from the windpipe into the lungs.

A dilation (widening) of the bronchi (the "breathing tubes"), often caused by infection. Serious complications may occur, and some patients require surgical removal of the affected part of the lungs.

Inflammation (swelling) of the mucous membrane of the two subdivisions of the trachea (air tube) that conveys air to and from the lungs.

An instrument used to examine the trachea and bronchi.

Visual inspection of the inside of the trachea and the bronchial passages of the lungs, using a rigid or flexible tube or catheter called a bronchoscope.

An abnormal sound heard when listening with a stethoscope over an organ or blood vessel such as the carotid artery in the neck.

Budd-Chiari syndrome
A blockage of one or more hepatic veins, which carry blood from the liver back toward the heart.

bulla, pl. bullae
A thin-walled air "cyst" within the lung, found in patients with emphysema.

bursa, pl. bursae
A closed sac or envelope lined with a membrane and containing lubricating fluid, usually found or formed in areas subject to friction; e.g., over an exposed or prominent part or where a tendon passes over a bone.