T - Glossary of Terms

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T - Glossary of Terms

tachy-	(tak'e-) Prefix meaning fast, swift; as tachycardia, rapidity of heart action.
tachycardia	(tak´´i-kar´de-a) An excessively rapid heart rate, usually in excess of 100 beats per minute (in contrast to bradycardia, in which the heart rate is very slow).
tactile	(tak´til) Pertaining to the sense of touch.
taeniae coli	(te´ne-e ko´li) The three longitudinal bands of muscle in the wall of the large intestine.
tangent	(tan'jent) Touching at a point; meeting a curve or surface at a point and then extending beyond without intersection; as a line or plane tangent to a curve, or a curve tangent to a line or a surface.
tangential	(tan-jen'shal) Directed along or arranged in a tangent, as in adjustment of a structure or a mass so that one or more points of its surface will be tangent to central ray.
target	The region of an X-ray tube anode struck by electrons emitted by the filament. See rotating anode tube, stationary anode tube, anode. The molecule (DNA) that is most sensitive to radiation.
target molecule	Molecule (DNA) that is few in number yet essential for cell survival and is particularly sensitive to the effects of ionising radiation.
target theory	The theory that a cell will die if target molecules are inactivated as a result of radiation exposure.
tarsus	(tar´sus) The region of the foot containing the seven tarsal bones.
taste bud	An organ containing the chemocreceptors associated with the sense of taste.
technique factors	Technical factors which describe how the X-ray unit should be set and operated in order to produce a radiograph; these include factors such as kVp, mA, time, distance, angle, intensifying screen/film speed, grid, etc.
tectorial membrane	(tek-to´re-al) A gelatinous membrane positioned over the hair cells of the spiral organ in the cochlea.
telangiectasia	Vascular lesion formed by dilatation of a group of small blood vessels.
tele-	(tel'e-) Prefix meaning far. at a distance; as telecardiographv.
telencephalon	(tel´´en-sef´a-lon) The anterior portion of the forebrain, constituting the cerebral hemispheres and related parts.
teleoroentgenogram	(tel"e-o-rent'gen-o¬gram") Radiograph made at a distance of 6 feet.
teleradiology	The transfer of images and patient reports to remote sites.
telophase	The final subphase of mitosis that is characterised by the disappearance of the structural chromosomes into a mass of DNA and the closing off of the nuclear membrane into two nuclei.
temperature	A measure of heat and cold.
temporal subtraction	Computer-assisted technique whereby an image obtained at one time is subtracted from an image obtained at a later time.
temporary magnet	A magnet that retains the properties of a magnet only while its magnetism is being induced.
tendo calcaneous	(ten´do kal-ka´ne-us) The tendon that attaches the calf muscles to the calcaneous bone; also called the Achilles tendon.
tendon	(ten´dun) A band of dense regular connective tissue that attaches muscle to bone.
tendon sheath	A covering of synovial membrane surrounding certain tendons.
tenosynovitis	Inflammation of a tendon sheath
tenth-value layer (TVL)	The thickness of absorber necessary to reduce an X-ray beam to one tenth its original intensity. 1 TVL = 3.3 half-value layers.
tentorium cerebelli	(ten-to´re-um ser´´e-bel´e) An extension of dura mater that forms a partition between the cerebral hemispheres and the cerebellum and covers the cerebellum.
teratogen	(te-rat´o-jen) Any agent or factor that causes a physical defect in a developing embryo or fetus.
teratoma	Neoplasm composed to various kinds of embryonic tissue.
terminal	An input and output device that uses a key¬board for input and a display screen for output.
terrestrial radiation	The radiation emitted from deposits of uranium, thorium, and other radionuclides in the Earth.
tesla (T)	The SI unit of magnetic field intensity. An older unit is the gauss (G). 1 T = 10,000 G.
test object	A passive device that provides echoes and permits eval‎uation of one or more parameters of an ultrasound system but does not necessarily duplicate the acoustical properties of the human body. A passive device of geometric shapes designed to eval‎uate the performance of X-ray and magnetic resonance imaging systems. See also phantom.
testis	(tes´tis) The primary reproductive organ of a male that produces spermatozoa and male sex hormones.
tetanus	(tet´n-us) A smooth contraction of a muscle (as opposed to muscle twitching).
thalamus	(thal´ua-mus) An oval mass of gray matter within the diencephalon that serves as a sensory relay center.
thebesian veins	small veins draining the myocardium directly into the chambers of the heart
theca	(the'kah) Protective case or sheath: as theca vertebralis, dura mater of spinal cord.
thermal energy	The energy of molecular motion; heat; infrared radiation.
thermal radiation	The transfer of heat by infrared emission.
thermaluminesecence dosimetry	The emission of light by a thermally stimulated crystal after irradiation.
thermionic emission	The process by which free electrons are produced at the cathode of an x-ray tube when the filament is electrically heated; the thermal energy imparted to the electrons is sufficient to overcome the atomic forces binding them to the atoms of the filament (the emission of electrons from a heated surface).
thermometer	A device that measures temperature.
thigh	The proximal portion of the lower extremity between the hip and the knee in which the femur is located (see leg)
thiosulfate	The fixing agent that removes unexposed and undeveloped silver halide crystals from the emulsion.
third ventricle	(ven´tri-k'l) A narrow cavity between the right and left halves of the thalamus and between the lateral ventricles that contains cerebrospinal fluid.
thoracentesis	(tho"rah-sen-te'sis) Surgical puncturing of chest wall for removal of fluid in pleural effusion: tapping; also called pleuracentesis.
thoracic	(tho-ras´ik) Pertaining to the chest region.
thoracic duct	The major lymphatic vessel of the body that drains lymph from the entire body, except for the upper right quadrant, and returns it to the left subclavian vein.
thoracoplasty	(tho'rah-ko-plas"te) Plastic surgery of thorax; especially resection of a part of several ribs to collapse lung in advanced unilateral tuberculosis.
thorax	(thor´aks) The chest.
three-phase electric power	The generation of three simultaneous voltage waveforms out of step with one another, thus never dropping the voltage to zero during exposure.
threshold dose	The dose below which a person has a negligible chance of sustaining specific biologic damage or the dose at which a response to an increasing X-ray intensity first occurs.
thrombocyte	(throm´bo-s-ite) A circular or oval disk called a platelet found in the blood that initiates blood clotting and prevents hemorrhage.
thrombus	(throm´bus) A blood clot produced by the formation of fibrin threads around a platelet plug.
thymine	A nitrogenous organic base that attaches to a deoxyribose molecule.
thymoma	Tumor originating from the thymus gland.
thymus	(thi´mus) this is found in children anterior to the trachea, extending from the level of the cricoid cartilage down to the retrosternal area (A bilobed lymphoid organ). In the adult the thymic tissue is more or less confined to the retrosternal area
thyroid cartilage	(thi´roid kar´ti-lij) The largest cartilage in the larynx that supports and protects the vocal cords; commonly called the Adam's apple.
tibial	can be used to mean medial in the leg (see fibular, peroneal)
time-interval-difference (TID) mode	Technique that produces subtracted images from progressive masks and the frames that follow.
Time-of-occupancy factor (T)	The amount of time the area being protected is used.
tinnitus	(tin-it´us) The spontaneous sensation of a ringing sound or other noise without sound stimuli.
tissue	A collection of cells of similar structure and function.
tissue weighting factor (WT)	The proportion of the risk of stochastic effects resulting from irradiation of the whole body when only an organ or tissue is irradiated. It accounts for the relative radiosensitivity of various tissues and organs.
tomogram	An X-ray image of a coronal, sagittal, transverse, or oblique section through the body.
tomographic angle/arc	Angle described by tube and film during a tomographic mo¬tion.
tomography	(to-mog'ra-fe) Imaging modality that brings into focus only the anatomic structure lying in a plane of interest while blurring structures on either side of that plane.
tone	(ton) Healthy function; resiliency; normal vigor and elasticity; especially, tension of involuntary muscles; tonus.
tongue	A protrusible muscular organ on the floor of the oral cavity.
tonic	(ton'ik) Pertaining to or characterised by normal tone or tension, particularly muscular tension; an agent that tends to produce or restore a healthy condition.
tonsil	(ton´sil) A node of lymphoid tissue located in the mucous membrane of the pharynx.
topical	(top-i-kal) Of or pertaining to a specific spot; local, or for local application; as a topical anesthetic.
torsion	(tor'shun) Act of turning or twisting or state of being full of turns and twists.
torticollis	(tor"ti-kol'is) Irregular contraction of cervical muscles, with twisting of neck and an unnatural position of head; commonly called wryneck.
tortuous	(tor'tu-us) Winding: circuitous; full of curves or bends; twisted.
total effective dose (TED)	The recommendation by the National Council on Radiation Protection and Measurement that a radiation worker's lifetime effective dose be limited to the worker's age in years multiplied by 10 mSv.
total filtration	Inherent filtration plus added filtration.
toxin	(tok´sin) A poison.
trabecula	(trah-bek'u'lah) A supporting framework of fibers crossing the substance of a structure, as in the lamellae of spongy bone. (see cancellous) also spelt trabeculae.
trabeculae	(tra-bek´u-le) A supporting framework of fibers crossing the substance of a structure, as in the lamellae of spongy bone. (see cancellous) also spelt trabecula.
trabeculations	ridges
trachea	(tra´ke-a) The airway leading from the larynx to the bronchi, composed of cartilaginous rings and a ciliated mucosal lining of the lumen; commonly called the windpipe.
tract	A bundle of nerve fibers within the central nervous system.
tragus	(tra'gus) Cartilaginous projection in front of external auditory meatus.
trans-	(trans) Prefix meaning across, through, over; to pass across or through: as transabdominal, passing through or across the abdomen, and transoral passing through or across mouth.
transaxial	Across the body; transverse.
transcription	The process of constructing mRNA
transfer	An addition of an amino acid during translation.
transformer	An electrical device operating on the principle of mutual induction to change the magnitude of current and voltage.
translation	The process of forming a protein molecule from messenger RNA.
translucent	A surface that allows light to be transmitted but greatly alters and reduces its intensity.
transmission	The passing of an X-ray beam through the anatomic part without any interaction with the atomic structures.
transmittance	The fraction of incident light that is transmitted through the film.
transparent	A surface that allows light to be transmitted almost unaltered.
transport roller	An agents that moves the film through the chemical tanks and dryer assembly.
transpyloric plane	Vertebral level L1. This intersects the rib cage at the tip of the 9th costal cartilage. It is about half way between the xiphiod process and the umbilicus and it marks the position of several internal structures (e.g. pylorus. gall bladder, renal hila, origin of superior mesenteric artery)
transtubercular plane	Vertebral level L5. a line between the tubercles of the iliac crests
transverse	(trans-verse') ). Crosswise, from side to side; horizontal; opposed to lengthwise and longitudinal. Transverse plane - plane that divides body or any one of its parts horizontally at any level.
transverse colon	(trans-vers´ ko´lon) A portion of the large intestine that extends from right to left across the abdomen between the hepatic and splenic flexures.
transverse fissure	(fish´ur) The prominent cleft that horizontally separates the cerebrum from the cerebellum.
transverse image	An image perpendicular to the long axis of the body.
transverse plane	A plane that divides the body into superior and inferior portions; also called a horizontal, or cross-sectional, plane.
trauma	(traw'mah) Injury; condition resulting from injury.
traumatic	(traw-mat'ik) Of, pertaining to or caused by a trauma.
tremor	(tre'mor) Involuntary trembling or shaking as result of undue strain. weakness. injury, or disease.
Trendelenburg position	(tren-del'en-berg) Position in which body is recumbent with feet higher than head for treatment of shock or to displace pelvic organs (on a plane inclined 45 degrees cranially).
trephine	(tre-fin') Circular saw or trepan for removing a disk of bone, used chiefly in brain surgery for perforating cranium; also to operate with a trephine or trepan.
tricuspid valve	(tri-kus´pid) The heart valve located between the right atrium and the right ventricle. (see mitral)
trifurcation	A branching of a single vessel into three.
trigone	(tri´g-on) A triangular area in the urinary bladder between the openings of the ureters and the urethra.
triradiate	Radiating in three directions.
trocar	(tro'kar) Sharp-pointed, rodlike instrument that is fitted into and used for insertion of a cannula or catheter.
trochanter	(tro-kan´ter) One of two protuberences on the proximal end of the femur.
trochanteric	(tro"kan-terik) Pertaining to a protuberance at the end of the femur.
trochlea	(trok´le-a) A pulleylike anatomical structure (e.g., the medial surface of the distal end of the humerus that articulates with the ulna).
trophoblastic	Relating to the layer by which the fertilized ovum is attached to the uterine wall and from which the developing embryo receives its nourishment.
true vocal cords	Folds of the mucous membrane in the larynx that produce sound as they are pulled taut and vibrated.
trunk	The thorax and abdomen together.
tubercle	(tu´ber-k'l) ) Small nodule or prominence; small rounded process on a bone. serving for attachment of muscles or ligaments.
tuberculosis	(tu-ber"ku-lo'sis). Infectious disease caused by tubercle bacillus and marked by production of tubercles, fever. night sweats, and progressive emaciation. The lungs are the most common site of infection, but such organs as the intestines. lymph nodes, larynx, kidneys, and bones are frequently involved.
tuberosity	(tu´bu-ros-it'e) Broad, roughened process on a bone, serving for attachment of muscles or ligaments.
tumor	(tumor) Circumscribed swelling; any morbid growth, innocent or malignant; neoplasm.
tungsten	A metal element that is the principal component of the cathode and the anode.
tunica albuginea	(too´ni-ka al´´byoo-jin´e-a) A tough, fibrous tissue surrounding the testis.
turnaround assembly	A device in the automatic processor for reversing the direction of the film.
turns ratio	The quotient of the number of turns in the secondary coil to the number of turns in the primary coil.
tympanic membrane	(tim-pan´ik) The membranous eardrum positioned between the external and middle ear