Imaging Equipment and Maintenance Flashcards
Is the most frequent used system. It consists of two sets of rails mounted to the ceiling directly over the radiographic table.
Ceiling support
When x-ray tube is centered above the examination table at the standard SID, the x-ray tube is in a preferred _____ position.
Detent
Has a single column with rollers at each end, one attached to a ceiling-mounted rail and other attached to a floor-mounted rail.
Floor ceiling support system
Interventional radiology suites often are quipped with C shape arm
C arm support system
guards against excessive radiation exposure and electric shock.
Protective housing
how many leakage of radiation thus the protective housing reduce?
less than 100mR/hr at 1m
30 to 50 cm long and 20 cm in diameter` size of x-ray tube
Pyrex glass to enable to withstand the tremendous heat generated.
GLASS/ METAL ENVELOPE OR ENCLOSURE
what is the area of the tube window?
5cm^2
what causes arcing and tube failure?
as the glass enclosure ages, some of the tungsten vaporizes to the walls of enclosure.
Is the negative side of the x-ray tube
cathode
what is the melting point of the tungsten?
3410 degree Celsius
Is a coil of wire similar to that in a kitchen toaster, except much smaller
Filament
what is the filament made out of?
thoriated tungsten
what is the dimensions of the filament?
2mm in diameter, 1 or 2 cm long
why does the thorium is added to the filament?
increases the efficiency of the thermionic emission and prolongs tube life
an x-ray tube filament emits electrons when it is heated. When the current through the filament is sufficiently high, the outer electrons of the filament atoms are “boiled off” and ejected from the filament.
thermionic emission
The filament is embedded in a metal cup called the
Focusing Cup
without focusing cup the electron beams are
spread beyond the anode
with focusing cup the electron beams are
condensed and directed to the target
what does it call when the xray tube have 2 focal spots?
dual spot
is used when better spatial resolution is required. SFS range from 0.1 to 1mm
small focal spot
is used when large body parts are imaged and when other techniques that produce high heat are required.
LFS range from 0.3 to 2mm
large focal spot
the positive side of the xray tube
anode
what are the two types of anode
stationary and rotating
x-rays tubes are used in dental x-ray imaging system, some portable imaging system and other special purpose units in which high tube current and power are not required
stationary anode
is a shaft-like structure made primarily of copper.
rotor
attaches the rotating target area to the rotor.
stem
is a circular, disk-like structure with a slanted or beveled edge. –It serves as the target for receiving electrons as they move from the cathode to anode.
target
is the area of the anode struck by the electrons from the cathode.
target
what are the reasons why tungsten is the element of choice in xray tube?
high atomic number (74)
thermal conductivity (efficeint for dissipating heat)
high melting point (3410)
x-ray tube allows the electron beam to interact with as much larger target area.
rotating anode
RPM of the rotating anode
3410- 10,000 RPM
copper, because it is poor heat conductor.
STEM
is used to turn the anode.
induction motor
it is an agulation of the anode to increase the focal spot size but still remain the small effective focal spot size that can result to increase in recorded detail and better spatial resolution
line focus principle
two focal spot is called
biangular target
results in smaller effective focal spot and less radiation intensity on the anode side of the x-ray beam.
anode heel effect
The _____ the anode angle, the _____ is the heel effect.
smaller, larger
some of the electrons bounce off the focal spot and then land on the other areas of the target, causing x-rays to be produced from outside the focal spot.
extrafocal radiation
