tube (toob) a hollow cylindrical organ or instrument.
x-ray tube,
x-ray tube,
auditory tube eustachian tube; the narrow channel connecting the middle ear and the nasopharynx. 
)
drainage tube a tube used in surgery to facilitate escape of fluids.
Durham's tube a jointed tracheotomy tube.
endobronchial tube a double-lumen tube inserted into the bronchus of one lung to deflate the other lung for anesthesia or thoracic surgery.
endotracheal tube an airway catheter inserted in the trachea in endotracheal intubation.
esophageal tube stomach t.
eustachian tube auditory t.
fallopian tube uterine t.
feeding tube one for introducing high-caloric fluids into the stomach.
Miller-Abbott tube a double-channel intestinal tube with an inflatable balloon at its distal end, for use in treatment of obstruction of the small intestine, and occasionally as a diagnostic aid.
nasogastric tube a soft tube to be inserted through a nostril and into the stomach, for instilling liquids or other substances, or for withdrawing gastric contents.
nasotracheal tube an endotracheal tube that passes through the nose.
neural tube the epithelial tube developed from the neural plate and forming the central nervous system of the embryo.
orotracheal tube an endotracheal tube that passes through the mouth. 
)
Orotracheal tube.
otopharyngeal tube , pharyngotympanic tube auditory t.
Sengstaken-Blakemore tube a multilumen tube used for tamponade of bleeding esophageal varices. 
)
Sengstaken-Blakemore tube for esophagogastric tamponade.
stomach tube a tube for feeding or for stomach irrigation; the most common kind is the nasogastric tube.
test tube a tube of thin glass, closed at one end; used in chemical tests and other laboratory procedures.
tracheal tube endotracheal t.
tracheostomy tube a curved endotracheal tube that is inserted into the trachea through a tracheostomy.
uterine tube fallopian tube; a slender tube extending from the uterus toward the ovary on the same side, for passage of oocytes to the cavity of the uterus and the usual site of fertilization. 
)
Uterine, or fallopian, tube.
Wangensteen tube a small nasogastric tube connected with a special suction apparatus to maintain gastric and duodenal decompression.
x-ray tube a vacuum tube used for the production of x-rays; when a suitable current is applied, high-speed electrons travel from the cathode to the anode, where they are suddenly arrested, giving rise to x-rays. 
)
Standard stationary anode x-ray tube; diagram in longitudinal section.
x-ray tube,
a large vacuum tube containing a tungsten filament cathode and an anode that often is a tungsten disk. When heated to incandescence, the cathode emits a cloud of electrons that produce x-rays when they strike the surface of the anode at high speed. The anode is designed to deflect the x-rays toward an object to be radiographed. X-ray tubes are produced in a variety of designs for different purposes. Low-kilovoltage x-ray tubes may contain anodes made of molybdenum rather than tungsten. Some anodes are stationary and others rotate at high speed. Because of the intense heat generated by x-ray production, the specific design usually includes devices to help dissipate the heat.
x-ray tube,
n an electronic tube in which roentgen rays can be generated. See radiographic tube.
)
X-ray
radiographic tube, Coolidge,
n.pr a vacuum tube in which roentgen rays are generated when the target (integral with the anode) is bombarded by electrons that are emitted from a heated filament (on the cathode) and accelerated toward the anode across a high-potential difference. Modern radiograph tubes are of this type. See also tube, Coolidge.
radiographic tube, Crookes',
n.pr a vacuum discharge tube used by Sir William Crookes in early experimental work with cathode rays. Wilhelm C. Roentgen first discovered that in addition to the production of cathode rays, radiographs were emitted during the operation of these tubes.
radiographic tube, gas,
n an early type of radiographic tube in which electrons were derived from residual gases within the tube.
x-ray
electromagnetic radiation of wavelengths ranging between 5.0 × 10−6 and 5.0 × 10−4 μm (including grenz rays).
X-rays are produced by the collision of a beam of electrons with a metal target in an x-ray tube. Called also roentgen rays. The penetrability and hardness of the x-rays increases with the voltage applied to the x-ray tube, which controls the speed with which the electrons strike the target. For diagnostic radiography, tube voltages in the range 50 to 120 kilovolts peak (kVp) are normally used. For radiation therapy, voltages in the 1 to 2 megavolt range are used for most treatment. Accelerating electrons to speeds high enough to produce megavoltage x-rays requires a linear accelerator (lineac).
The x-ray exposure is proportional to the tube current (milliamperage) and also to the exposure time. In diagnostic radiography, the tube voltage and current and exposure time are selected to produce a high-quality radiograph with the correct contrast and film density. In radiation therapy, these exposure factors are selected to deliver a precisely calculated radiation dose to the tumor. The total dose is usually fractionated so that tumor cells can be oxygenated as surrounding cells die; this increases the sensitivity of the cells to radiation.
Body tissues and other substances are classified according to the degree to which they allow the passage of x-rays (radiolucency) or absorb x-rays (radiopacity). Gases are very radiolucent; fatty tissue is moderately radiolucent. Compounds containing high-atomic-weight elements, such as barium and iodine, are very radiopaque; bone and deposits of calcium salts are moderately radiopaque. Water; muscle, skin, blood and cartilage and other connective tissue; and cholesterol and uric acid stones have intermediate density. See also radiation and radiation therapy.
A double contrast study uses both a radiopaque and a radiolucent contrast medium; for example, the walls of the stomach or intestine are coated with barium and the lumen is filled with air. The resulting radiographs clearly show the pattern of mucosal ridges.
x-ray tube
a glass vessel with a high vacuum and two electrodes. A very high voltage electrical current is passed across the tube and drives a stream of electrons produced by a tungsten filament set in the face of the cathode to collide with the anode and generate x-rays.
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