rpnm part01 biological effects web

7/27/2019 RPNM Part01 Biological Effects WEB

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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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Contents

Basic concepts, cellular effects Deterministic effects Stochastic effects Effects on embryo and fetus Risk estimates


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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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Radiation exposure affects

the center of life:

the cell

Chromosomes
http://www.viewimages.com/AltaVistaView.asp?imageid=240870&promotionid=1&partnerid=2&type=resultshttp://www.viewimages.com/AltaVistaView.asp?imageid=240870&promotionid=1&partnerid=2&type=resultshttp://www.viewimages.com/AltaVistaView.asp?imageid=240870&promotionid=1&partnerid=2&type=resultshttp://www.viewimages.com/AltaVistaView.asp?imageid=240870&promotionid=1&partnerid=2&type=results


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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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Nuclear Medicine Part 1. Biological effects of ionizing radiation 13

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 Glycosylasesrecognizes

lesion and releases damaged base

AP-endunucleasemakes incision

and releases remaining sugar

DNA-polymerasefillsresulting gap

but nick remains

DNA ligaseseals 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 bycel l surv ival curves

%s

urvivalcells(sem

ilog

ar

ithm

ic)

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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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 0.5 Gy

[ICRP statement on tissue reactions(http://www.icrp.org/docs/icrp%20stateme

nt%20on%20tissue%20reactions.pdf)]

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
http://www.icrp.org/docs/icrp%20statement%20on%20tissue%20reactions.pdfhttp://www.icrp.org/docs/icrp%20statement%20on%20tissue%20reactions.pdfhttp://www.icrp.org/docs/icrp%20statement%20on%20tissue%20reactions.pdfhttp://www.icrp.org/docs/icrp%20statement%20on%20tissue%20reactions.pdf


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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 reversib le): < 6 months e.g.:

inflammation, bleeding. Delayed (usually i r reversib le): > 6 months e.g.: atrophy,sclerosis, fibrosis.

Criteria of dose < 1 Gy: LOW DOSE

1-10 Gy: MODERATE DOSE > 10 Gy: HIGH DOSE Regenerationmeans replacement by the original tissue while

Repairmeans 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

Threshold

Dose to

Skin (Sv)

Weeks to

OnsetEarly transient erythema 2 52

Moist desquamation 15 4

Late erythema 15 6-10Dermal 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

Example:

After 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 proteinsoccurs 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)

> 0.10.5-2.0

Detectable

opacities

Sv/year for

many years

Sv single brief

exposure

Effect

The ICRP has stated in 2011 that the threshold for tissue reactions in lens of the eye is 0.5 Gy.

http://www.icrp.org/docs/icrp%20statement%20on%20tissue%20reactions.pdf
http://www.icrp.org/docs/icrp%20statement%20on%20tissue%20reactions.pdfhttp://www.icrp.org/docs/icrp%20statement%20on%20tissue%20reactions.pdf


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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 the

populat ion in 30days.

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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Module 1.3. Stochastic Effects

St h ti Eff t f I i i R di ti


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Stochatic Effects of Ionizing Radiation


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St h ti Eff t f I i i R di ti


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Stochatic Effects of Ionizing Radiation

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 Eff 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

Ionizing 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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Module 1.4. Effects on Embryo and Fetus

S iti it f th E l C 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 St ( 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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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


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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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:


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p g

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


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Variation of Cancer


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Variation of CancerIncidence with timefollowing theAtomic Bombs

Time Projection Models


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ICRP 60

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 RisksEffect Population Exposure

period

Probability

ICRP 1990

Probability

ICRP 2007

Hereditaryeffects

Wholepopulation

Lifetime 1 %/Sv(all

generations)

0.2 %/Sv(all

generations)

Fatal

cancer

Whole

population

Lifetime 5 %/Sv -

Fatalcancer

Workingpopulation

Age 18-65 4 %/Sv -

Health

detriment

Whole

population

Lifetime 7.3 %/Sv 5.7 %/Sv

Health

detriment

Working

population

Age 18-65 5.6 %/Sv 4.2 %/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 (2008) 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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Nuclear Medicine Part 1. Biological effects of ionizing radiation

82

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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83

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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84

Sensitivity chart of uncertainty component influence (population of all ages)

From NCRP, 1997

Radiation Risks - Embryo and Fetus


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Nuclear MedicinePart 1. Biological effects of ionizing radiation

85

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 IN

UTERO


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86

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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87

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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88

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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89

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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Doses and Risks for in Utero Radiodiagnostics


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91

g

Exposure Mean fetal 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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92

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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93

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

Annua l

Background

CT scan

Bone scanTypical

Radiotherapy

Fract ion

Example for Risk Calculation


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94

Assume Risk of 0.05 per Sv 1,000 people are exposed to 5 mSv/y for 20 y Expected additional cancer deaths is0.05 [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 bodyexposures


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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 Examination


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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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Nuclear Medicine

Part 1. Biological effects of ionizing radiation

100

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

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.

rpnm part01 biological effects web

Documents