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physics 2 > physics 1 review/ ch. 26-27 > Flashcards

physics 1 review/ ch. 26-27 Flashcards

1
Q

all factors affect radiographic quality except:

A
  • OID
  • focal spot size
  • motion
  • angle
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2
Q

all factors affect spatial resolution except:

A
  • mAs/kVp
  • beam restriction
  • anode heel effect
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3
Q

what factors affect contrast:

A
  • kVp
  • OID
  • beam restriction
  • patient factors
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4
Q

what factors affect distortion:

A
  • OID/SID
  • Patient factors
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5
Q

As filtration increases, kvp ___ and mAs ___

A

increases; decreases

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6
Q

what 2 things does beam restriction do

A
  • reduce patient dose
  • improve contrast
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7
Q

described as the variation of intensity towards the anode compared to the cathode and the thickest part of anatomy should be on the cathode end

A

anode heel effect

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8
Q

an increase in spatial resolution is directly proportional to a ____ in OID

A

decrease

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9
Q

where is the actual focal spot

A

on the anode

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10
Q

smaller anode angle gives better resolution by ___ the effective focal spot

A

decreasing

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11
Q

misalignment of the tube, part or receptor can affect…

A

spatial resolution

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12
Q

distortion depends on

A

object thickness, position and shape

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13
Q

insufficient techniques cause ___ on the image

A

mottle

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14
Q

what is in the high voltage circuit

A

step-up transformer and mA meter

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15
Q

ripple of the three-phase 6 pulse

A

13-14%

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16
Q

ripple of three-phase 12 pulse

A

4%

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17
Q

primary function of the transformers

A

adjust voltage

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18
Q

what is the last step of the circuit

A

rectifier

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19
Q

what are the external components of the x ray tube

A
  • protective housing
  • glass enclosure
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20
Q

internal components of the tube

A

cathode and anode

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21
Q

what is anode made up

A

tungsten with renium

22
Q

requirements of x-ray production

A
  • source of electrons
  • way to accelerate electrons
  • way to decelerate electrons
23
Q

by standardizing routine projections the probability of errors is

A

reduced and the cause for errors is narrowed

24
Q

what are the three general areas in which standardization should be sought

A
  • projections
  • exposure factors
  • image processing
25
Q

what is the most conducive approach for digital imaging

A

variable kVp

26
Q

approach in which only one variable is changed from projection to projection

A

fixed kVp

27
Q

3 goals of the fixed kVp are

A
  • assure sufficient penetration
  • keep image contrast consistent
  • simplify and standardize for accuracy
28
Q

approach in which both kVp and mAs are adjusted

A

variable kVp

29
Q

thin patients require a ___ in mAs

A

decrease

30
Q

as kVp increases, patient dose…

A

decreases

31
Q

the minimum kVp is the lowest kVp that still provides some degree of penetration

A

optimum kVp

32
Q

for every 15% change of kVp, adjust the mAs by a factor of

A

2

33
Q

what the minimum amount to change the mAs for a noticeable difference

A

35%

34
Q

approach in which a proper technique can be derived from a technique of another body part

A

proportional anatomy approach

35
Q

advantages of using technique charts

A

reduce exposure errors and patient exposure

36
Q

what is the 4 cm rule

A

double technique for an increase of 4 cm and half for a reduction of 4 cm

37
Q

3 advantages of AEC

A
  • achieve more consistent exposures
  • reduce repeats
  • decrease radiation exposure
38
Q

earlier AEC’s were employed using a ____, while modern AEC’s use ___

A

fluorescent screen; gas ion chamber

39
Q

what kind of patients absorb more radiation

A

larger pts

40
Q

what does a thyraton include

A
  • cathode filament
  • anode plate
  • one or more grids
41
Q

when does a “short” occur

A

when a sufficient number of ions and electrons are present

42
Q

AEC only controls what 2 things

A

exposure time and total mAs

43
Q

if the kVp is insufficient, what kind of exposure time is needed

A

longer

44
Q

the minimum amount of time it takes for the electric circuit to detect and react to radiation

A

minimum response time

45
Q

what are 2 reasons for using the back up mAs

A
  • to prevent excessive heat overload of the anode
  • to prevent excessive radiation exposure to the patient
46
Q

the back up time should never be set to more than

A

2 times the expected exposure time

47
Q

the maximum length of time x-ray exposures continue when using AEC

A

preset automatic back up mAs

48
Q

increases or decreases the preset sensitivity of the thyratron by specific percentages

A

intensity control

49
Q

what is one of the most common causes for resetting the intensity control

A

inaccurate positioning

50
Q

what is the solution

A

physics 2 (2 decks)

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