abdominal aorta
Part of the aorta, the largest artery in the body; it supplies oxygenated blood to the abdominal and pelvic organs and legs.

ablation
See radiofrequency ablation.

abscess
A localized infection consisting of pus surrounded by inflamed tissue.

absorption
(ab-sorp-shun)
    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.

acetaminophen
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®.

active surveillance
Also known as watchful waiting or observation, it simply means that a physician and a patient are working together to monitor the status of the disease with no treatment to be undertaken immediately. Together, the doctor and patient will decide when and if treatment is necessary.

adjuvant therapy
Treatment designed to be contributory or complementary to primary therapy.

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

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

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

amniocentesis
(am-nE-O-sen-tE-sis)
The suction of fluid from the amniotic sac through the use of a needle inserted through the abdomen.

amnion
(am-nE-on)
See amniotic sac.

amniotic sac
(am-nE-o-tik)
Membrane filled with fluid within the abdomen that holds the embryo/fetus.

analgesic
A drug that relieves pain.

anemia
A condition in which too few red blood cells are in the bloodstream, resulting in insufficient oxygen to tissues and organs.

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

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

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

aneurysm
(an-yur-izm)
A ballooning out of a segment of artery caused by disease or weakness in the vessel wall. It may lead to rupture and serious or fatal bleeding.

angina
(an-jye-nah)
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.

angiocardiography
(an-jE-O-kar-dE-O-gra-fE)
X-ray imaging of the heart and great vessels made visible by injection of a radiopaque solution.

angiogenesis
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.

angiogram
An imaging study depicting blood vessels. 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.

angiographic
(an-jE-O-graf-ik)
Relating to or utilizing angiography.

angiography
(an-jE-og-ra-fE)
Radiography of vessels after the injection of a radiopaque contrast material. Unlike angioplasty, which is an invasive procedure, angiography breaks the skin only for the insertion of a needle for administering a radiopaque catheter and positioning under fluoroscopic control. This technique is used to image arteries in the brain, heart, kidneys, gastrointestinal tract, aorta, neck, chest, limbs and pulmonary circuit.

angioplasty
(an-jE-O-plas-tE)
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.

angiostatic therapy
See angiogenesis inhibitors.

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

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

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

antibodies
Substances that neutralize body toxins and bacteria.

anticoagulant therapy
(an-tI-cO-ag-U-lant ther-a-pE)
The use of anticoagulant drugs to reduce or prevent intravascular or intracardiac clotting.

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.

aorta
(A-Or-ta)
The large artery leaving the heart that distributes blood to the entire body through branches.

appendicitis
An inflammation of the appendix, usually caused by a blockage of the opening of the "pouch" and a subsequent infection.

appendix
A wormlike "pouch" several inches long located near the top 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.

Applicator
A device used to hold a radioactive source in place during brachytherapy.

arachnoid membrane
A thin membrane enclosing the brain and spinal cord. The subarachnoid space lies between the arachnoid membrane and the 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.

arrhythmia
An abnormal rhythm of the heart.

arteriosclerosis
(ar-tEr-E-O-skler-O-sis)
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 communication between an artery and vein that may be present at birth or may result from injury or infection. Blood may flow directly from the artery to the vein, bypassing the small vessels where oxygen and tissue nutrients are exchanged. These unusual malformations 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.

artery
Vessels that carry blood away from the heart.

arthritis
(arth-rI-tis)
Inflammation of a joint or a state characterized by inflammation of joints.

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

artifact
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.

ascites
An accumulation of fluid in the abdomen that may be caused by cirrhosis (chronic liver disease), cancer, heart failure, kidney failure, tuberculosis and pancreatic disease.

atherosclerosis
(ath-er-O-skler-O-sis)
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).

atrophy
(at-rO-fE)
A wasting of tissues, organs, or the entire body.

attenuation
(u-ten-yU-A-shun)
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.

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

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

authorization
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.

automated needle
An automated needle is a spring-loaded device that cuts and retrieves a small tissue specimen in its collecting chamber.

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
(ax-il-ArE limf nOdz)
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.