x-ray tube

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tube

 [to̳b]
a hollow cylindrical organ or instrument. adj., adj tu´bal.
auditory tube eustachian tube.
Blakemore-Sengstaken tube Sengstaken-Blakemore tube.
chest tube see chest tube.
Dobhoff tube a small-lumen feeding tube that can be advanced into the duodenum.
drainage tube a tube used in surgery to facilitate escape of fluids.
Drieling tube a double-lumen tube having a metal weight at one end to carry it past the stomach into the duodenum. At the other end are two tails, one used to collect gastric specimens and the other to collect specimens from the duodenum. The tube is used in the secretin test for pancreatic exocrine function.
Durham's tube a jointed tracheostomy tube.
endobronchial tube a single- or double-lumen tube inserted into the bronchus of one lung and sealed with an inflatable cuff, permitting ventilation of the intubated lung and complete deflation of the other lung; used in anesthesia and thoracic surgery.
endotracheal tube see endotracheal tube.
esophageal tube stomach tube.
eustachian tube see eustachian tube.
Ewald tube a large lumen tube used in gastric lavage.
fallopian tube see fallopian tube.
feeding tube one for introducing high-caloric fluids into the stomach; see also tube feeding.
tube feeding a means of providing nutrition via a feeding tube inserted into the gastrointestinal tract; it may be done to maintain nutritional status over a period of time or as a treatment for malnutrition. It can be used as the only source of nutrition or as a supplement to oral feeding or parenteral nutrition.

Patients who may require tube feeding include those unable to take in an adequate supply of nutrients by mouth because of the side effects of chemotherapy or radiation therapy, those with depression or some other psychiatric disorder, and those suffering from severe hypermetabolic states such as burns or sepsis, or malabsorption syndromes. Other conditions that may require tube feeding include surgery or trauma to the oropharynx, esophageal fistula, and impaired swallowing such as that which occurs following stroke or that related to neuromuscular paralysis.

There are commercially prepared formulas for tube feeding. Some contain all six necessary nutrients (carbohydrates, fats, proteins, vitamins, minerals, and trace elements) and need no supplement as long as they are given in sufficient volume to meet nutritional and caloric needs. Other types of tube feeding formulas are incomplete and therefore will require some supplementation. Choice of formula is based on the patient's particular needs, presence of organ failure or metabolic aberration, lactose tolerance, gastrointestinal function, and how and where the feeding is to be given, that is, via nasogastric, gastrostomy, or enterostomy tube.
Patient Care. In addition to frequent and periodic checking for tube placement and monitoring of gastric residuals to prevent aspiration, other maintenance activities include monitoring effectiveness of the feeding and assessing the patient's tolerance to the tube and the feeding. Special mouth care is essential to maintain a healthy oral mucosa. A summary of the complications related to tube feeding, their causes and contributing factors, and interventions to treat or prevent each complication is presented in the accompanying table.
fermentation tube a U-shaped tube with one end closed, for determining gas production by bacteria.
Levin tube a gastroduodenal catheter of sufficiently small caliber to permit transnasal passage; see illustration.
Two types of nasogastric tubes. From Ignatavicius et al., 1995.
Linton tube a triple-lumen tube with a single balloon used to control hemorrhage from esophageal varices. Once it is positioned under fluoroscopic control and inflated, the balloon exerts pressure against the submucosal venous network at the cardioesophageal junction, thus restricting the flow of blood to the esophageal varices.
Miller-Abbott tube see miller-abbott tube.
Minnesota tube a tube with four lumens, used in treatment of esophageal varices; having a lumen for aspiration of esophageal secretions is its major difference from the sengstaken-blakemore tube.
nasogastric tube see nasogastric tube.
nasotracheal tube an endotracheal tube that passes through the nose.
neural tube the epithelial tube produced by folding of the neural plate in the early embryo.
orotracheal tube an endotracheal tube that passes through the mouth.
otopharyngeal tube eustachian tube.
Rehfuss tube a single-lumen oral tube used to obtain specimens of biliary secretions for diagnostic study; it is weighted on one end so that it can be passed through the mouth and positioned at the point where the bile duct empties into the duodenum. See also biliary drainage test.
Salem sump tube a double-lumen nasogastric tube used for suction and irrigation of the stomach. One lumen is attached to suction for the drainage of gastric contents and the second lumen is an air vent. See illustration.
Sengstaken-Blakemore tube see sengstaken-blakemore tube.
stomach tube see stomach tube.
T-tube one shaped like the letter T and inserted into the biliary tract to allow for drainage of bile; it is generally left in place for 10 days or more in order to develop a tract through which bile can drain after the tube is removed. A T-tube cholangiogram is usually performed prior to removal of the tube in order to determine that the common duct is patent and free of stones. If stones are found they can be removed through the tube tract by instruments inserted under x-ray guidance.
test tube a tube of thin glass, closed at one end; used in chemical tests and other laboratory procedures.
thoracostomy tube a tube inserted through an opening in the chest wall, for application of suction to the pleural cavity; used to drain fluid or blood or to reexpand the lung in pneumothorax. See also chest tube.
tracheal tube endotracheal tube.
tracheostomy tube a curved endotracheal tube that is inserted into the trachea through a tracheostomy; see discussion under tracheostomy.
tympanostomy tube ventilation tube.
uterine tube fallopian tube.
ventilation tube a tube inserted after myringotomy in chronic cases of middle ear effusion, such as in secretory or mucoid otitis media; it provides ventilation and drainage for the middle ear during healing, and is eventually extruded. Called also tympanostomy tube.
Tympanostomy (ventilation) tube. Polyethylene tubes are inserted surgically into the eardrum to relieve middle ear pressure and promote drainage of chronic or recurrent middle ear infections. Tubes extrude spontaneously in 6 months to 1 year. From Jarvis, 1996.
Wangensteen tube a small nasogastric tube connected with a special suction apparatus to maintain gastric and duodenal decompression.
Whelan-Moss T-tube a t-tube whose crossbar tube is larger in diameter than the drainage tube.
x-ray tube a glass vacuum bulb containing two electrodes; electrons are obtained either from gas in the tube or from a heated cathode. When suitable potential is applied, electrons travel at high velocity from cathode to anode, where they are suddenly arrested, giving rise to x-rays.

x-ray

(eks'rā),
1. The ionizing electromagnetic radiation emitted from a highly evacuated tube, resulting from the excitation of the inner orbital electrons by the bombardment of the target anode with a stream of electrons from a heated cathode. Synonym(s): roentgen ray Compare: glass rays, indirect rays.
2. Ionizing electromagnetic radiation produced by the excitation of the inner orbital electrons of an atom by other processes, such as nuclear delay and its sequelae.
3. Synonym(s): radiograph

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

(rā tūb)
Vacuum tube containing electrodes that are directed onto a metal target to produce an x-ray.
See also: x-ray

x-ray tube,

n an electronic tube in which roentgen rays can be generated. See radiographic tube.
Enlarge picture
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.