- For Patients

Glossary of terms

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z All 

abdominal aorta
The portion of the largest artery in the body that runs through the abdomen; it supplies oxygenated blood to the abdominal and pelvic organs and the legs.

abdominal aortic aneurysm (AAA)
Sometimes called triple A.
A ballooning out of a segment of artery caused by disease or weakness in the vessel wall (called an aneurysm) that occurs in the portion of the aorta that runs through the abdomen. For more information, see the Abdominal aortic aneurysm page.

abdominoperineal resection
A surgical procedure in which cancer cells in the anus, rectum and part of the large intestine are removed through an incision made in the abdomen.

See radiofrequency ablation.

A localized infection consisting of pus surrounded by inflamed tissue.

absence seizure
See petit mal seizure.


  1. In radiology, the uptake of energy from radiation by the tissue or medium through which it passes.
  2. In radiation or medical physics, the number of disintegrations per second of a radionuclide.

A drug that reduces pain and fever but not inflammation. A member of the family of drugs called analgesics, it is found in many over-the-counter medications, such as Tylenol®.

acquired immunodeficiency syndrome (AIDS)
A stage of human immunodeficiency virus (HIV) infection in which the immune system is so badly damaged the body is unable to fight off infections and disease.

Referring to the rapid onset of a disease or condition.

Also called brentuximab vedotin
A treatment for Hodgkin lymphoma that combines a chemotherapy drug with a monoclonal antibody that attaches to a specific molecule on the cancer cells.

adjuvant therapy
Treatment designed to be contributory or complementary to primary therapy. See also definitive treatment.

adrenal glands
Small glands that sit atop each kidney and produce hormones important in regulating metabolism, blood pressure and response to stress.

afterloaded implant
A brachytherapy treatment in which a remote-controlled machine pushes radioactive material through a delivery device to the site of a tumor.

A hypersensitive reaction to common, often harmless substances, most of which are found in the environment.

Involving genetically similar but not identical donor in a medical procedure such as a stem cell transplant.

Tissue graft from a separate donor.

A drug that lowers an elevated level of uric acid in the blood caused by some cancer treatments.

Alpha-1 antitrypsin (A1AT)
A protein that protects the lung. A1AT deficiency puts a person at risk of developing emphysema or chronic obstructive pulmonary disease (COPD).

Alpha-1 antitrypsin deficiency (A1AD)
A genetic disorder caused by low levels of alpha-1 antitrypsin, a protein that protects the lungs. Alpha-1 antitrypsin deficiency (A1AD) puts a person at risk of developing emphysema or chronic obstructive pulmonary disease (COPD). See the COPD page for additional information.

Tiny air sacs located at the end of the respiratory tract in the lungs that allow inhaled oxygen to enter the bloodstream and carbon dioxide to leave the bloodstream with exhalation.

The suction of fluid from the amniotic sac through the use of a needle inserted through the abdomen.

See amniotic sac.

amniotic sac
Membrane filled with fluid within the abdomen that holds the embryo/fetus.

A drug that relieves pain.

A group of hormones produced by both men and women. They are present in much higher levels in men and govern the growth and development of the male reproductive system. In women, they are converted to hormones called estrogens.

A condition in which too few red blood cells are in the bloodstream, resulting in insufficient oxygen to tissues and organs. For additional information see the Anemia page.

Drugs used to induce loss of sensation for the patient in preparation for operative procedures.

A physician specializing in the controlled loss of sensation through anesthesia.

Drugs used to induce loss of sensation for the patient in preparation for operative procedures.

A ballooning out of a segment of blood vessel caused by disease or weakness in the vessel wall. It may lead to rupture and serious or fatal bleeding.

Cramp-like pain that comes and goes, and is made worse by physical effort. It is a sign that the tissue or organ supplied by a narrowed artery is not getting enough blood or oxygen. For more information see the Angina Pectoris page.

X-ray imaging of the heart, coronary arteries and/or great vessels made visible by injection of a dye directly into the vessel via a catheter. In other instances, CT or MRI can be used to create three-dimensional pictures of blood vessels.

Formation of new blood vessels.

angiogenesis inhibitors
Drugs that interfere with the growth of blood vessels in the tumor, thus starving the tumor of the nutrients and oxygen it needs to grow. Also called angiostatic therapy.

In a conventional angiogram, a dye is injected into the bloodstream and x-rays are taken to visualize the blood vessels. In other instances, CT or MRI can be used to create three-dimensional pictures of blood vessels.

Relating to or utilizing angiography.

An examination of blood vessels that uses X-ray, CT or MR imaging and an injection of a radiopaque contrast material to image arteries in the brain, heart, kidneys, gastrointestinal tract, aorta, neck, chest, limbs and pulmonary circulatory system.

Reconstitution or reopening of a blood vessel; may involve balloon dilation, mechanical stripping of the inside of the blood vessel, forceful injection of a elastic filamentous protein, or placement of a stent. For details see the Angioplasty and Vascular Stenting page.

angiostatic therapy
See angiogenesis inhibitors.

The outer layer of intervertebral discs, sponge-like cushions between the vertebrae, or bones, of the spine.

The process of removing all indentifiers or codes that directly or indirectly link a sample or data to a specific identifiable person.

anterior fibromuscular stroma
The anterior surface of the prostate.

A class of medications used to treat bacterial infections by killing or inhibiting the growth of bacteria.

Substances that neutralize body toxins and bacteria.

anticoagulant therapy
The use of anticoagulant drugs (blood-thinners) to treat blood clots, including those due to pulmonary embolism and deep venous thrombosis in the calf.

A drug used to prevent or reduce the severity of seizures associated with epilepsy or other seizure disorders.

antiplatelet drug
A medication that interferes with the normal function of blood platelets and thereby reduces the tendency for blood to clot; commonly called a blood thinner.

The opening at the end of the gastrointestinal tract through which stool, or solid waste, leaves the body.

The largest artery in the body; it distributes blood from the heart to the entire body via the circulatory system.

aortic aneurysm
A ballooning-out of a segment of artery caused by disease or weakness in the vessel wall (called an aneurysm) the largest artery in the body, the aorta.

appendiceal lumen
Inside of the appendix where mucus, created by the appendix, travels and empties into the large intestines.

An inflammation (swelling) of the appendix, usually caused by a blockage at the opening of the appendix and a subsequent infection. See the appendicitis page for additional information.

A stone, calcification or calcific deposit in the appendix.

A wormlike "pouch" several inches long located near the beginning of the large intestine, in the lower right portion of the abdomen. At this time, the role the appendix plays in the human body is not known.

arachnoid membrane
A thin membrane enclosing the brain and spinal cord.

argon gas
A colorless, odorless gas found in the air and used in its liquefied state in cryosurgery to freeze and destroy diseased tissue, including cancer cells.

An abnormal rhythm of the heart.

Hardening of the arteries; types generally recognized are: atherosclerosis, Mönckeberg's arteriosclerosis, and arteriolosclerosis.

arteriovenous fistula
An abnormal connection between an artery and a vein. This can be surgically created for hemodialysis (see dialysis arteriovenous fistula) but can also be caused by trauma. These fistulas can commonly be treated by interventional radiologists.

arteriovenous malformation (AVM)

  1. An abnormal connection between arteries and veins that allows blood flow to bypass the small vessels where oxygen and tissue nutrients are exchanged. These unusual malformations may be present at birth or may result from injury or infection. They are often found in the brain and spinal cord, but may occur anywhere in the body.
  2. A tangle of dilated blood vessels that disrupts normal blood flow in the brain.

Vessels that carry blood away from the heart.

Inflammation (swelling) of a joint or a state characterized by inflammation of joints. See the Arthritis page for additional information.

An imaging study of a joint that uses a contrast material and either magnetic resonance imaging (MRI) or a special form of real-time x-ray imaging called fluoroscopy.

In radiology, something artificial that appears on a medical image but is not a part of the living tissue being examined. The image distortion could be due to an obstruction, such as a surgical metal clip, or to a problem with the imaging equipment.

A group of potentially dangerous, naturally occurring minerals with long, thin fibers; asbestos was once extensively used in building materials and commercial products. Asbestos inhalation can cause a variety of health problems (e.g., asbestosis, pleural effusion, mesothelioma or lung cancer).

A condition in which fluid accumulates in the abdomen and causes swelling; it may be caused by cirrhosis (chronic liver disease), cancer, heart failure, kidney failure, tuberculosis and/or pancreatic disease.

A member of the family of drugs called nonsteroidal anti-inflammatory agents (NSAID) that reduces pain, fever, inflammation, and blood clotting.

A condition of the lungs characterized by a narrowing of the airways and excessive mucus; can cause difficulty breathing, wheezing and coughing.

Having no signs or symptoms.

A minimally invasive treatment for blocked arteries that uses a catheter with a sharp blade or laser on the end to remove plaque from a blood vessel.

Arteriosclerosis characterized by irregularly distributed lipid deposits, or plaque, in large and medium-sized arteries; such deposits provoke fibrosis and calcification (hardening of the tissues).

A wasting away or gradual decline of tissues, organs, or the entire body.

Loss of energy of a beam of radiant energy due to absorption, scattering, beam divergence, and other causes as the beam propagates through a medium.

An information system log that keeps a record of all user activity by user identification.

A visual disturbance, such as flashing lights, wavy lines, blurry vision or blind spots, that sometimes occurs prior to the onset of a migraine headache.

Verifying the identity of a person/user to a computer system or assuring that a computer program is a trusted one.

Access controls that restrict access to a system to only authorized users; access control assigns right and privileges of users to resources via single sign-on databases; auto logoff to prevent someone other than the valid user from continuing a session; physical access control for critical computers to prevent console-based malicious attacks, power interruptions or other threats to security of the systems.

autoimmune disease
Any disorder that causes the immune system to attack the body’s own tissues.

Involving one individual as both donor and recipient in a medical procedure such as a stem cell transplant.

automatic spring-loaded needle
Also called core needle.
A spring-loaded device that cuts and retrieves a small tissue specimen in its collecting chamber. It is used for biopsy of many different organs in the body.

axillary lymph node dissection
Surgical exploration and removal of lymph nodes from the armpit area, as a part of breast cancer surgery. Some or all of these lymph nodes are examined under a microscope by a pathologist (a physician specializing in the examination of cells and tissues) to see if cancer cells are present.

axillary lymph nodes
Numerous nodes around the axillary (below the shoulder joint) veins which receive the lymphatic drainage from the upper limb, scapular region and pectoral region (including mammary gland); they drain into the subclavian trunk.

See nerve fibers.