Practice test deck 2 Flashcards
(181 cards)
1
Q
What component of a fluoro system speeds up electrons?
A
Accelerating anode
2
Q
How are operator and pt exposure related?
A
Directly proportional
3
Q
How is the overall resolution of an imaging system expressed
A
Modulation transfer function
**perfect is a MTF of 1
**overall MTF of a system is the product of the MTF of its components
4
Q
What is the genetic dose
A
Radiation exposure where damage occurs to precursor cells that can be passed onto offspring
5
Q
What must be done to the video signal when the electron beam produces a voltage that is sent to the television camera?
A
-It must be synchronized
-It must be amplified
6
Q
What is the maximum tabletop dose rate when imaging w/ high level fluoro?
A
20 rads (20 centigray) per minute
7
Q
Somatic dose measurements are taken at what anatomic sites
A
Bone marrow
Thyroid
Skin
8
Q
A photocathode gives off ___ in proportion to the intensity of fluorescent light
A
Electrons
9
Q
What is the skin and extremities (shallow-dose equivalent) annual occupational dose equivalent limit
A
0.5 Sv
10
Q
Personnel monitoring device examples
A
Pocket ion chambers
Thermoluminescent dosimeters
Film badge
11
Q
How much does brightness gain deteriorate each year due to the “aging” of the input and output screen phosphors
A
10%
12
Q
What is required on mobile fluoroscopic equipment
A
-A way to prevent operation when the collimating cone or diaphragm is not in place
-Device to prevent operation when the XR beam is not entirely intercepted by the image receptor
-An inherent system preventing operation at a source to skin distance less than 30 cm
13
Q
With optical coupling between an image intensifier and viewing and recording systems, how much light is sent to the viewing system?
A
10%
14
Q
This type of image receptor can use either direct or indirect methods to convert X-rays into an electrical charge
A
Flat panel detector
15
Q
Genetically significant dose
A
Developed to estimate the magnitude of genetic effects caused by radiation exposure to the population
***does NOT predict what adverse effects an individual/offspring may have
16
Q
Another name for the cathode-grid assembly
A
Electron gun
17
Q
How do pocket ionization chambers record radiation exposure
A
By discharging a capacitor
18
Q
Definition of air kerma
A
The amount of energy transferred from X-rays to charge particles per unit mass of air
19
Q
What is the relative increase in exposure when using magnification mode, where the center 6 inches of the input screen is now visualized over the entire 9 inch window?
A
2.25
20
Q
Around what acute dose of radiation do cataracts form
A
200 rads
21
Q
What is directly proportional to the exposure delivered to a patient
A
milliamperage
22
Q
What is the minimum total filtration required in fluoroscopic equipment at normal operating voltage?
A
2.5 mm AIuminum equivalent
23
Q
What components make up the target assembly of a TV camera tube
A
Target
Signal plate
Glass face plate
24
Q
How soon must the state dpt of health be notified if an occupational worker receives an exposure of 0.05 Sv to the skin or extremities?
A
No notification is needed
**Need to be notified if greater than 0.50 Sv in 24 hours
25
Which international organization is responsible for consistent data reporting and deals w/ units of measurement of radiation and measurement techniques
The International Commission on Radiation Units and Measurements
26
What is the abscissa on a dose-effect curve
X-coordinate
27
Which of the following affects the amount of scattered radiation during an x-ray exam
Pt entrance skin exposure
Exposure time
Kilovoltage
28
Which factors effect total brightness gain
Flux gain
Minification gain
29
How do you increase minification gain
increasing the size of the input screen
Decreasing the size of the output screen
30
This method improves imaging of the vasculature by subtracting digital images after contrast is injected
Digital Subtraction Angiography
31
Which cell type is the most radiosensitive
Leukocytes
32
What is the primary cause of size distortion
Object to image distance
33
Contrast agent volume is determined by which of the following factors
Patient size
Area being imaged
34
What is the estimated reduction in exposure from diagnostic x-rays that can be achieved w/o compromising pt benefit
50%
35
What is the conversion factor
Ratio of the intensity of the output phosphor to the input exposure rate to the input phosphor
36
What is high level fluoroscopy
Special activation capability of a fluoro system to provide significantly higher tube currents and significantly higher dose rates to the patient
**typically used for interventional angio or cardiography where it is needed to visualize small guidewires and catheters
37
Major source of secondary radiation in radiography is
pt's body
**scattered radiation
38
which of the following factors will influence the effect of radiation exposure
-radiation type
-radiation dose
-cell type
**cell size does NOT change
39
In digital imaging, if the field of view is held constant and the matrix size decreases, which of the following occurs
Pixel size increases
Spatial resolution decreases
40
Effect refers to the production of scattered radiation
Compton effect
41
Which international organization is responsible for consistent data reporting and deals w/ units of measurement of radiation and measurement techniques
International Commission on Radiation Units and Measurements
42
Cones function in daylight using this kind of vision
Photopic
43
What is the lifetime occupational exposure limit for a 45 year old worker
450 mSv
Max = 10 mSv x age
44
What is the function of automatic brightness control
Keep the light output of the image intensifier constant
45
During routine fluoro, the tabletop dose rate shall not exceed ___ rads per minute
10
46
Doubling the exposure area does what to the patient dose
doubles it
47
Why is a single anatomic dose reading NOT representative of the total somatic effect from radiological exams
-there is protective shielding
-the XR beam may be restricted to one area
-Radiation doses are not uniformly distributed
48
Film badge readings are recording using what unit of measurement
Sievert
49
Genetically significant dose is determined by:
-number of future children
-X-ray examination rate
-Average gonadal dose per examination
50
Mottle of an image can be adjusted by changing the
-kVp
-mA
-exposure factors
-number of available X-ray photons
51
Moving the fluoro tube too quickly during an exam will result in image blurring due to
lag in the image intensifier
52
Which body are has the largest distribution of fluoro examinations?
GI tract
(barium enema, upper GI series, KUB)
53
At what height above the tabletop should an unexposed border on the fluoro screen be visible when automatic collimating devices are used
all heights
(14 inches when collimators are fully opened, all heights when automatic collimating devices used!!)
54
Protective curtains also called
-lead panels
-hinged panels
-protective drapes
-sliding panels
55
Which personnel monitoring device allows immediate reading of radiation exposure
Pocket ionization chamber
56
Visibility of mottle in a system is determined by
-Resolution
-Contrast
-Sensitivity
57
In digital imaging, adjusting the window level changes the
Contrast
***brighter images can be viewed by increasing the window level and darker images can be viewed by decreasing the window level
58
A non-threshold dose-effect relationship has a curve that
Intersects the abscissa at the origin
59
This principle is a cornerstone of minimizing radiation exposure in medicine
As Low as Reasonably Achievable
60
This occurs when the diameter of the image form the optical system is larger than the shortest dimension of the film, resulting in part of the image being lost
Overframing
61
ALARA is the principle of keeping all radiation doses to what groups as low as possible
Patients
Operators
ALARA = As Low as Reasonably Achievable
62
If at one foot from the radiation source the intensity of exposure is 240 milliroentgens per hour and you remain at this location for 10 minutes, you will receive an exposure of 40 milliroentgens. What would be your exposure if you moved 2 feet away from the radiation source and remained there for 20 minutes
20 milliroentgens
***doubling the distance from a radiation source reduces the exposure by a factor 4
63
Ratio between vertical resolution and the number of scan lines in a television monitor
Kell factor
64
How does the actual radiation exposure compare to the amount recorded by a personnel monitoring device
It is sometimes much higher
65
What is the resolution of modern cesium iodide image intensifier tubes
4 line pairs per millimeter
66
What term refers to the standardized method of evaluating the brightness of an image intensifier
Conversion factor
67
Theory that any XR exposure risks the possibility of producing adverse effects
Non-threshold linear dose effect
68
How many horizontal lines do TV monitors typically have
525
69
Minification gain x flux gain =
Total brightness gain
70
Increasing the voltage in an image intensifier tube
-compresses the electron beam
-reduces the available input surface
-Moves the crossover point to further away from the output phosphor
71
The differentiation of small objects that are close together in an imaging system
Resolution
72
Roentgen is a unit of
Exposure
73
Approximate dose to the fetus from an upper-GI exam of a pregnant pt with a total skin exposure of 5 Roentgens
100 millirads
1 Roentgen = 1 Rad
1 rad = 1,000 millirads
74
This type of body habitus includes an athletic build and is the most common in the general population
Sthenic
75
Hypersthenic body types
Large and heavy, have high lungs and heart, transverse stomach, 5% population
76
Asthenic body types
Slender with a bony framework, long narrow thorax, low long stomach, 10% population
77
Hyposthenic body types
Slightly less robust than sthenic, have a stomach that sits higher in the abdomen, ~35% population
78
During standard fluoro use tube currently usually ranges b/w
0.5 and 5 mA
79
What increases pt fluoro exposure
-Inc pt to imagine intensifier distance
-Dec sensitivity of the image receptor
-inc exposure time
-lowering kVp
80
Scattered radiation exposure at 3 feet from the pt can be as high as
50 millirads (0.05 centigray) per hour
81
Equation used to calculate pixel size
Field of view / Matrix
82
Scattered radiation exposure at 1 foot from the patient could be as high as
500 millrads per hour
83
Legal aspects of taking XR fall under
-civil law
-regulatory law
-administrative law
84
Minimum lead equivalent thickness for protective curtains
0.25 mm
85
Purpose of image intensified fluoro
Dynamic viewing
-real time viewing
-transient image viewing
86
Does the number of horizontal lines change when switching from a 12 in TV to a 20 in TV monitor
NO
fixed at 525 lines
87
Which imaging method can reduce pt exposure by taking short XR w/ low frame rates
Pulsed fluoro
88
Examples of high bone marrow dose examinations
Barium enema
Upper GI series
Abd angiography
89
Which device synchronizes the pulses of voltage to produce a video singal
Camera control unit
90
Mobile screens are available in what lead equivalent thickness?
1 mm or 2 mm
91
Fluoro is the use of ____ for the obeservation of a dynamic image
Fluorescence
92
Annual eye dose limit for radiation
0.15 Sv
93
Latent period
Time before detectable effects of radiation occur after a pt has been exposed
94
Probability of an effect occuring, rather than its severity
Stochastic effect
95
Refers to a radiation dose w/ a threshold and a severity of effect that varies w/ dose
Non-stochastic effects
Deterministic effects
96
The focal spot size of a fluoro x-ray tube is ___ than the focal spot size of a radiographic x-ray tube
often smaller
97
In mobile fluoro, what is the minumum required source to skin distances
30 cm
98
Lowest radiation dose film badges can detect
10 millirads
99
A non-threshold dose-effect relationship has a curve that
Intersects the abscissa at the origin
100
How long does it take to change a fluoro system from a horizontal to a vertical imaging position
20 seconds
101
When XR are directed toward the patient, most are:
absorbed by the patient
102
The XR that pass through the patient
remnant rays
103
Which factors should be considered when positioning geriatric pts
Decreased hearing
Thin, delicate skin
104
According to the Law of Bergonie and Tribondeau, radiosensitivity depends on
The number of undifferentiated cells
the degree of mitotic activity of the cells
The life cycle of the exposed cell
105
Most commonly used video disc frame rate
30 frames/sec
106
Genetically significant dose is a dose received by which members of the population that would produce the same total effect on the population as the sum of the individual doses that member receives
Every member
107
Decreasing the target-to-panel distance ___ patient dose
Increases
108
Which group (s) of people provided early evidence of the potential harmful effects of large dose exposure to ioninizing radiation
-Radiologists
-Radium industry workers
109
The biological effects of ionizing radiation are effected by
-dose rate
-radiation dose
-cell type
110
Maximum monthly radiation dose to an embryo/fetus
0.5 mSv
111
Minimum lead equivalent for a gonadal shield?
0.5 mm
112
In digital imaging, adjusting the window level changes the
Contrast
113
During fluoroscopy, the room lighting should be ___ to enhance visualization of black and white television images
Dim
114
This act regulate the use and disclosure of protected health information as well as protects health coverage for workers when they lose their jobs
HIPAA
Health Insurance Portability and Accountability Act
115
What structure does light hit first in the human eye
Cornea
116
What does a photoconductive target do
Create an electrical current to signal a video image
117
Purpose of the electron gun
Produce a scanning electron beam
118
What is quantum mottle
Grainy appearance in an image caused by statistical fluctuation of absorbed X-ray photons
119
Characteristics of contrast media
Low toxicity
High atomic number
120
What kind of barrier must be in the walls and floors exposed to the primary beam
Primary barrier
121
Part of fluoroscopic system keeps the light output of the image intensifier constant over variations of pt thickness and density
Automatic brightness stabilization
122
Whole body dose means exposure to
head
trunk
arms above the elbows
legs above the knees
gonads
123
Pixel size equation
FOV / matrix
124
Mobile c arm fluoro systems require
-Primary protective barrier
-dead-man switch
-locking system b/w the tube and image intensifier
125
What is used to compare the spatial resolution of imaging systems
Modulation Transfer Function
126
Pincushion distortion is a result of
Projecting an image formed on a curve input phosphor to a flat output phosphor
127
Nonstochastic effects
Severity varies w/ radiation dose
(ex: cataracts, non-malignant skin damage, Bone marrow depltion)
128
Stochastic effect ex
Somatic effects
carcinogenesis
129
How thick in lead equivalents must protective curtains be
0.25 mm
130
What is the appropriate dose to the fetus from an upper GI exam of a pregnant pt w/ a total skin exposure of 5 Roentgens
100 millirads
1 Roentgen = 1 rad
1 rad = 1000 millirads
so 5 roentgen = 5,000 millirads
dose to fetus is 2% of the skin dose, 2% of 5,000 = 100
131
Examples of control methods by the brightness sensory in an automatic brightness tabilization
-variable mA, preset kVP
-variable mA w/ kVp following
-variable kVp w/ selected mA
-variable kVp w/ variable mA
132
Which long-term effects from radiation are a greater concern from a public health standpoint
genetic effects
carcinogenic effects
133
Another name for the cathode-grid assembly is
electron gun
134
When the x-ray tube is under-the-table, which tabletop material results in the lowest patient exposure
carbon fiber
135
What total filtration must be used in fluoro tubes operating above 70 kVp
2.5 mm aluminum equivalent
136
Parts of a c-arm fluoro system
-X-ray generator
-monitor
-image intensifier
137
Cell mutation can cause
-mild, moderate, severe, and no impairment of cell function
138
Changes that inc pt exposure
-inc exposure time
-dec target to panel distance
-excessive room lighting
139
Virtual image is
An image that is not created by the intersection of light rays and is used for computational purposes
140
Which recording system can reduce pt dose up to 95%
Video disc recording
141
Unit of measurement is used for air kerma
Gray (Gy)
142
What bone marrow area is typically exposed when wearing a lead apron
Clavicles
Skull
Arms
143
Whole body annual occupational dose equivalent limit
0.05 Sv
144
Annual skin and extremities annual occupational dose equivalent limit
0.5 Sv
145
Annual lens of the eye annual occupational dose equivalent limit
0.15 Sv
146
Closed-circuit systems transmit signals through
Cables
147
Term for the standardized method of evaluating the brightness of an image intensifier
Conversion factor
148
Magnitude of the effect of radiation on a patient is primarily dependent on
Total area exposed
149
Fluoro TV systems are ___ circuit
closed-circuit
150
What absorbed dose (rads) can result in spontaneous abortion of a fetus
50 rads
151
Can operature exposure occur after dead-man switch is released
No
152
What material are the thermoluminescent dosimeters made from?
Lithium Fluoride
153
Kell factor definition
ratio b/w the vertical and number of scan lines in a TV system
154
Which frame per second rates are possible w/ cinefluorography
Most common 30 frames per second, divisions of 60 are possible (7.5, 15, 30, 60, 90, 120)
155
Why is synchronization used in cinefluorography
-so that camera shutters open at the same frequency as x-ray pulses
156
Why is a single anatomic dose reading NOT representative of the total somatic effect from radiological examinations?
-protective shielding
-XR beam may be restricted to one area
-Radiation doses are not uniformly distributed
157
Film badges are used b/c
-They provide a record of exposure
-They measure operator exposure
158
What is the minification gain in an image intensifier w/ a 10 inch input phosphor and 1 inch output phosphor
100
minification gain = ratio of the input phosphor diameter squared to the output phosphor diameter squared
(10x10) / (1x1) = 100/1 = 100
159
What is the typical milliampere usage during spot filming
Over 100
160
What is the maximum tabletop dose when imaging w/ high level (boost) fluoro
20 rads per minute
161
What is considered occupational radiation exposure
dose received by individual in course of employment
**if you get exposure for your OWN medical diagnosis, it doesn't count
162
Total number of cycles per second available for display by the TV camera
Bandwith (bandpass)
163
What effect does doubling the exposure time have on the total exposure to the patient
Doubles the exposure
164
How many horizontal lines do TV monitors typically have
525
165
Why is it important to minimize radiation in peds
-The longer life span of a child allows more time for manifestation of long term effects of radiation
-Children are more sensitive to the effects of radiation
**while dose received is less, consequences of radiation are greater
166
When can the exposure rate at the tabletop exceed 10 rads/min
When using automatic brightness control on large patients (requires larger dose of radiation due to inc attenuation of the primary XR through soft tissue)
167
Why are personnel radiation monitors used
To check that individuals receive less than the maximum allowed radiation dose
168
What is the skin and extremities annual occupational dose equivalent limit
0.5 Sv
169
Somatic changes caused by radiation
Decreased fertility
Cancer
Injuries to a fetus
170
Which source accounts for the majority of the population's exposure from man-made radiation?
Medical use
171
Most fluoro TV cameras use this kind of tube
Vidicon
172
Maximum dose rate during c-arm fluoro
10 rads (10 centigray/minute)
173
Examples of high bone marrow dose exams
Barium enema
Upper GI series
Abd angiographyI
174
Immediate notification to the Radiologic Health Branch is required if:
A total effective dose equivalent of 0.25 Sv or more
2.5 Sv shallow dose equivalent
0.75 Sv eye dose equivalent
175
Ratio of the input phosphor diameter squared to the output phosphor diameter squared is
Minification gain
176
Operator protection is best achieved by
-Wearing a lead apron
-Standing as far from the patient as possible
177
Occurs when the diameter of the image from the optical system is larger than the shortest dimension of the film, resulting in part of the image being lost
Overframing
178
Which state of pregnancy is most important for morphological defects in newborn due to radiation exposure
1st trimester
179
A 0.25 mm lead equivalent apron will reduce radiation exposure at 75 kVp approximately how much?
97%
180
The bucky slot cover must be covered w/ at least ___ lead equivalent material
0.25 mm
181
