chapter 12 EXAM 6 FINAL Flashcards Preview

Radiation protection > chapter 12 EXAM 6 FINAL > Flashcards

Flashcards in chapter 12 EXAM 6 FINAL Deck (92):
1

radiographers must limit the patient's exposure by doing what

employing appropriate radiation reduction techniques
using protective devices

2

patient exposure can be reduced by:

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

3

2 types of patient motion

voluntarty
involuntary

4

voluntary motion

motion controlled by will

5

involuntary motion

motion is caused by muscle groups that cannot be willfully controlled

6

voluntary motion may be attributed to

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

7

voluntary motion may be eliminated by

gaining cooperation of pt.
immobilization

8

involuntary motion may be caused by

chills
tremors (aka parkinsons)
muscle spasms
pain
withdrawal

9

involuntary motion is reduced by

using high mA with a short exposure time

10

areas of the body that should be shielded whenever possible

lens of eye
breasts
reproductive organs

11

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

5 cm

12

what is the first line of defense for protecting the gonads

collimation

13

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

three times more exposure than males do

14

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

about 50%

15

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

90-95%

16

for females the shield should be placed where

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

17

4 types of gonadal shielding devices

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

18

flat contact shields

made of lead strips or lead materials 1mm thick
(normal ones)

19

shadow shields

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

20

shaped contact shields

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

21

shaped contact shields are not recommended for what

for PA projections because they only cover the anterior surface

22

clear lead shields

replacing some older shields
made of lead acrylic material with about 30% lead

23

for a scoli series what projection is always preferred

PA projections

24

gonadal shielding minimizes

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

25

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

the possibility of stochastic effects

26

for both digital and analog exams a high quality image has

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

27

with digital imaging, quantum mottle is cause when

too few xrays reach the IR

28

by establishing technique charts in imaging departments it ensures

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

29

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

true

30

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

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

31

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

increasing kVp by 15%

32

a quality control program ensures

the production of optimal quality images

33

Air gap technique

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

34

in the air gap technique, scatter is reduced by

increased OID

35

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

an 8:1 ratio grid

36

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

true

37

repeat image

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

38

repeat analysis program

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

39

categories established for discarded images

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

benefits of a repeat analysis program

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

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

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

42

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

entrance skin exposure ESE

43

conversion of entrance skin exposure to pt. skin dose

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

44

what is most often used to measure skin dose

TLD thermoluminescent dosimeters

45

what is the sensing material in TLDs

Lithium fluoride LiF

46

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

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

47

skin dose represents

the absorbed dose to the most superficial layers of the skin

48

the epidermis is composed of 5 layers

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

49

genetically significant dose (GSD)

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

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

0.20 mSv (20mrem)

51

bone marrow dose (mean marrow dose)

the average radiation dose to the entire active bone marrow

52

radiation dose to bone marrow may be responsible for

radiation induced leukemia

53

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

1mGt/year (100mrad/year)

54

fluoroscopically guided positioning

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

55

the repeat rate depends on

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

56

t or f
"blind positioning" provides the patient with the lowest dose

true

57

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

true

58

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

the radiographer

59

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

less than 1%

60

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

determine the absorbed EqD to the embryo fetus

61

patient dose in mamography should not exceed

3mGyt (300rad)

62

in mamo doses are usually not more than

2mGyt

63

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

every other year

64

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

annualy

65

hos is the dose reduced in mamo

by limiting the number of projections taken

66

helical CT scan

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

67

helical pitch ratio (pitch)

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

68

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

increases pt. dose

69

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

decreased pt. dose

70

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

skin dose and dose distribution

71

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

greater than the skin dose from a single scan

72

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

a routine fluoro exam.

73

approximate doses for head imaging in CT

30-50 mGy (3000-5000mrad)

74

approximate dose for body imagin in CT scan

20-40 mGy (2000 to 4000mrad)

75

In CT what is used for shielding

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

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

comparable to conventional CT

77

other factors that influence pt. dose

pixel size
slice thickness
tube mA

78

4 dose parameters in CT

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

79

1. CTDI

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

2. CTDIw

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

3. CTDIvol

the average absorbed dose within a scanned volume

82

4. dose length product DLP

the product of CTDIvoL and the irradiated scan length

83

what is DLP expressed in

mGy/cm

84

EfD is calculated by

EfD=DLPxEfDIP

85

the goal of CT imaging

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

86

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

founded in 2007
a partnership of medical societies whose purpose is to reduce the dose for pedi pts.

87

image gently campaign started in

january 22 2008

88

what is the goal of image gently campaign

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

what is the goal of image wisely campaign

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

90

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

Minnesota in December 2012

91

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

true

92

most medical procedures result in fetal exposures of less than

0.1 Gyt (1rad)