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Early and Late Radiation Effects

Learning Unit 4 Presentation
by

Brad Johnson

on 27 November 2017

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Transcript of Early and Late Radiation Effects

Early & Late Radiation Effects
Factors that Influence Response
Quantity
LET/RBE
Amt of body exposed
Specific body parts exposed
Somatic
Early Deterministic Somatic

Late Somatic
ARS
Acute Radiation Syndrome
affects individual
appear within minutes, hours, days, or weeks
not usually of concern in diagnostic imaging
4 Stages
Human observations
Forms
prodromal
latent
manifest illness
death or recovery
large, whole body dose over short period of time
Chernobyl - Nuclear Power Plant Accident
April 26, 1986
cesium-137, iodine-131, plutonium-239
2 died instantly, 29 died within 3 months
203 hospitalized for ARS
Hiroshima & Nagasaki - Atomic Bombing
Marshal Islanders
Radiation Therapy Patients
Hematopoietic Syndrome
(Bone Marrow Syndrome)
Gastrointestinal Syndrome
Cerebrovascular Syndrome
Dose: 1-10 Gy
Symptoms: p. 146
Death: 6-8 wks
Recovery: 3 wks- 6 mos
occurs within hours after receiving a dose of 1 Gy (100 rads) or more
symptoms include; NVD, fatigue, leukopenia
severity is dose dependent
last for a few hours to a few days
lasts for approx 1 week
no visible symptoms
symptoms become visible
Dose: 6-10 Gy
Symptoms: p. 146
Death: 3-10 days
Recovery: none
Dose: 50 Gy and above
Symptoms: p. 146
Death: hours to 3 days
Recovery: none
Late Deterministic Somatic

Late Stochastic Somatic
(Probalistic)
appear months or years after exposure
occur after high dose & low dose
severity of biologic damage directly related to dose
existence of a threshold
occurs months or years after high-level exposure
not likely to occur from diagnostic imaging procedures
cataractogenesis
probability proportional to dose
no threshold
occur after high-level and possibly after low-level exposure
opacity of the lens of the eye
Research comes from:
Japanese atomic bomb survivors
Nuclear physicists
Rad therapy patients
threshold, nonlinear response
2 Gy
Hiroshima
August 6, 1945
equivalent of 20,000 tons of TNT
Instantly killed 70,000
Instantly injured 70,000
1950 total deaths=200,000
Nagasaki
August 9, 1945
equivalent of 21,000 tons of TNT
Instantly killed 40,000
Instantly injured 60,000
1950 total death toll=140,000
location of 66 atomic bomb tests from 1946-1958
Bikini Atoll
March 1, 1954
U.S. detonated a 15 megaton atomic bomb (1000x greater than Hiroshima)
carcinogenesis
embryologic effects
(birth defects)
risks
radiation induced cancer
Low-level Dose
High Dose
No evidence that low-level doses less than 0.1 Sv significantly increase risk of malignancy.
www.radtechstudy.org
prior to 1940 - slightly higher risk of death from cancer
after 1940 - no evidence of elevated risk
absolute vs. relative risk models
estimates to predict cancer incidence in exposed populations
absolute: predicts a specific number of excess cancers
relative: predicts a percentage increase of excess cancers
epidemiologic studies
suggests that benefit far outways risk in diagnostic radiology
Japanese atomic bomb survivors - 5% increase in excess fatal cancers per Sv
Human evidence for high dose radiation induced cancers
radium watch dial painters (1920s-1930s)
workers ingested large quantities of radium
5 Gy or more
cancers included; bone, throat, sinus, head
uranium miners (1950s-1960s)
inhaled radon, drank radioactive water
10 Sv or more
lung cancer
affected families as well
early medical radiation workers (1896-1910)
1 Gy/year
cancerous skin lesions, blood disorders
patients injected with Thorotrast (1925-1945)
used in angiography
15-20 yr latent period
cancers included; liver, spleen, biliary duct
infants treated for enlarged thymus gland (1940s-1950s)
treated with 1.2-60 Gy of x-radiation
20 yr latent period
cancers included; thyroid
Japanese atomic bomb survivors
Leukemia
linear, nonthreshold
1 Gy or more
significant increase in incidence
occurs approx 2 yrs post exposure
highest risk 7-10 yrs post exposre
declines to almost zero 30 yrs post exposure
Breast Cancer
studies indicate a relative risk of 4:1 to 10:1
radiation not highly effective cancer-causing agent
82,000 surviors from 1950-1978
0.14 Sv
expected 4500 cancer deaths, 4750 occurred
Chernobyl
135,000 people evacuated within 10 mile radius
24,000 received 0.45 Sv
111,000 received 0.03-0.06 Sv
estimated that 20 countries received fallout
approximately 400,000 people received some exposure
Thyroid Cancer
10-20 yr latent period
increased dramatically among children in Belarus, Ukraine, & Russia
1996 - 700 cases
1998 - 1700 cases
Human evidence for low-level radiation induced cancers
Difficult to identify
Radiation induced cancer not distinguishable from natuarlly occuring cancer
# of cancers developed from radiation is small compared to natural occurence
May take 5 yrs or more to develop
Stages of Gestation
1. preimplantation: 0-9 days
2. organogenesis: 10 days to 6 weeks
3. fetal stage: 6 weeks to term
First trimester (1-3 mos)
extremely radiosensitive due to # of stem cells
preimplantation: 0.05-0.15 Gy = death
organogenesis: sensitive to radiation induced congenital abnormalites (i.e., growth inhibition, intellectual disabilities, microcephaly)
Second & Third trimesters (4-9 mos)
less sensitive to radiation
risk still exists for congenital abnormalities
some studies indicate higher cancer & leukemia deaths
Japaneses studies have not demonstrated significant rates of cancer or leukemia deaths
Chernobyl Data
2000 pregnant women among the 135,000 evacuees
exposed to 0.43 Sv (430 mSv )
300 babies born by Aug 1987 - no abnormalities
Ministry of Health in Ukraine 1986-1990
increase # of miscarriages, premature births, stillbirths
3x increase in rate of deformities & developmental abnormalities
Fetal Effects
United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR)
0.3% increased risk for every 10 mSv of fetal dose
6% normal risk
Low-level Radiation
documentation of effects is insufficient
exercise caution
most diagnostic procedures result in a dose of less than 0.01 Sv
not considered to be dangerous to embryo-fetus
Genetic
affects future generations
Natural Spontaneous Mutations
random
genetic disorder present in 10% of births in U.S.

Mutagens - increase the frequency of genetic mutations
elevated temperatures
ionizing radiation
viruses
chemicals
Dominant vs. Recessive
radiation believed to cause recessive mutations, if any
dominant: probably expressed in offspring
recessive: probably not expressed for several generations
Fruit Flies & Mice
high doses extrapolated to low doses
genetic effects are nonthreshold
Humans
contraindictory and inconclusive
Japanese - 3rd generation, no known genetic effects
2001, UNSCEAR - no radiation-induced genetic diseases demonstrated
Chernobyl - indicate increase in abnormalities
no evidence of genetic effects in diagnostic imaging personnel or their patients
Doubling Dose
dose that causes # of spontaneous mutations to double (i.e., 7% to 14%)
humans: 1.56 Sv (1560 mSv)
End
Reference: Statkiewicz-Sherer MA, Visconti PJ, Ritenour ER, Haynes KW. Radiation Protection in Medical Radiography.
http://www.bt.cdc.gov/radiation/arsphysicianfactsheet.asp
http://www.bt.cdc.gov/radiation/ars.asp
http://news.nationalgeographic.com/news/2006/04/0425_060425_chernobyl.html
http://www.chxa.com/img/bone-marrow-structure.gif
http://www.nlm.nih.gov/medlineplus/ency/images/ency/fullsize/17115.jpg
http://3.bp.blogspot.com/_4o85VqhQqmc/TFgqkN44YHI/AAAAAAAABAQ/wCV4xs7ua9k/s640/zombie.jpg
http://embryology.med.unsw.edu.au/wwwhuman/Stages/Images/Cst800.jpg
http://www.seewithlasik.com/docs/cataract_surgery.shtml
http://healthguide.howstuffworks.com/cataracts-in-depth.htm
http://erbc.vassar.edu/erbc/media_and_info/index.html
50,000 - 500,000 chest x-rays
(.00002 Gy bone marrow dose)
300,000 - 500,000 chest x-rays
(.00002 Gy bone marrow dose)
2.5 million chest x-rays
(.00002 Gy bone marrow dose)
Early deterministic somatic effects are of great concern in diagnostic imaging.

A. True
B. False
What period of ARS may be mistaken for recovery?

a. prodromal
b. latent
c. manifest
d. death or recovery
What syndrome will likely occur to a person exposed to a whole body dose of 5 Gy?

a. bone marrow syndrome
b. GI syndrome
c. cerebrovascular syndrome
Medical intervention can assist with recovery from which syndrome?

a. bone marrow syndrome
b. GI syndrome
c. cerebrovascular syndrome
no such thing as a "100% safe" gonad dose
www.xrayrisk.com
Lethal Dose (LD)
LD 50/30
(50% in 30 days)
LD 50/60
(50% in 60 days)
3 - 4 Gy
May be more accurate in humans
some may live past 30, but not past 60
Medical intervention may delay inevitable
Dose info table 8-2 p.166
Repair + Repopulation = Recovery
repair enzymes allow surviving cells to repopulate
repeated radiation has cumuulative effect
10% irrepairable
90% repairable
protraction vs. fractionation
continuous dose @ low rate
same dose rate, broken into equal portions @ regular intervals
Example:
6 Gy @ 2 Gy/min = death
Protraction:
6 Gy @ 0.01 Gy/min = survival
(3 minutes)
(600 minutes)
Example:
6 Gy @ 2 Gy/min = death
Fractionation
6 Gy total
2 Gy/min
12 equal fractions of 0.5 Gy
separated by 24 hrs
survival
Local Tissue Damage
Skin
composed of 3 layers
2% of body's surface replaced daily
2 Gy
induced in 24-48 hrs
shedding of outer layers termed desquamation
High-level Fluoroscopy
100 - 200 mGy/min
How do you avoid this?
Epidemiology: science that deals with the incidence, distribution, and control of disease in a population
Radiation Dose-Response Relationships
Goal=establish relationships between radiation and dose-response
-use information to predict the risk of cancer

threshold vs. nonthreshold
Risk Model used to predict:
Cancer Risk and Genetic Damage
Risk Model used to predict:
Leukemia, BRCA, Heritable Damage
Risk Model used to predict:
High-dose Cellular Response
https://rpop.iaea.org/RPOP/RPoP/Content/InformationFor/HealthProfessionals/5_InterventionalCardiology/skin-injuries.htm
2 View Chest x-ray = 0.1 mSv
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