Final Exam S2 Flashcards
(232 cards)
1
Q
Photoelectric effect strikes:
A
inner shell electron
2
Q
In photoelectric effect the x-ray photon ceases:
A
to exist
3
Q
In Photoelectric absorption the electron absorbs all:
A
the x-ray’s photon’s energy
4
Q
In photoelectric effect increased kVp leads to:
A
decreased photoelectric absorption
(Beam is too fast/intense)
4
Q
In Compton scatter the x-ray photon ceases:
A
to exist
5
Q
photoelectric effect is _____ likely to occur when the _____ of the incident x-ray is slightly ______ than the binding energy of the orbital electron
A
more
energy
higher
5
Q
In photoelectric effect the energy in excess of binding energy is given to:
A
the inner-shell electron
5
Q
In photoelectric effect the inner shell electron ____ ups &:
A
speeds (excites)
leaves the atom
6
Q
In photoelectric effect increased atomic number leads to increased
A
photoelectric absorption (attentuation)
(because more things to interact with)
7
Q
In Compton scatter the electron absorbs:
A
all the incident x-rays energy
8
Q
In Compton scatter _________ interacts (strikes) with an:
A
incident x-rays
outer shell electron
8
Q
In Coherent when an incident x-ray interacts with an orbital electron it is:
A
Thompson
8
Q
In Compton scatter some of the energy excess of binding energy is given to an:
A
outer shell electron
8
Q
In Compton scatter outer shell electron speeds up and leaves:
what is this called?
A
the atom (recoil electron)
(Excess energy leaves as a scatter photon)
9
Q
Attenuation can be affected by?
A
-Tissues thickness (every 4 cm = 50% xray beam attenuation)
-tissue atomic number (more z#= more attenuation)
-tissue density (most important ex: air vs muscle vs fat) muscle most dense/ air least dense
10
Q
In Compton scatter remaining energy is ______ as a new x-ray and leaves the _____ in a random direction
A
reemitted
atom
11
Q
Both the photoelectric effect and compton scatter lead to
A
ionization
(the removal of an electron from orbit and net positive charge to the atom)
11
Q
In coherent scatter the orbital electron reaches a temporary:
A
state of excitation
12
Q
Attenuation is?
What different interactions result in attenuation?
A
Reduction in the number/intensity of x-rays reaching the IR (through scatter/absorption)
Photoelectric (absorption)
Coherent scatter (absorption)
Compton (both scatter & absorption)
12
Q
mA is limited by what?
A
Focal spot size
12
Q
Compton scatter is proportionally more likely:
A
at high kVp levels
(this is bc higher kVp levels have lower absorption rate but compton remains consistent at all levels)
12
Q
In coherent scatter when an incident x-ray interacts with an entire atom is it called:
A
Rayleigh
13
Q
In coherent scatter when the energy of the incident photon is ______ than the ________ no ________ occurs
A
less
binding energy
ionization
13
Q
For each 4cm of tissue requires:
For every 4 cm of tissue how much x-ray beam attenuation is occuring?
A
doubling of mAs & kVp by:
15% kVp
100% mAs
- 50% x-ray beam attenuation
14
mAs is a measurement of what?
it is considered:
what is it not?
electron flow in a conductor
an electrical term
a unit of radiation output
14
mAs is the primary controller of:
intensity/quanity in the remnant beam
14
In coherent scatter the incident x-ray continues:
in a new direction
15
mAs math:
100 mA and .5 sec
50 mAs
15
In coherent scatter no _____ occurs
energy transfer
16
How do we reduce motion?
setting the shortest time while maintaining same mAs output
(Shorter time requires more mA)
16
To calculate the mAs we:
multiply mA x Time
17
Attenuation is absorption & scattering as a result of:
photoelectric effect
compton scatter
coherent scatter
18
mAs math:
300 mA and .2 sec
60 mAs
(300 x .2)
18
Radiologic time is measured in?
seconds
.25 secs or 250 ms or 1/4 second (all the same)
18
mAs math:
200 mA and .2 sec
40 mAs
18
Maintaining density:
150 mAs to 300 mAs
72 kVp to ___ ?
61.2 (reduced 15%, cuts exposure in half)'
mAs doubled
kVp needs to come down 15% to maintain
19
the small increase of 15% kvp will?
double the exposure to the image receptor
20
What is penumbra?
Is it good or bad?
blurry or unsharp edges of the shadow or image
bad
20
Doubling in mAs leads to:
doubling of intensity or quantity
20
Kilovoltage is the measurement of
electrical force
21
What does kVp control?
the quality of the x-ray beam
22
when the kvp increases 15% patient exposure increases by:
1/3
23
kVp math:
increase kVp 15% of 70 kvp:
decrease kVp 15% of 100 kVp:
80.5 (70 x 1.15)
85 (100 x .85)
24
kVp means?
kilo voltage peak (the highest value in electrical generator)
25
What does a higher kVp do?
increase the x-ray's ability to penetrate through a particular tissue
26
OID stands for?
object image distance (patient distance from IR)
26
What is remnant radiation?
the part of the x-ray beam that has passed through the patient
(Leftovers from the primary beam)
26
SID stands for?
source to image distance (x-ray tube to IR)
27
What is preferred, optimal kVp or minimal kvp?
what is higher in kVp out of the 2?
optimal kVp
27
SOD stands for?
Source to object distance (x-ray tube to patient)
28
What is umbra?
is the ''pure" shadow or image of uniform darkness
(crisp shadow line)
29
What is distortion?
misrepresentation of the size or shape of an object
29
As a radiographer do we want pneumbra?
no, we want to minimize this
29
What is elongation?
the object appears to be longer than its actual size
29
How much of the primary beam becomes remnant radiation?
less than 1%
30
What is shape distortion?
the difference between the actual shape of the object and the shape of its projected image
(Difference between actual object shapes
& the image shape)
30
What affects contrast?
kVp (low kvp = high contrast)
image receptor (grids)
computer algorithms (AEC)
patient factors (tissue density)
31
What is the relationship with SID and pneumbra & spatial resolution?
the greater the SID the smaller the pneumbra & higher the spatial resolution
31
what is foreshortening?
the object appears to be shorter than its actual size
32
How do we calculate the mag factor?
dividing SID/SOD
32
Mag Factor math:
An object that measures 6 cm is radiographed using SID of 48 and OID of 4. How many centimeters will the object measure on the completed radiograph?
6.54cm
(48 (SID) - 4 (OID) = 44 SOD
48 (SID) / 44 (SOD)= 1.09
1.09 x 6 cm= 6.54cm
33
How can size distortion (magnification) be reduced?
decreasing OID or
increasing SID
34
What can contrast be referred to as?
which is?
gray scale
the number of different brightness levels in a x-ray
34
What is size distortion?
What is it also called?
misrepresentation of the size of the object
aka magnification
34
How can we reduce shape distortion?
properly aligning the:
tube
(Object) part
Image receptor
35
Mag Factor math:
SID= 72
SOD=66
1.09 mag factor
36
What is spatial resolution?
What is also referred to as?
the sharpness of the structural edges around the image
AKA detail, sharpness, or decreased pneumbra (OR LOW BLUR)
37
what affects spatial resolution? (5)
motion
focal spot size
distance (SID, SOD, OID)
patient factors (OID or motion)
angulation (elongation/foreshortening)
37
What is postprocessing?
adjustment of the image by a rad tech or rad at a workstation
37
What is noise?
undesirable image input that interferes with ability to visualize the x-ray
37
How is resolution (spatial resolution) measured?
using a line-pair test tool
(measured in line-pairs per millimeter or LP/mm)
37
What is contrast?
the difference between 2 adjacent brightness levels
38
What can be used to increase subject (patient) contrast?
barium & iodine
38
Low contrast =
high contrast =
long scale (many greys)
short scale (black & white)
39
What is SNR?
What should it always be greater than?
Signal to noise ratio
one
40
More kvp = ____ scatter
more volume = _____ scatter more volume
more
more
(why collimation is key, and optimal kVp)
40
What is quantum mottle?
What is the opposite?
insufficient number of x-rays reaching the image receptor
scatter is too much x-rays reaching the image receptor
41
What causes quantum mottle?
What is usually the cause?
low mAs
low kVp
or difficult anatomy to penetrate
usually low technique, especially mAs
42
What is the rule regarding tissues thickness?
for every 4cm of tissue thickness 50% of x-ray beam is attenuated
42
Low contrast =
High contrast=
Long scale & low kvp
Short scale & high kVp
42
Low contrast =
High contrast=
Long scale & low kvp
Short scale & high kVp
43
What is window level?
What is window width?
post-processing of image brightness
post-processing if image contrast
43
For digital systems, what is preferred quantum mottle or scatter?
Scatter
(the digital systems are very good at filtering out too much information)
44
What does high tissue atomic number mean for attenuation?
means more attenuation due to more interactions
(more electrons higher chance for photelectric absorption)
44
Exam:
What does collimation do to radiologic contrast?
How?
improves the radiologic contrast
by limiting the volume of tissue that can create scatter
45
What does higher tissue density mean for attenuation?
more attenuation
(implants most, then bone, then muscle, then fat, and least dense is air)
more dense objects show up more dominantly on the x-ray
45
Exam:
What is the collimator?
adjustable lead shutters
46
Who sets the standards for optimal contrast/brightness settings?
the radiologists
47
Exam:
Collimation _____ patient dose by:
decreases
limiting the volume of tissue exposed to radiation
48
Exam:
What is the aperture diaphragm?
fixed opening between the x-ray tube & collimator box
49
Exam:
Light/radiation field can be off by:
+/- 2% of the SID
49
Exam:
What is PBL?
What does it do?
What can you do to manipulate this?
positive beam limitation
automatic collimator (based on IR size)
override if the desired field size is smaller than the IR
50
Exam:
What are the other beam limitations?
What are they?
aperture diaphragm: fixed opening between x-ray tube & collimator box)
Mask: lead sheet with an opening used to image specific anatomy of interest (skull x-ray with a hole cut through)
50
Exam:
Scatter occurs commonly with:
large field sizes
increased tissue volume
50
Exam:
What does scatter do to image recptor exposure?
scatter increases exposure to the IR
(also decreases contrast & increase noise ALL BAD)
51
Exam:
What happens to scatter at higher kVp levels?
What happens to compton?
scatter is increased at higher kVp
Compton interactions proportionally increase at higher kVp levels
52
Exam:
What does scatter do to noise?
how does scatter affect contrast?
what does scatter do to detail, magnification, or distortion?
scatter increases noise
scatter decreases contrast
scatter does not affect detail, magnification, or distortion
52
Exam:
What is scatter also known as?
Secondary radiation
52
Exam review:
What affects detail?
focal spot size
penumbra
52
Exam:
What do grids do?
affect scatter reaching the IR, not the PRODUCTION of scatter
53
Exam:
What is the number one source for of occupational exposure?
scatter radiation
53
Exam:
How do we calculate grid frequency?
number of lead strips per inch (100/inch)
53
Exam:
How can we reduce scatter?
what is the most effective way to reduce scatter?
second most effective?
increase collimation (most effective way to control)
decrease part volume (compression) (second most effective way)
reduce kVp
grids (affects scatter reaching the IR, not PRODUCTION)
distance (SID < SOD< OID) (no effect on scatter production)
54
Exam:
How are grids constructed?
alternating strips of lead & interspace material (AL most common but can also be plastic)
54
Exam:
The effectiveness of the grids is measured by:
also know as?
the ratio of the height of the lead strips to the width of the interspace material
grid ratio
54
Exam:
What is the purpose for grids?
What does it not affect?
restore subject contrast in an image
grids don't affect the production of scatter radiation
55
Exam review:
What are focused grids?
Linear?
crosshatched?
grids that follow the divergent beam
run up and down (only can angle one way)
run up/down & side to side
56
Exam:
Focused gridlines are directed to:
a convergence point (generally the focal spot)
56
Exam:
Grids can be _____ _____ or ______ (different types of grids)
linear
crosshatched
focused
56
Exam:
Grids are designed to be used
(need to be)
at a specific distance from the focal spot
56
Exam:
What are the grid ratios?
no grid:
5:1
6:1
8:1
10:1
12:1
16:1
1
2
3
4
5
5
6
57
Exam:
modern grids attenuate:
70-80% of scattered photons
57
Exam:
Grids allow the ______ ______ to pass through ______ _______ and absorb ____ ______
primary beam
lead strips
scattered x-rays
57
Exam:
Motion will?
blur the gridlines
58
Exam:
Grids should be used:
part thickness greater than 10cm
kVp greater than 70
large field sizes
59
Exam:
What type of grid errors are there?
what is the worst case scenario?
off-center
off-level
off- focus
upside down (worst outcome)
60
Exam:
increasing kVp by 15% _____ image receptor exposure but only increases patient dose by _______
doubles
1/3 (kVp math will be on the test)
61
Exam:
What does kVp affect?
the x-ray's beam's ability to penerate tissues
62
Exam:
Grid math:
Old
500 mA
1 sec
12:1 Grid
New
50 mA
___ sec
6:1 grid math
Steps:
500 mA x.1= 50mA
12:1 grid (6) to 6:1 (3) (new/old)
3/5= .6
50 x .6= 30mA
30 mA/ 50 mA= .6
62
Exam: grid math
Old
100 mA
5 secs
1no Grid
New
____ mA
.25 sec
6:1 Grid
Steps:
100 mA x .5= 50 mA
no grid (1/old) to 6:1 (3/new)= 3/1 new/old
50 mA x 3= 150 mA
150 mA/.25 secs= 600 mA
62
Exam:
How do generators affect penetration (x-ray technique)?
(generators affect technique by adjusting the kVp (penetration) of the created x-rays)
generators affect penetration by altering the average energy of created x-rays
62
Exam:
What is total filtration?
what filtration is not apart of this?
added + inherent filtration
compensating filtration
63
Exam:
two types of filtration:
inherent (built-in (x-ray tube glass, cooling oil, beryllium window)
added (usually aluminum but can be copper)
63
Exam:
What exams are compensating filters used on?
x-table shoulder
x-table hip
swimmers c-spine
63
Exam:
The primary purpose of beam filtration is?
(filtration)
to reduce patient exposure
63
Exam:
what is the required filtration?
what kind of filtration is this?
2.5 mm Al/Eq (legally)
total filtration
64
Exam:
What generator have an effective kVp equal to the set kVP?
portables
Portables are the only generators that have an effective kVp equal to the set kVp
65
Exam:
Increasing the kVp by 15%:
how much does patient dose increase?
doubles the number of x-ray photons that reach the image receptor
1/3
66
Exam:
what does filtration do to the average kVp?
why?
increases the average kVp
bc of the removal of weak x-rays by filtration
67
Exam:
What is compensating filtrations purpose?
to even out body parts that are inherently uneven
67
Exam:
How is penetration measured?
half-value layers (HVL)
(QC stuff)
68
Exam:
For postmortem how should our technique be adjusted:
in first 30 minutes
after 30 minutes
increased technique 35% in the first 30 minutes
increase technique 50% after the first 30 minutes increase technique
68
Exam:
Compensating filtration is not considered to be apart of:
inherent or added filtration
68
Exam:
what is hypersthenic?
what do we do to technique?
large body type, increased fatty tissue
increase kVp
68
Exam:
What is sthenic?
a healthy average person
69
Exam:
What is hyposthenic?
what do we do to technique?
thin but healthy
reduce mAs
69
Exam:
The caliper should:
measure along the central ray
69
Exam:
What is asthenic?
What do we do to technique?
thin and ill/old
reduce kVp
70
Exam:
Technique for fiberglass casts:
no change to the technique
70
Exam:
What is the technique for iodine studies?
what about single contrast studies?
what about double contrast studies?
80 kVp minimum for iodine studies (urinary systems)
120 kvp for single contrast GI studies using barium
90-100 kVp for double contrast studies with air and barium
70
Exam:
How are contrast agents appearing on an x-ray?
why?
contrast agents are easier to see on a radiograph due to their high atomic number (Z#)
71
Exam:
What is the caliper?
device to measure a part thickness
(accurately)
72
Exam:
How much change in a technique is required to demonstrate a noticeable difference in an x-ray?
35% change in technique is required to demonstrate a change to a radiographic
72
Exam:
What should we expect in postmortem patient in regards to technique & anatomy?
increase technique
expect less air in the chest and increased fluids
72
Exam:
Casts technique should:
be increased for plaster casts
73
Exam:
what is the average abdomen thickness?
AP:
LAT:
AP: 22 cm
Lat: 30 cm
73
Exam:
Contrast agents only affect:
image contrast
74
Exam:
What is needed for contrast agents regarding technique?
increase technique to partially penetrate the contrast agent
(the introduction of contrast agent requires an increase in technique to partially penetrate the contrast agent)
75
Exam:
Technique for dry casts:
double the kVp (+15%)
76
Exam:
Technique for wet casts:
triple the kVp (+15% kvp then +15% again)
76
Exam:
soft tissue Additive diseases:
What do we increase?
Actinomycosis: 50% mAs
Ascites: 50-75% mAs
Carcinomas, fibrous: 50% mAs
Cirrhosis: 50% mAs
pulmonary edema: 50% mAs
hydrocephalus: 50-75% mAs
hydropneumothorax: 50% mAs
pleural effusion: 35% mAs
pneumonia: 50% mAs
Syphilis: 50% mAs
Tuberculosis, pulmonary: 50% mAs
mAs
76
Exam:
for additive disease that have bony growth we increase:
kVp for bony growth in order to penetrate additional bony tissue
77
Exam:
Destructive disease pathologies:
What is being done to technique?
aseptic necrosis: 8% kVp
blastomycosis: 8% kVp
bowel obstruction: 8% kVp
cancers, osteolytic: 8% kVp
emphysema: 8% kVp
ewing's tumor: 8% kVp
exostosis: 8% kVp
Gout: 8% kVp
hodgkin's disease: 8% kVp
hyperparathyroidism: 8% kVp
osteitis fibrosa cystica: 8% kVp
osteomalacia: 8% kVp
osteomyelitis: 8% kVp
osteoporosis: 8% kVp
pneumothorax: 8% kVp
rheumatoid arthritis: 8% kVp
Deceasing kVp
77
Exam:
What is the typical anode angle?
15-17 degrees for diagnostic imaging
(typical anode angles for diagnostic imaging range from 15-17 degrees)
78
Exam:
Additive diseases require:
an increase in technique due to increase fluid, soft tissue, & bony growth
79
Exam:
for additive diseases with soft tissue we need to increase:
mAs to maintain subject contrast for soft tissue disease
80
Exam:
Destructive diseases require a decrease:
what should be reduced?
Why?
in technique due to increased air, fat, or bony destruction
kVp should be reduced as penetration is easier
81
Exam:
Which side of the x-ray beam is the weakest?
why?
the intensity is weakest on the anode side of the x-ray beam
due to the beam being attenuated bc of the material of the anode
81
Exam:
additive disease, bony growth:
acromegaly: 8-10 kVp
osteoarthritis (DJD) 8% kVp
osteochrondroma: 8% kVp
osteopetrosis: 8-12% kVp
pagets disease: 8% kVp
82
Exam:
What creates a small effective focal spot?
thin electron beam (cathode) + small anode bevel (angle, anode)
(the combination of a thin electron beam (cathode) from the cathode and small anode bevel (angle) creates a small effective focal spot)
83
Exam:
What and where is the effective focal spot?
also can be referred to as?
below the actual focal spot
projected focal spot
(the effective focal spot is the projected focal spot located directly below the actual focal spot)
83
Exam:
What are the typical focal spot sizes (cathode)?
small focal spot: 1 cm
large focal spot: 1.5cm-2cm
84
Exam:
What are the typical effective focal spot sizes?
small effective focal spot: 0.5-1mm
large effective focal spot: 1-2mm
84
Exam:
Focal spot affects:
when would we use a large focal spot?
when would we use a small focal spot?
spaital resoulition & heat capacity
the smaller the focal spot, the better the spatial resolution
large focal spots can be used when detail is not critical to reduce heat in the tube
(small+ better picture, large+ better for heat capacity)
85
Exam:
What is the anode heel effect?
x-ray intensity from the long axis of anode to cathode side
(the variation in x-ray intensity along the long axis of the x-ray beam from anode to cathode)
86
How would an increase in SID affect IR exposure?
Decrease IR exposure
87
Exam:
The anode-heel effect is more significant when using:
larger field sizes
shorter SID's
88
What does an increase in SID primarily affect?
Size distortion - decrease
because of magnification
89
What factors does an increase in SID affect?
Size Distortion: Decrease (Primary controller)
IR Exposure: Decrease
Sharpness: Increase
90
How would an increase in OID affect IR exposure?
Decrease (Air Gap)
90
An increase in SID would do what to sharpness?
Increase
91
What does an increase in OID primarily affect?
Sharpness - decrease
92
Increased alignment does what to shape distortion?
Decrease
93
What affects shape distortion?
Alignment
93
What factors are affected by an increase in motion?
Subject contrast goes down
Noise (blur) goes up
Sharpness goes down
94
How would an increase in OID affect subject contrast?
Increase (Air Gap)
94
What primary factors are affected by an increase in SOD?
Sharpness increase
Size Distortion decreases
94
How would an increase in OID without air gap technique affect noise?
No effect on noise or contrast
95
How would an increase in OID with air gap technique affect noise?
Decrease (Scatter)
96
Increased OID with air gap leads to ______ exposure to the IR
Decreased because there is less scatter hitting the IR
97
Increased OID leads to ______ penumbra and ______ spatial resolution
Increase penumbra
Decreased spatial resolution (detail and sharpness)
97
What affects spatial resolution?
SID
98
Where is the SID measured from?
Focal Spot to image receptor
98
What is the inverse square law used for?
Used to determine intensity of new exposure (mGy or mSv)
99
Why is the measuring tape on the collimator cut?
Accounts for focal spot to collimator
100
What is the square law used for?
Used to maintain IR exposure
(old/new)
100
What is the relationship of SID/SOD/OID?
SID = SOD + OID
101
What is a primary result of increased OID? (1)
What else does it affect? (4)
Decreased sharpness
Also:
Decreased IR exposure (air gap)
Increased subject contrast (air gap)
Decreased noise (scatter)
Increased size distortion (magnification)
101
What is a primary factor of increased SOD?(2)
Increased sharpness & decrease size distortion (lower penumbra)
101
What is a primary result for increased SID? (1)
What is also affected? (2)
Decreased size distortion
Also:
decreased IR exposure (beam divergence)
Increased sharpness (less penumbra)
102
What is the result of increased motion? (3)
Decreased subject contrast
Increased noise (blur)
Decreased sharpness
102
What is a primary result of increased alignment?
Decreased shape distortion
103
Increased SID without adjustment. How does it affect?
IR exposure?
Detail?
Magnification?
IR exposure goes down (beam divergence)
Detail increases (lower penumbra)
Magnification decreases (increase SID decreases magnification)
104
Increased SID and adjusted technique to compensate. How does this affect:
IR exposure?
Detail?
Magnification?
IR exposure stays the same (technique has been adjusted)
Detail increases due to increase SID (technique plays no role in this)
Magnification decreases due to increased SID (technique plays no role)
(Only factor affected here is IR exposure & that has been compensated for)
104
Increased OID without any adjustments. How does this affect:
Contrast?
Noise?
Shape distortion?
What is the primary factor with increased OID?
Increased contrast (air gap technique)
Noise decreased (less scatter)
Shape distortion stays the same (shape distortion= elongation + foreshortening)
Decreased sharpness
105
What affects spatial resolution?
SID affects (more SID less OID)
Time not affected
KVP not affected
105
Why is the measuring tape on the collimator cut?
To account for the distance within the x-ray tube (focal spot to the collimator)
106
What are the relationships between OID/SOD/SID?
OID + SOD = SID
SID - OID = SOD
SID- SOD =OID
106
In regards to formulas of the square & inverse square law what does these signs represent?
E=
D=
n=
O=
E= exposure (mGy or mSv)
D = Distance (SID)
N= new
O= old
107
What is the SID measured from?
From the source (x-ray tube/anode focal spot) to the image receptor (distance)
108
What happens when AEC encounters metal?
Time
motion
patient exposure
IR exposure all increase.
109
Density settings of ____ are needed to see a visible change.
+2 (1=25%)
110
Modulation Transfer Function:
What is it?
what can happen?
A way physicists measure contrast resolution
When line pairs become too small their penumbrae merge and reduce contrast.
110
Backup time should be to ____% of anticipated time.
150%
Ex: Anticipated: 0.4 sec; Backup Time: 0.6 sec.
111
Where is the AEC detector located?
Between the patient and the image receptor and use ionization.
111
How many lonization chambers do most AEC Systems consist of?
3 (the cells on the wall bucky)
112
The only thing AEC controls is:
Time
112
What does the air-gap techniq do?
increases size distortion (magnification)
improves contrast (decreasing scatter)
decreases detail (increased penumbra)
113
What's the primary reason for technique charts?
To maintain consistency
113
Air Gap Technique is based on creating a gap by increasing the ___
OID
114
What is magnification?
Size distortion
115
how do we calculate the magnification factor?
SID/SOD
116
How do you find the objects actual size?
divide projected size/magnification factor
117
How would you find the size of an anatomy on a projected image?
multiply actual size x mag factor
118
Elongation is:
anatomy appearing longer than normal
(angle on tube or IR)
118
What causes shape distortion?
Misalignment of tube, image receptor, or part
119
We should always have a minimum of ____ views
2
119
Foreshortening is:
part appears to be shorter than normal
(part is angled)
120
What is Ceiszynski’s Law?
angle 1/2 of the part's angle to minimize distortion through elongation/foreshortening
121
Increase SID = ____ IR Exposure
why?
decreased
bc of beam divergence
121
Motion is generally caused by:
Patients
122
increased focal spot size will _____ sharpness
Decrease.
(It is the one and only controller?)
123
Off-centering is the same as:
why?
Angling
bc of the beam divergence
124
Increasing the OID will decrease:
A. Shape distortion.
B. Subject contrast.
C. Size distortion.
D. Sharpness.
D. Sharpness.
125
Increasing collimation will result in increased:
A. IR Exposure
B. Subject contrast
C. Noise
D. Spatial Resolution
B. Subject Contrast
125
The smaller the focal spot size, the ______ spatial resolution
Higher
125
Decreasing the focal spot size will result in:
A. Increase contrast.
B. Decrease contrast.
C. Increase sharpness.
D. Decrease sharpness.
C. Increased sharpness.
125
Which one of the following pathologist would be MOST LIKELY to result in increased shape distortion?
A. Emphysema
B. Large bowel obstruction
C. Kyphosis
D. Cirrhosis
C. Kyphosis.
126
Reducing SID but adjusting mAs to compensate will result in decreased:
A. Subject contrast.
B. Sharpness.
C. Noise.
D. Size distortion.
B. Sharpness.
127
Decreasing kVp will result in:
A. Increased sharpness
B. Decreased sharpness
C. Increased IR Exposure
D. Decreased IR Exposure
D. Decreased IR EXPOSURE
127
Reducing mAs but adjusting kVp to compensate will result in decreased:
A. IR exposure
B. Size distortion
C. Subject contrast
D. Sharpness
C. Subject contrast.
127
A transthoracic humorous exam results in a radiograph that displays decreased subject contrast. If the image was repeated, which change would be MOST EFFECTIVE in improving subject contrast?
A. Increase mAs
B. Increase collimation
C. Decrease motion
D. Reduce kVp
B. Increase collimation
