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Quiz 2 - The X-ray Circuit
Terms in this set (97)
What is the function of the x-ray imaging system ?
Provides a controlled flow of electrons intense enough to produce an x-ray beam appropriate for imaging.
What are the three main components of the x-ray imaging system ?
Operating Console, X-ray tube, High- Voltage generator.
Term - Imaging System
provides a controlled flow of electrons intense enough to produce an x-ray beam appropriate for imaging
In the imaging system kinetic energy is converted into ____ ?
Electromagnetic Energy (x-rays)
Electrons → ____ ____ = X-rays
Basic x-ray circuit can be divided into ____ and ____ ?
Main Circuit, Filament Circuit
Term - supplies the x-ray tube with properly modified power = produce x-rays
The Main Circuit is divided into ____ and ____ ?
Low- voltage (control circuit), High- voltage circuit
Term - supplies the filament of the x-ray tube with properly modified power = purpose to create the appropriate thermionically emitted electron cloud at the filament
Where is the Operating console ?
Behind protective barrier in adjoining room
Where is the High- voltage generator ?
Always close to x-ray tube - equipment cabinet
How are systems identified ?
According to the energy of the x-rays they produce or the purpose for which they are intended
Diagnostic imaging systems are usually operated at voltages of ____ kVp and tube currents of ____ mA
25-150 kVp, 100 - 1200 mA
How is the Fluoroscopic unit identified ?
The foot/ head tilt (90/30)
Term - uniform in thickness, curved or flat, transparent to x-rays
Term - table that is strong and has a low absorption rate
Carbon fiber tabletops
Term - table that moves in various directions
Term - allows technologist to control the tube current and voltage → useful x-ray beam is of proper quantity and quality
What does the operating console control ?
Line compensation, kVp, mA, time
All circuits that connect meter and controls are ____ ?
Low Voltage (minimize possibly of shock)
What do meters monitor ?
kVp, mA, exposure time, and mAs
Numeric selections may be replace by ____
Icons, indicating body part, size, and shape
Most electrical systems are designed to operate on ____ ?
220V (some can operate on 110V or 440V)
Most controls and meters are ____ and features are ____ ?
The power supply and main switch are generally located in the ___?
Electrical service box
Term - circuits that connect meters and controls
Low- voltage or Control circuit
Term - Measures the voltage provided to the x-ray image system and adjusts that voltage to precisely 220V
The Line compensator is required because of ____ in ____ ____ so the hospital can fluctuate
Variations, Power Distribution
Term - changes voltage (potential energy) and emerges (amount) from high to low or the opposite, low to high
The transformer operates on ____ current
The degree to which transformers increase the voltage is determined by their ____
Term - the number of in the secondary coil (high-voltage) compared with the number of turns in primary coil (low voltage)
Turn ratios > 1 =
Turn ratios < 1 =
↑ Ratio =
Greater voltage ↑
Current ↓ ____ according to the transformer law equation
If Voltage is 2x, current is 1/2 which is ____ ?
Secondary voltage (Vs) ?
----------------------- = ----------------------------
Primary voltage (Vp) ?
# of winding enclosed by secondary connections (Ns)
# of winding enclosed by primary windings (Np)
Term - first to receive the power supplied to the imaging system is the kV selector - breaks down the voltage into increments (60, 74, 120)
The Autotransformer has a single winding (wire) → which is designed to ___ ?
Supply a precise voltage to the filament and the high- voltage circuits
When is the autotransformer used ?
When only a small step up/ down in voltage is required
Autotransformers are designed to step up voltage to ____ the input voltage value
Single winding has more than 1 connection along its length = ____ ?
Primary connections (Np)
Term - the connections located on the opposite side of the coil,
which are placed closely together (C B) allow for the autotransformer to step up voltage
Secondary Connections (Ns)
More widely spaced connections (D E B') allow a ____ ?
Decrease in voltage
Autotransformers operate on ____ ?
When voltage is received in the autotransformer and the voltage it provides are directly related to the ______ of the transformer enclosed by the respective connections.
# of turns
Term - wire wrapped around an iron core - induction of an electric current in the wire creates a magnetic field intensity of the magnetic field is proportional to the electric current.
An electric current can be induced in a conductor if it ____ ?
Moving through a magnetic field
An electric current can be induced in a conductor if a ____ ____ moves across it
Term - a moving electric current or magnetic field can induce a current in another object
kVp major and kVp minor are from ____ ?
Term - Fine tunes kVp,
- represents 2 separate series of connections on the autotransformer
Low voltage from the autotransformer becomes the ____ ?
Input to the high- voltage (step-up) transformer that ↑ the voltage to teh chosen kVp
Term - allows voltage to be monitored before an exposure
Prereading kVp meter
Term - connection that permits current to flow through the circuit
- also activates the rotating anode
Why most the anode be turning at sufficiently high speed ?
Avoid melting of the target area
X-ray units that utilize rotating anodes have circuitry that ?
Prevents an exposure until the anode is turning at the correct speed
The release of the exposure switch must ____ ?
Terminate the exposure
mAs → ____ ?
Total # of x-rays emitted
Term - will terminate exposure after a prescribed time (approx. .6 sec)
Timer circuit is ____ from other main circuits
The ____ is located on primary side of high voltage transformer: where the voltage is lower
Make/ break electronic device
What are the four types of timing circuits ?
Synchronous, Electronic, mAs timers, AEC
Term - precision device used to drive a shaft at 60 revolutions/second
Synchronous have a minimum exposure time of ____ ?
1 / 60
Synchronous ____ be used for serial exposures - must be reset after each exposure
Term - most accurate, sophisticated, complicated timing circuit
Controlled by a microprocessor ?
An electronic timing circuit consist of complex circuitry based on time required to charge a ____ ?
Capacitor through a variable resistance
Which timing circuit allows a wide range of time intervals - accurate as small as 1 ms
Electronic timing circuit
Which timing circuit is used for rapid serial exposures ?
Electronic timing circuit
Which timing circuit is is used for angiotenrventional procedures ?
Electronic timing circuit
Term - monitors the product of mA and time and terminates exposure when deserved mA value is attained
Designed to provide the safest tube current for shortest exposure for any mAs selected
Which electronic timer is located on the secondary side of high - voltage transformer (monitors mA)
Term - measures the quantity of radiation that reaches the IR
AEC (Automatic Exposure Control)
Automatically terminates exposure when IR has received the required radiation intensity ?
Incorporates flat ionization chamber ionization chamber between patient and IR
AEC - ionization w/in chamber creates a charge → exposure ____ when appropriate charge is reached
AEC is calibrated for what specific study's ?
kVp and mA
A backup time is always set to _____ expected exposure time ?
Term - cloud of electrons near filament (-) repel each other = cloud, this repulsion makes it difficult for subsequent electrons to join the cloud
Space Charge effect
Why does kVp raise the number of photons ?
As kVp raised → Anode becomes more attractive to electrons that would not have enough energy to leave the filament are space charge → electrons join the electron stream, which ↑ mA with kVp
X-ray current crossing from cathode to anode in the ____ ?
Term - controls-ray tube current - voltage provided by autotransformer
↑ Filament current → filament becomes hotter = ____ ?
↑ Electrons emitted by thermionic emission = ↑ in mA
Filament circuit operates on ____ ?
3 - 6 a (amps)
Is activated any time the mA is adjusted ?
Term - steps down voltage and provides current to heat the filament
Filament transformer operates on ____ ?
Primary winding: thin copper - current =
0.5 - 1 A
Secondary winding (connected to high voltage supply for the x-ray tube): thiccc current =
5 - 8 A
Resisters are used to _____ ?
Control voltage to correspond to mA selection
The # of electrons emitted by the filament are determined by ?
The temperature of the filament
Term - the release of electrons from a heated filament
↓ in diameter of filament wire = ____ ?
↑ heat → electron movement, formation of electron cloud
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