Xray tube

radiation intensity is greater at the _ side of the xray beam

cathode

the anode heel effect is more noticeable with a SID and a larger image receptor

short

what are 4 things needed to make xrays

source of element, appropriate target marterial, high voltage & vacuum

what 2 things control size of the effective focal spot

size of actual focal spot (which Is controlled by side of filament) & anode target angle

decreasing the size of the filament will decrease the size of

focal spot

the cathode side of the xray tube has a charge

negative

in an xray tube, the smaller the coil (filament) the _ the structure that can be imaged

smaller

turning something into a gas is called

vaporization or vaporize

inside the xray tube the component that is a shallow depression in the cathode assembly is called

focusing cup

a space from which air & gasses have been removed is called

vacuum

tungsten is the material of choice for filament because it

has a high melting plate & is difficult to vaporize

rotating anode xray tubes allow ____ exposures than stationary anode Xray tubes

bigger

large filaments (large focal spots) are used to image ____ body parts because the small filaments cant take the stress of making big exposures on big body parts.

larger

a cloud of electrons that forms when thermionic emission occurs is called

a thermionic cloud

Placing ___ on the back of rotating anodes can double the heat-loading capabilities

graphite

the material of choice for filament is usually ____ wire

Tungsten

Routinely delaying exposure (holding the rotor too long) while the filament is heating up (enduring maximum current) can shorten the tube life by about % to __%

50-60%

the xray tube consists of cathode, anode, glass envelope & the

protective housing

when electrons are set free from the xray tube filament, we sometimes say that they have been ____ off

boiled

The focusing cup is made of:

Nickel

an xray tube that is used to pulse the xrays on & off quickly is called

Grid based, Grid Pulsed, or grid controlled

increasing the speed that the anode rotates will ___ the heat loading capabilities of an xray tube

increase

what happens to vaporized electrons inside the xray tube

reduces the tube vacuum, causing tube to become too gassy & deposit on the inside of the glass envelope

most xray tubes have 2 filaments, & this is known as _ focus

dual

one of the primary caused of premature tube failure is the radiographers habit of holding the

rotor switch too long before making exposure

what are the two things that vaporized electrons that coat the inside of the xray tube can cause

high voltage arching & increased filtration of the primary xray beam which decreases tube efficiency

what makes the elections move across the xray tube from cathode to anode

high voltage

any protons that escape from the xray tube housing except at the port are called

leakage

the anode side of the xray tube has a ____ charge

positive

when the target angle is decreased, ____ focal spots can be achieved

smaller

The special glass used in xray tubes is

Pyrex

In addition to tungsten as a target material, ___ is added to provide greater elasticity when the focal track expands rapidly due to the intense heat

Rhenium

inside the xray tube, the coil of wire is known as

filament

The roughening of the anode during normal use is called

pitting

pitting _ the efficiency of an xray tube

decreases

special high speed anodes rotate between - rpm

10,000-12,000 rpm

the xray tube component that is used to direct the electron cloud into a stream of electrons as it heads for the anode is called

focusing cup

standard xray tube anodes normally rotate between - rpm

3,200- 3,600

the vast majority of high output xray tubes are now made with ____ envelopes

metal

what are the 3 main reasons that tungsten is the main material of choice for xray tube target

hight atomic number, high melting point, good heat-conducting ability

the ___ principle is used to reduce the effective area of the focal spot

line focus

the ____ focal spot is used to describe the area of the focal spot that is projected out of the xray tube towards the object being radiographed

effective

the ____ permits the best resolution of detail while permitting as large an actual area as possible to act as a target (to increase thermal conductivity)

line focus principle

the term___ refers to the very small focal spot, one that is a fraction of millimeter in size

fractional focal spot

as the mA increases, so does the size of the focal spot. this is called

blooming

some specialized mammography xray tubes use _ as the traget material

molybdenum

when the target angle is less than__ degrees the effective focal spot is smaller than the acfual focal spot

45 degrees

the point inside the xray tube where the xray photons are created is called

target, focus, focal point, focal spot or focal track

the most common diagnostic radiography target angle is ___ degrees. however tubes are available with angles ranging from 7-17 degrees.

12 degrees

the anode heel effect is more noticeable with ___ image receptors (or xray films)

large

Many xray tubes have a thinned area of the glass called the

window

in addition to tungsten, what 2 other materials are desirable for uses as the xray tube filament

rhenium or molybdenum

what is the process called that produces particles that deposit on surfaces and reduces the vacuum within the xray tube

vaporization

The length and width of the x-ray tube filament have a great effect on the ability of the x-ray tube to image fine

details

passing an electric occurring through a filament to the point where it heats up and causes electrons leave, the surface of a filament is wire is called

thermionic emission (create clouds)

what causes the electrons in the thermionic cloud to move across the x-ray tube from cathode to anode

high voltage

rough handling an old x-ray tube with a thin_ can cause it to break prematurely

filament

what part of the x-ray tube is responsible for narrowing the thermionic cloud as it's driven towards the anode

focus cup

when the rotor is activated during an exposure, a higher current is sent to the filament. This increases the filament heating and it is what causes most of the _ of the filament

vaporization

the ____ the anode rotates, the better the heat dissipation

faster

rotating anodes disks are composed of

molybdenum

an _ relieved anode dissipates heat much more efficiently than a standard x-ray tube and node

stress

the sid is measured from the to the ir

target, focus, focal point, focal spot or focal track

rotating anode xray tubes have much greater ____ capacities than stationary anode xray tubes

heat loading

the line focus principle is used to ___ the effective area of the focal spot

reduce

The use of the line-focus principle causes a problem known as the

anode heel effect

The intensity of radiation emitted by the x-ray tube target various by about_% between the anode side & the cathode side

45%

with the anode heel effect, the ____ side has more intense xray beam

cathode

If a high-speed anode tube-housing is quickly rotated from one position to another (for example: from horizontal to vertical), the Effect can cause trauma to the anode disk and bearings, causing destruction of the tube.

gyroscopic

a metal envelope xray tube has a longer tube life because they eliminate the problems of

tungsten evaporation

when the xray photons are produced at the anode, they are emitted ____ (in al directions).

isotropically (the opposite is atropically)

what are the three functions of the positive side of the x-ray tube

serves as a target surface, serves as a primary thermal conductor, conducts the high voltage from the cathode back into the x-ray generator

some specialized mammography x-ray tubes have a special window made of_ to cut down on the absorption of x-rays, leaving the x-ray tube

berillium

Failure to warm up the x-ray tube may cause the anode to:

crack