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International Atomic Energy Agency
RADIATION PROTECTION INNUCLEAR MEDICINE
Part 1: Biological effects ofionizing radiation
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Nuclear Medicine Part 1. Biological effects of ionizing radiation2
OBJECTIVE
To become familiar with the mechanisms of different
types of biological effects following exposure to
ionizing radiation and results of epidemiological
studies of exposed population to ionizing radiation. Tobe aware of the models used to derive risk coefficients
for estimating the detriment
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CONTENT
Basic concepts, cellular effects Deterministic effects Stochastic effects Effects on embryo and fetus Risk estimates
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International Atomic Energy Agency
Part 1. Biological effects
Module 1.1. Basic concepts
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1895 X-rays discovered by Roentgen
1896 First skin burns reported
1896 First use of x-rays in the treatment of cancer
1896 Becquerel: Discovery of radioactivity 1897 First cases of skin damage reported
1902 First report of x-ray induced cancer
1911 First report of leukaemia in humans and lung
cancer from occupational exposure
1911 94 cases of tumour reported in Germany (50
being radiologists)
Early Observations of the Effects of
Ionizing Radiation
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Information comes from: studies of humans (epidemiology)
studies of animals and plants (experimental
radiobiology)
fundamental studies of cells and their components
(cellular and molecular biology)
The key to understanding the health effects of
radiation is the interaction between these sources of
information.
Effects of Radiation Exposure
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Chromosomes
Radiation exposure affects the center
of life: the cell
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The critical target: DNA
I t ti f i i i di ti
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Interaction of ionizing radiation
with DNA
DIRECT ACTION INDIRECT ACTION
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Damage to DNA
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radiation
hit cell
nucleus!
No change
DNA mutation
Exposure of the cell
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DNA Mutation
Cell survives
but mutated
Cancer?
Cell death
Mutation
repaired
Unviable Cell
Viable Cell
Outcomes after cell exposure
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How is DNA
repaired?
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Altered base
Enzyme Glycosylases recognizeslesion and releases damaged base
AP-endunucleasemakes incisionand releases remaining sugar
DNA-polymerasefillsresulting gapbut nick remains
DNA ligase seals the nick. Repair
completed.DNA has been repaired with no
loss of genetic information
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Repair
The human body contains about 1014 cells. An
absorbed dose of 1 mGy per year (natural sources)
will produce about 1016 ionizations, which means
100 per cell in the body. If we assume that the
mass of DNA is 1% of the mass of the cell, the result
will be one ionization in the DNA-molecule in every
cell in the body each year.
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order of magnitudes
999 of 1000 lesions are repaired 999 of 1000 damaged cells die (not a major
problem as millions of cells die every day
in every person)
many cells may live with damage (could bemutated)
C ll killi
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Cell killingRadiosensitivity
RS = Probability of a cell, tissueor organ of suffering an effect per
unit of dose.
Bergonie and Tribondeau (1906):RS LAWS: RS will be greater ifthe cell:
Is highly mitotic.
Is undifferentiated.
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RADIOSENSITIVITY
High RS Medium RS Low RS
Bone Marrow
Spleen
Thymus
Lymphatic
nodes
Gonads
Eye lensLymphocytes(exception to the RS
laws)
Skin
Mesoderm
organs (liver,
heart, lungs)
Muscle
Bones
Nervous system
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Biological effects at cellular level
Possible mechanismsof cell death:
Physical death
Functional death Death duringinterphase
Mitotic delay
Reproductive failure
Cellular effects of ionizing radiation
are studied bycell survival curves
%s
urvivalcells(semilog
arithmic)
Dose
n = targets
Dq
D0
(threshold)
(radiosensitivity)
100%
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Physical LET (linear energy transfer): RS Dose rate: RS Temperature RS
Chemical Increase RS: OXYGEN, cytotoxic
drugs. Decrease RS: SULFURE (cys,
cysteamine)
Biological Cycle status:
RS: G2, M RS: S Repair of damage (sub-lethal
damage may be repaired e.g.fractionated dose)
G1
S
G2
M
G0
LET LET%s
urvivorcells
Factors affecting radiosensitivity
CELL SURVIVAL
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.....
.....
.............
Lg LET
Hg LETlow LET
high LEThigh LET
low LET
Absorbed dose
Surviving fraction
LET (linear energy transfer) is the amount of energy (MeV) a particle will loose
in traversing
a certain distance (m) of a material.
CELL SURVIVALRadiation quality
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Adapted from Marco Zaider (2000)
IONIZATION PATTERN
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Direct
effects
Indirect
effects
Cell death
Primary
damage
Modifiedcell
Damage
to organ
Somatic
cells
Germ
cells
Hereditary
effects
Cancer
Leukemia
Death of
organism
Repair
Deterministic
effects
Stochastic
effects
BIOLOGICAL EFFECTS
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10-6
10-12
10-9
10-15
10-3
1 second
1 hour
1 day
1 year
100 years
1 ms
100
109
106
103
Energy deposition
Excitation/ionization
Initial particle tracks
Radical formation
PHYSICAL INTERACTIONS
PHYSICO-CHEMICAL INTERACTIONS
BIOLOGICAL RESPONSE
MEDICAL EFFECTS
Diffusion, chemical reactions
Initial DNA damage
DNA breaks / base damage
Repair processes
Damage fixation
Cell killing
Promotion/completion
Teratogenesis
Cancer
Hereditary defects
Proliferation of "damaged" cellsMutations/transformations/aberrations
TIME(sec)
Timing of events leading to radiation effects
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International Atomic Energy Agency
Part 1. Biological effects
Module 1.2. Deterministic effects
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EFFECTS OF CELL DEATH
Dose(mSv)
Probability of death
D
100%
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0
1
2
3
4
5
6
7
8
9
10
FREQUENCY
ABSORBED DOSE
SEVERITY
Diagnostic
threshold
Threshold
dose
Most radiosensitive
individualMost radioresistant
individual
Deterministic effects
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Cataracts of the lens of the eye 2-10 Gy
Permanent sterility
males 3.5-6 Gy females 2.5-6 Gy
Temporary sterility
males 0.15 Gy females 0.6 Gy dose
Severity of
effect
threshold
Threshold Doses for Deterministic Effects
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Note on threshold values
Depend on dose delivery mode: single high dose most effective fractionation increases threshold dose in
most cases significantly decreasing the dose rate increases threshold
in most cases
Threshold may differ in different persons
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Systemic effects
Effects may be morphological and/or functional
Factors: Which Organ Which Dose
Effects Immediate (usually reversible): < 6 months e.g.:
inflammation, bleeding. Delayed (usually irreversible): > 6 months e.g.: atrophy,sclerosis, fibrosis.
Criteria of dose < 1 Gy: LOW DOSE
1-10 Gy: MODERATE DOSE > 10 Gy: HIGH DOSE Regeneration means replacement by the original tissue while
Repair means replacement by connective tissue.
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Skin effects Following the RS laws
(Bergonie and Tribondeau), themost RS cells are those fromthe basal stratum of theepidermis.
Effects are:
Erythema: 1-24 hours afterirradiation of about 3-5 Gy Alopecia: 5 Gy is reversible; 20 Gy
is irreversible.
Pigmentation: Reversible, appears8 days after irradiation.
Dry or moist desquamation:traduces epidermal hypoplasia(dose about 20 Gy).
Delayed effects: teleangiectasia,fibrosis.
DERMIS
EPIDERMIS
Histologic view of the skin
Basal stratum cells, highly
mitotic, some of them with
melanin, responsible of
pigmentation.
From Atlas de Histologia.... J. Boya
Skin effects
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Skin effects
Injury ThresholdDose to
Skin (Sv)
Weeks toOnset
Early transient erythema 2 52
Moist desquamation 15 4
Late erythema 15 6-10
Dermal necrosis 18 >10
Secondary ulceration 20 >6
Skin damage
from prolonged
fluoroscopicexposure
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SKIN EFFECTS
By handling unshielded syringes and vials containing
radioactive material the threshold dose of skin erythema
will be reached in a short time.
Example: The dose rate at the surface of a vial
containing 30 GBq Tc99m is of the order of 2 Gy/hmeaning that the threshold dose will be reached after
2 h of exposure. This corresponds to 36 s per working
day in a year
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SKIN EFFECTS
ExampleAfter an extravascular injection of 500 MBq of a Tc99m
radiopharmaceutical, the locally absorbed dose at the
injection site might be as high as 5-20 Gy!
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Effects in eye
Eye lens is highly RS. Coagulation of proteinsoccur with doses greater
than 2 Gy.
There are 2 basic effects:
From Atlas de Histologia.... J.Boya
Histologic view of eye:
Eye lens is highly RS, moreover, it
is surrounded by highly RS cuboid
cells.
> 0.155.0
Visualimpairment
(cataract)
> 0.10.5-2.0Detectable
opacities
Sv/year for
many years
Sv single
brief
exposure
Effect
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Eye injuries
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Whole body response : adult
Acute irradiation syndrome
Chronic
irradiation
syndrome
Dose
Steps:
1. Prodromic
2. Latency
3. Manifestation
Lethal dose 50 / 30
BMS
(bone
marrow)
GIS
(gastrointestinal) CNS
(central nervous
system)
1-10 Gy
10-50 Gy
> 50 Gy
Whole body clinic
of a partial-body
irradiation
Mechanism:
Neurovegetative
disorder
Similar to a sick
feeling
Quite frequent in
fractionated
radiotherapy
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Lethal dose 50 / 30
It is an expression of the per centlethal dose as a function of time.
It means: Dose which wouldcause death to 50% of thepopulation in 30 days.
Its value is about 2-3 Gy forhumans for whole body irradiation.
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Whole body exposure
Absorbed dose
(Gy)
Syndrome or
tissue involved
Symptoms
1-10 Bone marrow
syndrome
Leucopenia,
thrombopenia,
hemorrhage,
infections
10-50 Gastrointestinal Diarrhoea,
fever,
electrolytic
imbalance
>50 Central nervous
syndrome
Cramps,
tremor, ataxia,
lethargy,
impaired
vision, coma
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Whole body exposure
Absorbeddose (Gy)
Therapy Prognosis
1-10 Symptomatic
Transfusions of
leucocytes andplatelets. Bone
marrow
transplantation
Growth stimu-
lating factors
Excellent to
uncertain
10-50 Palliative Very poor
>50 Symptomatic Hopeless
Lethality
0-90%
90-100%
100%
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International Atomic Energy Agency
Part 1. Biological effects
Module 1.3. Stochastic effects
STOCHASTIC EFFECTS OF IONIZING
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STOCHASTIC EFFECTS OF IONIZINGRADIATION
STOCHASTIC EFFECTS OF IONIZING
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STOCHASTIC EFFECTS OF IONIZINGRADIATION
Health consequencesof Chernobyl accident
1800 children diagnosedwith thyroid cancer (1998)
STOCHASTIC EFFECTS OF IONIZING
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STOCHASTIC EFFECTS OF IONIZINGRADIATION
Thyroid cancer diagnosed up to 1998 amongchildren 0-17 years at the time of the Chernobyl
accident
0
50
100
150
200
250
300
1990 1991 1992 1993 1994 1995 1996 1997 1998
Year
Number Belarus
Russian Federation
Ukraine
Total
G ti ff t
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Frequency (%)
10 20 30 40
Absorbed dose (Gy)
10
5
0
Genetic effects
G ff
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Genetic Effects
Ionising radiation is known to cause heritablemutations in many plants and animals
BUT
intensive studies of 70,000 offspring of theatomic bomb survivors have failed to identify
an increase in congenital anomalies, cancer,
chromosome aberrations in circulating
lymphocytes or mutational blood protein
changes.
Neel et al. Am. J. Hum. Genet. 1990, 46:1053-1072
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Part 1. Biological effects
Module 1.4. Effects on embryo and fetus
S iti it f th l t
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Sensitivity of the early conceptus
Till early 1980s, early conceptus wasconsidered to be very sensitive to radiation -although no one knew how sensitive?
Realization that: organogenesis starts 3-5 weeks after conception In the period before organogenesis high radiation
exposure may lead to failure to implant. Low dose
may not have any observable effect.
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Incidence of
Prenatal &
Neonatal Death
andAbnormalities
Hall, Radiobiology for
the Radiologist pg 365
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PRE-IMPLANTATION
P i l t t ( t 10 d )
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Pre-implant stage (up to 10 days)
Only lethal effect, all or none
Embryo contains only few cells which are
not specialized
If too many cell are damaged-embryo is
resorbed If only few killed-remaining pluripotent
cells replace the cells loss within few cell
divisions
Atomic Bomb survivors - high incidence
of both - normal birth and spontaneous
abortion
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Fetal Radiation Risk
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Fetal Radiation Risk
There are radiation-related risks throughoutpregnancy which are related to the stage ofpregnancy and absorbed dose
Radiation risks are most significant during
organogenesis and in the early fetal periodsomewhat less in the 2nd trimester and
least in the third trimester
Less LeastMost
risk
Radiation Induced Malformations
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Radiation-Induced Malformations
Malformations have a threshold of 100-200mGy or higherand are typically associatedwith central nervous system problems
Fetal doses of 100 mGy are not reachedeven with 3 pelvic CT scans or 20
conventional diagnostic x-rayexaminations
These levels can be reached withfluoroscopically guided interventional
procedures of the pelvis and withradiotherapy
C t l N S t Eff t
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Central Nervous System Effects
During 8-25 weeks post-conception theCNS is particularly sensitive to radiation Fetal doses in excess of 100 mGy can
result in some reduction of IQ (intelligence
quotient)
Fetal doses in the range of 1000 mGy canresult in severe mental retardation
particularly during 8-15 weeks and to alesser extent at 16-25 weeks
H t t i tt ( ) th t i l
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Heterotopic gray matter (arrows) near the ventricles
in a mentally retarded individual occurring as a
result of high dose in-utero radiation exposure
Effects on embryo and fetus
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Effects on embryo and fetus
Effects on embryo and fetus
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Age Threshold for
lethal effects(mGy)
Threshold for
malformations(mGy)
1 day 100 No effect
14 days 250 -
18 days 500 250
20 days >500 250
50 days >1000 500
50 days to
birth
>1000 >500
Effects on embryo and fetus
Leukemia and Cancer
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Leukemia and Cancer
Radiation has been shown to increasethe risk for leukemia and many types ofcancer in adults and children
Throughout most of pregnancy, theembryo/fetus is assumed to be at aboutthe same risk for carcinogenic effects as
children
Leukemia and Cancer
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Leukemia and Cancer
The relative risk may be as high as 1.4(40% increase over normal incidence)due to a fetal dose of 10 mGy
Individual risk, however, is small with therisk of cancer at ages 0-15 being about 1excess cancer death per 1,700 children
exposed in utero to 10 mGy
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International Atomic Energy Agency
Part 1. Biological effects
Module 1.5. Risk estimates
Ri k E ti t
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Risk Estimates
Risk = probability of effect Different effects can be looked at - one
needs to carefully look at what effect is
considered: E.g. Thyroid cancer mortalityis NOT identical to thyroid cancer
incidence!!!!
Risk estimates usually obtained from highdoses and extrapolated to low doses
EPIDEMIOLOGICAL DATA FROM:
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Hiroshima-Nagasaki
Patients with
ancylosing spondylitis
cervical cancer
tuberculosis
mastitis
tinea capitis
thymus enlargement
thyrotoxicosis
hemangiomas
and more may come
ChernobylTecha river
Semiplatinsk
Nevada
..
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Populations used in the UNSCEAR Reports
Characteristic Atomic BombSurvivors SpondylitisSeries Cervical CancerSeries
Number 86,500 14,000 83,000
Age at irradiation 0 -> 90 > 15 < 30 -> 70
Averagefollow-up
28.8 y 23.0 y 7.6 y
Mean dose 0.24 Gy 1.9 Gy Inhomogeneous
Range of doses 0.01 6.0 Gy 0 8.06 Gy
Type ofirradiation
Instantaneous /whole-body
Fractionated /partial-body
Chronic /partial-body
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How to use epidemiological data
to estimate radiation risks at low
doses?
Dose-response curve
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Dose-response curve
Frequency of leukemia (cases/1 miljon)
Equivalent dose (mSv)
Mortality of the Atomic Bomb
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ySurvivors
Dose response curve for Solid Cancer The dose response is linear up to about 3 Sv
with a slope of 0.37 ERR/Sv
The excess lifetime risk per Sv for thoseexposed at age 30 is estimated at 0.10 and0.14 for males and females respectively
The lowest dose at which there is astatistically significant excess risk is shownto be 50 mSv
Pierce DA et al, Rad Res 1996; 146:1-27
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Latest news from the Hiroshima-Nagasaki cohort
Extra years 1986-1990
There are now 10 500 survivors with DS86-dosimetry out of a total population
of 86 572, who were irradiated
44% had died by the end of 1990. The data is incomplete in that deaths in the
first five years are not included. 7 827 have died from cancer, there being 420excess cancer deaths.
1945-1950 1950-90 (1986-90)
Leukemia ? 87 (3)
Solid cancer ? 335 (88)
-------------------------------------------------------------------
420
Risk for children/Risk for adults = 1.4 - 1.7
RADIATION RISKS
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RADIATION RISKS
0 1 2 3 4 5 6 7 8 910
ABSORBED DOSE
P
ROBABILITYOFFATALCANC
Observations
Deterministic effects
Linear-quadratic model
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What happens at the low-dose end of the graph?
a) Linear extrapolation
b) Threshold dose
c) Lower risk per
dose for low doses
d) Higher risk per dose
for for low doses
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Low doses:
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Epidemiological Evidence
1
10
100
1000
10000
0.1 1 10 100 1000 10000
Dose (mGy)
Cancerdeaths/year/1Mp
eople
natural cancermortality
additional cancerdeaths due to radiation
Linear No-Threshold (LNT)
Hypothesis reduced at low
dose and dose rate by a
factor of 2 - in general
agreement with data
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CANCER
initiation
pre-cancer stage
promotion
growth
detection
metastasis
Elimination and repair
latency period
period ofsuffering
death
lifetime loss
Carcinogenic Effects
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Carcinogenic Effects
An assessment of the atomic bomb survivors showed:
the leukaemia risk peaked at 10 years after exposure
thyroid cancer was the first solid cancer reported
the incidence of breast cancer was higher in youngwomen than older women
other cancer, with a latent period of up to 30 years,included lung, stomach, colon, bladder and oesophagus
Shimizu et al JAMA 1990, 264:601-604
Variation of Cancer Incidence with time following the
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Variation of Cancer Incidence with time following theAtomic Bombs
Variation of Cancer
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Variation of CancerIncidence with timefollowing theAtomic Bombs
Time projection models
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ICRP 60
p j
Lifetime Expression, Comparison ofAbsolute and Relative Risk Models
Absolute Risk Relative Risk
Incidence Incidence
0 xo xo+l 90 0 xo xo+l 90
Incidence after
irradiation
Spontaneous
incidence
RADIATION RISKS
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RADIATION RISKS
Effect Population Exposure
period
Probability
Hereditary
effects
Whole
population
Lifetime 1 %/Sv
(all
generations)
Fatal cancer Whole
population
Lifetime 5 %/Sv
Fatal cancer Working
population
Age 18-65 4 %/Sv
Healthdetriment Wholepopulation Lifetime 7.3 %/Sv
Health
detriment
Working
population
Age 18-65 5.6 %/Sv
Risk (%/ Sv) for Cancer inductionby Age at exposure and Sex
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0 10 20 30 40 50 60 70 80
(age at exposure)
20
15
10
5
0
Male
Female
by Age at exposure and Sex
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UNSCEAR has recently (2000) further assessed the
cancer risk from radiation exposures.
For a population of all ages and both genders, the life-
time risk of dying from radiation induced cancer after an
acute dose of 1000 mSv is about 9% for men and 13%
for women or 11% as a mean. Applying a DDREF of 2,
these data confirm the 10 years old ICRP estimate.
Life-time risk of dying from radiation
induced cancer = 5% per sievert
EFFECTS AT LOW DOSES
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In the latest Hiroshima-Nagasaki Life Span Study (1986-
1990), LSS Report 12, (Pierce et al., 1996) find the
nominal estimates of risk (5% per Sv) to apply down to a
dose of about 50 mSv.
For childhood cancer following fetal irradiation, verysimilar risk estimates (6% per Sv) are found to apply to
doses of 10 mSv (Doll and Wakeford, 1997).
The risk estimates and the uncertainties associated withthem are expected to apply at low doses.
Uncertainties in fatal cancer risk estimate
(5% per Sv)
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NCRP, 1997
Probability distribution of lifetime risk coefficient. The 90%
confidence interval is shown by the arrows (5% should be read
as 1% - 9%).
(5% per Sv)
Lifetime Risk Coefficient (%/Sv)
0.00
1.20
2.75 5.50 8.25
8.84
11.0
0.000
0.007
0.013
0.020
0.027
Frequency chart 100 000 Trials Shown
Probability
Uncertainties in fatal cancer risk estimates
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Sensitivity chart of uncertainty component influence (population of all ages)
From NCRP, 1997
Radiation risks - embryo and fetus
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Threshold dose
deterministic effects 50-100 mSv
Mental retardation 40% / Sv
Cancer and leukemia
before 10 y of age 2% / Sv
lifetime 15% / Sv
Hereditary effects 1% / Sv
TYPES OF EFFECTS FOLLOWING IRRADIATION INUTERO
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Time after Effect Normal incidence
conception in live-born
First three weeks No deterministic or stochastic -
effects in live-born child
3rd through 8th Potential for malformation of 0.06weeks organsa (1 in 17)
8th through 25th Potential for severe mental 5 x 10-3
weeks retardationb (1 in 200)
4th week throughout Cancer in childhood or in adult 1 x 10-3
pregnancy lifec (1 in 1000)
a Deterministic effect. Threshold ~ 0.1 Gyb 30 IQ units shift: 8-15th week;
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Radiation risks
embryo and fetus
Dose
(mGy)
Lethal effects
malformations
Mental
retardation
Cancer &
leukemia before 10years
Cancer &
leukemia wholelife
1 none -> 1*10-4
4*10-4
5*10-5
1.5*10-4
10 none -> 1*10-3
4*10-3
5*10-4
1.5*10-3
50 none -> 5*10-3
2*10-2
2.5*10-3
7.5*10-3
100 none -> 1*10-2
4*10-2
5*10-3
1.5*10-2
Other reasons 3*10-3 4*10-2 7*10-3 1*10-3 0.2
Data from Sweden 1992
Risks in a pregnant population not exposed tomedical radiation
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medical radiation
Spontaneous abortion > 15%
incidence of genetic abnormalities 4-10%
intrauterine growth retardation 4%
incidence of major malformation 2-4%
Probability of bearing healthy children as a function of
radiation dose
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radiation dose
Dose to conceptus(mGy) above naturalbackground
Probability ofno malformation
Probability of nocancer
(0-19 years)
0 97 99.7
1 97 99.7
5 97 99.7
10 97 99.6
50 97 99.4
100 97 99.1
>100 possible, see text higher
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Approximate fetal whole body dose (mGy) from common nuclear
medicine procedures done in early and late pregnancy
Procedure Activity (MBq) Early 9 months
Tc-99m
Bone scanLung V/Q scan
Liver colloid
Thyroid scan
Renal DTPA
Red Cell
750240
300
400
750
930
4.70.9
0.6
4.4
9.0
6.0
1.80.9
1.1
3.7
3.5
2.5
I-123 thyroid uptake 30 0.6 0.3
I-131 thyroid uptake 0.55 0.04 0.15
Doses and Risks for in Utero Radiodiagnostics
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g
Exposure Mean foetal dose Hered. Disease Fatal cancer
(mGy) to age 14 yX-ray
Abdomen 2.6 6.2 10-5 7.7 10-5
Barium enema 16 3.9 10-4 4.8 10-4
Barium meal 2.8 6.7 10-5 8.4 10-5
IV urography 3.2 7.7 10-5 9.6 10-5Lumbar spine 3.2 7.6 10-5 9.5 10-5
Pelvis 1.7 4.0 10-5 5.1 10-5
Computed tomography
Abdomen 8.0 1.9 10-4 2.4 10-4
Lumbar spine 2.4 5.7 10-5 7.1 10-5Pelvis 25 6.1 10-4 7.7 10-4
Nuclear medicine
Tc bone scan 3.3 7.9 10-4 1.0 10-4
Tc brain scan 4.3 1.0 10-5 1.3 10-4
Comment on Fetus/Embryo
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y
Fetus/embryo is more sensitive to ionizingradiation than the adult human
Increased incidence of spontaneous abortion afew days after conception
Increased incidence Mental retardation Microcephaly (small head size) especially 8-15 weeks
after conception
Malformations: skeletal, stunted growth, genital
Higher risk of cancer (esp. leukemia) Both in childhood and later life
Scale of Radiation Exposures
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1
10
100
1000
10000
0.1 1 10 100 1000 10000
Dose (mGy)
Cancerdeaths/year/1Mp
eople
natural cancermortality
additional cancerdeaths due to radiation
AnnualBackground
CT scan
Bone scanTypical
RadiotherapyFraction
Example for Risk Calculation
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Assume Risk of 0.05 per Sv 1,000 people are exposed to 5 mSv/y for 20 y Expected additional cancer deaths is
0.05 [cancers/Sv]x0.005[Sv/y]x20[y]x1,000[people]= 5 additional cancer deaths due to radiation(5/1000)
General population: 23% (230/1000) of alldeaths due to cancer (difficult to ascertain 5additional ones caused by radiation)
Calculations become more complex forindividual tissue exposures vs. whole body
exposures
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Examination Skin dose Effective dose Risk
(mGy) (mGy) (%)
Urography 30 8 0.04
Lumbar spine 40 5 0.025
Abdomen 10 2.5 0.013
Chest 2 0.25 0.0013
Extremities 3 0.025 0.00013
RADIATION RISKS IN
X-RAY EXAMINATIONS
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Examination Radiopharmaceutical Effective dose Risk
(mSv) (%)
Myocardium Tl-201 chloride 23 0.12
Bone Tc-99m MDP 3.6 0.018
Thyroid Tc-99m pertechnetate 1.1 0.006
Lungs Tc-99m MAA 0.9 0.005
Kidney clearance Cr-51 EDTA 0.01 0.00005
RADIATION RISKS IN
NUCLEAR MEDICINE
Average Annual Risk of Death in the UK from
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Average Annual Risk of Death in the UK from
Industrial Accidents and from Cancers due to
Radiation Work
Coal mining 1 in 7,000
Oil and gas extraction 1 in 8,000
Construction 1 in 16,000
Radiation work (1.5 mSv/y) 1 in 17,000Metal manufacture 1 in 34,000
All manufacture 1 in 90,000
Chemical production 1 in 100,000
All services 1 in 220,000
From L Collins 2000
These figures can be compared to an estimate of 1 in 17000 for 1.5 mSv/year received by
radiation workers
Comparison of Radiation Worker Risks to
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Comparison of Radiation Worker Risks to
Other Workers
Mean death rate 1989
(10-6/y)
Trade 40
Manufacture 60Service 40
Government 90
Transport/utilities 240
Construction 320
Agriculture 400
Mines/quarries 430
Safe industries 2 mSv/y (100 mSv over
a lifetime)
max permissible exposure(20 mSv/year or 1000 mSvover a lifetime
RISKS
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The following activities are associated witha risk of death that is 1/1000000
10 days work in a nuclear medicine department
smoking 1.4 cigarette
living 2 days in a polluted city
traveling 6 min in a canoe
1.5 min mountaineering
traveling 480 km in a car
traveling 1600 km in an airplane
living 2 months together with a smoker drinking 30 cans of diet soda
RISKS
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Expected reduction of life
Unmarried man 3500 days
Smoking man 2250 days
Unmarried woman 1600 days30% overweight 1300 days
Cancer 980 days
Construction work 300 days
Car accident 207 days
Accident at home 95 daysAdministrative work 30 days
Radiological examination 6 days
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Questions??
DISCUSSION
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A woman was referred to a bone scan.After the examination she turned out to
be pregnant at a very early stage. She is
extremely worried and wants to have an
abortion. Discuss how to act.
DISCUSSION
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Dose fractionation results in: increased radiation sensitivity forphotons?
decreased radiation sensitivity forphotons?
decreased radiation sensitivity for heavycharged particles?
increased radiation sensitivity for heavycharged particles?
DISCUSSION
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A patient (radiobiologist) wants to knowthe radiation risk he will suffer in an
examination of the cerebral blood flow
(1000 MBq 99mTc).
What to answer?
Where to Get More Information
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Other sessions Part 2 Radiation Physics
Further readings WHO/IAEA. Manual on Radiation Protection in
Hospital and General Practice. Volume 1. Basicrequirements (draft manuscript)
ICRP publications (41, 60, 84) UNSCEAR reports ALPEN E.L Radiation Biophysics. Academic Press,
1998 RUSSEL, J.G.B., Diagnostic radiation, pregnancy
and termination, Br. J. Radiol. 62 733 (1989) 92-3.