Image Production Flashcards
(98 cards)
1
Q
What conditions are required to produce x-rays?
A
- source of electrons
- means to accelerate electrons
- sudden stoppage of electrons against target material
2
Q
What is the Autotransformer?
A
single coil of wire with an iron core
3
Q
What does the Autotransformer do?
A
Determines the voltage applied to the xray tube (kVP selection controls transformer
4
Q
Where is the Autotransformer located?
A
beginning portion of the control counsel in the circuit
5
Q
What is the voltage of the primary turns in the autotransformer?
A
220V
6
Q
What is the voltage of the secondary turns in the autotransformer?
A
selected by radiographer
7
Q
What is the Line compensator?
A
Measures the voltage provided to the xray machine imaging system and adjusts it to 220V
8
Q
What is the kVP meter (aka prereading voltmeter)
A
Allows voltage be monitored before an exposure
9
Q
Where is the kVp meter (aka prereading voltmeter) located?
A
between the autotransformer and high voltage transformer
10
Q
What is the timing circuit (exposure timer)
A
regulates the duration of x-ray exposure
11
Q
Where is the exposure timer (timing circuit) located in the circuit?
A
between the autotransformer and high voltage transformer
12
Q
What are the 4 types of timing circuits
A
- synchronous
- electronic
- mAs
- automatic exposure control
13
Q
What is an AEC back up timer
A
- a backup timer that can terminate exposure in event of malfunction
- protects patient exposure and tube heating
- setting too short a time will result in underexposed images
14
Q
name the parts of the primary circuit
A
- Line compensator
- autotransformer
- major and minor kvp selector
- kVp meter
- timing circuit
- primary side of step up transformer
15
Q
What is a step up transformer?
A
- Used to increase the voltage from the autotransformer to the kV needed
16
Q
What is the high voltage generator
A
respondsible for increasing the output voltage from the autotransformer to the kV
17
Q
What are the three parts of a high voltage generator
A
- high voltage (step up transformer)
- filament transformer
- rectifiers
18
Q
What type of current is required for a step up transformer?
A
alternating current
19
Q
The primary side of the step up transformer is measured in what? secondary side?
A
volts -> kilovolts
20
Q
What is the mA meter?
A
monitors the x-ray tube current
21
Q
Which ciruit is the mA meter located in?
A
secondary circuit
22
Q
What is a rectifier?
A
changes AC to DC
23
Q
What does a rectifier consist of?
A
solid state semiconductor diode (contains two electrodes)
24
Q
Where is the rectifier located?
A
In the secondary circuit between the step up transformer and the xray tube
25
Define half wave rectification
- voltage does not swing negatively during cycle
- 0,1,2 diodes
- long exposure time ( waste of power)
26
Define Full Wave rectification
- negative half of cycle is inverse voltage making anode always positive
- 4 diodes
- exposure time cut in half
27
What is a diode
an electronic component that acts as a one-way switch for current in a circuit, allowing it to flow in one direction but not the other.
28
Single phase power
- results in pulsating x-ray beam
- low energy
- low penetrability
29
Three phase power
-multiple waveforms that maintain a nearly constant high voltage
- voltage never drops to zero during exposure
30
Define ripple
the energy that fluctuates from zero to the max voltage (peak of wave)
31
Which has more ripple single phase or 3 phase?
Single phase has %100 ripple 3 phase has significantly less (3.5-13%)
32
Which of the following will be more consistent in producing the kVP that is selected? (6 pulse or 12 pulse) only for three phase power
12 Pulse
33
What kind of current does the x-ray tube require?
Direct current DC
34
what is the voltage ripple for High frequency generator
around %1 = %99 of produced kVp is the selected amount
- results in lower patient dose
35
What is the mA meter?
measures tube current in milliamperes
36
Where is the mA meter located?
between the rectifier and x-ray tube
37
What is the Filament circuit
controls the degree and duration the filament is heated
38
What is the unit of measurement for resistance?
Ohms
39
What is the unit of current?
Amperes
40
What is the unit of voltage?
volts
41
Define resistance
a quantity that measure the reduction of electric current through a device or material
42
Define Current
The measure of the amount of electric charge transferred per unit of time
43
Define voltage
The electric potential between two points in an electric field
44
Equation to Find resistance?
(R) resistance = (V) voltage / (I) current
45
What is Ohm's law?
The current along a conductor is proportional to the potential difference (V = I x R)
46
What is coulombs law?
The force between two charges is inversely proportional to the square of the distance between them
F = ((Q1 x Q2)/ (d^2)) k
47
What is the energy formula?
Used to calculate the energy of a photon of electromagnetic energy
(E = hf)
- h = plancks constant
48
What is wave formula
used to calculate the wavelength (frequency) of electromagnetic energy
(C = f(wave length)
49
What is Faraday's law?
An electric current is induced in a circuit if some part of that circuit is in a changing magnetic field
50
What does the step down transformer do?
reduces voltage and increases current
51
The x-ray tube consists of what?
Cathode
Anode
protective housing and glass envelope
52
The high voltage section consists of what?
- step up transformer
- mA meter
- focal spot selector
- rectifier
53
Describe the Cathode
- located in x-ray tube
- negatively charged
- contains the focusing cup and tungsten filament
54
What is the tungsten filament of the cathode
- produces electrons after heating
55
What is the focusing cup of the cathode
concentrates the electrons to aim at small area of anode
56
Describe the anode
- positively charged
- consists of tungsten target, stem/neck, and rotor and stator
57
What is the tungsten target of the anode?
a means to stop electrons connected to the rotor by the anode stem
58
The area electrons hit the target is called the?
focal spot
59
What is the purpose of the target angle?
larger actual focal spot and smaller effective focal spot and heat dissipation
60
What is the effective focal spot?
the portion that is seen by the IR
61
What is the line focus principle?
- The angling of the anode results in the effective focal spot being smaller than the actual focal spot
- allows for a large area for heating while maintaining a small focal spot
Larger angle = larger effictive focal spot = actual focal = decrease spatial resolution
62
What is the anode heel effect?
The radiation intensity on the cathode side of the x-ray field is higher than that of the anode side
63
Decreasing the anode angle does what to the heel effect?
Increases heel effect
(angle and effect are inversely proportional)
64
Deceasing the SID does what to the heel effect?
increases the heel effect
(SID and Effect are inversely proportional)
65
Increasing the field size does what to the heel effect?
increases the heel effect
(proportional)
66
What are the two types of x-ray productions?
Bremsstrahlung and Characteristic
67
What is the difference between xray productions and xray interactions?
Productions are the creations of x-rays, interactions are the x-rays coming into contact with matter
68
Describe bremsstrahlung radiation
- incident electron moves towards atoms nucleus
- electron is (-) nucleus is (+) causing electron to slow
- the braking of the electron speed releases energy as x-ray photon
- majority of diagnostic x-rays are brems
69
Which production interaction makes up a majority of x-ray photons?
Bremsstrahlung
70
Describe Characteristic radiation
- incident electron collides with inner shell electron of anode target
- removes the inner shell electron from orbit and ionizes atom
- vacancy from inner shell electron is filled from adjacent outer shell electron
- in the process outer shell electron sheds energy in form of x-ray photon
- process continues to fill the next vacancy
- x-ray photons energy is equal to the difference in binding energies of the two shells
71
What x-rays in Characteristic radiation are sufficient to be used in diagnostic radiography?
k-shell only
72
At what kVp are characteristic x-rays produced?
kVp higher than 70
73
Define wavelength
the distance from peak to peak of a wave
74
Define Frequency
The number of waves passing a given point per unit time
75
What is the relation between wavelength and frequency?
Inversely proportional
76
What wavelength is more penetrating?
short wavelength
77
An x-ray beam containing many different energies is termed what?
heterogeneous
78
Best ideal for anode angle
Small effective spot large actual focal spot
79
what is the minimum for the total filtration of the x-ray tube
at least 2.5 mm aluminum equivalent
80
Removing low energy "soft" rays does what?
- hardens beam
- lowers patient skin dose
81
Define half value layer
amount of filtration that reduces the beam intensity by half
82
What is the equation to find the heat unit of a single-phase, full wave rectified equipment
kVp x mAs
83
What is the equation to find the heat unit of a three-phase 6 pulse full wave rectified equipment?
kVp x mAs x 1.35
84
What is the equation to find the heat unit of a three- phase 12 pulse full wave rectified equipment?
kVp x mAs x 1.41
85
What is the process of automatic adjustment of kVp and mA in fluoroscopy?
Automatic brightness control (ABC)
- aka automatic brightness
- aka automatic gain control
86
What is the image intensifier?
converts x-ray energy into visible light and then into an electronic signal that is displayed on a monitor
- used in fluoroscopy
87
Define input phosphor
receives exit rays from the patient and converts the rays into visible light
88
Describe the process that occurs in the image intensifier (fluoroscopy)
- input phosphor receives exit rays and converts into visible light
- visible light strikes photocathode
- photocathode releases electrons
- electrons directed towards anode end of image intensifier
- electrons strike output phosphor
- energy of electrons converted to much greater amount of visible light
-
89
Define flux gain
gain in brightness caused by the acceleration of electronic beam inside of image intensifier (fluoro only)
90
Define minification gain
gain in brightness caused by the minification of the image at the output phosphor compared to that of the input phosphor
91
A flat panel IR is provides better resolution of large or small anatomy?
smaller anatomy
92
What is the difference of digital fluoroscopy vs conventional
- Digital has all equipment similar to conventional but adds an operating console and computer workstation
- image intensifier is replaced by a flat panel IR
- patient dose is lower due to pulse fluoro
- utilizes analog to digital converter
- allows for posprocessing
- ABC still utilized in both
93
What is the accuracy requirement for collimator/ light to field alignment?
within 2%
94
What is the accuracy for effective focal spot size?
Within 50%
95
What is the required accuracy for kVp?
within 5% of what is displayed on the indicator
96
Which utilizes a cassette? DR or CR?
CR
97
What is the layering of the IR in computed radiography (CR)
1) Protective layer
2) Photostimulable Phosphor plate (PSP): Barium fluorohalide / Europium
3) conductive (antistatic): reduce electron charge
4) support base
5) reflective (light shield): reflects light
6) protective layer
98
