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Radiation protection > chapter 12 EXAM 6 FINAL > Flashcards

chapter 12 EXAM 6 FINAL Flashcards

1
Q

radiographers must limit the patient’s exposure by doing what

A

employing appropriate radiation reduction techniques

using protective devices

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2
Q

patient exposure can be reduced by:

A 
effective communication 
proper body part immobilization 
motion reduction techniques 
beam limitation devices
filtration of xray beam 
shielding 
suitable exposure factors 
elimination of repeat exposures
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3
Q

2 types of patient motion

A

voluntarty

involuntary

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4
Q

voluntary motion

A

motion controlled by will

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5
Q

involuntary motion

A

motion is caused by muscle groups that cannot be willfully controlled

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6
Q

voluntary motion may be attributed to

A 
pts. age 
breathing patterns/problems
anxiety
physical/mental discomfort
fear of exam/ bad diagnosis
mental instability
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7
Q

voluntary motion may be eliminated by

A

gaining cooperation of pt.

immobilization

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8
Q

involuntary motion may be caused by

A 
chills
tremors (aka parkinsons) 
muscle spasms 
pain 
withdrawal
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9
Q

involuntary motion is reduced by

A

using high mA with a short exposure time

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10
Q

areas of the body that should be shielded whenever possible

A

lens of eye
breasts
reproductive organs

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11
Q

gonadal shielding is used to protect reproductive organs when they are in or within approximately what distance of a properly collimated beam

A

5 cm

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12
Q

what is the first line of defense for protecting the gonads

A

collimation

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13
Q

female reproductive organs receive about how many more times exposure than males for radiographic exams of the pelvic region

A

three times more exposure than males do

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14
Q

for female pts. the use of a flat contact shield placed over reproductive organs reduces exposure by

A

about 50%

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15
Q

for male pts. the use of shielding over the gonads can reduce exposure by

A

90-95%

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16
Q

for females the shield should be placed where

A

2.5cm (1inch) medial to each ASIS to protect the ovaries

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17
Q

4 types of gonadal shielding devices

A
  1. flat contact shields
  2. shadow shields
  3. shaped contact shields
  4. clear lead shields
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18
Q

flat contact shields

A

made of lead strips or lead materials 1mm thick

normal ones

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19
Q

shadow shields

A

suspended over the region of interest and casts a shadow over the area to be shielded
just as effective as a contact shield

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20
Q

shaped contact shields

A

contain 1mm lead and contoured to enclose the male reproductive organs
(looks like a cup)

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21
Q

shaped contact shields are not recommended for what

A

for PA projections because they only cover the anterior surface

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22
Q

clear lead shields

A

replacing some older shields

made of lead acrylic material with about 30% lead

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23
Q

for a scoli series what projection is always preferred

A

PA projections

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24
Q

gonadal shielding minimizes

A

the number of potentially harmful xray induced mutations expressed in future generations

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25
Q

specific area shielding reduces exposure to those areas and should be used whenever possible to minimize

A

the possibility of stochastic effects

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26
Q

for both digital and analog exams a high quality image has

A

sufficient density
appropriate level of contrast
maximum amt. of recorded detail
minimal amount of distortion

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27
Q

with digital imaging, quantum mottle is cause when

A

too few xrays reach the IR

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28
Q

by establishing technique charts in imaging departments it ensures

A

consistency in the diagnostic quality of digital exams and minimizes the potential for exposure technique errors

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29
Q

T or F

the use of high kVp and low mAs reduces pt. dose

A

true

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30
Q

with screen film imaging as kVp increases and mAs decreases, the contrast is

A

reduced and the amt. of useful info in the recorded image is less

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31
Q

increasing kVp by what with the appropriate decrease in mAs reduces pt. dose

A

increasing kVp by 15%

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32
Q

a quality control program ensures

A

the production of optimal quality images

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33
Q

Air gap technique

A

an alternative procedure to the use of a grid for reducing scatter

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34
Q

in the air gap technique, scatter is reduced by

A

increased OID

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35
Q

in the air gap technique, selection of exposure factors are comparable to those used with a what ratio grid

A

an 8:1 ratio grid

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36
Q

T or F

with kVp settings of 90 or above air gap techniques are not as effective

A

true

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37
Q

repeat image

A

any image that must be performed more than once because of human or mechanical error during the production of the initial image

38
Q

repeat analysis program

A

an attempt to record the various causes of inadequate quality on occasions when an image has to be retaken

39
Q

categories established for discarded images

A 
images too dark or light because of wrong exposure factors 
incorrect positioning
incorrect centering
pt. motion
improper collimation 
presence of foreign bodies
processing artifacts
40
Q

benefits of a repeat analysis program

A
  1. increase awareness among staff/students for the need to produce optimal quality images
  2. radiographers become more careful in producing images cuz they know they’re being reviewed
  3. in service education programs may be designed for imaging personnel
41
Q

the quantity of radiation received by a pt. during an imaging procedure can be specified in 3 ways

A
  1. entrance skin exposure ESE
  2. gonadal dose
  3. bone marrow dose
42
Q

out of the 3 ways the quantity of radiation received by a pt. during an imaging procedure which is the easiest to obtain and the most widely used

A

entrance skin exposure ESE

43
Q

conversion of entrance skin exposure to pt. skin dose

A

ESE may be converted to pt. skin dose by using established well documented multiplicative factors

44
Q

what is most often used to measure skin dose

A

TLD thermoluminescent dosimeters

45
Q

what is the sensing material in TLDs

A

Lithium fluoride LiF

46
Q

in fluoro, the amt of radiation a pt. receives is estimated by

A

measuring the exposure rate at tabletop and multiplying it by the fluoro time

47
Q

skin dose represents

A

the absorbed dose to the most superficial layers of the skin

48
Q

the epidermis is composed of 5 layers

A
  1. horny, outer layer
  2. translucent, clear layer
  3. granular layer
  4. prickle cell layer
  5. germinal, basal cell layer
49
Q

genetically significant dose (GSD)

A

the equivalent dose (EqD) to the reproductive organs, that if received by every member of the population, would produce the total genetic effect on the population as the sum of the individual doses actually received

50
Q

according to the US public helath service the estimated GSD for population of the united states is aprox.

A

0.20 mSv (20mrem)

51
Q

bone marrow dose (mean marrow dose)

A

the average radiation dose to the entire active bone marrow

52
Q

radiation dose to bone marrow may be responsible for

A

radiation induced leukemia

53
Q

in the US the mean marrow dose from diagnostic xray exams averaged over the entire population is

A

1mGt/year (100mrad/year)

54
Q

fluoroscopically guided positioning

A

practice of using fluoro to determine the exact location of the CR before taking a radiographic exposure
ASRT says its unethical

55
Q

the repeat rate depends on

A

the techs skills in operation of fluoro equipment
communication between radiographer and pt.
pts. cooperation
pts. condition

56
Q

t or f

“blind positioning” provides the patient with the lowest dose

A

true

57
Q

t or f

studies have shown that pt. ESE increases with the use of FGP when repeat exposure is needed

A

true

58
Q

who’s responsibility is it to question the pt. of childbearing age about pregnancy

A

the radiographer

59
Q

it’s estimated that less than how many women referred for an xray exam are potentially pregnant

A

less than 1%

60
Q

if the pt. has an xray and is pregnant, the RSO or medical physicist must

A

determine the absorbed EqD to the embryo fetus

61
Q

patient dose in mamography should not exceed

A

3mGyt (300rad)

62
Q

in mamo doses are usually not more than

A

2mGyt

63
Q

for women age 40-49 ACR recommends mamo screenings at least

A

every other year

64
Q

for women 50 and older, ACR recommends mamo screenings to be done

A

annualy

65
Q

hos is the dose reduced in mamo

A

by limiting the number of projections taken

66
Q

helical CT scan

A

the xray tube rotates continuously and the couch moves the pt. through the plane of the rotating xray beam

67
Q

helical pitch ratio (pitch)

A

the relationship between the couch movement and the xray beam width
expressed as a ratio

68
Q

a lower pitch like 0.5:1 does what to pt. dose

A

increases pt. dose

69
Q

a higher pitch like 2:1 does what to pt. dose

A

decreased pt. dose

70
Q

what are the 2 concerns related to pt. dose in CT scans

A

skin dose and dose distribution

71
Q

skin dose from a succession of adjacent slices is lesser or greater than the skin dose from a single scan

A

greater than the skin dose from a single scan

72
Q

the entrance exposure from a CT exam may be compared with the entrance exposure received during

A

a routine fluoro exam.

73
Q

approximate doses for head imaging in CT

A

30-50 mGy (3000-5000mrad)

74
Q

approximate dose for body imagin in CT scan

A

20-40 mGy (2000 to 4000mrad)

75
Q

In CT what is used for shielding

A

the collimators. because of the rotational nature of the exposure a shield is not more effective than the collimators that exist on the scanner

76
Q

when the pitch ratio is 1:1 the spiral CT scan dose is

A

comparable to conventional CT

77
Q

other factors that influence pt. dose

A

pixel size
slice thickness
tube mA

78
Q

4 dose parameters in CT

A
  1. CTDI
  2. CTDIw
  3. CTDIvol
  4. dose length product (DLP)
79
Q
  1. CTDI
A

an ionization chamber is inserted into an acrylic phantom similar in diameter to human head or abdomen. all other holes are filled with acrylic plugs

80
Q
  1. CTDIw
A

A weighted average of two measured CTDI values, one that is obtained in the center of the phantom and the other from the average of the 4 peripheral cavity measurements

81
Q
  1. CTDIvol
A

the average absorbed dose within a scanned volume

82
Q
  1. dose length product DLP
A

the product of CTDIvoL and the irradiated scan length

83
Q

what is DLP expressed in

A

mGy/cm

84
Q

EfD is calculated by

A

EfD=DLPxEfDIP

85
Q

the goal of CT imaging

A

to obtain the best possible image while delivering acceptable level of ionizing radiation to the pt.

86
Q

alliance for radiation safety in pediatric imaging was founded in and is what

A

founded in 2007

a partnership of medical societies whose purpose is to reduce the dose for pedi pts.

87
Q

image gently campaign started in

A

january 22 2008

88
Q

what is the goal of image gently campaign

A

to increase awareness of the need to reduce pt. dose for pedi pts. especially in CT
lowers pts. dose by child sizing the kV and mA

89
Q

what is the goal of image wisely campaign

A

to address concerns about the increase of public exposure to ionizing radiation from medical radiation

90
Q

what state became the first state to endorse the image wisely and image gently campaigns and when

A

Minnesota in December 2012

91
Q

t or f

for pedi pts. you use short exposure times with high mA stations

A

true

92
Q

most medical procedures result in fetal exposures of less than

A

0.1 Gyt (1rad)

Radiation protection (12 decks)

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