Vascular Terminology Exam, Exams of Medicine

Download Vascular Terminology Exam and more Exams Medicine in PDF only on Docsity! Vascular Terminology Exam A-C coupling (Alternating Current) - Type of output signal to graphic display connection which responds to changes faster than 0.5Hz. This reduces baseline shifts and results in a stable graphic tracing. A-Mode - A mode of operation in which the display plots time along a horizontal axis and echo amplitude along a vertical axis. In ultrasound, this is referred to as the amplitude mode. Abdominal aorta - A portion of the descending aorta and is located at the level of the diaphragm and extends to its bifurcation (the common iliac arteries) Abduction - Drawing away from the midline, opposite of adduction. Absecess - A localized collection of pus surrounded by inflamed tissue. Absorptioin - A process of conversion of acoustic energy to heat, resulting in a loss of energy. Absorption is a factor in attenuation. Acceleration Index (AI) - This is the systolic acceleration of the Doppler spectral waveform determined by the change in distance between the onset of systolic flow and the peak systolic velocity (cm/sec), divided by the acceleration time (AT). This is reported in frequency units as KJHz/sec/MHz or velocity units as cm/sec2. Acceleration Time (AT) - This is the time interval from the onset of flow to the initial peak-not peak systole. Achrocyanosis - Coldness and blueness of an extremity; a vasospastic condition. Symptoms include a symmetrical, mottled cyanosis of the hands and feet, cold seat on the digits. Cold accentuates, warmth relieves the symptoms. Acoustic - Having to do with sound. Acoustic field - The distribution pattern of sound energy in space and time. Acoustic impedance - Property of a medium equal to the product of density and propagation speed. The intensity of reflection (echo production) is related to the ratio of difference in acoustic impedance at an interface. The greater the difference in impedance the grater the intensity of reflection. Acoustic shadow - Loss of acoustic properties of targets lying behind an attenuating structure. In the arteries, the most common cause of this is calcified plaque (see calcification). Acoustic varaibles - Pressure, density, temperature, and particle motion. Sound is identified as the rhythmical cyclic of acoustic variables. Acute - Short, severe symptoms of sudden onset or short duration; i.e., not chronic. Adduction - Drawing toward the midline. Adventitia - The outermost layer of an artery. Aliasing - A phenomenon associated with pulsed Doppler; a misrepresentation of the Doppler shift in a negative direction occurs when the Doppler shift exceeds half the pulse repetition frequency. Allen test - A test performed to check the continuity of the palmar arch normally supplied by both the radial and ulnar arteries. The test may be performed using a Doppler, a PPG, or Strain Gauge Plethysmograph. Amaurosis fugax - Temporary blindness (partial or total) resulting from transient ischemia of the retinal arteries secondary to cerebral arterial disease. The most likely etiology is embolic. Ampere - A unit of electromotive force; one volt acting against the resistance of one ohm (see Ohm's law). Amplifier - An electric device for increasing the amplitude of a signal. Amplitude - The maximum variation in an acoustic variable. It is the difference between the average value and the maximum value of an acoustic variable. Units used with amplitude coincide with the acoustic variable used. Aorta - The main trunk of the arterial system with its origin off the surface of the left ventricle. It is usually described in several portions, the ascending aorta, the aortic arch, and the descending aorta (thoracic and abdominal). Aphasia - Impairment of speech due to cerebral dysfunction. Sensory aphasia: inability to recognize written or spoken words. Motor aphasia: Loss of ability to articulate language. Arcus senilis - An opaque ring around the cornea, seen in the elderly. Array - Transducer array. Arryhthmia - Abnormal heart rhythm. Arterial compliance - The expansile and contractile properties of an artery. Arterial inflow - Pertaining to blood flow into the lower extremities proximal to the level of the common femoral arteries. Arterial insufficiency - Reduction in blood flow within the arterial system. Inadequate blood flow results in hypoxia; the symptoms produced by arterial insufficiency vary with the end organ site. Arterial occlusioin - Complete blockage of an artery. Arterial outflow - Normally pertaining to the medium size blood vessels, common femoral through the popliteal artery. Outflow could also pertain to the vessels carrying blood away from a bypass graft. Arterial runoff - The infra-popliteal vessels (tibial and other distal vessels in the calf). Arterial ulceration - A local defect or excavation which is produced by sloughing of inflammatory necrotic tissue. Arteriography - A radiologic procedure in which an opaque substance is injected into an artery and subsequent x-ray films are taken in order to visualize the arterial system. Arteriography is an invasive procedure with a small but definite associated morbidity and mortality. Arteriole - A minute artery whose distal end leads to a capillary. Arteriosclerosis - Degenerative changes in the artery associated with aging. Arteriotomy - Incision into an artery. Arteriovenous malformation - Congenital nomalies resulting from faulty development of arterial, capillary, venous or lymphatic structures or any combination thereof. These lesions are though to be present from birth and do not represent neoplasms. Arteritis - A disease characterized by inflammation of the walls of the blood vessels (vasculitis). The vessels affected are the arteries (hence the name "arteritis") This usually affects patients over 50 years of age. Cranial arteritis is also known as temporal arteritis or giant cell arteritis. It can lead to blindness and/or stroke. Artery - Any of the blood vessels which carry blood from the heart to the other parts of the body. With the exception of the pulmonary and umbilical arteries, arteries transport oxygenated blood. Arteries are composed of three layers: the intima, media, and adventitia. Artifact - In ultrasound usage, refers to an echo which does not correspond to a real target. In general, refers to any artificial finding which may resemble the expected findings. Artifacts may be intrinsic, e.g., reverberation or extrinsic, e.g., probe or limb movement during an examination. Cuff artifact refers to abnormally high pressures associated with the use of cuffs which are proportionately too narrow for the limb they are encircling. Ascites - Accumulation of serous fluid in spaces between tissues and organs in the abdominal cavity. Atheroma - Fatty degeneration or thickening of the arterial intima. Atherosclerosis - Disease of the arterial intima, characterized by intimal proliferation (hyperplasia), deposition of fatty substances and luminal reduction. Atrophy - Diminution in size or function, wasting. Attenuation - Reduction in amplitude and intensity as a sound wave passes through a medium. Factors contributing to attenuation include: absorption, reflection, refraction, and scattering. Augmentation - To cause to augment or increase. When used in conjunction with Doppler examinations of the venous or cerebral systems, refer to the increased flow velocity which is noted after one or more compression/release maneuvers. Auscultation - Listening to body sounds with a stethoscope. Autologous vein graft - Self generation vein specimen (your own vein), used for bypass conduit, same as autogenous. Axilla - Pertains to the armpit. Axillary artery - A continuation of the subclavian artery that begins at the outer border of the first rib and terminates at the lower border of the teres major muscle and becomes the brachial artery. Axial resolution - Separation required to distinguish two reflectors along the same longitudinal plane, i.e., parallel to the beam axis. Axial resolution is equal to one-half the spatial pulse length. B-Mode - A method of operation in which the intensity of the returning echo is displayed as a spot, brightening for each pulse; brightness mode. Bandwidth - The range of frequency components within a signal. When referring to a device or system, bandwidth is the range of the frequencies that the system is capable of processing. Basilic vein - Large vein on the inner side of the arm (medial), near the brachial veins, a superficial vein. Beam - The acoustic field produced by a transducer. Bernoulli effect - he reduction in pressure which accompanies an increase in velocity of fluid flow. Carotid sinus - A slight dilation of the carotid bifurcation area which contains pressure receptors (baroreceptors) that respond to changes in blood pressure by altering the heart rate. Catherization - Passage of a small catheter into the artery or vein to obtain blood samples, used with interventional and diagnostic procedures on the arteries in the heart or the body. Catheter - A tube passed through the body for evacuat- ing fluid or injecting them into the body cavities. Typically made of elastic, elastic web, rubber, glass, metal, or plastic. Cathode Ray Tube (CRT) - A television, or a large vacuum tube. The inner surface of the CRT screen is coated with phosphors that glow when struck with electrodes. Caval - Pertaining to the vena cava. Cavity - A hollow space. Caudal - In a direction toward the feet (or tail), the opposite of cephalad. Caudate lobe - The lobe of the liver that lies anterior to the inferior vena cava and posterior to the left lobe. Causalgia - Severe neuralgic pain; also called reflex sympathetic dystrophy. Celiac artery - First branch of the abdominal aorta. The branches of the celiac artery (left gastric, hepatic, and splenic arteries) supply blood to the stomach, liver, spleen, duodenum, and pancreas. Cellulitis - Inflammation of cellular or connective tissue. An infection in or close to the skin is usually localized by the body defense mechanisms. Centimeter - One hundredth of a meter. Cephalad - Toward the head. Cephalic - Crania; superior in position. Cephalic vein - A superficial vein that ascends from the dorsal aspect of the radial border of the forearm, to the anterior surface and subcutaneously up thearm and ends in the axillary vein near the clavicle. Frequently used for arteriovenous fistula formation for dialysis access. Cerebral - Pertaining to the brain. Cerebrovascular - Pertaining to the blood supply and blood vessels to the brain. Cerebrovascular accident (CVA) - Catastrophic event in which cerebral ischemia results in a neurologic deficit (lasting longer than 48 hours). The type of symptoms depends upon the cerebral hemisphere and territory involved. The etiology of CVA can be thrombotic, hemorrhagic, or embolic. Cervical rib - An extra rib in the cervical region; may cause symptoms by compression of the brachial plexus (see thoracic outlet syndrome). Cholesterol - Monohydric alcohol; a sterol widely distributed in animal tissues and occurring in egg yolks, various oils, fats, the nerve tissue of the brain and spinal cord, the liver, kidneys and adrenal glands. Chronic - Of long duration, or occurring with repeated frequency; opposite of acute. Occurring over a long period of time, old versus new. Circle of Willis - Arterial circle of the cerebrum composed of left and right internal, anterior, posterior, and middle cerebral arteries as well as anterior and posterior communicating arteries. This important anastomosis connects the bilateral carotid circulation with the vertebral circulation and may be a source of collateralization in internal carotid occlusive disease. Circulation - The continuous passage of blood throughout the arterial and venous systems. Cirrhosis - A chronic disease of the liver; dense conective tissue forms, liver cells cease to function. Claudication - Literally, "to limp" symptoms associated with arterial insufficiency of the extremity; intermittent leg pain (ache, cramp, etc.) brought on by exercise and relieved by rest. Coagulate - To become clotted or congealed. Coagulation - To change from a fluid to a semi solid mass. Coapt - To meet or join. When performing a venous duplex exam, with light probe pressure, the walls of normal veins collapse and come together (compression). Coarctation - A stricture or narrowing of a vessel, usually of a congenital nature. Collagen disease - Any of various clinical syndromes characterized by widespread alterations of connective tissue including inflammation and degeneration. Included are polyarteritis, systemic lupus erythematosus, Marfan's syndrome. Collateral circulation - An alternate, natural circulatory pathway. When there is interference in the arterial supply because of obstruction, communicating channels develop to accommodate blood flow. The peripheral resistance of the collateral vessels is higher because of the smaller diameter of the vessels. Colon - The large intestine from the terminal ileum to the rectum; divided into ascending, transverse, descending, and sigmoid colon. Common bile duct (CBD) - Passes very obliquely through the muscular wall of the duodenum and joins with the pancreatic duct to form the ampulla of vater; carries bile to the duodenum and after receiving it from the cystic duct of the gall bladder and the hepatic ducts from the liver. Common Carotid Artery - The common carotid artery (CCA) is the main artery that supplies the head and neck. It arises from the innominate (brachiocephalic) artery on the right and from the aorta on the left CCA. Each CCA branches into the internal and external carotid arteries. Compartment syndrome - This syndrome occurs when increased pressure in the noncompliant fascia compromises circulation and neuromuscular function in that anatomic space. Critical stenosis - A stenosis of sufficient diameter reduction that flow rate and pressure are significantly affected. Sometimes called "hemodynamically significant" stenosis. Crosstalk - Occurs when a strong Doppler signal in one direction channel passes into the other channel. This can produce the Doppler mirror-image artifact. Cuff artifact - Consistently high segmental blood pressure in the lower extremity resulting from the use of narrow segmental cuffs which may not completely transmit cuff pressure to the vessels in the central part of the limb (i.e., femoral artery). This effect is most pronounced in the upper thigh. Cuff artifact must be considered to avoid false negative examinations. Cyanosis - A slight bluish, grayish, slate like or dark purple discoloration of the skin caused by reduced amounts of hemoglobin in the blood. Etiology: a deficiency of oxygen. Cycle - A complete variation of an acoustic variable. Cyst - A closed sac or pouch, with a definite wall, con- tains fluid, semi fluid, or solid material. A simple cyst is usually spherical, with echo enhancement posterior to cyst. Complex cysts can have internal debris and septations. D-C coupled (Direct Current) - Type of output signal to graphic display connection which responds to steady state conditions; results in baseline shifts. Damping - A technique used to reduce the amplitude of an ultrasound pulse at its point of origin in the transducer or upon its return to the transducer. Damping factor - he ratio of proximal and distal pulsatility indices (Gosling). DF = Proximal Pl Distal Pl Damping material (backing material) - A material that is bonded to the backside of the active element and acts to limit the "ringing" of the crystal. D-Dimer - D-Dimer is formed as fibrin is broken down. Lab testing can reveal its presence in the blood. Positive levels are suggestive of a thrombotic event such as deep vein thrombosis or pulmonary embolism. Negative levels can virtually rule out the presence of DVT or PE, sparing the patient further expensive, uncomfortable and/or invasive testing. Dead zone - The region close to the transducer that cannot be imaged accurately. Deceleartion - A decrease in velocity. Decibel (dB) - The unit for expressing logarithmically the pressure or power (intensity or loudness) of sound. Decubitus, lateral - Refers to a patient lying on their side. Deep vein thrombosis (DVT) - Obstruction of the deep veins by blood clot. At one time referred to as phlebothrombosis; DVT is a non-inflammatory process. The possibility of the loosely attached thrombus dislodging is always present. DVT can lead to valvular destruction, post-phlebitic syndrome, and pulmonary embolism. Demarcation - A distinct dividing line that is visually noted, separating living and necrotic tissue. Dependent rubor - Abnormal redness noted of the toes (filling of the small vessels) and forefoot when the leg is in the dependent position. This is usually noted in patients with severe occlusive disease. Describes the classic redness which occurs in an ischemic limb on dependency following a period of elevation. Depth of penetration - That depth wherein echoes are no longer detectable; a function of the operating frequency of the transducer. Dermatitis - Inflammation of skin evidence by itching, redness, and various skin lesions. Diabetes mellitus - A chronic disease characterized by hyperglycemia secondary to inadequate production or reduced effectiveness of insulin. Juvenile onset diabetes develops before the age of 40 and is associated with lack of insulin. Adult-onset diabetes occurs later in life, primarily in the obese; these patients have inadequate insulin supply but can usually be managed by dietary treatment or oral hypoglycemic agents. Diabetes accelerates the atherosclerotic process and in its later stages results in a variety of vascular complications. Medial-wall calcification is commonly found in diabetic patients. Diagnosis - the art of identifying a disease. Diaphragm - A musculomembranous wall separating the abdomen from the thoracic cavity. It contracts and expands with respiration. Diastole - Relaxation period of the cardiac cycle. Diastolic bruit - A bruit which extends into diastole. This is indicative of a very severe stenosis. Diastolic pressure - The period of least pressure in the arterial vascular system. Digit - A toe or finger. Digital signal - A signal which occurs in discrete steps over time and in sequence; signals converted into nu- merical values or multiples of the numerical. Digital data information is then translated (e.g., through a digital scan converter) for display purposes. Digital subtraction angiography (DSA) - An invasive computerized radiologic procedure performed to visualize major vessels, the bone and soft tissue is subtracted electronically to enhance the images. This procedure can be intra-arterial or intravenous. Dilatation - A vessel is stretched beyond normal dimensions. Dissecting aneurysm - Splitting or dissection of an arterial wall by blood entering through an intimal tear or interwall hemorrhage. Usually in aortic arch and thoracic aorta. Dissection - Separation of tissues; usually surgically (see aneurysm, dissecting). Disseminated intravascular coagulation (DIC) - A pathological form of coagulation that is diffuse rather than localized, as would be the case of normal coagulation. The process damages rather than Dysarthria - A speech disorder in which the pronunciation is unclear although the linguistic content and meaning are normal. Dysesthesia - Abnormal sensations on the skin, such as feelings of numbness, tingling, prickling, or a burning or cutting pain. Dysfunction - Abnormal, inadequate, or impaired action of an organ or part. Dyskinesia - A defect in the ability to perform voluntary movement. Dysphagia - A condition in which the action of swallowing is either difficult to perform, painful, or in which swallowed material seems to be held up in passage to the stomach. Dysphasia - Lack of coordination of speech, and failure to arrange words in an understandable way; related to cortical damage. Ecchymosis - A skin discoloration consisting of large irregularity formed hemorrhagic areas. Echo - Reflection of acoustic energy. Echogenic - The acoustic property of a medium which renders it capable of producing echoes. Echoic - The area of an ultrasound image that depicts strong echoes created by strong interfaces. Ectatic - Distended or stretched. Ectopic - In an abnormal position. Originating in an area of the heart other than the sinoatrial node causing an ectopic heart beat. Edema - Elasticity - Willingness of a medium to distort from its original size and shape and restore to its original form after the external influence is removed. Elevation pallor - Pallor induced by elevation of the limb. Embolectomy - Removal of an embolus from a vessel. Embolism - An obstruction in a vessel from a foreign substance or blood clot. Embolus - A mass of undissolved matter present in a blood or lymphatic vessel and carried there by the blood or lymph current. Endarterectomy - Surgical removal of atherosclerosis material and intimal lining from within an artery. Endarteritis - Inflammation of the innermost layer (intima) of an artery. Endograft - A graft placed within a vessel. Endoleak - A term that describes the presence of persistent flow of blood into the aneurysm sac after device placement. There are 4 types dependent on their etiology. Endoleak, attachment (Type I) - Is due to an incompetent seal at either the proximal or distal attachment site. Endoleak, branch (Type II) - The most prevalent type and describe flow into and out of the aneurysm sac from patent branch vessels. They are most often identified on the post procedural CT, appearing as collections of contrast outside of the endograft, but within the aneurysm sac. The most frequent sources of type II endoleaks are collateral back flow through patent lumbar arteries and a patent inferior mesenteric artery. Because the sac fills through a collateral network, the endoleak may not be visualized on the arterial phase of CT scanning; thus, delayed imaging is required. Endoleak (Type III) - These endoleaks are less common and represent flow into the aneurysm sac from separation between components of a modular system, or tears in the endograft fabric. Endoleak (Type IV) - These endoleaks are due to egress of blood through the pores in the fabric. Endotension - An enlarging of the aneurismal sac without a visible endoleak. Endothelium - Endovascular - A catheter-based, imaging-guided procedure that allows one to work within a vessel. Enhancement - An image artifact created behind a low attenuating medium. Erythema - Reddening of the skin. Erythrocyte - A mature red blood cell (RBC) or corpuscle. Esophageal varices - Varicosities of the branches of the azygos vein that anastomose with the tributaries of the portal vein in the lower esophagus; occurs in patients with portal hypertension. Ethics - A code of moral principles, individually or collectively defined; derived from a set of values or beliefs. Etiology - Study of the causation of disease. Eversion - To turn inside out. Exogenous - Originating outside an organ or part. External carotid artery (ECA) - The vessel which arise from the common carotid artery at the carotid bulb and course anteromedially, supplying the exterior of the head, the face, and the greater part of the neck (normally has eight branches). External iliac artery (EIA) - The branch of the iliac bifurcation that arises from the common iliac artery that sup- plies the pelvic and genital organs. This artery is also known as the hypogastric artery. Gangrene - Tissue death, usually as a result of inadequate blood supply; occasionally due to infection. Lack of blood supply may be due to atherosclerosis, embolism, spasm, frostbite, tourniquets, etc. Gastric - Pertaining to the stomach. Gastric artery - Arises from the celiac axis; usually the first branch; divides into right and left; supplies blood to the stomach. Gastro-duodenal artery - Arises from the common hepatic trunk and supplies the stomach and duodenum. Gastrointestinal (GI) - Pertaining to the stomach and intestines. Gastrocnemius - That large muscle of the posterior portion of the lower leg that propels venous blood up the leg as it contracts. Commonly referred to as the calf muscle pump, this superficial muscle extends the foot and helps to flex the knee. Gate - Electronically controlled device which controls transmission or reception of a signal. Glaucoma - An ocular disease characterized by increased intraocular pressure. Presence of this disease should be noted prior to performing OPG or OPG-G testing. Glomerulonephritis - A variety of nephritis characterized by inflammation of the capillary loops in the glomeruli of the kidney. It occurs in acute, subacute, and chronic forms and is usually secondary to an infection, especially with the hemolytic streptococcus. Graft - The material used, either organic or inorganic, that is surgically inserted to replace a defect in the body. Gravitational - Pertaining to the force of gravity. Gray scale - A display format in which the intensity information is recorded as changes in brightness. Also known as B-mode. Greater saphenous vein (GSV) - One of the two major superficial veins of the lower limb. It originates on the dorsum of the foot, ascends medially along the calf and thigh, and drains into the common femoral vein. It is the longest vein in the body and is the vessel of choice for lower extremity bypass procedures and is also used for coronary artery bypass. Hard copy - A method of preserving or recording observed data, e.g., Polaroid pictures of images, analog tracings of Doppler shifted signals and digital images. Heat - Energy resulting from thermal molecular motion. Hemangioma - A tumor, growth, or abnormal mass composed of blood vessels. Hematoma - A blood-filled swelling. Hemianopia - Blindness in one-half of the visual field; may affect one or both eyes. Hemiparesis - Muscular weakness affecting one side of the body. Hemiparalysis - Paralysis of one side of the body; may be permanent (stroke) or temporary (TIA). Hemiplegia - Paralysis of one side of the body. Hemispheric - Pertaining to one side of the brain. Stroke is referred to as being right or left hemispheric; this is in relation to the side of the brain that is affected, not the side of the body that is afflicted. Hemodynamics - Pertaining to the physical principles governing blood flow (i.e., blood pressure, blood flow, vascular volumes, heart rate, ventricular function). Hemoglobin - The iron containing pigment of the red blood cells. Its function is to carry oxygen from the lungs to the tissues. The amount of hemoglobin in the blood averages 14-16 grams per 100ml. Hemorrhage - Escape of blood from a vessel (arterial or venous). Abnormal bleeding. Heparin - Substance used to inhibit coagulation of blood; frequently used in the treatment of deep venous thrombosis. Hepatic artery (common) - Arises from the celiac trunk and supplies the stomach, pancreas, duodenum, liver, gallbladder, and greater omentum. Divides into proper hepatic and gastroduodenal arteries. Hepatic artery (proper) - Arises from the common hepatic artery and supplies the liver and gallbladder. Hepatic veins - Drain blood flow from the liver into the inferior vena cava. There are three main veins, the left, middle and the right. Hepatofugal flow - Directed or flowing away from the liver. Hepatopedal flow - Directed or flowing toward the liver. Hertz (Hz) - The basic unit of frequency, equal to one cycle per second. Heterogeneous - Of different kind or species; used in ultrasound to describe sonographic characteristics of atherosclerotic plaque; opposite of homogeneous. Hilum - A depression or pit at that portion of an organ where vessels, ducts, and nerves enter. The indented part of the kidney. Histogram - A graphic representation of a frequency distribution. Holosystolic - Throughout systole, used interchangeably with pansystolic. Holosystolic bruit - A bruit which extends throughout the period of systole from the first to the second heart sound; consistent with a severe stenosis. Iliac artery - Originates at the terminal bifurcation of the abdominal aorta forming the right and left iliac arteries. The common iliac branches into the external and internal iliac arteries. Iliac vein - Formed by the union of the internal iliac vein which drains the pelvis and the external iliac vein which is a continuation of the common femoral vein. The right and left common iliac veins unite to form the inferior vena cava. Image update - The ability of a duplex scanner to alternate between the two functions of imaging and Doppler. Impedance - Impedance plethysmography - A noninvasive diagnostic technique used in the diagnosis of deep venous thrombosis. Four electrodes are placed around the calf and a small electrical current is sent through the underlying tissues. A recording is made of changes in venous capacitance occurring during a period of obstruction to venous outflow (via an occluding thigh cuff). Since the current is held constant any changes in resistance (or impedance) detected by the skin electrodes are associated with volume changes in the calf. By plotting venous filling (capacitance) and venous emptying (outflow) on a graph, conclusions can be drawn about the patency of the venous system (see Ohm's law). Impotence - In the male, inability to achieve penile erection. The etiology can be neurogenic, metabolic, vasculogenic, or psychogenic. Identification of the primary etiology is complex and involves serum hormonal studies, nocturnal tumescence study, and noninvasive vascular examination (see penile-brachial index). In situ - In position. Used to describe a vascular surgery procedure where the greater saphenous vein remains in its anatomical position as the vessel is transformed into an arterial conduit. The valves are surgically removed and the branches are ligated before the proximal and distal anastomoses are made. Incidence angle - Angle between propagated sound beam direction and line perpendicular to media boundary. Imcompetent - Unable to perform natural function. Used to refer to venous valves which no longer close completely, permitting blood to flow in a backward direction. Incompressible vessel - Inability to eliminate the arterial flow signal with maximal cuff pressures most likely due to medial calcification of the arterial wall and resulting in falsely high pressures. Inertia - Resistance to acceleration. Infarct - A localized area of ischemic tissue necrosis due to inadequate arterial blood supply. Infarction - An event occurring when there is an arte- rial occlusion or stenosis to the point of insufficient blood flow to an organ. Inflow obstruction - Arterial blood flow is severely restricted due to a proximal obstructing lesion. Inferior - Lower than, beneath. Inferior mesenteric artery (IMA) - Originates from the distal aorta and supplies the left portion of the transverse colon, the descending colon, the sigmoid colon, and part of the rectum. Inferior mesenteric vein (IMV) - Is usually small in size and runs to the left of the superior mesenteric vein to join the splenic vein. Inferior vena cava (IVC) - Infrapopliteal - Located below the popliteal artery or popliteal space. Infrarenal - Located below the renal artery. Inguinal ligament - A fibrous band extending from the anterior superficial iliac spine to the pubis tubercle in the groin. Innominate artery - Arising from the arch of the aorta, dividing into the right subclavian and right common carotid arteries. Innominate vein - Formed by the union of the internal jugular with the subclavian vein. Insonate - To expose to ultrasound waves, to examine utilizing sound waves. Insulin - Pancreatic hormone required for carbohydrate metabolism (see diabetes). Intensity - Total energy in an acoustic wave as it travels through a space per unit time; equal to the power in the wave divided by the area over which the power is spread. Intensity = power (watts) area (CM2) Interface - Surface forming the boundary between two media having different properties/densities (i.e., acoustic impedance). Intermittent - Occurring at intervals, not constant. Used when describing claudication. Internal - Inside, opposite of external. Internal carotid artery (ICA) - Arises from the common carotid artery at the carotid bulb, and courses posterolaterally to the base of the skull where it gives rise to vessels which feed the brain, nose, orbit, internal ear, and forehead. It is divided into four parts: cervical, petrous, cavernous, and cerebral. Interosseous artery - A branch of the ulnar artery, which in some individuals continues to the wrist. Intima - Innermost layer of an artery; comprised of an endothelial lining, a thin layer of connective tissue, and an internal elastic membrane. A statistical measure- ment/ parameter used to define the extent of athero- genesis in its early phase (discrimination threshold in the resolution area of ultrasound equipment: > 100um). - A statistical measurement/ parameter used to define the extent of atherogenesis in its early phase (discrimination threshold in the resolution area of ultrasound equipment: > 100um). Intimal flap - A loosened portion of the innermost wall of the artery. LSV varies; terminations include the popliteal 2-4 cm near knee crease, distal SFV, or GSV (either directly or via a perforating vein). Ligamentum teres - Echogenic structure in the left lobe of the liver (a remnant of the ductus venosum) in which the umbilical vein runs. Ligate - To tie off, e.g., to tie off a blood vessel at surgery. Light reflection rheography (LRR) - An instrument, similar to the photoplethysmograph, which measures, by means of three infrared lights and a receiving di- ode, changes in skin blood perfusion. This instrument is used to assess venous disease (i.e., venous reflux, obstruction). Linear - Relating to, consisting of, or resembling a line. Linear transducer; multiple elements arranged in a line. Linear array - An electronically steered real time transducer composed of multiple transducer elements, each element can be fired independently or in combination. Linear phased array - Is operated by applying voltage pulses to all elements with small time variants. This allows the beam to be shaped and steered. Linear switched array - Operated by applying voltage pulses to groups of elements in succession. Lipid - Generic term used to describe any of the water soluble fats. Lobe - A well-defined portion of any organ, is usually demarcated in some way. Longitudinal - Along the path of a sound beam; or along a lengthwise course, as in a longitudinal scan. Lumen - The space inside a tube, blood vessel, or duct. Lymph - Transparent fluid, comprised of white blood cells (lymphocytes), conveyed in the lymphatic vessels. Lymphangitis - Inflammation of a lymph vessel. Lymphedema - Fluid retention in the tissues as a result of obstruction in the lymphatic system. Can present symptoms similar to deep venous thrombosis. Lymphoceles - Fluid collections, which result from lymphatic leakage from, disrupted channels along the iliac vessels. M-Mode - Method of display in which a brightening spot for each pulse produces a one-dimensional time display of reflector position; motion mode. Manometer - An instrument for measuring pressure. Matching layer - The material placed in front of the front face of the transducer element to reduce the reflection at the transducer element face. Maximum venous outflow - Describes the maximum rate of venous emptying which occurs in a limb following rapid cuff deflation post venous occlusion. Mean - Midway between two points or measurements, the arithmetic average. Mechanical scanners - A single transducer or several transducers are oscillated within the scan head steering the sound beam over the region of interest. Media - Middle layer of an artery. Medial - Towards the midline, opposite of lateral. Median - The middle number in a distribution, half of the numbers will be above and half of the numbers will be below it. Median cubital vein - Located in the antecubital fossa and crosses from the medial to the lateral side of the fossa and connects the basilic and cephalic veins. Medium - Substance through which a sound wave travels. Medulla - The inner part of the kidney containing the renal pyramids which appear hyperechoic on ultrasound. Megahertz (MHz) - 1,000,000 Hertz or cycles per second (see Hertz, frequency). Most clinical Doppler instruments operate between 2-20 MHz. Membrane - A thin lining or covering. Memory - A collection of integrated circuits in which data is stored. Binary data is stored as electrical signals. Menu - A list of all the programs that can be used with the system or a listing of all the functions within a program. The menu lists the options available to the operator; options are selected by pressing a key. Mesenteric artery, superior (SMA) - The SMA arises from the abdominal aorta, approximately 1 cm below the celiac trunk. The SMA and its branches (inferior pancreatic, duodenal, colic, ileocolic and intestinal ar- teries) supply blood to the small intestines and to the proximal half of the colon. Mesenteric artery, inferior (IMA) - The IMA arises from the abdominal aorta approximately at the level of the 3rd and 4th vertebra. The IMA and its branches (left colic, sigmoid and superior rectus arteries) sup- ply blood to the descending colon, sigmoid colon and rectum. Microprocessor - An integrated circuit that performs basic data processing operations; i.e., the processing of electronic signals. Migraine - Periodic, throbbing headache, often unilateral. Mirror image artifact - Identical representation of an object on the other side of a strong reflector (sonography). Identical representation of the spectrum on the other side of the baseline (Doppler). Nondirectional - A Doppler instrument which assesses flow, via frequency shift, without regard for direction of blood flow. Noninvasive - Refers to any procedure or examination in which the body is not penetrated by a substance or instrument. Plethysmographic and ultrasonic examinations are examples of noninvasive examinations. Venography or arteriography are examples of invasive examinations. Nonocclusive - Not totally obstructed. Normotensive - Of normal pressure. North America Symptomatic Carotid Endarterectomy Trial (NASCET) - A technique for measuring a carotid stenosis using the smallest residual internal carotid artery diameter in the stenosis (a) divided by the normal ICA diameter beyond the stenosis (b). Percent stenosis = a/b × 100. Nyquist limit - The highest frequency in a sampled signal that can be represented unambiguously; equal to one-half the pulse repetition frequency. Nystagmous - Involuntary, repetitive, jerky movements of the eye. Objective - Pertains to things or events that are external to one's self. Objective tests are those in whichthe results can be observed by individuals other than the examiner. Objective signs are those which can be noted by an observer, as opposed to those signs (such as pain) which are described by a patient. Opposite of subjective. Obstructive Raynaud's syndrome - Episodic attacks of vasospasm resulting in the closure of small arteries and arterioles of the distal extremities in response to cold or stress with obstruction of the palmar and digital arteries. Occlusion - The complete closure of an opening, duct or vessel. Ocular - Pertaining to the eye. Oculoplethysmography - A noninvasive diagnostic procedure designed to detect flow reducing lesions of the internal carotid artery. Changes in ocular volume are related to changes in arterial blood flow. These changes in volume are detected (via small corneal eye cups attached to a transducer) and recorded (ocular pulse recordings). A delay in ocular pulse arrival time is associated with a hemodynamic stenosis. This is an indirect measurement of internal carotid artery status. Oculopneumoplethysmography - A noninvasive diagnostic procedure designed to detect flow reducing lesions of the internal carotid artery. Intraocular pressure is measured by placing small cups (which are attached to a transducer) on the sclera. A negative vacuum is applied to obliterate arterial inflow. The degree of vacuum corresponds to a specific intraocular pressure. As the vacuum is released, ocular pulsations return and the intraocular pressure is recorded. Differences in intraocular pressure between the eyes is associated with a hemodynamic stenosis. Like the OPG, this is an indirect measurement of internal carotid artery status. Ohm - Unit of electrical resistance; one ohm is the resistance which permits one ampere of current to flow under an electromotive force of one volt. Ohm's Law - States that voltage equals current multiplied by resistance (impedance). Voltage = Current × Resistance This is the basis for strain gauge and impedance plethysmographic testing. When voltage and current are held constant, the changes in resistance can only be due to changes in limb volume. Ophthalmic - Pertaining to the eye. Ophthalmic artery - Arises from the internal carotid artery, just as that vessel is emerging from the cavernous sinus, on the inner side of the anterior clinoid process, and enters the orbit through the optic foramen, below and on the outer side of the optic nerve. Ophthalmoscope - An illuminating instrument used to examine the interior of the eye. Origin - The source or starting point; i.e., the point where an artery begins. Orthostatic hypotension - A fall in blood pressure that is associated with standing upright. Orthotic - Any device (including prostheses) applied to the body in the management of disability or impairment. For example, the special implements used to facilitate eating in the stroke patient are orthotic devices. Oscillation - Vibration. Overall accuracy - Sum of true positive tests and true negative tests divided by the total number of tests per- formed. Pallor - Abnormal paleness or lack of color in the skin. Palmar - Pertaining to the palm of the hand, as in palmar arch. The palmar arch is formed by the anastomoses of ulnar and radial arteries, both superficial and deep. Palpation - The act of examining by touch, manually. To assess skin temperature or pulses by touch is to palpate. Pancreas - A large elongated gland, located behind the stomach, it stretches transversely between the spleen and duodenum. Produces digestive enzymes and insulin. Pansystolic - Extending throughout systole, as in pansystolic bruit. Used interchangeably with holosystolic. Papaverine - A vasodilating agent used in patients with suspected vasculogenic impotence. The intracavernosal injection bypasses the psychoerotic and neurologic pathways that normally induce an erection. Papilledema - Edema of the optic disc (choked disc); indicates increased intracranial pressure. Paralysis - Complete or incomplete loss of nervous function to the body or body part, may be motor or sensory or both. Stroke is only one of the many causes of paralysis. Parasympathetic - A division of the autonomic nervous system involved primarily with restorative functions. The parasympathetic nerves are derived from intracranial and sacral nerves and travel via the vagus nerves. The vagi participate in visceral reflexes including pressures and chemical receptors located in the aortic arch. Parasympathetic activity is mediated by acetylcholine. Perm Cath catheter - Used for acute dialysis access. These catheters may be used immediately. Their softer material is better tolerated by patients and allows the catheter to remain in place for prolonged periods. Petechia - A very small hemorrhagic spot. Peyronie's disease - A condition when scarring thickens and may even calcify the tunica albuginea that surrounds the corpora cavernosa. Symptoms include painless curvature with erection or sometimes enough pain with erection that detumescence results. Phantom - Materials used with similar characteristics of normal tissue (e.g., scattering or attenuation). Phased array - A type of electronically steered transducer in which there are multiple transducer elements. The ultrasound energy from a phased array is steered by pulsing all of the elements as a group but with a small time (or phase) difference between the elements. A phased array produces a sector B-scan. Phasicity - Normal venous flow increases and decreases in response to respiration. In a normal lower extremity, flow will diminish or cease with respiration. Phasicity is reversed in the upper extremity veins. Phlebitis - Inflammation of a vein. Phlebography - Radiologic procedure in which an opaque substance is injected into a vein; subsequent x- ray pictures are taken in order to visualize the venous system. Synonymous with venography. Phleborheography (PRG) - A noninvasive diagnostic technique used to identify the presence of deep venous thrombosis. This is a plethysmographic technique in which air-filled cuffs are placed on the extremity and the volume changes associated with the respiratory variability of venous blood flow are recorded. In the absence of venous obstruction, respiratory waves are present in the limb. Compression of the limb distal to the recording cuffs should produce no change in the baseline recordings. Phleborthrombosis - Term used to describe occlusion of vein by clot in the absence of an inflammatory pro- cess (see deep venous thrombosis). Phlegmasia alba dolens - Extensive iliofemoral DVT that causes marked swelling of lower extremity with pain, pitting edema, and blanching without cyanosis. Also called milk leg or white leg. Phlegmasia cerulea dolens - When DVT involves the major veins proximal to the inguinal ligament. Commonly referred to as iliofemoral thrombosis. Translates to "painful blue inflammation." Phonoangiography - A process of recording bruits and analyzing their frequency components. The device consists of a sensitive microphone and a storage oscilloscope commonly called CPA. See carotid phonoangiography (CPA). Photoplethysmograph (PPG) - A device (transducer) which assesses minute changes in skin blood perfu- sion. Infrared light is emitted from a transmitting diode and reflected back to a receiving diode; changes in red blood cell density associated with arterial pulsation are detected by the transducer. Thus, it detects changes in red blood cell volume; the signal output is in the form of a pulse wave form. This is used in a number of noninvasive diagnostic examinations; venous reflux plethysmography, supraorbital plethysmography, digital pressures, Allen's test, and thoracic outlet maneuvers to name a few. Piezoelectric - The property of certain crystals cause them to emit electricity when deformed or squeezed. When electricity is applied to the crystal, the crystal changes its shape and the crystal vibrates; this is the source of the ultrasound wave. Piezoelectric effect - Changing of mechanical to electrical energy and vice versa. Pignoli's double line measurement - Characteristic double lines on images that represent the combined thickness of the intima and media of the arterial wall. Pixel - The individual picture cell on a television screen. A screen is divided into many horizontal scan lines, which are in turn divided into pixels. The result is a grid made of many, many pixels. Plantar - Pertaining to the sole of the foot. Plaque - Generic term used to describe an atheroscle- rotic lesion. It can consist of platelets, fibrin, lipids, and calcium. Plasma - Fluid portion of the blood. Platelet - A round or oval disk, 1/3 to 1/2 the size of an erythrocyte found in the blood. Platelets number from 150,000 to 450,000 per cc. Function: Platelets play an important role in blood coagulation, hemostasis and blood thrombus formation. When a vessel is injured, platelets adhere to each other and the edges of the injury and form a plug which covers the area. The plug or blood clot formed soon retract and stops the loss of blood. Plethsymograph - Any device, instrument, or transducer which measures volume changes in size or amount. Air plethysmographs include: phleborheography, volume pulse recordings, and ocular pulse recordings. Water plethysmography is typified by the OPG. Impedance plethysmography and strain gauge are similar in concept and detect changes in calf size associated with venous filling of a limb. Photoplethysmography detects the volume of red blood cells in the skin. Poiseuille's law - Formula describing the relationship between flow, pressure, and resistance in a laminar flow system. The following formula is an abbreviated version the pressure/volume flow relationship. Q = P/R Q = Flow, P = Pressure, R = Resistance Polycystic disease - Multiple cysts of varying sizes found in the kidneys and the liver. Polytetrafluorethylene (PTFE) - A synthetic or prosthetic graft or material used for bypass or patching arteries. Popliteal artery - Originates as a continuation of the femoral artery in the popliteal space, bifurcating at the lower border of the popliteus muscle into the anterior and posterior tibials. Its branches also include the lateral and medial superior geniculars, middle genicular, the lateral and medial inferior genicular, and sural arteries. Portacaval shunt - The surgical creation of anastomosis between the portal vein and vena cava. Porta hepatis - The transverse fissure on the visceral surface of the liver where the common bile duct exits the liver and the hepatic artery and portal vein enter the liver Pulmonary embolus - Embolus (blood clot, air, fat) which is carried through the venous system ultimately lodging in the pulmonary vasculature. PE is a serious and occasionally fatal complication of deep venous thrombosis. Pulsatility index (PI) - A parameter used to convey the pulsatility of a time varying waveform such as the maximum Doppler shift frequency of the signal from an artery. Indices of pulsatility are usually ratios of Doppler shift frequencies and are hence independent of Doppler angle. The most common definition of pulsatility index (Pl) of a waveform such as that defined by the maximum Doppler shift frequency, is the difference between the maximum and minimum value, divided by the mean value of the waveform over the cardiac cycle. PI = Peak to Peak Velocity/Mean Pulse - The regular, palpable wave of distention or volume change transmitted to the arteries. This is due to blood ejected from the heart during ventricular contraction. Pulse pressure - The difference between the peak systolic and minimum diastolic pressure in the cardiac cycle. Pulse reappearance time - An index of arterial insuffi- ciency defined by Fronek; the time period required for the return of toe pulse waves (via strain gauge or PPG) after four minutes of arterial occlusion by cuff. Pulse repetition frequency (pulse repetition rate) - The rate of repetition of pulses per unit time; in a pulsed system, the number of pulses generated every second. Not to be confused with frequency, PRF is the rate of pulse repetition. Pulse volume recorder (PVR) - Plethysmographic technique in which air filled cuffs are placed segmentally on an extremity; changes in limb volume associated with arterial pulsation are translated in pulse waveforms. Alterations in the shape of the waveform at each level are associated with obstruction proximal to the cuff. Pulse wave Doppler (PW) - Timed bursts of ultrasound (pulses); a single transducer alternately transmits and receives impulses. Permits more discrete sampling from a select depth and volume. Sample volume is selected through the process of range gating, i.e., receiving reflections after a defined time period has elapsed (see gate, sample volume). Pulsed wave - Refers to an intermittent wave of sound (frequency) produced by applying short bursts of electrical impulses to an ultrasound transducer. Pulseless Disease - Takayasu's disease; progressive obliterative arteritis. Pulsus tardus/pulsus parvus - Terms used to describe dampened, post obstructive waveforms. Tardus refers to delayed arrival of the systolic peak, and parvus refers to overall low velocity. Pyelonephritis (chronic) - Repeated infections of the kidneys that cause scaring in some areas of the parenchyma. Pyramids - Conical structures within the medulla of the kidney where blood is filtered and absorbed, leaving urine behind. Q's law - Quality before quantity. Quadriplegia - Paralysis of all four limbs. Qualitative - A non-objective measurement relating to quality; descriptive assessment of attributes, traits, or characteristics. Measurements in which an exact numerical value cannot be assigned; scales or grades can be used. Quantitative - An observable quantity which can be described in objective, measurable terms, i.e., numbers. Radial artery - It begins at the division of the brachial artery below the bend of the elbow, and passes along the radial side of the forearm to the wrist where the pulse is readily palpated. Radiography - Generic terms referring to any type of x-ray procedure; venography, arteriography are two types of radiographic techniques. Range - The distance between the reflector (target) and the transducer; equal to one half of the total ultrasound path length. range ambiguity - Occurs when the pulse repetition frequency is too high, causing misrepresentation of echoes ranges. Range gating - With range gating the transducer will only accept echoes from a selected depth based on echo arrival times. Raster - On a cathode ray tube, the pattern of horizontal lines beginning at the top of the screen and progressing from left to right. Each line is made of many pixels. Raynaud's disease - Vasospastic disease characterized by intermittent pallor, cyanosis and rubor of the digits; rarely results in tissue necrosis. Symptoms are induced by exposure to cold or emotional upset. Raynaud's disease is a primary condition and exists in the absence of arterial obstruction and has no clear-cut association with any other systemic disease. Syndromes with similar symptoms, but with secondary etiology, are referred to as Raynaud's phenomenon. Raynaud's phenomenon - Describes any numberof conditions which present symptoms suggestive of digital arterial vasospasm (see Raynaud's disease). The phenomenon follows the color sequence of pallor, cyanosis, rubor. Pain may be present and occasionally there may be gangrene of the digital tips. The underlying etiology may include; collagen vascular disease, nerve compressions, occupational trauma, and arterial obstruction. Reactive hyperemia - Response to ischemia characterized by rapid increase in blood flow following cessation of a period of induced ischemia. A technique to assess the degree of functional arterial impairment. Resting ankle pressures are recorded prior to the application of an occlusive cuff to the thigh. Following a period of ischemia, the cuff is deflated and ankle pressures are measured. The degree of drop in ankle pressure immediately following release is indicative of the degree of impairment. This technique is sometimes used in lieu of exercise/treadmill testing. Real-Time display - Display system in which an image is continuously updated and reviewed as the target changes or moves. Recanalization - The formation of a new canal or channel of blood flow through an obstruction, such as blood clot or thrombus (deep vein thrombosis). Reconstruction - When a main artery is again patent distal to a segment of occlusion (SFA/POP) due to collateral flow. Reflection - The acoustic energy returned (reflected) back to the transducer from a structure (target). The intensity of the reflection is dependent upon the acoustic impedance ratio at the tissue interface. The greater the impedance ratio the greater the reflection. Scattering - Diffuse reflection and refraction of an acoustic wave in many directions; caused by irregular interfaces, heterogeneous media, or particle suspensions (blood). Scleroderma - A disease of the connective tissue in which the skin forms scar tissue (fibrous tissue). This may also occur in other organs of the body. Sclerosis - Generic term used to describe an abnormal hardening or fibrosis of an artery (see atherosclerosis, Monckeberg's sclerosis, calcification, diabetes). Segmental blood pressures - Obtaining blood pressure measurements at different levels of the upper or lower extremities, the comparison of pressure change across each segment of the limb in order to determine the level of occlusive disease. Sensitivity - The ability of a diagnostic technique to identify the presence of disease when disease is actually present. Sens. = TP/TP+FN x 100 = % Sequential bypass - Arterial bypasses in series; a continuation and/or additional bypass performed to maintain patency of previous surgery. Serum creatinine - When the kidneys do not work properly this waste product accumulates in the blood. Levels above 1.0 are considered to be elevated and abnormal in a female. Levels above 1.3 are considered elevated and abnormal in a male. Shadowing - Reduction in reflection amplitude from reflectors that lie behind a strongly reflecting or attenuating structure. Shunt - Term used to describe a pathway other than the usual to divert blood from one point to another; may be a natural channel, i.e., an arteriovenous fistula or a surgically created channel, i.e., a bypass graft. In carotid endarterectomy a shunt is often used to divert blood from the common carotid artery to the internal system during the procedure. Shunt is synonymous with bypass. Side effect - Any physiological change (other than the expected one) which occurs as a result of a prescribed treatment or procedure. Sinus - The renal sinus contains the collecting system, renal arteries and veins, lymphatics, fat and fibrous tissue. The renal sinus has an ultrasound appearance that is highly echodense. Snell's law (simplified) - In ultrasound, states that the angle of reflection is equal to the angle of incidence. Spatial pulse length - Distance traveled by an ultrasound pulse; equal to the product of wavelength and the number of cycles in a pulse. Specificity - The ability of a diagnostic technique to identify the absence of disease (normalcy) when no disease is actually present. Spec. = TN/TN+FP x 100 = % Spectral analysis - A method of analyzing and/or dis- playing the Doppler signal output. The Doppler shifted signal is made up of a range of frequencies. Spectral analysis, using a microprocessor, is capable of analyz- ing and displaying the complete range of frequencies in each waveform. This technique may be used with pulsed or continuous wave Doppler systems. Time is displayed on the horizontal axis, frequency on the ver- tical axis and amplitude of the signal by the intensity of the gray scale. Spectral analysis provides the most complete assessment of the Doppler waveform and is a useful technique for quantifying degree of arterial stenosis. Spectral broadening - The width of the Doppler spectrum on a sonogram display corresponds to the range of Doppler shift frequencies present at a given time. Spectral broadening will be seen when this range is increased; an example is the Doppler signal obtained when laminar flow with a blunt flow profile becomes disturbed. Spindle - Hour glass shaped. Spleen - A large, glandlike and ductless organ; situated in the upper abdomen; disintegrates red blood cells and sets free hemoglobin which the liver transforms to bilirubin; creates red blood cells in the fetus and in the newborn; produces lymphocytes and plasma, etc. Splenic artery - Originates from the celiac artery and supplies the pancreas, spleen, stomach, and greater omentum. Splenic vein - Collects blood from the spleen and part of the stomach and joins with the superior mesenteric vein to form the portal vein. Spontaneity - In normal veins flow occurs passively. It should be detectable in all major veins. Stasis - Refers to the stagnation of blood; cessation of normal blood flow. In the venous system of the lower extremity, stagnant blood flow as the result of immobility contributes to venous thrombosis. Stagnation of venous blood in the extremity because of valvular dysfunction (or post- phlebitic syndrome) results in pigmentation changes and ulceration. Stenosis - The narrowing or constriction of a tube, specifically the lumen of an arterial blood vessel. Plural, stenoses. A stenosis of sufficient caliber to reduce blood flow is termed a hemodynamically significant stenosis. This is equal to a 75% area reduction or a 50% diameter reduction. Stent - A tube made of metal or plastic that is inserted into a vessel or passage to keep it open and prevent closure due to a stricture or external compression. Stent Graft - A stent-graft is an intraluminal device that consists of a supporting framework (currently made of metal such as stainless steel or nitinol) and a synthetic graft material. Stent-grafts can be either self-expanding or balloon-expandable, depending on the type of metal in the stent. The stent may be located inside, outside, or within the graft material, and it may be along the entire length of the graft or restricted to the ends. To deliver the stent-graft through a small vascular access, the device is compacted onto a catheter or compressed into a sheath. With the use of imaging guidance, the device is advanced into an appropriate location in the aorta from a remote access site and deployed. Stethoscope - An instrument used to listen to body sounds; an auscultatory device. Most stethoscopes have dual components, a diaphragm and a bell. Bruits are best assessed with the bell of the stethoscope. Stokes-Adams syndrome - Syncope of cardiac origin occurring most often in patients with a pulse rate of less than 40 beats/minute and complete atrioventricular heart block. Strain gauge plethysmography (SPG) - A noninvasive diagnostic technique used primarily for the detection of deep venous thrombosis. The strain gauge consists of an electroconductive material enclosed in a thin elastic tubing. The strain gauge is placed around an extremity and limb volume changes are detected by measuring changes in impedance. Strain gauge is most often used to record maximum venous capacitance/ outflow ratios as in impedance plethysmography but may also be Temporal arteritis - Also called giant cell arteritis or cranial arteritis. (See arteritis). Test object - Device used to measure some characteristics of an imaging system without having tissue-like properties. Testicular torsion - A condition in which the testicle is twisted on its mesentery, impairing blood supply and causing pain. Thermal biofeedback - A technique used in the treatment of Raynaud's phenomenon; used when symptoms are related to stress or anxiety; patients are taught to increase skin temperature through biofeedback techniques. Thermocouple - A device that converts temperature to a voltage. Thermography - Diagnostic technique in which body temperature differences are recorded on photographic paper; temperature differences associated with reduced blood flow can be documented in this manner. Thoracic outlet syndrome (TOS) - A symptom coplex associated with compression of the arteries, veins, or nerves of the upper extremity at the outlet from the thoracic cavity. Symptoms include numbness or pain of the arm associated with activity, elevation, or hyperabduction. The cause is usually related to brachial nerve plexus compression rather than arterial compression. To identify or rule out arterial compression, Doppler, or PPG may be used to document obliteration of flow during specific arm movements. Thrombectomy - Surgical removal of a blood clot from a vessel. Thromboangiitis - Clot formation within an inflamed vessel; Buerger's disease was referred to as thromboangiitis obliterans. Thromboendarterectomy - Surgical removal of a blood clot from within an artery. Thrombogenic - Capable of causing blood clotting. Thromnolysis - The breaking up of thrombus. Thrombolytic - Capable of disintegrating a blood clot. TPA, Streptokinase and Urokinase are used to dissolve clots. This agent acts by stimulating the conversion of plasminogen to plasmin (an enzyme which breaks down fibrin). Thrombolytic therapy - Used success-fully in the treatment of deep venous thrombosis, for acute arterial thrombosis, and graft occlusion. Thrombophlebitis - Inflammation of a vein with secondary thrombosis in the involved segment. Thrombosis - The formation of an intravascular blood clot formation. Thrombus - An intravascular blood clot; plural, thrombi. Time gain compensation - Selective gain amplification over time used in real-time imaging to compensate for loss in echo intensity due to attenuation; permits echoes from greater depths to have the same intensity as those from shallow sites. Increases the gain in the far field without saturating the echoes in the near field. Tortuous - Twisting or turning of the vessel. Sometimes making it difficult to interrogate throughout its length with Doppler. Tourniquet - An apparatus which encircles a limb for the purpose of compressing blood vessels to occlude flow. May be a simple rubber strip or a pneumatic cuff. Tissue plasminogen activator (tPA) - A generic term for a group of substances that have the ability to cleave to plasminogen and convert it to plasmin in its active form; it is used for therapeutic thrombolysis. Transcranial Doppler (TCD) - Doppler evaluation of the major intracerebral arteries via a cranial "window" (transorbital, transtemporal, suboccipital). The method utilizes a pulsed Doppler combined with spectral analysis to obtain velocities of the major vessels. Transcutaneous - Transdermal, entering through skin as in the administration of a drug applied to the skin in ointment or patch form. Transducer - Any device which converts one form of energy to another, e.g., pressure to electrical, acoustic to electrical, electrical to acoustic. Transient ischemic attack (TIA) - Fleeting neurologi- cal dysfunction without residual symptoms lasts less than 24 hours, more typically 15-30 minutes. Depending on the cerebral territory involved, symptoms may include: sensory/motor dysfunction of an arm/leg, speech impairment (aphasia), and visual disturbances (amaurosis fugax); etiology is usually embolic. TIA is often the precursor of a cerebrovascular accident. Transluminal angioplasty - Dilatation of a blood vessel by means of a balloon catheter inserted through the skin and through the lumen of the vessel to the site of narrowing, where the balloon is inflated to compress plaque against the arterial wall. Transmetatarsal amputation - Removal of one or all of the toes across the end of the metatarsal heads. Transplant - To transfer tissue or organs from one part of the body to another or from one body to another. Transposition - The state of being transposed, or being on the wrong side of the body. Transverse - Cross-sectional. Trifurcation - The site of separation into three branches. Triphasic - Having three phases or variations; forward flow in systole, brief reverse flow, and a third forward flow component (multiphasic). Trophic - Pertaining to nutrition; trophic changes on an extremity (e.g., nail thickening, atrophied skin) are the results of ischemia or lack of nutrition to the skin. Tumor - A growth of tissue in which the multiplication of cells is uncontrolled and progressive; can be neoplasm. Tunica - A coat; lining membrane, as in tunica intima, tunica media, tunica adventitia. Velocity detector - An ultrasound Doppler instrument which detects the velocity of blood flow transcutaneously. Vena cava filter - A device placed in the IVC to catch emboli and prevent them from getting to the lungs. Venography - A radiographic procedure in which an opaque substance is injected into the veins. Subsequent x-ray pictures are taken for the purpose of visualizing the venous system (see phlebography). Venous - Pertaining to the veins. Venous air embolism - An air bubble which may enter the venous system during any surgical procedure in which the surgical site is above the level of the right atrium. Doppler ultrasound is the most sensitive method of detection of air emboli in the right atrium. Venous insufficiency - Condition in which faulty or damaged venous valves permit retrograde or backward flow of blood. Stagnant venous blood in the lower extremity may result in pigmentation changes, edema, pain, and ulceration (see post phlebitic syndrome). Venule - A small vein. Vertebral artery - First branch arising from the subclavian artery, coursing through the posterior neck and terminating in the basilar artery. Along with the internal carotid arteries, the vertebral arteries are the source of blood supply to the brain. Vertigo - Dizziness or giddiness; feeling of spinning. Vessel - A tube, ducrt, or canal which holds or conveys a fluid. Virchow's triad - The three mechanisms of thrombosis--injury to the vessel wall, decrease in blood flow (stasis), and blood hypercoagulability. Viscosity - Resistance of a fluid to flow when a pressure is applied. Volt - A unit of electrical force. Vortices - Areas of circular flow which are present in turbulence. Wallfilter - An electrical filter that removes strong low frequency Doppler shifts (e.g., pulsating heart or vessel walls) while allowing frequencies above a certain level to pass. Waveform - A curve or undulation traced by a recording device and reflecting alterations in electrical activity; the shape of a wave on a graph (see triphasic). Wavelength - Distance required for a complete cycle. Wrap around - An incorrect shift of Doppler information to the other side of base line (caused by aliasing). Xanthaloma - Cholesterol deposition under the skin producing a yellowish lesion. Xiphoid process - The pointed part of cartilage located at the lower end of the sternum. Zero-Crossing device - A method of processing a Doppler signal whereby the incoming signal passes through a zero point and produces an output proportional to the average frequency at which the crossing occurs. The output information is both antegrade and retrograde (above or below the zero point); however, the output is an average of the frequencies at any given point in time and therefore not as accurate as spectral analysis.