Equipment Operation and Quality Assurance Flashcards
(132 cards)
1
Q
What makes up the cathode?
A
Filament
Filament wires
Focusing cup
2
Q
What is the filament made of?
A
Thoriated tungsten
3
Q
What charge is the focusing cup?
A
Negative
4
Q
How do electrons flow in the tube?
A
Negative to positive (cathode to anode)
5
Q
The size of the focal spot directed toward the IR is ________ (smaller/larger) than the size of the focal spot measured on the surface of the anode
A
Smaller
6
Q
Benefits of line focus principle
A
Longer tube life
Greater spatial resolution
7
Q
The smaller the anode angle, the _______ the spatial resolution
A
Greater
8
Q
The smaller the anode angle, the ________ the heel effect
A
Greater
9
Q
What is the anode made of?
A
Tungsten with rhenium
10
Q
What is the neck and base of the anode made of?
A
Molybdenum or graphite
11
Q
What makes up the induction motor?
A
Stator and rotor
12
Q
The stators are comprised of:
A
Paired sets of electromagnets
13
Q
X-rays are produced isotropically, which means:
A
They are produced with equal intensity in all directions
14
Q
Leakage radiation should not exceed:
A
1 mGy/hr at 1 meter
15
Q
Flow of x-rays from tube to bucky
A
Tube
Patient
Table
Grid
AEC
IR
Bucky
16
Q
Benefits of AEC
A
Images taken on a mixed population will fall within an acceptable range
Less repeats due to over or under exposure
17
Q
Cons of AEC
A
Improper positioning
18
Q
Purpose of the back-up timer in AEC
A
Provides a level of radiation protection fo the patient
19
Q
What is MRT (minimum response time)?
A
The time it takes for a system to respond and send the signal to terminate the exposure
20
Q
Ohm’s Law
A
V=IR
21
Q
How to convert milliseconds to seconds
A
Divide by 1000
22
Q
How to determine total resistance in series circuit:
A
R1+R2+R3+R4
23
Q
How to determine total resistance in parallel circuit?
A
1/(1/R1)+(1/R2)+(1/R3)
24
Q
What is the shortcut to determine total resistance in a parallel circuit?
A
Total resistance must always be less than the least resistor and will be appox. 1/2 of it
25
Which side of the circuit is the AC supply located?
Primary side
26
What supplies the x-ray unti with 220 volts?
AC supply
27
What type of current is the electrical energy supplied to the x-ray unit?
AC
28
What is the principle function of the transformer?
Covert incoming low voltage into high voltage necessary to produce x-rays
29
How efficient are transformers?
95%
30
What regulates voltage within the x-ray circuit?
Transformers
31
Transformers operate on the principle of electromagnetic induction and require ____________ current to operate
Alternating
32
What is electromagnetic induction?
Creating an electromotive force (voltage) within a conductor material that cuts across magnetic lines of force
33
What are the two types of induction?
Self induction
Mutual induction
34
What factors determine the strength of the EMF induced within the conductor material?
Speed
Strength
Angle
Number of turns
35
As speed increases, a _______ EMF is produced
Greater
36
As the magnetic field increases, a __________ EMF is produced
Greater
37
As the angle between the conductor and the direction of the magnetic field _________ (approches 90 degrees), a greater EMF is produced
Increases
38
As the number of turns ___________, a greater EMF is produced
Increases
39
That magnitude of a voltage change in a transformer is dependent on:
The turns ratio
40
What is the turns ratio?
Secondary turns:primary turns
41
What is the source for kVp?
Autotransformer
42
Which circuit is the autotransformer located in?
Primary
43
What is the purpose of the autotransformer?
Determine the amount of line voltage that will be sent to the step-up transformer
44
The autotransformer operates on the principle of:
Self-induction (one wire)
45
What separates the x-ray circuit into primary and secondary voltage sections?
Step-up transformer
46
Step-up transformer operates on the principle of:
Mutual induction (two wires)
47
Which part of the circuit is the filament transformer located in?
Low voltage
48
Formula for power
P=IV
49
Which part of the circuit is the exposure time located in?
Low voltage circuit
50
What is the purpose of the exposure timer?
Controls the duration of the exposure
51
What is the most accurate type of exposure timer?
Electronic - accurate up to 1 millisecond
52
What type of exposure timer establishes the highest, safest mA at the shortest exposure time?
mAs timer
53
What type of exposure timer utilizes an ionization chamber placed between the patient and the IR?
AEC
54
What is a rheostat and where is it located?
Variable resistor within the filament circuit
55
What is the function of a capacitor?
Momentarily stores electrical charge
56
What type of wave is unrectified? (AC or DC)
AC
57
What is the function of rectifiers?
Convert AC to DC
58
How are x-rays converted to visible light in an image intensifier?
X-rays - Light - Electrons - Light - Monitor
59
What is the function of the input phosphor in an image intensifier?
Coverts x-ray photons into light photons
60
What is the input phosphor made of in an image intensifier?
Cesium iodide
61
What is the purpose of the photo cathode in an image intensifier?
Converts light photons from input phosphor into free elctrons
62
What are the components of the image intensifier?
Input phosphor
Photo cathode
Electrostatic focusing lens
Anode
Output phosphor
63
What is the purpose of the electrostatic lenses of the image intensifier?
Focuses path of electrons from the photocathode to the surface of the output phosphor screen
64
Where are the electrostatic lenses of the image intensifier located?
Along the full length of the image intensifier tube
65
What is the purpose of the output phosphor in the image intensifier?
Converts electrons into light photons
66
What is the output phosphor in the image intensifier made of?
Zinc cadmium sulfide
67
What type of array is used in flat panel detectors for fluoroscopy?
Solid state detection
68
How are x-rays converted to light in indirect solid state systems?
X-rays are converted into light and then into electronic signal
69
What are the advantages of a flat panel detector?
Better stability
Lower patient dose
Wider dynamic range
70
What is the equation for brightness gain?
Minificiation gain x flux gain
71
Bright light vision uses which type of cells (cone or rod)?
Cone cells
72
Low/night vision uses which type of cells (cone or rod)?
Rod cells
73
Fluoroscopic mA is directly related to the ___________ of the image
Brightness
74
What is the relationship between the input phosphor size and magnificiation?
As the input phosphor size decreases, magnification increases
75
How does the electron focal point move in mag mode?
Closer to the input phosphor
76
What happens to patient dose when the distance from the II to the fixed source of radiaiton decreases?
Patient dose decreases
77
How does mag mode affect patient dose, spatial resolution, and contrast?
Increased patient dose
Increased spat. res.
Increases contrast
78
What is the single greatest source of acute radiation exposure to the patient in the diagnostic radiology environment?
Fluoroscopy
79
What is a bit?
A single unit of data
80
1 byte = __ bits
8 bits
81
Formula for bit depth
2^bit depth
82
Number of bit values
2 (0 or 1)
83
What are the layers of the cassette used for CR?
Protective layer
Phosphor layer
Light reflective layer
Conductive layer
Support layer
Light shielding layer
Backing layer
84
What is the function of the phosphor layer in a PSP imaging cassette?
Traps electrons
85
What is the phosphor layer made of in a PSP imaging cassette?
Europium-activated barium fluorohalide
86
What is a latent image in CR?
Electronic image of valence electrons stored in high-energy traps
87
What is the manifest image in CR?
Visible image made by exposure to the latent image with a high energy laser
88
What is the function of the laser in CR?
Causes the stored electrons to return to their valence bands with the emission of violet light
89
How does an imaging plate reader work in CR?
Employs the laser that reads the energy stored in the conductive layer, causing light to be emitted
90
What are the two types of scans in an imaging plate reader?
Fast scan - raster pattern movement of the laser across the PSP plate
Slow scan - mechanical movement of the PSP plate into the CR reader
91
How are CR plates erased?
Bright light
92
Exposure terms used by manufactures that indiciate amount are:
S, EI, lgM
93
What type of relationship do S numbers have with the amount of exposure?
Indirect
94
What type of relationship do EI numbers have with the amount of exposure?
Direct
95
What type of relationship do lgM numbers have with the amount of exposure?
Direct
96
If the deviation index is +3.0 or greater, what is exposure deviation? Patient exposure? Recommended action?
100% too hgih
Excessive patient exposure
No repeat, unless burnout occurs
97
If the deviation index is -3.0 or less what is exposure deviation? Patient exposure? Recommended action?
<50% low
Excessive under-exposure
Repeat
98
What is the process in indirect DR to convert x-rays into a digital image?
1. Scintillator converts x-ray photons to light photons
2. Light from the scintillator strikes the CCD and is converted to electric signal
3. The signal is sent to an ADC where is becomes a data set to form the digital images
or..
Electrons are sent to TFT to ampify the signal and then sent to ADC
99
What is the scintillator material in indirect DR?
Cesium idodie or gadolinium
100
What is the process in direct DR to convert x-rays into a digital image?
1. Uses amorphous selenium to convert x-rays to electrons
2. TFT collects electrons and amplifies signal. Sends to ADC
3. Converts electric signal to digital signal
101
What is a histogram?
Graphical representation of optimal densities during an exposure
102
What are values of interest?
Digital data set of information that is arranged into a histogram distribution
103
What is gray scale?
The number of shades of gray in an image
104
A reference to evaluate the raw information and to correct the luminance values
LUT
105
Results when the signal average inludes fewer pixels in the neighborhood. Used when fine details in an image are shown with some blur
Edge enhancement
106
How do high pass and low pass filters work in edge enhancement processing?
High pass filers increase contrast by amplifying areas of interest
Low pass filters causes a smoothing effect by averaging pixel values
107
What is the image processing technique that provides contrast enhancement or grayscale enhancement?
Equaliziation
108
Describes the contribution of all system components towards total resolution.
Modulation Transfer Function
109
What is the MTF value with the best resolution
1
110
What is the intensity of light that represents each pixel on the monitor?
Brightness
111
What is the differences in brightness?
Contrast
112
What are the boundaries of an object on an image?
Region of interest
113
What is accomplished by suppressing frequencies of lesser importance?
Cropping/masking
114
What is shuttering and when is it used?
Removes or replaces the background
Used when distracting light surrounds an image
115
Ability to alter the receptor exposure and contrast of a digital image
Windowing
116
As the number of pixels in the image matrix increases; spatial resolution:
Increases
117
Each pixel is given a numeric value known as:
CT number or Hounsfield unit
118
Diameter of the image reconstruction is called:
Field of view
119
When the FOV is increased for a fixed matrix size, the size of each pixel is:
Increased
120
Volume of tissue imaged is given a value called:
Value element or voxel
121
Window level determines: (brightness or contrast?)
Brightness
122
Window width determines: (brightness or contrast?)
Contrast
123
Which information system contrains full patient information?
Hopsital information system
124
Which information system contains radiology specific imformation?
Radiology information system
125
What is the difference between WAN and LAN?
WAN - spans great distances such as cities or states
LAN - small in size, computers are connected with wireless access points, much faster than WAN
126
Accepted standard for networked medical devices to exchange images and information
DICOM
127
Laser image receptor digitizers use a ________ type of laser beam for conversion of analog images into digital images
Helium-neon
128
Beam restricition must be within plus or minus __% of the source to image distance
2%
129
Linearity variation cannot exceed plus or minus __%
10%
130
Reproducibility must be within + or - ___%
5%
131
How often should lead aprons and gloves be tested?
Annually
132
Aprons and gloves should be tested under fluoro. What color will a crack show up?
White
