X-Ray Circuits Flashcards
1
Q
Three parts of General X-ray Circuit
A
- Primary Circuit
- Secondary Circuit
- Filament Circuit
2
Q
General X-ray Circuit
Main power switch, circuit breakers, the autotransformer, the timer circuit, primary side of the step-up transformer
A
Primary Circuit
3
Q
General X-ray Circuit
Secondary side of the step-up transformer, the milliampere meter, a rectifier bank, and the x-
ray tube (except for the filaments)
A
Secondary Circuit
4
Q
General X-ray Circuit
Rheostat, step-down transformer, the filaments
A
Filament Circuit
5
Q
incorporates a meter to measure the voltage provided to the x-ray machine and a control to adjust that voltage to precisely 220 volts.
A
Line Compensator
6
Q
Included in the primary circuit to protect against short circuits and electric shock
A
Circuit Breakers
7
Q
Is an adjustable transformer controlled by the kVp selector on the operating console
A
Autotransformer
8
Q
Autotransformer
An autotransformer operates in the principle of?
A
self-induction
9
Q
Autotransformer
When a radiographer selects a ——, he or she determines the number of turns on the —— to be included in the circuit element and with it the output voltage.
A
- kVp setting
- secondary side
10
Q
Autotransformer is sometimes called
A
kVp selector
11
Q
Autotransformer
The primary Purpose is to provide a ——- that will be increased by the ———- to produce the —— selected at the operating console.
A
*a voltage
* step-up transformer
* kilovoltage
12
Q
The radiographer controls the autotransformer through —————–, and through this directly determines the ——- applied to the x-ray tube to produce x-rays.
A
- the kVp selector on the operating console
- voltage
13
Q
When a radiographer selects a kVp setting, he or she determines ——— to be included in the circuit element and with it the output voltage.
A
number of turns on the secondary side
14
Q
- Used to increase the voltage from the autotransformer to the kilovoltage necessary for x-ray production.
- Not adjustable and increases the voltage from the autotransformer by a fixed amount.
A
Step-Up Transformer
15
Q
Consists of mechanical and electronic devices whose action is to “make” and “break” the high voltage across the x-ray tube.
A
Timer Circuit
16
Q
- Cause the x-ray tube to emit x-rays for a specific time as determined by the radiographer or by AEC.
- Controls the length of exposure
A
Exposure Timers
17
Q
- Simple devices use in some portable and dental units
- Operates by clockwork
- inexpensive but not very accurate
- Exposure times greater than 250 ms
A
Mechanical Timers
18
Q
Minimum exposure time possible 1/60 second
A
Synchronous Timer
19
Q
- Most sophisticated, most complicated, most accurate
- Used for rapid serial exposures
- Exposure time as small as 1 ms
- Wide range of time intervals
- Based on the time it takes to charge a capacitor through a variable resistor
A
Electronic Timers
20
Q
_________ designed for accurate control of tube current and exposure time, Terminates the exposure once desired mAs is attained and is located in _________
A
- mAs timers
- secondary circuit
21
Q
Automatically terminates the exposure when sufficient radiation to provide the required optical density has reached the image receptor.
A
Automatic Exposure control
22
Q
Device that measures the quantity of radiation reaching the image receptor.
A
Phototimer
23
Q
Two types of Phototimer
A
- Photomultiplier tube
- Ionization chamber
24
Q
Method used to check the accuracy of exposure timer
A
Spinning Top Test
25
Is a device placed in the secondary circuit that monitors x-ray tube current
mA meter
26
assembled into electronic circuits to
convert alternating current into the direct current necessary for the operation of an x-ray tube
Rectifiers
27
is responsible for converting the low voltage from the electric power company into a kilovoltage of proper waveform.
High-Voltage Generator
28
Three primary parts of a High voltage-transformer
(H, F, R)
* High-voltage transformer
* Filament transformer
* rectifiers
29
Is a step-up transformer. The secondary voltage is greater than the primary voltage because the
number of secondary windings is greater than the number of primary windings.
High Voltage-Transformer
30
The ratio of the number of secondary windings to the number of primary windings.
Turns Ratio
31
# Sample Problem: Turns Ratio
The turns ratio of a high-voltage transformer is 700:1, and the supply voltage is peaked at 120 volts.
What is the secondary voltage supplied to the x-ray tube?
84,000 Vp or 84 kVp
32
process of converting alternating voltage to direct voltage and therefor alternating current to
direct current.
Rectification
33
Property of an x-ray tube which means that it acts as a valve permitting the flow of current in only one
direction, from the cathode to the anode.
Self-Rectification
34
Represents condition in which the voltage is not allowed to swing negatively during the negative half of its cycle.
* Contain zero, one, or two diode
* X-ray output is pulsating, with 60 x-ray pulses per second
Half-Wave Rectification
35
In Half-Wave Rectification:
* Contains how many diodes
* X-ray output is pulsating with ------- ?
* Contains zero, one or two diodes
* 60 x-ray pulses per second
36
the negative half cycle corresponding to the inverse voltage is reversed so that a positive voltage is always directed across the x-ray tube.
Full-wave Rectification/ Full-wave rectified circuit
37
In Full-wave Rectification:
* Contains how many diodes
* X-ray output is pulsating with ------- ?
* at least 4 diodes
* 120 x-ray pulses per second
38
* Results in pulsating x-ray beam
* Alternate swing from zero to maximum potential 120 times per second
* Low energy, low penetrability, low diagnostic value
Single-Phase Power
39
* Generates three simultaneous voltage waveforms out of step with one another.
* Voltage across x-ray tube is nearly constant and never drops to zero during exposure.
* Requires additional size and cost
Three-Phase Power
40
* Can be place in the x-ray tube housing
* Produce nearly constant potential
* Improves image quality
* Lower patient dose
High-Frequency Generator
41
* Are high-speed switches, or choppers, that convert DC into a series of square pulses.
* Used by a high-frequency voltage generation.
Inverter Circuits
42
Uses nickel-cadmium (NiCd) battery
Capacitor Discharge Generator
43
delivers the maximum possible mA for the selected kVp by considering the instantaneous heat load characteristics of the x-ray tube.
Falling-load capability
44
This delivers the desired amount of radiation to the image receptor in the shortest possible exposure time.
Falling-load Generator Control Circuit
45
# Failing-load Generator Control Circuit
During capacitor , the voltage falls approximately?
1 kv/mAs
46
works on the principle that a small current is drawn from the mains to charge a capacitor before the x-ray exposure, and this capactor is allowed to discharge through the x- ray tube during exposure.
Capacitor Discharge mobile
47
Is the variation in peak voltage waveform.
Voltage Ripple
48
100% voltage ripple
* The voltage varies from zero to its maximum value
Single-phase Generator
49
# Three-phase Generator
3-phased, 6 pulse generator = ?
3-phased, 12 pulse generator = ?
* 13% voltage ripple
* 4 % voltage ripple
50
Less than 3% voltage ripple
High-Frequency Generator
51
Formula for Power Rating
Power = current x potential
Watts = Amperes x volts
52
When specifying high-voltage generators, the industry standard is to use the maximum tube current(mA) possible at 100 kVp for an exposure of 100 ms.
Maximum Available Power
53
3 phase generator and high frequency formula for power rating
Power Rating = mA x kVp/ 1000
54
# Sample Problem: Power Rating
A radiographic single-phased unit installed in a private office has a maximum capacity of 100 ms of 120 kVp and 500 mA. What is its power rating?
42 kW
55
A variable resistor controlled by the mA selector on the operating console
Rheostat
56
When the radiographer adjusts milliamperage on the operating console, he or she is adjusting this ------- and ultimately the amount of current applied to the filament (filament current) in the x-ray
tube.
Rheostat
57
# Rheostat
The higher milliamperage station number, the ?
the lower resistance
58
The goal of it is to literally boil electrons out of the filament wire.
Filament circuit
59
Normally, a rather large filament current of --------- required to produce a tube current in the range of milliamperes.
5 to 7 amperes
60
# FIlament Circuit
Rheostat controls ?
filament temperature
61
Used in filament circuit to increase the current by reducing the voltage that is applied to the filament.
Step-down Transformer
62
The purpose is to control the degree and duration that the filament is heated, which in turn controls the number of electrons boiled off that will ultimately become the tube current.
Filament Circuit
63
Two kinds of Filaments
Small and Large filaments
64
Represented on the operating console by the “large focal spot” and “small focal spot”.
Filaments
65
# Principles of Circuit Operation
* The ------- adjusts the autotransformer and determines the number of turns on the secondary side necessary to produce a voltage, through self-induction, that will be sent to the step-up transformer.
* The ------------ increases this voltage by a fixed amount and, through mutual induction, produces the kilovoltage selected on the operating console.
* This ------- must be rectified.
* The -------- draws electricity from the autotransformer, which then travels to the rheostat.
* The ------------- sets the resistance in the filament circuit.
* From the rheostat, electricity travels to the ------.
* The kilovoltage applied to the x-ray tube creates a --------- on the anode and a --------- on the cathode.
* kVp selected
* step-up transformer
* kilovoltage
* filament circuit
* selected mA station
* step-down transforment
* large positive charge and large negative charge
66
Allows radiographer to control the x-ray tube current and voltage so that the useful x-ray beam is of proper quality and quantity.
Operating Console/Control Panel
67
# X-ray Quantity and Quality
Refers to the number of x-rays or intensity of the beam usually expressed in mR or mR per
mAs.
Quantity
68
# X-ray Quantity and Quality
Refers to the penetrating qualities of the x-ray beam and is expressed by kVp or HVL
Quality
69
Factors that Affect X-ray Quantity
* mAs
* kVp
* Distance
* Filtration
70
Factors that Affect X-ray Quality
* kVp
* Filtration
71
Some Basic Controls For Every Panel
* On/off switch
* mAs selection
* kVp selection
* Table or wall unit activation
* Exposure switch.
* mAs and kVp meters.
72
# Extending Tube Life
* X-ray tube life may be extended by using -------------- appropriate for each examination.
* Use of ---------
* --------- results in reduced x-ray tube life.
* minimum radiographic factors of ma, kVp, and exposure time
* faster image receptors.
* Excessive heat
73
# Extending Tube Life
* X-ray tube life may be extended by using -------------- appropriate for each examination.
* Use of ---------
* --------- results in reduced x-ray tube life.
* minimum radiographic factors of ma, kVp, and exposure time
* faster image receptors.
* Excessive heat
74
Prepares the x-ray tube to receive high heat load.
Warm up Procedures
75
An example of a warm-up technique
an initial exposure of ------------------
followed by a second exposure in which the mA is raised to ---
* 50 kVp, 100 mA, at 1/30 second
* 200
76
# Other Ways of Extending Tube Life
* Minimize ------- (preparation) time.
* Limit -------- operations.
* Use ------------ (mA).
* Do not make a ------- on a cold tube.
* Adhere to --------------
* Limit operations to ---- of maximum single exposure ratings.
* Do not exceed the -------------- or dissipation rate of the target.
* Do not ---------- rapidly from one position to another.
* Avoid ------ between spot-films
* filament boost
* rotor/start/stop
* lower tube current
* high mA exposure
* rating charts and anode heating and cooling curves
* 80%
* anode thermal capacity
* rotate the tube housing
* long intervals
77
# X-ray Tube Aging
* ---------- to the internal surface of the glass envelope will cause some electrons strike the glass envelope
Deposition of Filament Tungsten
78
# X-ray Tube Aging
----------- at tube window will add -----------,
will harden the beam (less useful x-ray will emit from tube window).
* Tungesten layer deposited
* extra filtration
79
# X-ray Tube Aging
By the time, glass envelope that struck by electrons -------------, which cause tube failure due to x-ray tube is not vacuum anymore.
produces gas (gassy tube)
80
# X-ray Tube Aging
can be diagnosed, as oil sucked into the tube insert, when the tube is turned, can easily be heard.
Punctured Tube
81
# X-ray Tube Aging
Careless handling might break the glass envelope, stress fracture may occur (affect vacuum condition).
Carelessness
82
# X-ray Tube Aging
5. Damages to Anode
* ------------ - cause to different expansion and reduce the radiation output.
* ------------ - sudden injection of great heat. (not apply warm up)
## Footnote
Damages to Anode
* Surface crazing (rough)
* Anode disc may crack
83
# X-ray Tube Aging
cause to slow rotation / not rotate. Due to surface melting, it will release gas (gassy
tube) because the heat applied to small area.
Bearing Damage
| Damages to Rotor and Bearings
83
# X-ray Tube Aging
Recommendations
* ------ (as necessary only)
* provide ------ to reduce speed after exposure (special unit)
* ----------- prevent or terminate exposures if anode is not rotating
| Damages to Rotor and Bearings
* minimize time
* braking
* interlock circuit
84
# X-ray Tube Aging
Filament thin with age or time through evaporization or mechanical damage.
Damages to Filament
85
# X-ray Tube Aging
1) As filament becomes thinner (evaporization), its -------- decreases - reducing mA.
2) --------- (on and off) fault — problem on filament circuit
* resistance
* Intermittent
86
# X-ray Tube Aging
Reccomendations:
1. boosting the filament the -------- as possible
2. avoid the use of ------ unnecessarily
| Damages to Filament
* shortest time as possible
* high mA
87
# X-ray Tube Aging
Oil escape from tube will cause a reduction of insulation level and it is harmful to operator.
Damages to Tube Housing
88
# X-ray Tube Aging
Evidences of leakage:
* ---- outside the housing
* a ------- on the floor under the tube
* oil
* a spot of oil
89
# X-ray Tube Aging
Broken in stator windings (which provide electromagnetic field) will cause no or intermittent rotation.
As a result, it will harm to the -----.
* Damages to Stator
* anode target
90
Recommendation
* Provide safety circuit to ------
## Footnote
Damages to Stator
terminate exposure
91
single phase power rating
V = (0.7) kV x mA/1000
