1. wk 2 x ray generators & components Flashcards
ended at 35
The anode has a ___ charge
+
the cathode has a ___ charge
-
____ is where the x ray is produced
anode
the ____ occurs in the cathode
thermionic emission
the filament is made of _____ metal
thoriated tungsten
- has a high melting pt
tungsten provides for a higher ____ emission
thermionic
Melting pt of tungsten
3410 C
the focusing cup is ___ charged
negatively
- to repell electrons
_____: used to direct the meg. charged e- into a smaller area on the target
focusing cup
if I want a very detailed x ray i will use the ___ filament
small filament
the small filament is used when better ___ is required
spatial resolution
the large focal spot is ued when _______ are imaged
large body parts
____ draws the ep from the cathode toward it bc of its + charge
anode
**The anode has three main fxn
- electrical conductor
- mechanical support for the target
- thermal dissipator
the target of the anode is made of tungsten for 3 reasons
- atomic number = high efficiency & nrg x rays bc of the wt. of it
- thermal conductivity
- high melting pt
3 main factors that alter the anode heel effect
- anode angle
- distance
- x ray field
The ___ the angle, the ___ the heel effect
smaller angle = greaer heel effect
the ___ the distance, the ___ the heel effect
shorter distance = greater heel effect
the ___ the field size. the ___ the heel effect
larger the field size= greater heel effect
______: anode rotates inside the enclosure w/ no mech connection to the outside
induction motor
___ holds the electromagnets outside of the induction motor
stator
the ___ is the portion on the inside of the induction motor
rotor
the rotor consists of the _____ shaft
copper/iron shaft
velocity = ___ x ___
freq x wavelength
in the freq increases the wavelength _____
decreases
the value of velocity is the ____
speed of light
the x ray machine consists of 3 components
operating console
high voltage generator
x ray tube
x ray imaging systems are designed to operate on ___v power
220v
- the _____ measures the voltage provided o the x ray machine and adjusts that voltage to ____
LINE COMPENSATOR
220V
radiation quantity refers to the _____ of x rays or ___ of the beam
number of x rays
intensity of the beam
radiation is expressed in ____ or ___
milliroentgens (mR)
milliroentgens/milliampere-second (mR/mAs)
_____: refers to the penetrability of the x ray beam
radiation NRG (kVp)
radiation energy is expressed in _____
kilovolt peak (kVp)
______: tells how many x rays are made during a unit of time
radiation quantity (mAs)
the number of x rays that reach the image receptor is directly related to both the ______ and the _____
x ray tube current (mA)
the time (s) that the tube is energized
(2) things that must occur for an x ray to be produced
- reach high voltage potential
2. direct current (DC)
(3) characterisitics of a voltage rectifier
- current to flow in one direction
- converts AC to DC
- uses diodes
high voltage generators require (2)
- high voltage transformers
2. voltage rectifier
What is the limited factor as to how many x rays can be made in a single exposure
the amt of wasted heat energy by the x ray
the lower voltage ripple = the greater the x ray ___ & ___ , as a result of constant voltage supplied in tube
quantity and NRG
- when x rays are produced, the are emitted ____
isotrophically
- equal intensity in all directions
_____/____: x rays that are emitted through the window of the tube
useful beam, or primary beam
_____: x rays that escape through the protective housing
leakage radiation
leakage radiation must not exceed ____
100mR/hr at 1 meter
the _____ is where the x rays are created
x ray tube
- components: cathode and anode
What is the basic internal component of a x ray tube
cathode
anode
most common cause of tube failure
as the tube ages, tungsten vaporizes and coats the inside of the glass
cathode is ___ charged
negatively
_______: when an electricity circuit sends electrons to the filaments in the focusing cup. Heats up the pt of boiling off a clous of e-
thermionic emission
the filaments are hold in the _____
focusing cup of the cathode
- it is neg. charged
the cloud of e- produced at the cathode is known as ______
space change
the build up of neg charge makes it difficult for e- to be emitted by the filament due to _____
electrostatic repulsion
- limiting factor
the anode is _____charged
positively
- draws e- from the cathode towards it
x rays are created when e- are shot over from the ___ and slam into the ____
from the cathode to the anode
name 2 types of anodes
stationary
rotating
_____anodes are used in xray units in which high tube current and power are not req.
stationary anodes
ex: dental, portable units
What are the two reasons as to why rotating anodes are able to produce higher nrg xrays and shorter exposure time
- more surface area
2. heat dissipation
if the freq increases, the wavelength would ____
decrease
(3) components of an x ray machine
operating console
high voltage generators
x ray tube
Most x ray imaging systems are designed to operate at ___v power
220V
_____ measures the voltage provided to the xray machine
line compensator
____ refers tot the number of x rays / intensity of the x ray beam
radiation quantity
Radiation NRG refers to the _____ of the x ray
penetrability
