Chapter 3: The Dental X-ray machine: Components and Functions

Dental Hygiene 304 with Bruhn at Old Dominion University

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By: Meghan Sheerin
Created: 2010-09-25
Size: 48 flashcards
Views: 10

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alternating current

a flow of electrons in one direction, followed by a flow in the opposite direction

amperage

the strength of an electric current measured in amperes

ampere

the unit of intesity of an electric current produced by 1 volt acting through a resistance of 1 ohm

anode

the positive electrode (terminal) in the x-ray tube. Tungsten block, normally set at a 20-degree angle facing the cathode, embedded in the copper portion of the terminal

autotransformer

a special single-coil transformer that corrects fluctuations in the current flowing through the x-ray machine

cathode

the negative electrode (terminal) in the x-ray tube. The cathode consists of a tungsten filament wire that is set in a molybdenum focusing cup that directs the cathode stream toward the target on the anode

central ray

the central portion of the primary beam of radiatioon

collimator

a diaphragm, usually lead, designed to restrict the dimensions of the useful beam

control panel

that portion of the x-ray machine that houses the major controls. Includes the line switch, timer, milliamperage and kilvoltage selectors and the exposure button

"dead-man" switch

a switch so constructed that a circuit-closing contact can only be maintained by continuous pressure by the operator

direct current

electric current that flows continuously in one direction. Similar to current produces in batteries. Ideal for use with digital imaging

electric current

the flow of electrons throufh a conductor

electrical circuits

a path of electrical current

electrode

either of two terminals of an electric source. In the x-ray tube, either the anode or the cathode

electron cloud

a mass of free electrons that hovers around the filament wire of the cathode when it is heated to incandescence. The number of free electrons increases as the milliamperage is increased

exposure button

key pad or switch that activates the x-ray production process

extension arm

flexible arm from which the tube head of the c-ray machine is suspended

filament

the spiral tungsten coil in the focusing cup of the cathode od the x-ray tube

filter

absorbng material, usually aluminum, placed in the path of the beam of radiation to remove a high percentage of the low energy (longer wavelength) x-ray

focal spot

small area on the target on the anode toward which the electrons from the focusing cup of the cathode are directed. X-rays originate at the focal spot

focusing cup

a curved device around the cathode wire filament that is designed to focus the ffree electrons toward the tungsten target of the anode

impulse

measure of exposure time. There are 60 impulses per second

incandescence

stage when the tungsten filament in the cathode becomes red hot and glows. Free electrons are liberated and swarm around the glowing wire to form the electron cloud

intensity

intensity is the total energy of the x-ray beam. Intensity of the x-ray beam is the product of the number of x-rays (quantity) and energy of each x-ray (quality) per unit of area per time of exposure

kilovolt (kV)

a unit of electromotive force, equal to 1,000 volts. High kilovoltage is essential for the production of dental x-rays

kilovolt peak (kVp)

the crest value in kilovolts of the potential difference of a pulsating generator

line switch

toggle switch that is used to turn the x-ray machine on or off

millampere (mA)

one thousandth of an ampere. Milliamperage determines the number of electrons available at the filament. See ampere

polychromatic

a term derived from the Greek meaning "having many colors" Used in dental radiography to decribe the x-ray beam because it is composed of many different wavelengths

port

opening in the tube head that is covered with a permanent seal of gladd, beryllium, or aluminum through which the x-rays exot. The port is opposite the window in the x-ray tube and is the place where the PID attached to the tube head

primary beam

the origional undeflected usedul beam of radiation that emanates at the focal spot of the x-ray tube and emerges throught the aperture of the tube head

quality

term used when describing the intensity of the x-ray beam. Refers to the penetrating ability of the beam

radiator

a large mass of copper just outside the x-ray tube and connected to teh anode terminal. The radiator functions to carry off the excess heat produced in the energy xchange that takes place when the electrons of the cathode stream are converted into about 1% x-rays and 99% heat. The radiator conducts the heat away from the target and cools the tube

step-down transformer

device consisting of two-metal cores and coils so positioned within the circuitry of the tube head to decrease the line voltage to between 3 and 12 volts. Low voltage is required in the cathode to warm up the filament wire

step-up transformer

device consisting of two metal cores and coils positioned within the circuitry of the tube head to increase the potential of the line current to the high kilovoltage required to produce x-radiation

target

small block of tungsten embedded in the face of the anode, bombarded by the electrons streaming from the cathode. The focal spot is located on the target

thermionic emission

the release of electrons when a material such as tungsten is heated to incandescence. Electrons are boiled off from the cathode filament in the x-ray tube when electric current is passed through it

timer

a mechanical, electrical, or electronic device that can be set to predetermine the determine the duration of the interva that current flows through the x-ray machine to produce x-ray

transformer

one of several types of electrical devices capable of increasing or decreasing the voltage of an alternating current by mutual induction between primary and secondary coils or windings on cores of metal.

tube head

protective metal covering that contains the x-ray tube, the high voltage and low voltage transformers, and insulating oil. Attached to the flexible extension arm by a yoke. The PID attaches to the tube head at the port

tungsten

element with an atomic number of 74. High melting point makes this metal ideal for use as the cathode filament and as the anode target

useful beam

that part of the primary beam that is permitted to emerge from the tube head and limited by the port, collimator and lead-lined PID

volt (V)

unit of electromotive force or potential that is sufficient to cause a current of 1 ampere (A) to flow through resistance of 1 ohm (W)

voltage

electrical prsure or force that drives the electric current throught the cirrcuit of the x-ray machine

voltmeter

device for measuring the electromotive force (the differnece in potential or voltage) across teh x-ray tube

x-ray tube

electronic tube located in the tube head that generates x-rays

yoke

curved portion of the x-ray machine that is connected to the extension arm. The tube head is suspended within the yoke and can be rotated vertically and horixontal within it

quantity

term used when describing the intensity of the x-ray beam. Refers to the number of x-rays in teh beam

About this deck

By: Meghan Sheerin
Created: 2010-09-25
Size: 48 flashcards
Views: 10

About StudyBlue

“I have used this website for three exams, and I see a huge difference in my test results.”
Naj