Questios From Practicee Test Flashcards
(182 cards)
1
Q
What is contrast resolution effected by
A
Number of gray levels a pixel has (bit depth)
-higher the bit depth -> higher contrast resolution
-contrast resolution adjusted using window level and window width
2
Q
What is used to adjust contrast resolution?
A
Window level
Window width
3
Q
What is the target material of an X-ray tube usually made of?
A
Tungsten (anode) b/c high melting point and high anatomic number -> more efficient at producing x rays
4
Q
What are the parts of an X-ray tube?
A
Cathode: source of electrons
Anode: target that produces X rays -> made of Tungsten
5
Q
What is the function of automatic brightness control
A
Keep the light output of the image intensifier constant
(Over different pt tissue density and thickness)
6
Q
A
7
Q
When X-rays are directed toward the patient most are
A
Absorbed by the patient
8
Q
What happens to the X-rays which pass through the patient
A
Remnant rays
Strike the image intensifier and contribute to image formation
9
Q
Moderate contrast reactions include:
A
-protracted N/V
-diffuse urticaria
-diffuse erythema
-facial edema w/o difficulty breathing
-hoarseness w/o difficulty breathing
-wheezing w/o hypoxia
10
Q
Mild contrast reactions
A
Mild N/V
-limited urticaria
-limited “itchy” throat
-nasal congestion
-sneezy/runny nose
11
Q
Severe contrast reactions
A
-facial edema w/ difficulty breathing
-diffuse erythema w/ hypotension
-laryngeal edema
-wheezing w/ hypoxia
-anaphylactic shock
12
Q
Minimum lead equivalent required to cover the Bucky tray
A
0.25 mm
13
Q
Exposure for patient w/ 5 min of fluoro?
A
10-30 rads
14
Q
How much radiation exposure per minute in fluoro?
A
1-5 rads/min
15
Q
What is an erg?
A
A unit of energy used to denote work
16
Q
How many ergs is 1 rad?
A
Dose necessary to cause 100 ergs to be absorbed by 1 g of tissue
17
Q
Minimization gain x flux gain =
A
Total brightness gain
18
Q
Mutations from radiation exposure tend to be
A
Deleterious
19
Q
What is the gonadal dose to a female patient during a barium enema exam
A
790 millirads
20
Q
The image characteristics greatest at the center of the image intensifier?
A
-Resolution
-Detail
-Briigthness
21
Q
What is resolution
A
Ability to distinguish small objects when placed close together
22
Q
A diagnostic fluoroscopy exam usually uses around what dose rate?
A
1 to 5 rads/min
23
Q
What diagnostic fluoro exam should not exceed what?
A
5 rads/min
24
Q
What is the radiation dose to the active bone marrow from an upper GI series?
A
120 millirads
25
Somatic dose measurements are taken at what anatomic sites?
-bone marrow
-thyroid
-skin
26
When reproductive cells are irradiated there may be changes in
-genes
-membrane permeability
-chromosomes
27
A grain or blotchy appearance of a fluoroscopic image is a result of
-Statistical fluctuations
-Quantum mottle
-Low number of absorbed photons
28
Examples of digital image processing
Edge enhancement
Road mapping
-Temporal frame averaging
29
What is a Radiology information system
Software used to manage pt data in an imaging department
30
How many rads of acute X-radiation in the diagnostic energy range to the eyes will result in cataracts?
Several hundred rads
31
What is the most commonly used video disc frame rate
30 frames/sec
32
Sperm precursors are
Spermatogonia
33
What are radiation-induced cancers
-female breast
Lung
-bone
-GI tract
34
At what height above the tabletop should an unexposed border on the fluoroscopic screen be visible when the collimators are fully open
14 inches
35
At what height above the tabletop should an unexposed border on the fluoroscopic screen be visible when the collimators are fully open
14 inches
36
The theory that any x-ray exposure risks the possibility of producing adverse effects:
Non-threshold linear dose effect
37
Control methods by the brightness sensor in an automatic brightness stabilization circuit
-Variable mA, preset kVp
-Variable mA w/ kVp following
-Variable kVp with selected mA
-Variable kVp, variable mA
38
Doubling the exposure area does what to the patient dose
Doubles it
39
What is the annual radiation dose limit for members of the public
1 mSv or 0.02 mSv in any hour
40
What is the radiation dose to the active bone marrow from an upper Gi series?
120 millirads
41
What is the maximum dose rate during c-arm fluoroscopy
10 rads (10 centigray/minute)
42
Doubling the exposure area does what to the patient dose?
Doubles it
43
What is the most commonly used video disc frame rat?
30 frames / second
44
What device controls the reproduction of an image on the television monitor by using the output phosphor from the vidicon?
Camera control unit
output phosphor of an imagine intensifier is coupled to a television camera -> converts the electron signal to video signal -> signal transmitted through cable to camera control unit--> amplified and forward to TV monitor
45
In digital imaging, if the field of view is held constant, what will improve spatial resolution?
-Increasing the number of pixels
-Decreasing pixel size
-Increasing matrix size
46
The long-term biologic effects of chronic low=dose exposure to radiation
have accumulated since WWII
47
Moving the fluoroscopic tube too quickly during an exam will result in image blurring due to
Lag in the image intensifier
(takes time for imagine to build up and decay on the target)
48
Example of overhanging shield
Supported by ceiling ex: lead glass or aprons
49
How is pixel size determined?
FOV / Matrix
-matrix size inc or FOV decreases -> pixel size decreases -> inc in spatial resolution
50
IN digital imaging, if the field of view is held constant and the matrix size inc, what happens to pixel size and spatial resolution?
Pixel size decreases
Spatial resolution increases
51
What is vignetting
Decreased brightness seen at the periphery of the output screen
**result of an unequal distribution of x rays at the center of the screen
52
Frequency range of a video signal is called
Bandpass
53
Skin dose is a good indicator of:
dose to nearby organs
-Skin does not attenuate the X ray significantly, so can indicate underlying organ doses
54
What is the f- number?
ratio of the focal length to the diameter of a lens
55
How to get a lower f-number
-decreasing the focal length
-increasing the lens diameter
56
A lower f number means more ___ is available to form an image
Light
57
female germ cells
Oocytes
58
What is the maximum exposure rate allowed for fluoro equipment made after August 1st 1974 w/o automatic exposure controls?
5 rads/min
59
What dose of radiation might result in cessation of sperm formation
greater than 30 rads can produce temporary sterility
60
Doubling the exposure time increases the patient and operator dose by a factor of
TWO
**directly proportional
61
What should be checked to confirm pt's identity prior to radiographic exam?
2 identifiers; name, DOB
62
What kind of barrier must be in the walls and floors exposed to the primary beam
Primary barrier
**primary protective barrier must be used in any area exposed to the primary x-ray beam
63
What the potential difference (kVp) is required in an image intensifier to speed up electrons by the accelerating anode
25 kVp
64
What is required on mobile fluoroscopic equipment?
1. A way to prevent operation when the collimating cone or diaphragm is not in place
2. Device to prevent operation when the X-ray beam is not entirely intercepted by the image receptor
3. Inherent system preventing operation at a source to skin distance (SSD) less than 30 cm
65
What direction from the primary beam is most scattered radiation during fluroscopy? in degrees
120 and 135 degrees
66
Distortion around the edge of an image due to geometric problems in the shape of an image intensification tube is called
Pincushion distortion
**due to projeting the image formed on a curved input phosphor onto a flat output phosphor -> slightly higher magnification of input image towards edge of the screen
67
Potential Radiation impacts on a cell
1. pass through cell w/o damaging
2. kill a cell
3. damage a cell
68
Fraction of radiation available for image production in a detector element is known as
Fill factor
69
What is the typical fill factor (efficiency) of a detector element?
60-80%
70
Probability of an effect occurring, rather than its severity
Stochastic effect
71
Gonadal dose to a female pt during a barium enema exam
790 millirads
72
How is resolving power measured
Line pairs per millimeter
73
What is resolving power
ability to distinguish separate image of line pairs
74
What is the genetically significant dose
Developed to estimate the magnitude of genetic effects caused by radiation exposure to the population
**does NOT predict or forecast what adverse effects and individual or their offspring may have
75
What thickness are thyroid shields typically available in
0.25mm and 0.5mm lead equivalent
76
In digital imaging, if the field of view is held constant, what will improve spatial resolution?
-Increasing the number of pixels
-Decreasing pixel size
-Inc matrix size
77
Effect refers to the production of scattered radiation
Compton effect
78
Strong correlation b/w mean radiation dose received by bone marrow and
Leukemia
79
The fraction of radiation for image production in a detector element (DEL) is known as
Fill factor
80
What device controls the reproduction of an image on the television monitor by using the output phosphor from the vidicon
Camera control unit
81
What is the half-value layer?
The thickness of absorbing material necessary to reduce the X-ray intensity to half its original value
**important in shielding**
82
Mobile C-arm fluoroscopy what is the minimum required source to skin distance?
30 cm
83
The focal spot size of a fluoroscopic X-ray tube is ___ than the focal spot size of a radiographic x-ray tube
often smaller
84
Difference between fluoroscopic x-ray tubes to traditional x-ray tubes
-Fluoroscopic tubes are designed w/ smaller focal spots, operate for a longer time and at much lower mA
85
Deterministic effects
Nonstochastic
-the severity varies w/ radiation dose and for which there may be a threshold
86
Term refers to the probability of an effect occurring rather than its severity
Stochastic effect
87
What is the latent period
The time before detectable effects of radiation occur after a patient has been exposed
88
Skin dose is a good indicator of:
dose to nearby organs
(skin doesn't attenuate the x-ray beam so its a good indicator)
89
90
Purpose of the radiation control for heath and safety act of 1968 was
-minimize operator exposure
-minimize patient exposure
91
Minimum required thickness of protective curtains
0.25mm lead
92
At what height above the tabletop should an unxposed border on the fluoroscopic screen be visible when the collimators are fully open
14 inches
93
Advantages of three-phase generators
-close to constant potential
-high mA for very short exposures
-higher effective kV
94
Constrast agent volume is determined by what
Patient size
Area being imaged
94
The visibililty of mottle in a system is determined by
Resolution
Contrast
Sensitivity
95
Minimum lead equivalent thickness for a gonadal shiel
0.5 m
96
Doubling the exposure time increases the patient and operator dose by a factor of
2
97
What does a collimator do
Used to reduce patient radiation exposure
98
Examples of personal protective devices
Lead glasses
Lead apron
Thyroid shieldm
99
effects of radiation exposure refer to what time period
Minutes
Days
Weeks
100
What is the conversion factor
Ratio of the intensity of the output phosphor to the input exposure rate in millirads/sec
101
What material(s) is suitable for use as a tabletop material in an X-ray for fluoroscopic system
Carbon fiber
Aluminum
Bakelite
102
Cones function in daylight using this kind of vision
Photopic
103
Rods function at night using this type of vision
Scotopic
104
What is the half-value layer
The thickness of absorbing material necessary to reduce the X-ray intensity to half its original value
105
What is a greater concern to the public health standpoint, short or long term effects
Long-term effects due to the possibility of genetic and carcinogenic effects
106
Refers to the total number of cycles per second available for display by the television camera
Bandwith (bandpass)
107
What is frequency bandwith
measure of the horizontal resolving power of a camera pick-up tube and monitor
108
Goals of fluoroscopic exams
-minimize pt exposure
-minimize operator exposure
-obtain necessary diagnostic information
109
What can reduce radiation dose by 95%
Video disc recording
110
The radiation dose received by children during fluoro exams is typically ___ the dose received by adults
LESS than
111
During routine fluro the tabletop dose rate shall not exceed ___ rads/min
10
112
Which method of gonadal shielding is approved for use in the upright position during fluoroscopy?
Shaped, contact shielding
Shaped, contact shield in an athletic supporter
**shaped contact important b/c protection as well as scatters from different angles
113
Some factors that are important for obtaining high quality fluoro images
-centering the area of interest
-no motion during imaging
-appropriate patient positioning
114
Photoelectric effect
collision occurs b/w an x-ray photon and an inner orbital electron
115
Compton scattering
an interaction b/w an x-ray photon and an outer oribtal electron
116
Pair production
an incident x-ray photon is annihilated near the nucleaus of an atom and an electron and positron pair are emitted
117
What people must be monitored regardless of their likely exposure
-people who operate mobile x-ray equipment
-people who enter a high radiation area
118
Mobile C-arm fluoro systems require
-locked system b/w the tube and image intensifier
-dead-man switch
-primary protective barrier
-collimator
119
For fluoro systems w/ x-ray tubes located under the table, where is most scattered radiation directed?
towards the floor
120
Most important action to reduce radiation exposure is the use of appropriate
Collimation
121
A photocathode gives of ___ in proportion to the intensity oof fluorescent light
Electrons
122
Which organization is considered the world authority on the safe use of ionizing radiation
The International Commission on Radiological Protection
123
What is the purpose of the cumulative manual-reset timer?
To protect the patient from prolonged radiation exposure
-reminder to the operator of how much total exposure time has been used to try and limit
124
Film badge readings are recorded using what unit of measurement
Sievert
125
Characteristics of contrast media?
Low toxicity
High atomic number
126
The visual acuity of rods (scotopic vision) is ____ compared to cones (photopic vision)
worse
**cones function in daylight to perceive color, while rods function at night to perceive grays
127
Annual radiation dose limit for members of the public?
1 mSv
128
Radiation limit for one hour?
0.02 mSv
129
Which personnel monitoring device is accurate within 9% of the actual exposure dose?
Thermoluminescent dosimeter
130
How long does it take to change a fluoroscopic system from a verticial to a horizonal imaging position
20 seconds
**operator dependent
131
A "controlled area" is
An area in which radiation safety rules are enforced and the occupational exposure of personnel is under the supervision of the radiation safety officer
132
Film badges are used b/c
-they provide a record of exposure
-they measure operator exposure
133
Somatic effects damage
the individual
**do NOT effect genetic tissue -> does NOT pass to future generations
134
What unit is used to measure the input intensity of an x-ray tube
Milliamperes
135
In Compton scattering what 2 components are interacting
-x-ray photon
-outer orbital electron
**interaction b/w x-ray photon and an outer orbital electron -> produces an x-ray photon of less energy => this lesser energy x-ray photon is the scattered radiationo that is seen by the operator
136
When should the state be notified if an occupational worker receives an exposure of 0.02 Sv for 3 consecutive calendar quarters?
w/i 24 hours
137
Whole body dose refers to exposure to
Head
Trunk
Arms above the elbow
legs above the knee
(think of what lead covers NOTTT hand/forearm/feet)
138
Scatter radiationc ould be as high as 500 millirads/hr at ___ from the patient
1 foot
139
Which state of pregnancy is most important for morphological defects in a newborn due to radiation exposure
First trimester
140
Which personnel monitoring device indicates radiation exposure by giving off a sound?
Audible warning device
(ex: Geiger counter)
141
Radiation dose of the embryo/fetus should not exceed ___ for the entire pregnancy
5 mSv
142
The focal spot size of a fluoroscopic x-ray tube is ___ than the focal spot size of a radiographic x-ray tube
often smaller
143
What is the target material of an x-ray tube usually made of?
Tungsten
144
What absorbed dose (rads) can result in spotaneous abortion of a fetus
50 rads
145
Limiting exposure to no more than 0.05 Sv/yr will do what to stochastic effects of radiation?
Limit them
146
The half-value layer is
The thickness of absorbing material necessary to reduce the x-ray intensijty to 1/2 its original value
147
What unit is used to measure the input intensity of an x-ray tube?
Milliamperes
148
What effects pt radiation exposure
Exposure time
Exposure rate
Room lighting
Target to panel distsance
149
The increase in output image brightness of an image intensifier tube due to the size reduction of the output image is:
Minification gain
150
Somatic effects damage
The individual
DO NOT affect genetic tissue
151
Purpose of the radiation control for health and safety act of 1968 was to
-minimize operator exposure
-minimize patient exposure
152
When an electron charge is converted into a proportional voltage it is sent to
the camera control unit
153
What unit of measurement is used for air kerma
Gray (Gy)
154
What is kerma
Kinetic energy released in matter
-the amount of energy transferred from incident x-rays to charged particles per unit mass
155
What cell type is the most sensitive to radiation
Lymphocytes or white blood cells
156
What cell type is the least sensitive to radiation
Muscle cells
157
What is the main disadvantage of thermoluminescent dosimeters
Exposures can only be read once
158
Components of a closed-circuit television system
Vidicon camera
Camera control unit
Monitor
159
What is the typical milliampere usage during spot filming
Over 100
160
In an imaging system the statistical quality is determined by the number of
X-ray photons
161
What is the occupational exposure limit for the entire gestational period for a pregnant worker
5 mSv
162
Fluroscopic exposure rates should not exceed
5 rads/min, 30 cm from image intensifier using a phantom 9 inches ofo water
163
Cine camera most commonly operated at
30 framers per second
164
Which frames per second rates are possible w/ cinefluorography
Divisions of 60
7, 5, 15, 30, 90, 120
165
How does room lighting affect pt exposure
excessive room lighting dec operators ability to resolve detail on the TV screen and can lead to inc mA/kVp settings -> inc pt exposure
166
How does high freq generators affect pt expsoure
it doesn't
167
How many horizontal lines do TV monitors typically have
525
**independent of TV size
168
Roentgen is a measure of
Exposure
-describes the ionization of atoms by x-rays
169
Biological effects of ionizing radiation that are manifested in offspring are
-genetic effects
-inherited effects
**they ARE passed on
170
Why are film badges used
They are an easy way of determining long-term exposure rates
171
How do film badges work
A film holder w/ variety of filters and packed film -> filters permit dose measurements over a wide range of energies -> radiation exposure to the film is accumulated over time and then radiation exposure dose is determined by comparing to a film w/ a known dose of exposure
172
Who decides if a fluoroscopic operator is required to wear a personnel monitoring device?
It's always required
173
Refers to the random probability of an effect occurring
Stochastic effect
174
According to the California Radiation Control Regulations what is the limit for occupational whole-body dose equivalent radiation exposure for adults?
12.5 mSv per calendar quarter
50 mSv per year
175
Roentgen is a unit of
Exposure
176
Component that converts an electrical signal into a visible image
Monitor
177
What must be included on fluoroscopic images
Pts DOB
Pts name
178
What percentage of the active bone marrow of the body does a lead apron cover
80%
NOT: skull, arms, clavicles
179
Doubling the exposure time increases the pt and operator dose by a factor of
2
180
If the Bucky tray is moved to the end of the exam table, leaving an opening at the gonadal level, this must be automatically covered w/ at least
0.25 mm lead equivalent
181
