Exam 2 Flashcards

1
Q

Exam:
Collimation _____ patient dose by:

A

decreases
limiting the volume of tissue exposed to radiation

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2
Q

Exam:
What does collimation do to radiologic contrast?
How?

A

improves the radiologic contrast
by limiting the volume of tissue that can create scatter

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3
Q

Exam:
What is the aperture diaphragm?

A

fixed opening between the x-ray tube & collimator box

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4
Q

Exam:
What is the collimator?

A

adjustable lead shutters

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4
Q

Exam:
What is PBL?
What does it do?
What can you do to manipulate this?

A

positive beam limitation
automatic collimator based on IR size
override if the desired field size is smaller than the IR

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4
Q

Exam:
Scatter occurs commonly with:

A

large field sizes
increased tissue volume

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5
Q

Exam:
What are the other beam limitations?
What are they?

A

aperture diaphragm: immovable 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)

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5
Q

Exam:
What does scatter do to exposure?

A

scatter increases exposure to the IR

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5
Q

Exam:
Light/radiation field can be off by:

A

+/- 2% of the SID

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6
Q

Exam:
What is scatter also known as?

A

Secondary radiation

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6
Q

Exam:
What happens to scatter at higher kVp levels?
What happens to compton?

A

scatter is increased at higher kVp
Compton interactions proportionally increase at higher kVp levels

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7
Q

Exam:
What does scatter do to noise?
how does scatter affect contrast?
what does scatter do to detail, magnification, or distortion?

A

scatter increases noise
scatter decreases contrast
scatter does not affect detail, magnification, or distortion

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7
Q

Exam:
What is the number one source for of occupational exposure?

A

scatter radiation

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8
Q

Exam:
How can we reduce scatter?
what is the most effective way to reduce scatter?
second most effective?

A

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)

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9
Q

Exam review:
What affects detail?

A

focal spot size
penumbra

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9
Q

Exam:
What do grids do?

A

affect scatter reaching the IR, not the PRODUCTION of scatter

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10
Q

Exam:
What is the purpose for grids?
What does it not affect?

A

restore subject contrast in an image
grids don’t affect the production of scatter radiation

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11
Q

Exam:
How are grids constructed?

A

alternating strips of lead & interspace material (AL most common but can also be plastic)

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12
Q

Exam:
How do we calculate grid frequency?

A

number of lead strips per inch (100/inch)

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13
Q

Exam review:
What are focused grids?
Linear?
crosshatched?

A

grids that follow the divergent beam
run up and down (only can angle one way)
run up/down & side to side

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13
Q

Exam:
Grids can be _____ _____ or ______ (different types of grids)

A

linear
crosshatched
focused

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14
Q

Exam:
Grids are designed to be used:

A

at a specific distance from the focal spot

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14
Q

Exam:
Grids allow the ______ ______ to pass through ______ _______ and absorb ____ ______

A

primary beam
lead strips
scattered x-rays

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15
Q

Exam:
Focused gridlines are directed to:

A

a convergence point (generally the focal spot)

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15
Q

Exam:
Motion will?

A

blur the gridlines

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16
Q

Exam:
modern grids attenuate:

A

70-80% of scattered photons

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17
Q

Exam:
Grids should be used:

A

part thickness greater than 10cm
kVp greater than 70
large field sizes

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18
Q

Exam:
The effectiveness of the grids is measured by:
also know as?

A

the ratio of the height of the lead strips to the width of the interspace material
grid ratio

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18
Q

Exam:
What type of grid errors are there?
what is the worst case scenario?

A

off-center
off-level
off- focus
upside down (worst outcome)

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19
Q

Exam:
What are the grid ratios?
no grid:
5:1
6:1
8:1
10:1
12:1
16:1

A

1
2
3
4
5
5
6

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20
Q

Exam:
Grid math:
Old
500 mA
1 sec
12:1 Grid
New
50 mA
___ sec
6:1 grid math

A

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

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20
Q

Exam: grid math
Old
100 mA
5 secs
1no Grid

New
____ mA
.25 sec
6:1 Grid

A

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

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21
Q

Exam: Grid math

A
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21
Q

Exam: Grid math:

A
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22
Q

Exam:
How do generators affect x-ray technique?

A

generators affect penetration by altering the average energy of created x-rays

22
Q

Exam:
What generator have an effective kVp equal to the set kVP?

A

portables
Portables are the only generators that have an effective kVp equal to the set kVp

23
Q

Exam:
What does kVp affect?

A

the x-ray’s beam’s ability to penerate tissues

24
Q

Exam:
Increasing the kVp by 15%:

A

doubles the number of x-ray photons that reach the image receptor

24
Q

Exam:
increasing kVp by 15% _____ image receptor exposure but only increases patient dose by _______

A

doubles
1/3 (kVp math will be on the test)

24
Q

Exam:
The primary purpose of beam filtration is?

A

to reduce patient exposure

24
Q

Exam:
two types of filtration:

A

inherent (built-in (x-ray tube glass, cooling oil, beryllium window)
added (usually aluminum but can be copper)

25
Q

Exam:
What is total filtration?

A

added + inherent filtration

26
Q

Exam:
what is the required filtration?

A

2.5 mm Al/Eq (legally)

26
Q

Exam:
what does filtration do to the average kVp?
why?

A

increases the average kVp
bc of the removal of weak x-rays by filtration

26
Q

Exam:
How is penetration measured?

A

half-value layers (HVL)
(QC stuff)

27
Q

Exam:
Compensating filtration is not considered to be apart of:

A

inherent or added filtration

28
Q

Exam:
What is compensating filtrations purpose?

A

to even out body parts that are inherently uneven

29
Q

Exam:
What exams are compensating filters used on?

A

x-table shoulder
x-table hip
swimmers c-spine

30
Q

Exam:
What is sthenic?

A

a healthy average person

31
Q

Exam:
What is hyposthenic?
what do we do to technique?

A

thin but healthy
reduce mAs

32
Q

Exam:
What is asthenic?
What do we do to technique?

A

thin and ill/old
reduce kVp

33
Q

Exam:
what is hypersthenic?
what do we do to technique?

A

large body type, increased fatty tissue
increase kVp

33
Q

Exam:
For postmortem how should our technique be adjusted:
in first 30 minutes
after 30 minutes

A

increased technique 35% in the first 30 minutes
increase technique 50% after the first 30 minutes increase technique

34
Q

Exam:
What is the caliper?

A

device used to accurate measure a part thickness

34
Q

Exam:
The caliper should:

A

measure along the central ray

34
Q

Exam:
what is the average abdomen thickness?
AP:
LAT:

A

AP: 22 cm
Lat: 30 cm

35
Q

Exam:
How much change in a technique is required to demonstrate a noticeable difference in an x-ray?

A

35% change in technique is required to demonstrate a change to a radiographic

35
Q

Exam:
What should we expect in postmortem in regards to technique?

A

expect less air in the chest and increased fluids

35
Q

Exam:
How are contrast agents appearing on an x-ray?

A

contrast agents are easier to see on a radiograph due to their high atomic number (Z#)

35
Q

Exam:
What is needed for contrast agents regarding technique?

A

the introduction of contrast agent requires an increase in technique to partially penetrate the contrast agent

35
Q

Exam:
What is the technique for iodine studies?
what about single contrast studies?
what about double contrast studies?

A

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

35
Q

Exam:
Contrast agents only affect:

A

image contrast

36
Q

Exam:
Casts technique should:

A

be increased for plaster casts

36
Q

Exam:
Technique for:
Dry casts:
Wet casts:
fiberglass casts:

A

double the kVp (+15%)
triple the kVp (+15% kvp then +15% again)
no change to the technique

37
Q

Exam:
Additive diseases require:

A

an increase in technique due to increase fluid/bony growth

37
Q

Exam:
for additive diseases with soft tissue we need to increase:

A

mAs to maintain subject contrast for soft tissue disease

38
Q

Exam:
for additive disease that have bony growth we increase:

A

kVp for bony growth in order to penetrate additional bony tissue

38
Q

Exam:
soft tissue Additive diseases:
What do we increase?

A

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

39
Q

Exam:
bony growth additive disease:

A

acromegaly: 8-10 kVp
osteoarthritis (DJD) 8% kVp
osteochrondroma: 8% kVp
osteopetrosis: 8-12% kVp
pagets disease: 8% kVp

40
Q

Exam:
Destructive diseases require a decrease:
what should be reduced?

A

in technique due to increased air, fat, or bony destruction
kVp should be reduced as penetration is easier

41
Q

Exam:
Destructive disease pathologies:

A

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

41
Q

Exam:
What creates a small effective focal spot?

A

the combination of a thin electron beam (cathode) from the cathode and small anode bevel (angle) creates a small effective focal spot

42
Q

Exam:
What and where is the effective focal spot?

A

the effective focal spot is the projected focal spot located directly below the actual focal spot

42
Q

Exam:
What is the typical anode angle?

A

typical anode angles for diagnostic imaging range from 15-17 degrees

43
Q

Exam:
What are the typical cathode sizes?

A

small focal spot: 1 cm
large focal spot: 1.5cm-2cm

43
Q

Exam:
What are the typical effective focal spot sizes?

A

small effective focal spot: 0.5-1mm
large effective focal spot: 1-2mm

43
Q

Exam:
Focal spot effects:

A

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)

43
Q

Exam:
What is the anode heel effect?

A

the variation in x-ray intensity along the long axis of the x-ray beam from anode to cathode

43
Q

Exam:
Which side of the x-ray beam is the weakest?

A

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)

44
Q

Exam:
The anode-heel effect is more significant when using:

A

larger field sizes
shorter SID’s

45
Q

Exam:

A
46
Q

Exam:

A
46
Q

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46
Q

Exam:

A
46
Q

Exam:

A