H - Glossary of Terms

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H - Glossary of Terms

habitus	(hab'it-us) (Latin for habit) Fixed practice established by frequent usage; bodily appearance; general form or architecture of body.
haemarthrosis	(he-mar-thro-sis) Accumulation of blood in a joint or joint cavity.
hair	A threadlike appendage of the epidermis consisting of keratinised dead cells that have been pushed up from a dividing basal layer.
hair cells	Specialised receptor nerve endings for detecting sensations, such as in the spiral organ (organ of Corti).
hair follicle	(fol´li-k'l) A tubular depression in the dermis of the skin in which a hair develops.
halation	The reflection of screen light transmitted through the emulsion and base.
half-life	The time required for a quantity of radioactivity to be reduced to half its original value.
half-valve layer (HVL)	The thickness of absorber necessary to reduce an X-ray beam to half its original intensity.
half-wave rectification	An AC circuit in which the negative potential portion of the cycle is eliminated by means of a rectifier, the voltage remaining at zero for that period of the cycle.
hallucis	Latin hallex = great toe (hallucis = of the great toe).
hand	The terminal portion of the upper extremity, containing the carpal bones, metacarpal bones, and phalanges.
hard copy	A permanent image on film or paper, as opposed to an image on a cathode ray tube, disk, or magnetic tape.
hard palate	(pal´it) The bony partition between the oral and nasal cavities, formed by the maxillae and palatine bones and lined by mucous membrane.
hard x-ray	An X-ray that has high penetrability and therefore is of high quality.
hardener	A chemical, usually potassium glutaraldehyde in the fixer, that is used to stiffen and shrink the emulsion.
hardware	The visible parts of the computer.
haustra	(haws´tra) Sacculations or pouches of the colon.
haustrum	(haws'trum) Any one of recesses formed by sacculations of colon.
haversian canal	(hua-ver´shan) See central canal.
haversian system	See osteon.
head	(The uppermost portion of a human that contains the brain and major sense organs.
health physics	The science concerned with the recognition, evaluation, and control of radiation hazards.
heart	A four-chambered, muscular pumping organ positioned in the thoracic cavity, slightly to the left of midline.
heart murmur	An auscultatory sound of cardiac or vascular origin, usually caused by an abnormal flow of blood in the heart as a result of structural defects of the valves or septum.
Heberden's nodes	Small, hard nodules at the distal interphalanageal joints of the fingers produced by calcific spurs of the articular cartilage and associated with osteoarthritis.
heel effect	A consequence of the angle of the target of the tube which results in greater radiation intensities on the cathode side as compared to the anode side of the radiation field.
hem-, haem-, hemo	Prefix denoting blood or relation to blood: as hematuria, presence of blood in urine.
hemangioma	(he-man"je-o'mah). Tumor consisting of newly formed blood vessels.
hemarthrosis	(he-mar-thro-sis) Accumulation of blood in a joint or joint cavity. (also haemarthrosis)
hematogenous	Spread by means of the blood stream.
hemodynamic	Pertaining to the movements involved in the circulation of the blood.
hemoptysis	Coughing up blood or bloodstained sputum.
hepatic duct	(he-pat´ik) A duct formed from the fusion of several bile ducts that drain bile from the liver. The hepatic duct merges with the cystic duct from the gallbladder to form the common bile duct.
hepatic portal circulation	The return of venous blood from the digestive organs and spleen through a capillary network within the liver before draining into the heart
hepatopancreatic ampulla	(hep´´a-to-pan´´kre-at´ik) A small, elevated area within the duodenum where the combined pancreatic and common bile duct empties; also called the ampulla of Vater
hematologic syndrome	A form of acute radiation syndrome after whole-body exposure to doses ranging from approximately 1 to 10 Gy (100 to 1000 rad). It is characterised by the reduction in white cells, red cells, and platelets in the circulating blood.
hematoma	(he"mah-to'mah). Tumor or swelling containing effused blood.
hemi-	(hem'i-) Prefix signifying one half; pertaining to or affecting one side of body; as hemiplegia, paralysis of one side of body.
hemoptysis	(he-mop'ti-sis). Presence of blood in sputum; expectoration of blood.
hemorrhage	(hem'o-rij). Discharge of blood from vessels in any region; bleeding.
hemorrhoid	(hem'o-roid). Vascular tumor situated at orifice of or within anal canal.
hepatic	(he-pat'ik). Of or pertaining to liver.
hepat-	(hep'at) Prefix signifying relation to liver; as hepatomegalia, enlargement of liver.
hepato-	(hep'a-to-) Prefix signifying relation to liver; as hepatomegalia, enlargement of liver.
Hering-Breuer reflex	A reflex in which distension of the lungs stimulates stretch receptors, which in turn act to inhibit further distension of the lungs.
hermaphrodite	(her-maf´ro-d-it) An organism having both testes and ovaries.
hernia	(her'ne-ah) Protrusion of a part of an organ through normal or abnormal opening in wall of its natural cavity; a rupture.
herniation	(her-ne-arshun) Hernial protrusion; formation of a hernia.
herpes	(her'pez) Acute inflammation of skin or mucous membrane, in which clusters of small vesicles form and tend to spread.
hertz (Hz)	The unit of frequency; the number of cycles or oscillations each second of a simple harmonic motion.
hetero-	(het'er-o-). Prefix signifying other, or other than usual; difference or dissimilarity between constituents; to or from a different source; opposite of homo-.
heterogeneous	(het"er-o-je'ne-us) Differing in kind or nature; composed of unlike elements or ingredients or having dissimilar characteristics; opposed to homogeneous.
heterogenous	(het"er-oj'e-nus) Arising or originating outside body; opposed to autogenous.
hematogenous dissemination	Widely but discontinuously distributed throughout an organ or type of tissue. The pattern of hematogenous dissemination is the result of pathology delivered to an organ via the circulation. In the lung the pattern is usually one of well-defined nodules of various sizes distributed throughout the lung, perhaps with a slight basal predominance due to the relatively greater blood flow present in the bases.
hexadecimal number system	Number system used by low-level applications to represent a set of four bits.
hiatal hernia	(hi-a´tal her´ne-a) A protrusion of an abdominal structure through the esophageal hiatus of the diaphragm into the thoracic cavity.
hiatus	(hi-atus) Latin = a gap, An opening; a space, gap, or fissure for transmission of a nerve, vessel, or tubular passage.
high-contrast resolution	The ability to image small objects having high subject contrast; spatial resolution.
high-voltage generator	One of three principal parts of an X-ray imaging system; it is always close to the X-ray tube.
hilum	(hi´lum) ) Depression on a gland or organ that marks site of entrance and exit of nerves, vessels, and ducts; as hilum of kidney or of lung.
hilus	(hi'lus) Same as hilum.
hinge joint	A type of synovial articulation characterized by a convex surface of one bone fitting into a concave surface of another such that movement is confined to one plane, as in the elbow or interphalangeal joint.
histology	(hi-stol´o-je) Microscopic anatomy of the structure and function of tissues.
hit	Radiation interaction with the target.
homeo-	(ho'me-o-) Prefix meaning like, similar; as homeomorphous, of similar structure and form.
homeostasis	A state of equilibrium among tissue and organs. The ability of the body to return to normal function despite infection and environmental changes.
homo-	(ho'mo-) Prefix meaning one and same, common, similar; as homodox, homocentric, homologue; opposed to hetero-.
homogeneous	(ho"mo-je'ne-us) Of same kind or nature; composed of similar elements or ingredients or having similar uniform characteristics; opposed to heterogeneous.
homologous	(ho-mol'o-gus). Corresponding in position or structure but not necessarily resembling in function; cf. analogous
honeycomb pattern	A number of closely approximated ring shadows representing coalesced airspaces, usually lined with bronchiolar epithelium, 5–10 mm in diameter with walls 2–3 mm thick composed of dense fibrous tissue. This finding implies “end-stage” lung fibrosis.
horizontal	(transverse, axial) plane A directional plane that divides the body, organ, or appendage into superior and inferior or proximal and distal portions.
hormone	(hor´m-one) A protein manufactured by various endocrine glands and carried by the blood to regulate body functions such as growth and development.
horsepower (hp)	The British unit of power.
hounds field unit (HU)	The scale of computed tomographic numbers used to judge the nature of tissue.
hyaline cartilage	(hi´a-l-in) A cartilage with a homogeneous matrix. It is the most common type, occurring at the articular ends of bones, in the trachea, and within the nose. Most of the bones in the body are formed from hyaline cartilage.
hyaline membrane disease	A disease affecting premature infants who lack pulmonary surfactant, it is characterized by collapse of the alveoli (atelectasis) and pulmonary edema; also called respiratory distress syndrome.
hybrid subtraction	A technique that combines temporal and energy subtraction.
hydro-	(hi'dro-) Prefix meaning water or denoting some relation to water or to hydrogen.
hydrocele	(hi'dro-sel) An accumulation of fluid, usually in a sacculated cavity such as scrotum.
hydrocephalus	(hi"dro-sefa-lus) Condition characterised by excessive amount of cerebrospinal fluid in cerebral ventricles, accompanied by dilatation of ventricles, and causing atrophy of brain substance and enlargement of head.
hydronephrosis	(hi"dro-nef-rosis). Accumulation of urine in pelvis of kidney, caused by obstruction of ureter, with resultant dilatation of renal pelvis and atrophy of organ itself.
hydrophilic	(hi´´dro-fil´ik) Denoting a substance that readily absorbs water; literally, "water loving."
hydrophobic	(hi´´dro-fo´bik) Denoting a substance that repels, and that is repelled by, water; "water fearing."
hydropneumothorax	The presence of both gas and fluid in the pleural cavity.
hydrops	(hi'drops) Excessive accumulation of fluid in a cavity of body; dropsy.
hydroquinone	The principal compound used in the chemical composition of film developers.
hymen	(hi´men) A developmental remnant (vestige) of membranous tissue that partially covers the vaginal opening.
hyper-	(hi'per) Prefix meaning over; above in position; beyond usual or normal extent or degree; excessive; opposite of hypo-.
hyperextension	(hi´´per-ek-sten´shun) Extension beyond the normal anatomical position.
hyperlucency	Overly black appearance on a radiograph.
hypermotility	(hi"per-mo-til'i-te). Excessive movement or motility of involuntary muscles, especially those of gastrointestinal tract.
hyperopia	(hi´´per-o´pe-a) A refractive disorder in which rays of light are brought to a focus behind the retina as a result of the eyeball being too short; also called longsightedness
hyperplasia	(hi´´per-pla´zha) An increase in organ size due to an increase in cell numbers as a result of mitotic cell division (in contrast to hypertrophy).
hyperpnea	(hi"perp-ne'ah) Abnormally rapid respiratory movements.
hypersthenic	(hi"per-sthen'ik) Excessive strength or tonicity of body or of any part Type of bodily habitus characterised by massive proportions.
hypertension	(hi´´per-ten´shun) Elevated or excessive blood pressure.
hyperthyroid	(hi"per-thT'roid). Excessive functional activity of thyroid gland, pertaining to hyperthyroidism.
hypertrophic	(hi"per-trofik) Pertaining to or affected with hypertrophy.
hypertrophy	(hi´´per´tro-fe) Growth of an organ due to an increase in the size of its cells (in contrast to hyperplasia).
hyperventilation	(hi´´per-ven´´ti-la´shun) A high rate and depth of breathing that results in a decrease in the blood carbon dioxide concentration to below normal.
hypo-	(hi'po-) Prefix meaning under; below or beneath in position; less than usual or normal extent or degree; deficient; opposite of hyper-. Sodium thiosulfate, a fixing agent that removes unexposed and undeveloped silver halide crystals from the emulsion.
hypo retention	The undesirable retention of the fixer in the emulsion.
hypochondriac region	An abdominal region (see umbilical, epigastric, lumbar, inguinal and hypogastric)
hypodermis	(hi´´po-der´mis) A layer of fat beneath the dermis of the skin.
hyponychium	(hi´´po-nik´e-um) A thickened, supportive layer of stratum corneum at the distal end of a digit under the free edge of the nail.
hyposthenic	(hi"pos-then"ik) Referring to a body habitus of a patient who is thin but healthy looking.
hypotension	Low blood pressure.
hypothalamus	(hi´´po-thal´a-mus) A portion of the forebrain within the diencephalon that lies below the thalamus, where it functions as an autonomic nerve center and regulates the pituitary gland.
hypothyroid	(hipo-thy'roid). Deficient functional activity of thyroid gland, pertain¬ing to hypothyroidism.
hypoxia	Deficiency (lack) of oxygen.
hysteresis	(his"ter-e'sis) The additional resistance created by the alternate reversal of the magnetic field caused by the alternating current. Lagging or retardation of one of two associated phenomena; failure to act in unison
hystero-	(his'ter-o-) Prefix denoting relation to uterus; as hysterectomy, surgical removal of uterus.
hysterography	(hisler-og'ra-fe). Radiographic examination of uterus after injection of contrast medium; uterography.
hysterosalpingography	(his"ter-o-sal-ping-gog'ra-fe) Radiographic examination of uterus and oviducts after injection of con¬trast medium; uterosalpingography.

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