Rad 107 /exposure Factor Selection (Chap.10)

Front 1

-------- standardizes the selection of exposure factors to help produce consistent quality radiographs while minimizing pt exposure

Back 1

Exposure technique charts

Front 2

------------ is the primary pt factor that determines the selection of exposure factors.
a) Age c) physical condition
b) Part measurement d) weight

Back 2

Part Measurement

Front 3

T/F Exposure Technique charts are universal regardless of body build or pathologic condition.

Back 3

false, they are designed for the average pt. When dealing w/ pts with additive or destructive diseases more or less penetration may be required regardless of part thickness

Front 4

A primary goal of exposure technique charts is...
a) extend the life of the tube
b) improve the radiographers accuracy
c) consistently produce quality images
d) increase the pt work flow

Back 4

consistently produce quality images

Front 5

T/F If a single generator is used for more than one tube one exposure technique chart is used for both.

Back 5

false

Front 6

What three conditions must be met in order to ensure that an exposure technique chart will be effective?

Back 6

1. calibration of the tube
2. consistent processing
3.accurate part measurement

Front 7

what are two types of exposure technique charts?

Back 7

-Fixed kVp/variable mAs
-Variable kVp/ fixed mAs

Front 8

In order to reduce pt expose, reduce repeat radiographs and ensure that correct exposure factors are selected a radiographer would consult a----------

Back 8

exposure technique chart

Front 9

With what type of exposure chart is the tubes heat load increased?

Back 9

variable kVp/fixed mAs

Front 10

with what type of exposure technique chart is the contrast more uniform?

Back 10

fixed kVp/ variable mAs

Front 11

using the fixed kVp/variable mAs exposure chart, if a part measuring 21cm is exposed at 80@32, what technique would you use for a part measuring 25cm?

Back 11

80@64

Front 12

Using the variable kVp/fixed mAs, a part measuring 10cm was radioraphed w/ 70@4. What would the technique be for a part measuring 11cm?

Back 12

72@4

Front 13

For which exposure chart is the patient dose higher?

Back 13

Variable kVp/ fixed mAs

Front 14

For which exposure technique chart is part measurement the most critical?

Back 14

Variable kVp/ fixed mAs

Front 15

Which chart generally lacks adequate penetration, and is only really useful with small anatomical parts such as a hand?

Back 15

Variable kVp/ fixed mAs

Front 16

kVp that is high enough to ensure adequate penetration, but not so high that it jeopardizes contrast is said to be-----------

Back 16

Optimal kVp

Front 17

when someone mathematically estimates something , the answer is said to have been--------

Back 17

extrapolated

Front 18

If you are faced with an anatomical part that you do not have a technique for, but notice that it is the same thickness as another part that you do have a good technique for you can use this technique as long as the minimum kVp needed to penetrate the part is used. In coming to this conclusion you have used---------

Back 18

comparative anatomy

Front 19

In order to construct an exposure technique chart you will need what?

Back 19

a phantom
calipers
a calculator

Front 20

What type of exposure chart uses a fixed mAs regardless of part thickness?

Back 20

a variable kVp/ fixed mAs

Front 21

in creating either type of exposure technique chart, what is most important?

Back 21

achieving adequate penetration of the anatomical part.

Front 22

for every 4 to 5cm change in part thickness mAs is adjusted by a factor of 2. This describes which exposure technique chart?

Back 22

Fixed kVp variable mAs

Front 23

Has anyone seen the roaming gnome?

Back 23

I have, it was last spotted wearing a red hat....

Front 24

for every 1cm change in part thickness, kVp is adjusted by plus or minus 2, describes which exposure technique chart?

Back 24

Variable kVp/ fixed

Front 25

The radiographers primary task is to......

Back 25

produce the highest quality radiographs while delivering the least amount of radiation exposure.

Front 26

ALARA stands for...

Back 26

as low as reasonable achievable

Front 27

which concept states that different parts of the same size can be radiographed by use of the same exposure factors given that the minimum kVp needed to penetrate the part is used?

Back 27

Comparative anatomy

Front 28

Optimal Technique for a radiograph is given at 6 cm; 70 kVp and 4 mAs - using the fixed kVp rule what would the mAs be at 18 cm?

Back 28

32 mAs ~ because for every 4-5 cm; change the mAs by a factor of 2

Front 29

Optimal technique for aradiograph is given at 10 cm; 70 kVp and 8 mAs. using the fixed kVp rule what would the mAs be at 2 cm?

Back 29

2 mAs ~ becaue for every 4-5 cm; change the mAs by a factor of 2

Front 30

Optimal technique for a radiograph is given at 10 cm; 70 kVp; 8 mAs... using the variable kV rule - what would the kVp be for 8 cm?

Back 30

66 kVp ~ because for every 1 cm; kVp is changed by +/- 2

Front 31

Optimal techiqe for a radiograph is given at 11 cm; 72 kVp; 8 mAs... using the variable kV rule; what would the kV be at 13 cm?

Back 31

76 kVp ~ because for every 1 cm; kVp is changed by +/- 2

Front 32

what is the purpose of exposure technique charts?

Back 32

it provides consistancy and a baseline

Front 33

What are the benefits of the fixed kVp technique charts:

Back 33

fixed kVP: 1. the charts are more forgiving when it comes to part thickness 2. easier to use 3. more consistant

Front 34

What needs to be considered when using a variable kVp chart?

Back 34

must be concise on part thickness

Front 35

When would a variable kVp technique chart be used?

Back 35

with pediatrics & small extremeties

Front 36

what would be used for a baseline for techniques on xrays?

Back 36

exposure technique chart

Front 37

what are technique charts based on?

Back 37

part thickness

Front 38

why would you use an exposure technique chart?

Back 38

1. to help tech choose correct technique factors 2. reduces repeat exposures 3. reduces patient exposure

Front 39

Design characteristics

Back 39

konw items on chart (fig. 10.1 page 260)

Front 40

what are the 2 types of exposure technique charts?

Back 40

1. fixed kVp; variable mAs
2. Variable kVp; fixed mAs

Front 41

T or F:
variable kVp/ fixed mAs charts are based on adjusting kVp depending on thickness of the part

Back 41

True

Front 42

T or F:
the problem with variable kVp and fixed mAs is that it causes a change in density.

Back 42

False; it causes a change in contrast.

Front 43

T or F:
variable kVp; fixed mAs is less accurate than fixed kVp.

Back 43

true ~ and it may lack accuarate penetration of the part.

Front 44

what is the most used exposure technique chart?

Back 44

fixed kVp

Front 45

on a fixed kVp; variable mAs exposure technique chart; what does the change in mAs depend on?

Back 45

body part thickness

Front 46

Essentially, what does optimal kVp mean?

Back 46

optimal kVp has adequate penetration and appropriate contrast for the part.

Front 47

COMPARATIVE ANATOMY WILL BE ON TEST!

Back 47

I don't have pages right now, but around 263 I believe

Front 48

List the 2 types of exposrue technique charts.

Back 48

Fixed kVp/ variable mAs
variable kVp/ fixed mAs

Front 49

how do the 2 types of exposure technique charts work?

Back 49

variable kVp: for every 1 cm change +/- 2; fixed kVp: for every 4-5 cm; change by a factor of 2

Front 50

what are the 2 types of AEC systems?

Back 50

1. PM - photo multiplier tube system
2. ionization chamber

Front 51

AEC detectors work by measuring what?

Back 51

they measure the amount of photons that enter the chamber

Front 52

What factors DIRECTLY control AEC?

Back 52

time

Front 53

the purpose of using AEC with film-screen imaging is to control?

Back 53

density

Front 54

the purpose of using AEC with digital imaging is to control?

Back 54

image quality by controlling the s#

Front 55

how does kVp and mA selections effect AEC?

Back 55

they INFLUENCE AEC (time/AEC directly go together)

Front 56

what is the function of density controls on the control panel

Back 56

overides calibration or length of time

Front 57

what is defined as preestablished guidelines used to select standardized exposure factors?

Back 57

exposure technique chart

Front 58

_________ is the primary patient factor that determines the selection of exposure factors.

Back 58

part measurement

Front 59

a primary goal of exposure technique charts is to

Back 59

consistently produce quality images

Front 60

which of the following is an important condition required for technique charts to be effective>

Back 60

equipment must be calibrated to perform properly

Front 61

which of the follwoing factors would not be standardized on technique charts?

Back 61

patient age

Front 62

what type of exposure technique system uses a fixed mAs regardless of part thickness

Back 62

variable kVp

Front 63

of the follwoing, which is most important when using a technique chart?
a. one radiographer revises the chart
b. a high mA value is set
c. the part is measured accurately
d. patient history is included

Back 63

the part is measured accurately

Front 64

what is an advantage of the fied kVp technique chart?

Back 64

it reduces patient exposure

Front 65

what is a disadvantage of the variable kVp technique chart?

Back 65

it increases heat load on the x-ray tube

Front 66

in creating either type of exposure technique chart, what is most important?

Back 66

achieving adequate penetration of the anatomic part.

Front 67

the purpose of using AEC with film-screen imaging is to control?

Back 67

density

Front 68

AEC devices work by measuring?

Back 68

radiation that exits the patient

Front 69

how many detectors are typically found in an AEC system?

Back 69

3

Front 70

minimum repsonse time refers to?

Back 70

the shortest exposure time possible when an AEC device is used

Front 71

which of the following statements about AEC w/ film-screen exams is true?
a. adjusting the mA value affects image density
b. adjusting the kVp value affects the image density
c. adjusting the backup time affects image density
d. adjusting the density controls affects image density

Back 71

adjusting hte density controls affects image density

Front 72

T/F
ionization chamber systems measure radiation before it interacts with the image

Back 72

true

Front 73

the purpose of the back up timer is to?

Back 73

limit unnecessary xray exposure

Front 74

what happens if AEC is activated for a stretcher chest study?

Back 74

an inapproprately long exposure occurs

Front 75

the purpose of anatomic probramming is to?

Back 75

present the radiographer with a preselected set of exposure factors

Front 76

T/F
the tasks involved with practicing radiography generally are made more difficult w/ AEC & APR systems

Back 76

False

Front 77

T/F
the individual judgement and discretion of the radiographer is still necessary when using AEC & APR

Back 77

true

Front 78

when using AEC w/ digital imaging systems, assuming all other factors are correct, selecting the center chamber on a PA chest results in?

Back 78

approprate density in the lung area

Front 79

when using AEC w/ digital imaging systems, assuming all other factors are correct, selecting the minus 2 density on a PA chest results in?

Back 79

appropriate density in the lung area AND increased quantum mottle in the image

Front 80

using a film-screen system and AEC, a chest in the lateral position is imaged w/ 70 kVp instead of the typical 120 kVp. Compared to an optimal lateral chest image, this image would have

Back 80

increased contrast

Front 81

when using AEC with a film-screen system, assuming all other factors are correct, selecting the center chamber on a PA chest results in?

Back 81

increased density in the lung area

Front 82

using film-screen and AEC, the central ray for an oblique lumbar spine position is centered over soft tissue instead of the spine. the spine will appear

Back 82

underexposed

Front 83

using a digital system and AEC, the central ray for an oblique lumbar spine position is centered over soft tissue instead of the spine. the spine will appear

Back 83

with optimal density AND with increased quantum mottle

Front 84

what can be set by using the control panel; controls time of exposure and acts as safety precaution to cut off exposure at the 150-200% range?

Back 84

back up time

Front 85

T/F
AEC can be used on table top setting

Back 85

FALSE

Front 86

why is mAs readout important?

Back 86

when using AEC it flashes technique used. can repeat w/ same technique if good or change appropriately if necessary

Front 87

a optimal density is achieved at one technique using 200 speed film. Can the same technique be used for same results with 400 film?

Back 87

no. this is a limitation of AEC system. they are calibrated for certain uses (speed films, etc.)

Front 88

what does density selection do?

Back 88

it controls the AEC system by adding or subracting factors (time to AEC #s).
+1 = 25% increase in time
+2 = 50% increase in time
-1 = 25% decrease in time
-2 = 50% decrease in time

Front 89

Why is collimation important when using AEC?

Back 89

detectors cannot distinguish between scatter radiation & transmitted radiation therefore may shut off early/ late.

Front 90

if an image results in a high s# will the image be under or over exposed?

Back 90

under exposed

Front 91

why is AEC used?

Back 91

to produce an appropriate amount of radiographic density on a radiograph by using the length of exposure time.

Front 92

what does kVp control?

Back 92

contrast

Front 93

what does mA control

Back 93

number of electrons (boil this many e-)

Front 94

what does AEC control?

Back 94

how long exposure will last

Front 95

T/F
the more technique (mAs) the darker our image will be

Back 95

True

Front 96

what does the sensitometric curve represent?

Back 96

it demonstrates the relationship between xray exposure and radiographic density

Front 97

what is the biggest difference between the 2 AEC systems?

Back 97

how the 2 systems convert radiation into electric current

Front 98

how does the photomultipier (PM) tube system work?

Back 98

converts xray photons to light photons then converts light photons to electric current

Front 99

why don't we use photomultiplier tube AEC system?

Back 99

more prone to failure than ionization chamber systems; however it is more accurate than ionzation chamber system.

Front 100

how does ionzation chamber AEC system work?

Back 100

xray photons that go through patient then knock out gas electron which is released into energy

Front 101

T/F
Ionization chamber AEC system is the most common system used today

Back 101

True

Front 102

T/F
Ionization chamber AEC system is less accurate than the PM system

Back 102

True

Front 103

T/F
when using AEC centering the part is not that important

Back 103

False

Front 104

T/F
AEC directly provides contrast

Back 104

False

Front 105

how do we control penetration of body part?

Back 105

kVp

Front 106

low kVp = _____ contrast

Back 106

high

Front 107

high kVp = ______

Back 107

Low

Front 108

AEC only determines ______ of exposure

Back 108

length (time)

Front 109

when using AEC system and we decrease mA what will happen to the time of exposure?

Back 109

increase

Front 110

when using AEC system and we increase kVp you'll use _____ mAs. and why?

Back 110

less mAs; because more xray photons will travel through part/ patient