Carcinogenesis, Hereditary & Embryonic Effects, & Radiation Protection Flashcards
1
Q
Children who receive cranial radiation are most at risk for developing ….?
A
Meningiomas
2
Q
Which organ can develop both malignant and benign growths following radiation?
A
Thyroid
3
Q
What % of TBI patients develop life-threatening leukemias?
A
15%
4
Q
What kind of cancers have and have not been detected in children treated w/ RT for tinea capitis?
A
Have:
- Brain
- Thyroid
- Adenomas
- Leukemias (non-CLL)
- Breast
Have NOT
- H&N
5
Q
What kind of cancers did radium dial painters develop, and why?
A
Osteosarcomas: They licked their paint brushes and ingested radium, which localized to their bones.
6
Q
Does radiation cause death from causes other than second cancers?
A
Yes, from toxicity to the circulatory, digestive, and respiratory systems.
7
Q
What kind of a trend b/w dose and cancer risk do solid tumors fit?
A
- Linear
- Non-threshold (stochastic)
8
Q
What kind of a trend b/w dose and cancer do leukemias fit?
A
- Linear-quadratic
- Non-threshold (Stochastic)
9
Q
Does radiation risk depend on gender?
A
Yes!
10
Q
Does radiation risk depend on age?
A
- Yes, very young children are most at risk
– Children < 5 yrs are 3x more susceptible than the average population, or 10x more susceptible than older adults - Very old individuals are also more radiosensitive
11
Q
What is a stochastic effect?
A
An effect whose probability but NOT severity increases with dose. It usually does not have a threshold dose and is an all-or-none effect.
12
Q
What is a deterministic effect?
A
- Has a threshold dose
- Severity related to dose
- Continuous effect, as opposed to all or none
13
Q
What was the cause of thyroid cancers in children affected by the Chernobyl disaster?
A
Ingestion of I-131
14
Q
When did thyroid cancers occur in children affected by the Chernobyl disaster?
A
7-10 yrs post-disaster
15
Q
What is radiogenic cancer?
A
Cancer linked to radiation
16
Q
Which source contributes the most to radiation exposure in the US?
A
Medical ≥ 50%
17
Q
Which source is the second most common source of radiation exposure to people in the US?
A
Background ≥ 37%
18
Q
Which medical procedure(s) contribute the most to medical radiation exposure?
A
- CT Scanners
- NM procedures
19
Q
Individuals treated for enlarged thymus as children are at an increased risk of which cancer?
A
Thyroid
20
Q
What is the tissue weighting factor for the breast, lungs, bone marrow, stomach, colon, and other tissues not mentioned elsewhere?
A
0.12
21
Q
What is the tissue weighting factor for the gonads?
A
0.08
MNEMONIC: 2 round testes, 2 ovaries → 8
22
Q
What is the tissue weighting factor for the thyroid, esophagus, bladder, and liver?
A
- 0.04
- The BELT organs: Bladder, Esophagus, Liver, Thyroid
23
Q
What’s the sum of all tissue weighting factors?
A
1 (100%)
24
Q
What is the tissue weighting factor for the brain, skin, bone surface, and salivary glands?
A
0.01
25
What is the increased % risk for the development of fatal cancers in radiation oncologists?
1%
26
Did the use of X-rays during the 50s and 60s increase the risk of childhood cancer in children who received these exams in utero?
Yes!
27
What is the radiation-induced malignancy rate for low DDREF radiation for all and working populations?
All - 5%
Working - 4%
28
What is the radiation-induced malignancy rate for high DDREF radiation for all and working populations?
All - 10 %
Working - 8%
29
What is a low dose and dose rate effectiveness factor (DDREF)?
Low LET radiation AND
Dose < 0.2 Gy OR Dose Rate < 0.1 Gy/hr
30
What is a high dose and dose rate effectiveness factor (DDREF)?
Low LET radiation AND
Dose > 0.2 Gy OR Dose Rate > 0.1 Gy/hr
OR
High LET radiation at any dose or dose rate
31
What is an equivalent dose (Sv)?
It is dose weighed for radiation type
32
What is an effective dose (Sv)?
The sum of weighted equivalent doses for all tissues and organs of the body is called the “effective dose”
33
What is the latent period for radiation-induced leukemias?
3-7 yrs
34
What is the minimum latent period for radiation-induced solid tumors?
≥ 10 yreas
35
Treatment for which benign spine disease is linked to an increased incidence of leukemia?
Ankylosing Spondylitis - 2/2 bone marrow expxosure
36
How many lung cancer deaths per year are attributable to exposure to indoor radon?
10-20%
20k out of 160k
37
What % of second malignancies in breast cancer patients are attributable to radiation?
5%
38
What kind of second malignancies are irradiated breast cancer patients most at risk for?
Esophagus
Lung
Soft tissues
39
What is the absolute risk model for radiation carcinogenesis?
Predicts the appearance of a distinct crop of radiation-induced cancers after a latent period following irradiation.
40
What is the relative risk model for radiation carcinogenesis?
Radiation-induced cancer risk is the natural incidence multiplied by a factor.
41
Has the incidence of cancer in the Japanese atomic bomb survivors plateaued?
No, it continues to increase to this day.
42
The incidence of which cancer was increased in women receiving fluoroscopies for pulmonary TB treatment?
Breast
43
What % of cancers in the Japanese atomic bomb survivors are leukemias?
20%
44
What is the probability of hereditary disorder in the first generation born to parents exposed to radiation for whole and working population?
- Working population: 0.1%/Gy
- Whole population: 0.2%/Gy
45
What is the annual dose of radiation attributed to medical diagnostic tests?
3 mSv (50%)
46
How does background radiation vary with altitude?
Increase, since there is a decrease in atmospheric shielding of cosmic rays
47
What is the annual dose of radiation attributed to a combined exposure to cosmic, terrestrial, and internal background radiation?
3 mSv
48
Under what condition are the equivalent and effective radiation doses equal?
When the whoel body is irradiated
49
What is the largest contibuter to background radiation in the US?
Radon
50
How much of the annual medical radiation exposure is received by the gonads?
0.3 mSv (10%)
51
How much of the annual medical radiation exposure is received by the gonads?
0.3 mSv (10%)
52
What sources of radiation are exempted from the annual radiation dose limit?
Background radiation, and radiation from medically necessary procedures.
53
Is metal retardation deterministic or stochastic?
Both.
It is deterministic when the fetus received radiation in utero.
It is stochastic when the egg/sperm received radiation prior to conception.
54
What's doubling dose?
- Dose required to produce **as many** mutations as would occur spontaneously (spontaneous = radiation-induced)
- The **total** amount of mutations would thus be doubled (spontaneous + radiation-induced)
55
In the megamouse study, what was the doubling dose?
1 Gy
56
What're the main conclusions of the mega mouse project?
1. Radiosensitivity of different mutations varies 2/2 differences in gene sizes
2. Dose rate effect: Acute doses of radiation result in more mutations than low-dose-rate exposures 2/2 DNA repair
3. Heritable consequences of radiation can be greatly reduced by allowing time between irradiation and conception 2/2 repair
3. The estimated doubling dose is 1 Gy w/ low-dose-rate exposure
57
in the mega mouse study, which sex was more susceptible to radiation-induced mutagenesis?
Males > Females
58
In the mega mouse study, what was the effect of low dose rate on mutagenesis?
Low dose rate decreased mutagenesis 2/2 ability to repair DNA at low doses
59
A study of Japanese A-bomb survivors by the Radiation Effects Research Foundation showed what effect of radiation on mutations in the F1 generation?
No effect, contrary to animal studies
60
What was the average dose received by the Japanese A-bomb survivors?
≤ 100 mSv
61
Do we have accurate dosimetry for the radiation exposure of the Japanese A-bomb survivors?
Yes!
62
Are the Japanese A-bomb survivors compliant with continued follow-up and testing?!
VERY
63
Does radiation induce new mutations in the population?
No, it only increases the frequency of mutations already seen within the population.
64
Is there a high rate of mutations in children with at least one parent exposed to radiation prior to cocneption?
No
65
What percentage of spontaneous genetic mutations in humans are attributable to background radiation?
1-6%
66
What is the % human mutation rate from radiation exposure?
0.1-0.6% per Sv
67
Can females get temporary sterility?
A big, fat no!
68
Does radiation sterility affect libido, hormone balance, or physical capabilities in human males?
No, since hormone production isn't affected unless unlikely doses of radiation are received (≥ 100 Gy)
69
What is the presentation of radiation sterility in human females?
- Permanent ovarian failure
- Menopausal sx
70
At what age is a woman most sensitive to radiation-induced ovarian failure?
The closer in age she is to menopause, the more sensitive she is to radiation
71
At what doses does radiation cause sterility in human females?
Young, prepubertal: 12 Gy
Premenopausal: 2 Gy
Range: 2-12 Gy
72
Is there a latent period in female sterility affected by radiation?
No, unlike males
73
Annual dose limit for the general public, including exposure for education and training?
- Infrequent exposure (infrequent visit to a nuclear power plant, etc): 5 mSv
- Chronic exposure: 1 mSv
74
Annual dose limit for a radiation worker?
- 50 mSv per year
- Age x 10 mSv
Whichever is lower
75
Dose limit for a radiation worker after declaration of pregnancy?
0.5 mSv/mo
76
How does the intrauterine growth retardation (IUGR) response caused by radiation vary during different weeks of gestation?
- < 8 wks: more severe; reversible IUGR
- > 8 wks: less severe, permanent IUGR
77
What is the most sensitive period for development of mental retardation in human fetuses?
- 8-15 wks
-- Risk: 40% / Sv
78
What is the shift in IQ points/Gy for humans?
30
79
What stage of in-utero development affected by radiation causes temporary growth retardation in animals (but not humans)?
Embryonic (organogenesis) stage!
80
From what point forward does a developing fetus start to incorporate radioactive iodine?
10th week onwards
Mnemonic: **10**dine
81
At what exposure should a doctor discuss possible radiation-induced birth defects with a pregnant woman?
0.1 Gy
82
What's the annual limit for the public for exposure to radiation from radioactive waste?
1 mSv
83
What is a genetically significant dose (GSD)?
Annual average gonadal dose to the human population weighted for age and sex distribution in those people who are expected to have children (Annual average gonadal dose multiplied by the probability of conception)
In the US, it is 0.3 mSv
It is NOT an estimate of effects on the offspring.
84
What radiation dose can cause oligospermia and reduced fertility in males?
0.15 Gy
85
What gestational age is most radiosensitive with respect to embryonic mortality?
0-1 weeks
Right after conception but prior to implantation.
86
What is the late fetal period?
16-40 wks
87
What are the fetal risks if it received radiation during the late fetal period?
- Mental retardation (low risk, 4-fold decrease compared to the early fetal period (10%))
- Growth retardation
- Carcinogenesis
88
What is the affected underlying biological process that causes mental retardation?
Migration of neural cells
89
What is the LD50 for oocytes?
0.5 Gy
Mnemonic: 50 / **OO**cytes
90
What are the dose limits to the eyes (lenses) and skin of radiation workers?
- Eye (lenses):
-- ICRP: 20 mSv / yr (avg. over 5 yrs, w/ no year > 50 mSv)
-- NCRP: 50 mSv
- Any other organ: 500 mSv / yr
91
What is the tissue weighting factor?
The proportion of the risk for stochastic effects resulting from uniform, whole-body irradiation
92
What is the committed effective dose?
Effective dose integrated over 50 years (radionuclides)
93
What is the committed equivalent dose?
Equivalent dose integrated over 50 years (radionuclides)
94
What is the collective dose?
The sum of the individual dose equivalents received over a defined time period by an irradiated population
95
What is the percentage risk for fatal cancers per Sv?
5%
96
Do radiation-induced cancers occur within our outside the radiation field?
Both!
97
Do Japanese atomic bomb survivors have an increased risk of skin cancers?
No!
98
How long should males receiving significant radiation doses to the gonads for a diagnostic procedure delay conception?
3-6 mo, based on animal studies
99
What is the GSD for post-menopausal women?
0, since they cannot bear children
100
How soon after exposure to radioactive iodine should KI be given?
12-24 hrs
101
Which step do you need to take when giving radioactive iodine to a mother for thyroid cancer?
Chase it w/ non-radioactive iodine to avoid accumulation in the fetus. Radioactive iodine crosses the placenta.
102
Which CT procedure gives the highest dose to a patient?
CT Angiography
103
What are the exposure dose threshold and time of onset for early transient erythema?
- 2 Gy
- 2-24 hrs
104
What are the exposure dose threshold and time of onset of main erythema rx?
6 Gy
1.5-3 wks
105
What are the exposure dose threshold and time of onset of temporary epilation?
3 Gy
3 wks
106
What are the exposure dose threshold and time of onset of permanent epilation?
7 Gy
3 wks
107
What are the exposure dose threshold and time of onset of dry desquamation?
14 Gy
4 wks
108
What are the exposure dose threshold and time of onset of moist desquamation?
18 Gy
4 wks
109
What are the exposure dose threshold and time of onset of secondary ulceration?
24 Gy
8-10 wks
110
What are the exposure dose threshold and time of onset of late erythema?
15 Gy
8-10 wks
111
What are the exposure dose threshold and time of onset of ischemic dermal necrosis?
18 Gy
> 10 wks
112
What are the exposure dose threshold and time of onset of dermal atrophy (1st phase)?
10 Gy
> 12 wks
113
What are the exposure dose threshold and time of onset of dermal atrophy (2nd phase)?
10 Gy
> 52 wks
114
What are the exposure dose threshold and time of onset of telangiectasis?
10 Gy
> 52 wks
115
What are the exposure dose threshold and time of onset of delayed necrosis
12
> 52 wks (related to trauma)
116
What are the exposure dose threshold and time of onset of skin cancer?
Dose: unknown
Time: >15 yrs
117
What is the dose range for loss of sperm production?
3.5 Gy - 8 Gy
118
What are the dose limits to the eyes and skin of the general population?
Eyes (lenses): 15 mSv / yr
Any other organ: 50 mSv / yr
119
How long should females receiving significant radiation dose to the gonads for a diagnostic procedure delay conception?
Unknown, unlike males
120
What is the dose threshold for radiation-induced cataracts?
0.5 Gy
121
How is the latent period of cataractogenesis related to dose?
Inversely
Greater the dose, the shorter the latent period
122
Radiation causes cataracts in which part of the lens?
Posterior subcapsular region
123
Which stage of gestation has the highest radiosensitivity?
Preimplantaion: 0.05-0.15 Gy
124
What is the radiation sensitivity of the embryonic (organogenesis) stage of gestation?
1 Gy results in 100% malformations
125
What percentage of secondary cancers are attributable to radiation?
3.4-9%
126
What is the weighting factor for photons and electrons?
1
127
What is the weighting factor for protons and charged pions?
2
128
What is the weighting factor for alpha particles, fission fragments, and heavy ions?
20
129
What is the radiation weighting factor for neutrons?
Continuous curve based on neutron energy, ranging between 2-20
130
How many tracks per dose limit?
5 mSv - 1 track/yr
50 mSv - 10 tracks/yr
131
How many tracks per dose during a single CT scan?
1-50 tracks/CT scan
132
How many tracks per Gy?
1 Gy → 1000 tracks
133
How were the dose limits established (calculated)?
- The NRCP looked at the trends in fatal accidents for employees of different industries
- They extrapolated the risk to radiation workers from the AVERAGE number of fatal accidents across all industries
134
Can you exceed recommended radiation doses for life-saving purposes?
- Yes, w/ several caveats
- Dose: 0.5 - 5 Sv or Gy
- Radioprotective equipment required
- Must be an emergency responder
- Must be considered a once-in-a-lifetime exposure
135
Where do we store our radioactive waste?
- A salt mine (WIPP site) in Carlsbad, New Mexico
- Chosen because any accident would bury the waste in salt
136
What's the estimated maximum organ dose for a mammogram?
2-4 mGy
137
What's the estimated maximum organ dose for a PET scan?
55-80 mGy
138
What's the estimated maximum organ dose for a chest CT scan?
20-30 mGy
139
What's the estimated maximum organ dose for a Head CT?
30-50 mGy
140
What's the estimated maximum organ dose for an abdominal CT?
22-60 mGy
141
What's the estimated maximum organ dose for a full-body CT?
50-100 mGy
142
What's the estimated maximum organ dose for a barium contrast GI procedure?
10-22 mGy
143
What's the estimated maximum organ dose for cardiac catheterization?
12-40 mGy
144
What's the estimated maximum organ dose for the Transjugular intrahepatic portosystemic shunt (TIPS) procedure?
400-1400 mGy
145
What's the estimated maximum organ dose for chest XR?
0.14 mGy
146
What's the estimated maximum organ dose for a dental panoramic XR?
0.7 mGy
147
What is the estimated maximum organ dose for an L-S Spine XR?
2-3 mGy
148
A uranium mine worker was likely exposed to which radioactive source, and what cancer are they most at risk for?
Uranium-238 → Radium-228 → Radion-224
Radon decays quickly, releasing an α particle, which can accumulate in the lungs and cause cancer.
149
What's the average dose from an orthogonal kV image?
0.2-1 cGy
150
What's the average dose from an orthogonal MV image?
1-2 cGy
151
What's the dose from a kV CBCT?
1-2 cGy
152
What's the dose from a cardiac catheterization?
1-4 cGy
153
What's the dose from a diagnostic CT?
3-10 cGy
154
How much does an OBGYN XR exam increase the risk fo childhood cancer?
40%
155
What's the threshold radiation dose after which there is an increased risk of detecting a subsequent childhood cancer?
- 10 mGy
- 1 cGy
1**c**Gy → **c**hildhood cancer
156
What is radiation exposure during the third trimester linked to?
Increased risk of carcinogenesis later in life
157
Which areas in the world receive the highest doses of natural background radiation?
- Ramsar, Iran (260 mSv/yr)
- Kerala, India (13 mSv/yr)
- Coastal Brazil (5 mSv/yr)
- Burgundy, France (3.5 mSv/yr)
...
- Denver, CO (0.5 mSv/yr)
158
What's the rate of congenital abnormalities worldwide?
5-10%
