Chapter 11 - Radbiology and Radiation Safety Flashcards
(134 cards)
1
Q
define ionization radiation
A
a radiation that ionizes particles once it passes through a body
2
Q
define radiation protection
A
the measures taken to safeguard patients, personnel, and the public from unnecessary exposure to ionizing radiation.
3
Q
what is the SI unit for exposure
A
Air Kerma (Gy-a)
4
Q
what is the SI unit for absorbed dose?
A
Gray (Gy-t)
5
Q
what is the SI unit for dose equivalent?
A
Sieverts (Sv)
6
Q
how do you convert Gy to mGy?
A
Gy x 1,000
7
Q
define air kerma
A
- a measurement of the radiation intensity in the air
- the ionization of air resulting from interaction with the x-ray beam.
- amount of x-rays that are in the air between the x-ray tube and the patient
8
Q
define absorbed dose/Gray
A
- the amount of energy (x-ray) absorbed by the irradiated tissue
- measures the amount of energy that is absorbed by the patient
9
Q
the patient receives both ____ and an _____
A
exposure; absorbed dose
10
Q
which one will have a higher number: air kerma or absorbed dose/gray?
A
air exposure
11
Q
define dose equivalent
A
to describe or clarify the absorbed dose in the body based on the type and energy of the radiation the person was exposed to.
12
Q
define radiation weight factor
A
a radiation weighting factor is assigned to each type of radiation, based on the variation in biologic damage that is produced when an individual receives exposure from different types of radiation
13
Q
list the different types of radiation
A
- x-ray photons
- gamma photons
- low-energy internal protons
- fast neutrons
- alpha particles
14
Q
what is the radiation weight factor of x-ray photons?
A
1
15
Q
what is the radiation weight factor of gamma photons?
A
1
16
Q
what is the radiation weight factor of low-energy internal protons?
A
2
17
Q
what is the radiation weight factor of fast neutrons?
A
20
18
Q
what is the radiation weight factor of alpha particles?
A
20
19
Q
Because the weighting factor for x-ray photons is “1”, the absorbed dose and the dose equivalent are always _____ numbers.
A
identical
20
Q
convert 0.005 Gy-t to mGy-t
A
1
21
Q
convert 0.010 Gy-t to mGy-t
A
10
22
Q
convert 0.050 Gy-t to mGy-t
A
50
23
Q
convert 0.100 Gy-t to mGy-t
A
100
24
Q
convert 0.250 Gy-t to mGy-t
A
250
25
convert 0.500 Gy-t to mGy-t
500
26
convert 1.00 Gy-t to mGy-t
1000
27
convert 2.50 Gy-t to mGy-t
2500
28
what values determine the absorbed dose a patient receives?
- mAs
- kVp
- SID
29
define entrance skin exposure (ESE)
calculating patient dose by how much exposure the skin receives
30
how much ESE(mGy-a) does a skull receive?
2.00
31
how much mean bone marrow dose (mGy-t) does a skull receive?
0.10
32
how much gonad dose does a skull receive?
<1 (less than)
33
how much ESE (mGy-a) does a chest receive?
0.1
34
how much mean bone marrow (mGy-t) does a chest have?
0.02
35
how much gonad dose (mGy-t) does a chest receive?
<1
36
how much ESE (mGy-a) does a cervical spine receive?
1.5
37
how much mean bone marrow (mGy-t) does a cervical spine receive?
0.20
38
how much gonad dose (mGy-t) does a cervical spine receive?
<1
39
how much ESE (mGy-a) does an abdomen receive?
4.0
40
how much mean bone marrow (mGy-t) does an abdomen receive?
0.30
41
how much gonad dose (mGy-t) does an abdomen receive?
1.25
42
how much does ESE (mGy-a) does a pelvis receive?
1.5
43
how much does mean bone marrow (mGy-t) does a pelvis receive?
0.20
44
how much gonad dose (mGy-t) does a pelvis receive?
1.50
45
how much ESE (mGy-a) does a limb receive?
0.5
46
how much mean bone marrow (mGy-t) does a limb receive?
0.02
47
how much gonad dose (mGy-t) does a limb receive?
<1
48
define linear energy transfer (LET)
how much radiation was absorbed in a given section of tissue corresponding to the path through the tissue of the x-ray photons
49
define oxygen enhancement ratio (OER)
- another concept that describes radiation absorbed in tissues.
- When there is more oxygen in the tissues, it is more sensitive to radiation compared to tissues with low oxygen.
- "oxygen effect"
50
define the law of bergonie and tribondeau
a law, which states that cell sensitivity to radiation exposure depends on four characteristics of the cell
- age
- differentiation
- metabolic rate
- mitotic rate
51
define age in the law of bergonie and tribondeau
younger patient cells are more sensitive than older ones
52
define differentiation in the law of bergonie and tribondeau
simple cells are more sensitive than highly complex cells
53
define metabolic rate in the law of bergonie and tribondeau
cells that use energy rapidly are more sensitive than those that have a slower metabolic rate
54
define mitotic rate in the law of bergonie and tribondeau
cells that divide and multiply rapidly are more sensitive than those that replicate slowly
55
what other cells/tissues are highly sensitive to radiation?
- blood cells (#1 lymphocytes)
- skin/mucous membranes (lining the mouth, nose, stomach)
- thyroid gland
- breast tissue
56
what cell is NOT sensitive to radiation exposure
nerve and muscle cells
57
ionizing radiation produces _____ as it interacts with the body tissue
biological damage
58
what biological effect occurs at a radiation dose equivalent of 250 mSv?
Blood changes (e.g., measurable hematologic depression, decreases in the number of lymphocytes present in the circulating blood)
59
what biological effect occurs at a radiation dose equivalent of 1500 mSv?
Nausea, diarrhea
60
what biological effect occurs at a radiation dose equivalent of 2000 mSv?
Erythema (diffuse redness over an area of skin after irradiation)
61
what biological effect occurs at a radiation dose equivalent of 2500 mSv?
If dose is to gonads, temporary sterility
62
what biological effect occurs at a radiation dose equivalent of 3000 mSv?
50% chance of death; lethal dose for 50% of population over 30 days (LD 50/30)
63
what biological effect occurs at a radiation dose equivalent of 6000 mSv?
50% chance of death; lethal dose for 50% of population over 30 days (LD 50/30)
64
list the different radiation effect classifications
- short-term
- long-term
- somatic
- genetic
65
define short-term effects
- observed within 3 days of exposure
- high radiation absorbed doses (> 500 mGy-t)
- referred as acute radiation syndrome (ARS)
66
define acute radiation syndrome (ARS)
Patients become sick very fast because they receive whole-body doses in a very short period of time.
67
what are different categories in ARS
- hematologic system (blood)
- gastrointestinal system (digestive tract)
- central nervous system (CNS) (brain and spinal cord)
68
define long term effects
- also known as latent effect
- not observed until several years after exposure (30 years)
- we are most concerned about in diagnostic radiology.
- the effects shown after a patient has undergone many years of average to high radiation exposure.
69
define somatic effects
- affect the body and tissues of the individual who is irradiated
- are both short term and long term effects
70
define genetic effects
a result of damage to the reproductive cells of the irradiated person and are observed as defects in the children or grandchildren of the irradiated individual
71
what are some short-term somatic effects
- occur with high dose of radiation
- they're predictable
- erythema/radiation burn
- can occur with a dose of 2000 mSv
- (high doses) CNS effects -> seizures, coma, death
- (low doses) radiation sickness -> GI effect, low immune system, WBC death
- (lesser dose) hematologic
72
define erythema dose
the amount of radiation necessary to produce reddening of the skin
73
Human beings who receive whole-body doses of radiation in excess of ________ may die within ____ to ___ days
5000 mGy-t; 30 - 60
74
define LD 50/30
50% of the population will die within 30 days due to lethal dose
75
list long-term somatic effects
- becomes apparent in 5-30 years
- long-term effects are random
- involve small doses
- cataractogenesis
- carcinogenesis
- lifespan shortening
- leukemia
76
define cataractogenesis
- formation of cataracts
- clouding of the lens of the eye
77
define carcinogenesis
- increased risk of malignant disease
- cancer of the skin, leukemia, thyroid, breast
78
define lifespan shortening
shorter lifespan then those who were not exposed to ionizing radiation
79
define leukemia
cancer of the blood or bone marrow
80
define genetic effects
changes or mutation to the genes of the reproductive cell
81
individuals who contain any mutation in their genes will result to-
some type of deformity, defect, or characteristic less suited for survival
82
what will be some examples of mutation?
- cleft palates
- spina bifida
- polydactyly
83
define ALARA
all radiation exposure to humans should be limited to levels that are "as low as reasonably achievable"
84
what are ways we can keep radiatin exposure to a minimum?
- reducing repeat exposures
- avoiding mistakes
- using the smallest radiation field
- using the highest kVp
- maintaining SID at 40"
85
The greatest cause of unnecessary radiation to patients that can be controlled by limited operators is-
repeat exposures
86
what are ways to minimize repeat exposures?
- double check you are examining the correct patient
- strictly follow procedures and rules
- provide clear instructions to patient
87
what is another cause of unnecessary exposure?
size of radiation field
88
what is one way to minimize exposure with the size of radiation field?
- use proper collimation
- use the smallest radiation field that will cover the area of clinical interest
89
what technique setting is desirable to minimize patient exposure?
high kVp, low mAs
90
The use of the 15% rule to increase kVp and decrease mAs results in a dose reduction of approximately ____%
34%
91
good communication:
* Encourages reduction in anxiety and emotional stress.
* Enhances the professional image of the x-ray operator as a person who cares about the patient’s well-being.
* Increases the chance for successful completion of the x-ray examination, thereby reducing the potential of repeat exposures.
92
Published studies indicate the risk of a radiation-induced leukemia in children after a substantial dose of ionizing radiation is approximately _______ that of adults
two times
93
what are ways to reduce radiation exposure in prediatrics?
* Gain cooperation by having entertainment and distraction devices. Use restraint equipment in a fun manner and always smile.
* Patient motion can be a major source of repeat x-rays. To minimize the problem of motion, use high mA settings which reduce the exposure time to very short levels. This may require using manual exposure techniques.
* Use gonad shielding.
* Collimate. Smaller children may be imaged on larger cassettes and the operator should always collimate as close to the part as necessary to see only the part being examined.
* All scoliosis images should be done using the PA projection, and should not be done AP.
94
define gonadal shields
used to reduce the likelihood of genetic radiation effects
95
a lead shield placed between the patient and the x-ray tube should be at least-
0.5mm Pb equivalent
96
define shadow shields
shields attached to the collimator
97
define contact shields
shields placed on or near the patient's body
98
which shield is more effective? Shadow or contact shields?
contact shields
99
the pubic symphysis is at the same level as-
the greater trochanter of the femur
100
Whenever the gonads are within ____ of the margin of the radiation field, gonad dose will be significantly _____ by shielding.
5cm; reduced
101
what examinations prevent women from wearing a shield?
- abdomen
- sacrum
- coccyx
102
what is one way to reduce patient dose for a woman?
if patient can be radiographed prone
103
limited operators are not allowed to ____ patients or image receptors during x-ray exposures
hold
104
when assistance to position is needed, who can the radiographer use?
- nonoccupational exposed personnel
- personnel who is not pregnant
- personnel wearing protective apparel
105
define portable radiography?
mobile radiographic examinations
106
what occupation in radiology receives the most exposure?
fluoroscopy and mobile radiography
107
what is the greatest exposure hazard for radiography personnel?
scatter radiation from the patient and other objects
108
what are the three principal methods used to protect operators?
- time
- distance
- shielding
109
how can time help us reduce occupational exposure?
using a low exposure time
110
how can distance help us reduce occupational exposure?
increasing distance will minimize receiving intense photons
111
how can shielding help us reduce exposure?
using shielding in places where the examination is not being done. it will absorb those weak/unnecessary photons
112
define quality control check
performed in aprons and gloves used in the department to meet state and federal regulations
113
what is the minimum Pb equivalency in aprons?
0.5mm Pb equivallency
114
what is the minimum Pb equivalency in gloves?
0.25mm Pb equivalency
115
when is quality control check done?
every 6 months
116
what must be done of there are any tears present in the lead equipment?
must be taken out of service
117
define personnel dosimeters
devices for monitoring radiation exposure of radiation workers
118
Monitoring is required whenever radiation workers are likely to risk receiving ____ or more of the annual occupational effective dose (EfD) limit of ____ mSv.
10%; 50
119
define optically stimulated luminescence (OSL)
- uses aluminum oxide as a radiation detector
- can measure small doses more precisely and can be reanalyzed to confirm results
- accurate over a wide dose range
- excellent long-term stability
120
control dosimeters should never be used to-
measure occupational dose or for other purposes
121
what information is given to radiation dosimeter service companies?
- name
- birth date
- social security
122
where should personal dosimeters be placed?
- Personal dosimeters should be worn in the region of the collar on the anterior surface of the body
- should be outside the lead apron when a lead apron is worn
123
when a lead apron is worn, personal dosimeters should be placed-
outside of the lead apron
124
define NCRP
- The National council on radiation protection and measurement
- prepares the standards and makes the recommendations to the government with regards to the amount of radiation an occupationally exposed person receives annually and in his or her lifetime
125
define effective dose (EfD)
a limiting system used to calculate the upper limit of occupational exposure permissible.
- measured by the personal dosimeter readings
126
what is the limit of effective dose (EfD) for occupational exposed personnel?
50 mSv
127
define cumulative effective dose (CumEfD)
The CumEfD limits a radiation worker’s lifetime effective dose to his or her age in years times 10 mSv.
128
what are the effects of radiation exposure to embryos?
- spontaneous abortions (miscarriage)
- congenital defects
- increased risk of malignant disease in childhood
- increase in genetic abnormalities
129
the NCRP confirms that high doses in excess of ___ to the uterus is cause for concern
150 mGy-t
130
what is the greatest risk for birth defects during a pregnancy?
- first trimester of pregnancy
- the first 3 months
131
define declared pregnancy
When a worker voluntarily notifies her employer, in writing, that she is pregnant, the employer is responsible for ensuring that her dose equivalent remains below the established limit for pregnancy
132
what is the monthly equivalent dose for a fetus?
0.5 mSV
133
what is the equivalent dose for the whole gestation period?
5.0 mSv
134
where should the dosimeter be placed for a pregnant worker?
one around the color, the other around the waist
