R - Glossary of Terms

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R - Glossary of Terms

racemose	(ras'e-m5s) (having clusters like a bunch or grapes). Compound saccular gland (such as pancreas) having numerous branching ducts ending in acini arranged like grapes on a stalk.
rachio-	- (ra'ki-o) Prefix denoting relation to spine, as in rachiocentesis, rachioplegia, rachitis.
radial	This is the preferred term for the lateral side of forearm and hand (see ulnar)
radiation	The propagation of energy from point to point through space or through matter. Radiography, magnetic resonance imaging, ultrasound, lasers and nuclear medicine all utilise forms of radiation.
radiation biology	The branch of biology concerned with the effects of ionising radiation on living systems.
radiation exposure	X-ray quantity or intensity, measured in roentgens.
radiation fog	Artifact caused by unintentional exposure to radiation.
radiation hormesis	The theory that suggests that very low radiation doses may be beneficial.
radiation quality	The relative penetrability of an X-ray beam determined by its average energy; usually measured by half-value layer or kilovolt peak.
radiation quantity	The intensity of radiation; usually measured in milliroentgen (mR).
radiation standards	The recommendations, rules, and regulations regarding permissible concentrations, safe handling, techniques, transportation, industrial control of radioactive material.
radiation (thermal)	The transfer of heat by the emission of infrared electromagnetic radiation.
radiation weighting factor (Wk)	The factor used for radiation-protection that accounts for differences in biologic effectiveness between different radiations. Formerly called quality factor.
radio-	(ra'di-o) Prefix denoting radial or radially, as lines radiating from a center radial, as in radiomuscular relation to lateral and larger of bones of forearm, as in radioulnar, radiohumeral relation to radiant energy, especially to roentgen and radium radiation, as in radioactive, radiosensitive, radionecrosis.
radioactive decay	A naturally occurring process whereby an unstable atomic nucleus relieves its instability through the emission of one or more energetic particles.
radioactive disintegration	The process by which the nucleus spontaneously emits particles and energy and transforms itself into another atom to reach stability.
radioactive half-life	The time required for a radioisotope to decay to half its original activity.
radioactivity	The rate of decay or disintegration of radioactive material. Expressed in curie (Ci) or becquerel (Bq). 1 Ci = 3.7 10 ¹⁰ Bq.
radiodontia	(ra"di-o-don'shi-ah) Radiographic examination of teeth and their supporting structures.
radio frequency (RF)	Electromagnetic radiation having frequencies from 0.3 kHz to 300 GHz; magnetic resonance imaging uses RF in the range of approximately 1 to 100 mHz.
radiographer	A radiologic technologist who deals specifically with X-ray imaging.
radiographic artifacts	Any abnormal appearance on the film that is the result of improper storage, handling, exposure, or processing of that film.
radiographic contrast	The differences in optical densities between different portions of the radiograph that enable image details to be visualised. The final radiographic contrast visualised on the film is dependent on two independent factors, subject contrast and film contrast.
radiographic intensifying screen	A device that converts the energy of the X-ray beam into visible light to increase the brightness of an X-ray image.
radiographic mottle	The nonuniform density of a uniformly exposed film due to quantum mottle, structure mottle, and film graininess.
radiographic noise	The undesirable fluctuation in the optical density of the image.
radiographic technique	The combination of settings selected on the control panel of the X-ray imaging system to produce a quality image on the radiograph.
radiographic technique chart	A guide that describes standard methods for consistently producing high-quality images.
radiography	An imaging modality that uses X-ray film and usually an X-ray tube mounted from the ceiling on a track that allows the tube to be moved in any direction and provides fixed images.
radioisotopes	Radioactive atoms having the same number of protons. They are changed into a different atomic species by disintegration of the nucleus accompanied by the emission of ionising radiation.
radiologist	A physician specialising in medical imaging using X-rays, ultrasound, and magnetic resonance imaging.
radiolucent	(ra"di-o-lu'sent) Materials offering little resistance to passage of X-radiation; those that have insufficient physical density to cast an appreciable image on film when exposed to kilovoltages used in radiography of the body.
radiolysis of water	The dissociation of water into other molecular products as a result of irradiation.
radionuclides	Any nucleus that emits radiation.
radiopaque	(ra"di-o-pak') Referring to a tissue or material that absorbs X-rays and appears bright on a radiograph.
radioparent	(rad"di-o-par'ent) Materials wholly transparent to X-radiation; radiolucent.
radiosensitivity	The relative susceptibility of cells, tissues, and organs to the harmful action of ionising radiation.
radius	(ra'di-us) Line extending from centre to periphery of a circle; semidiameter Lateral and larger bone of forearm.
radon	A colorless, odorless, naturally occurring ra¬dioactive gas (²²²Ra) that decays via alpha emission and has a half-life of 3.8 days.
RAID	Acronymn for (redundant array of inexpensive disks). A system consisting of at multiple disk drives within a single cabinet that collectively act as a single storage system.
RAM	Random access memory, data that can be stored or accessed at random from anywhere in main memory in approximately equal amounts of time, regardless of where they are located.
ramus	(ra´mus) Branch or branchlike process, as one of primary divisions of a nerve or blood vessel, or a projecting part of an irregularly shaped bone.
random access memory (RAM)	Data that can be stored or accessed at random from anywhere in main memory in approximately equal amounts of time, regardless of where they are located.
raphe	(ra´fe) A ridge or a seamlike structure between two similar parts of a body organ, as in the scrotum.
rare earth element	An element that is a transitional metal found in low abundance in nature.
rare earth screen	A radiographic intensifying screen made from rare earth elements, making it more useful for radiographic imaging.
rarefaction	(rar"e-fak'shun) State of being or process of becoming thin and porous or less dense without a diminution in size or volume; loss of substance; opposed to condensation and destruction.
raster pattern	The pattern produced on the screen of a television picture tube by the movement of electron beams.
ratio	The mathematical relationship between similar quantities.
read-only memory (ROM)	A data-storage device that contains information supplied by the manufacturer and cannot be written on or erased.
real time	A display for which the image is continuously renewed, often to view anatomic motion, in fluoroscopy and ultrasound.
receptor	(re-sep´tor) A sense organ or a specialized distal end of a sensory neuron that receives stimuli from the environment.
reciprocity law	The principle stating that optical density on a radiograph is proportional only to the total energy imparted to the radiographic film.
reconstruction	The creation of an image from data.
reconstruction time	The time needed for the computer to present a digital image after an examination is completed.
recorded detail	The degree of sharpness of structural lines on a radiograph.
recovery	Repair and repopulation.
rectification	The process of converting alternating current to direct current.
rectifier	The electronic device that allows current flow in only one direction.
rectum	(rek´tum) The terminal portion of the GI tract, between the sigmoid colon and the anal canal.
recumbent	(re-kum'bent) Reclining; lying down.
red filter	A filter that transmits light only above 600 nm; it is used with both green and blue sensitive film.
red marrow	(mar´o) A tissue that forms blood cells, located in the medullary cavity of certain bones.
red nucleus	(noo´kle-us) An aggregation of grey matter of a reddish colour located in the upper portion of the midbrain. It sends fibers to certain brain tracts.
redox	Simultaneous reduction and oxidation reactions.
reducing agent	The chemical responsible for reduction.
reduction	The process by which an electron is given up by a chemical to neutralize a positive ion.
reflection	The return or reentry of an X-ray.
reflective layer	The layer of the intensifying screen that intercepts light headed in other directions and redirects it to the film.
reflex	(re´fleks) A rapid involuntary response to a stimulus.
refraction	The deviation of course when photons of visible light traveling in straight lines pass from one transparent medium to another.
regional anatomy	The division of anatomy concerned with structural arrangement in specific areas of the body, such as the head, neck, thorax, or abdomen.
Region of interest (ROI)	The area of an anatomic structure on a reconstructed digital image as defined by the operator using a cursor.
regurgitation	(re-gur"ji-ta-shun) To flow or be cast backward, as blood from a heart chamber in insufficiency of a valve; egestion, or casting up, of incompletely digested food.
Reid's base line	(redz) (Robert William Reid, Scottish anatomist, 1851-1938). See anthropologic base line.
Relative age-response relationship	The increased incidence of a disease proportional to its natural incidence.
Relative biologic effectiveness (RBE)	The ratio of the dose of standard radiation necessary to produce a given effect to the dose of test radiation needed for the same effect.
relative risk	The estimation of late radiation effects in large populations without having any precise knowledge of their radiation dose.
relay	An electrical device based on electromagnetic induction that serves as a switch.
rem (radiation equivalent man)	The special unit for dose equivalent and effective dose. It has been replaced by the sievert (Sv) in the SI system. 1 rem = 0.01 Sv.
remnant radiation	The x-rays that pass through the patient and interact with the image receptor.
renal	(re´nal) Pertaining to the kidney.
renal corpuscle	(kor´pus'l) The portion of the nephron consisting of the glomerulus and a glomerular capsule; also called the malpighian corpuscle.
renal cortex	The outer portion of the kidney, primarily vascular.
renal medulla	(mue-dul´ua) The inner portion of the kidney, including the renal pyramids and renal columns.
renal pelvis	The inner cavity of the kidney formed by the expanded ureter and into which the calyces open.
renal pyramid	A triangular structure within the renal medulla composed of nephron loops and the collecting ducts.
replenishment	The replacement of developer and of fixer in the automatic processing of film.
repopulation	Replication by surviving cells.
resistance	An opposition to a force.
resolution	A measure of the ability of a system to image two separate objects and visually distinguish one from the other.
resolution of intensifying screens	Measure of the maximum detail or smallest element detectable when using a film-screen combination. Usually measured in line-pairs/mm.
resorption	(re-sorp'shun) Process of absorbing again; removal by absorption of an exudate or of bone.
respiration	(res´´pi-ra´shun) The exchange of gases between the external environment and the cells of an organism.
respiratory	(re-spi-r'ah-to"re) Of or pertaining to respiration or respiratory organs.
respiratory center	The structure or portion of the brain stem that regulates the depth and rate of breathing.
respiratory distress syndrome	A lung disease of the newborn, most frequently occurring in premature infants, that is caused by abnormally high alveolar surface tension as a result of a deficiency in lung surfactant; also called hyaline membrane disease.
respiratory membrane	A thin, moistened membrane within the lungs, composed of an alveolar portion and a capillary portion, through which gaseous exchange occurs.
restrainer	A compound that restricts the action of the developing agent to only irradiated silver halide crystals.
resus	(re-sus) Slang term most commonly used to refer to area/room of the emergency department where the most critical or unstable patients would be, especially if they may require resuscitation, emergency life support or intervention.
rete testis	(re´te tes´tis) A network of ducts in the center of the testis associated with the production of spermatozoa.
reticular formation	(re-tik´yuu-lar) A network of nervous tissue fibers in the brain stem that arouses the higher brain centers.
reticular pattern (reticulation)	A collection of innumerable small linear opacities that together produce the appearance of a net.
reticulonodular pattern	A collection of innumerable small linear and small nodular opacities that together produce a pattern composite appearance resembling a net with small superimposed nodules. The linear and nodular elements are usually similar in magnitude.
retina	(ret´i-na) The principal portion of the internal tunic of the eyeball that contains the photoreceptors.
retinaculum	Latin = a tether; hence, a thickened band of deep fascia which retains tendons or the patella
retraction	(re-trak´shun) The movement of a body part, such as the mandible, backward on a plane parallel with the ground; the opposite of protraction.
retro-	(ret'ro-) Prefix signifying backward, as in retroflexion; behind, as in retrosternal; reversed, or against natural course, as in retrostalsis.
retroflexion	Latin retro = backwards, and flexion = bent; hence, the position of being bent backwards, applied to the angulation of the body of the uterus on the cervix (see anteflexion)
retrograde	(re'tro-grad). Directed against natural course; specifically, retrograde pyelography, in which contrast solution is injected in a direction contrary to natural of urinary secretions (opposite of antegrade).
retroperitoneal	(ret´´ro-per´´u1-tuo-ne´al) Positioned behind the parietal peritoneum.
retrosternal clear space	The lung parenchyma visible on the lateral radiograph posterior to the sternum. Usually only a few pulmonary blood vessels are visible in this region.
retroversion	Latin retro = backwards, and version = turned; hence, the position of being turned backwards, applied to the angulation of the cervix uteri on the vagina. (see anteversion)
rhinal	(ri'nal). Of or pertaining to nose, nasal.
rhythmicity area	(rith-mis´i-te) A portion of the respiratory control center located in the medulla oblongata that controls inspiratory and expiratory phases.
ribonucleic acid (RNA)	Molecules that are involved in the growth and development of a cell through a number of small, spherical cytoplasmic organelles that attach to the endoplasmic reticulum.
ribosome	(ri´bo-s-om) A cytoplasmic organelle composed of protein and RNA in which protein synthesis occurs.
rickets	(rik´ets) A condition caused by a deficiency of vitamin D and associated with an interference of the normal ossification of bone.
right-hand rule	The rule by which the direction of the magnetic field lines can be determined.
right lymphatic duct	(lim-fat´ik) A major vessel of the lymphatic system that drains lymph from the upper right portion of the body into the right subclavian vein.
right paratracheal stripe	A vertically oriented linear opacity 2–3 mm wide that extends from the thoracic inlet to the right tracheobronchial angle on the AP/PA chest radiograph. It is situated between the air shadow of the trachea and the right lung and is formed by the right wall of the trachea and contiguous mediastinal tissue and adjacent pleura.
rigor mortis	(rig´or mor´tis) The stiffening of a dead body due to the depletion of ATP and the production of rigor complexes between actin and myosin in muscles.
rod	A photoreceptor in the retina of the eye that is specialized for colorless, dim-light vision.
roentgen	The special unit of exposure. This is only defined for X-ray or gamma radiation in air.
roller subassembly	One of three principal film-transport subsystems in an imaging system.
root canal	The hollow, tubular extension of the pulp cavity into the root of the tooth that contains vessels and nerves.
rotating anode	An X-ray tube design in which the anode is a rotating disk. During an exposure the actual focal area is projected onto an annular region of the anode, thereby distributing the heat over a larger area around the anode, and allowing more intense exposure techniques at higher mA. Virtually all X-ray tubes in radiology have rotating anodes. Non-rotating anodes are utilized in dentistry.
rotation	(ro-ta´shun) The movement of a bone around its own longitudinal axis.
rotor	The rotating part of an electromagnetic induction motor; it is located inside the glass envelope.
round window	A round, membrane-covered opening between the middle and inner ear, directly below the oval window; also called the cochlear window.
rudimentary	Imperfectly developed.
ruga	(roo'gah) Wrinkle or fold of mucous membrane: specifically, rugae or folds of gastric mucosa in empty or nearly empty stomach.
rugae	(roo´je) Latin = a wrinkle. The folds or ridges of the mucosa of an organ.