adenosine triphospate (ATP) - a phosphorylated nucleotide composed of adenosine and three phosphate groups that supplies energy for many biochemical cellular processes by undergoing enzymatic hydrolysis especially to ADP -- called also adenosine triphosphate

aneurysm - an abnormal blood-filled dilatation of a blood vessel and especially an artery resulting from disease of the vessel wall

apoptosis - a genetically determined process of cell self-destruction that is marked by the fragmentation of nuclear DNA , is activated either by the presence of a stimulus or by the removal of a stimulus or suppressing agent, is a normal physiological process eliminating DNA -damaged, superfluous, or unwanted cells (as immune cells targeted against the self in the development of self-tolerance or larval cells in amphibians undergoing metamorphosis), and when halted (as by genetic mutation) may result in uncontrolled cell growth and tumor formation -- called also programmed cell death

carotid artery - either of the two main arteries that supply blood to the head of which the left in humans arises from the arch of the aorta and the right by bifurcation of the brachiocephalic artery with each passing along the corresponding anterolateral aspect of the neck and dividing opposite the upper border of the thyroid cartilage into an external branch supplying the face, tongue, and external parts of the head and an internal branch supplying the brain, eye, and other internal parts of the head -- called also carotid

clinical trial - a scientifically controlled study of the safety and effectiveness of a therapeutic agent (as a drug or vaccine) using consenting human subjects

double blind - The design of a study in which neither the investigator or the subject knows which medication (or placebo) the subject is receiving.*

endarterectomy - surgical removal of the inner layer of an artery when thickened and atheromatous or occluded (as by intimal plaques)

embolus - an abnormal particle (as an air bubble) circulating in the blood

exclusion criteria - Refers to the characteristics that would prevent a subject from participating in a clinical trial, as outlined in the study protocol.

hemorrhagic stroke - stroke caused by the rupture of a blood vessel with bleeding into the tissue of the brain*

infarct - an area of necrosis in a tissue or organ resulting from obstruction of the local circulation by a thrombus or embolus

ischemic - deficient supply of blood to a body part (as the heart or brain) that is due to obstruction of the inflow of arterial blood (as by the narrowing of arteries by spasm or disease)

ischemic stroke - stroke caused by thrombosis or embolism

little stroke - a usually transient blockage of one or more arteries in the cerebrum causing temporary numbness or impaired function of a part, slowed mentation, speech defects, dizziness, and nausea

mitochondrion - any of various round or long cellular organelles of most eukaryotes that are found outside the nucleus, produce energy for the cell through cellular respiration, and are rich in fats, proteins, and enzymes -- called also chondriosome

National Institute of Health Stroke Scale (NIHSS) - questionnaire administered by a trained professional to determine the severity of a stroke

penumbra - a blurred area in a radiograph at the edge of an anatomical structure

perfusion - an act or instance of perfusing; specifically : the pumping of a fluid through an organ or tissue

pharmacoeconomics - The study of cost-benefit ratios of drugs with other therapies or with similar drugs. Pharmacoeconomic studies compare various treatment options in terms of their cost, both financial and quality-of-life. Also referred to as "outcomes research".*

phase I study - The first of four phases of clinical trials, Phase I studies are designed to establish the effects of a new drug in humans. These studies are usually conducted on small populations of healthy humans to specifically determine a drug's toxicity, absorption, distribution and metabolism.*

phase II study - After the successful completion of phase I trials, a drug is then tested for safety and efficacy in a slightly larger population of individuals who are afflicted with the disease or condition for which the drug was developed.*

phase III study - The third and last pre-approval round of testing of a drug is conducted on large populations of afflicted patients. Phase III studies usually test the new drug in comparison with the standard therapy currently being used for the disease in question. The results of these trials usually provide the information that is included in the package insert and labeling.*

phase IV study - After a drug has been approved by the FDA, phase IV studies are conducted to compare the drug to a competitor, explore additional patient populations, or to further study any adverse events.*

photo - light: radiant energy

photochemical - of, relating to, or resulting from the chemical action of radiant energy and especially light

photochemotherapy - treatment especially for psoriasis in which administration of a photosensitizing drug is followed by exposure to ultraviolet radiation or sunlight

photodynamic - of, relating to, or having the property of intensifying or inducing a toxic reaction to light (as the destruction of cancer cells stained with a light-sensitive dye) in a living system

photosensitize - to make sensitive to the influence of radiant energy and especially light

phototherapy - the application of light for therapeutic purposes

pivotal study - Usually a phase III study which presents the data that the FDA uses to decide whether or not to approve a drug. A pivotal study will generally be well-controlled, randomized, of adequate size, and whenever possible, double-blind.*

placebo - An inactive substance designed to resemble the drug being tested. It is used as a control to rule out any psychological effects testing may present. Most well-designed studies include a control group which is unwittingly taking a placebo.*

randomization - Study participants are usually assigned to groups in such a way that each participant has an equal chance of being assigned to each treatment (or control) group. Since randomization ensures that no specific criteria are used to assign any patients to a particular group, all the groups will be equally comparable.

stroke volume - the volume of blood pumped from a ventricle of the heart in one beat

therapy - therapeutic treatment of a mental or bodily disorder

thrombus - a clot of blood formed within a blood vessel and remaining attached to its place of origin

transient ischemic attack - a brief episode of cerebral ischemia that is usually characterized by temporary blurring of vision, slurring of speech, numbness, paralysis, or syncope and that is often predictive of a serious stroke -- abbreviation TIA; called also mini-stroke