Ppt. on Radiation Hazards by Dr. Brajesh K. Ben

RADIATION HAZARDS

Presented by – Dr. Brajesh Ben, JR 1Moderator – Dr. Shailesh kumar Singh ,MD

Asstt. Professor

RADIATION BASICS

Radiation – Energy in transit:– electromagnetic waves (gamma-γ or x-ray), or – high speed particles ( alpha-α, beta-β, neutron-η, etc.)

Ionizing Radiation – Radiation with sufficient energy to remove electrons during interaction with an atom, causing it to become charged or ionized– Can be produced by spontaneous radioactive decay or by

accelerating charged particles across an electric potential (eg x-rays)

Incoming photon

Ejected electron

Photon

Positive Ion

Ionization

Photon

Incoming photon

Excited electron Excitation

IONISATION• Ionization is another process where the radiations interact

with matter to form ions; • High-energy electromagnetic radiation and particle

radiation are capable of producing ions in their passage through matter.

• Types of ionizing radiation include alpha and beta particles, X-Rays, gamma rays, etc. X-Ray machines and Radioisotopes are the two important and potential sources of ionizing radiation.

CLASSIFICATION OF IONISING RADIATION

IONIZING VS NON-IONIZING• Ionizing radiation has high energy and displaces

electrons from their orbits creating charged atoms (ions)/molecules– Creates DNA damage– Outright cell death– Bystander effect– Genomic instability

• Non-ionizing radiation creates heat due to low energy e.g. infrared, MRI

TYPES OF IONIZING RADIATION

Alpha

Beta

Gama and x rays

Neutron (dose dependent)

Paper Plastic Lead Concrete

Helium nucleus (2 protons, 2 neutrons ): +2 charge

Electron: +1 or – 1 charge

Photon: 0 charge

Neutron: 0 charge

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• The unit rad (radiation absorbed dose) is used as the unit of absorbed dose following exposure to any type of ionizing radiation. One rad is equal to the radiation necessary to deposit energy of 100 ergs in 1 g of irradiated material (100ergs/g).

• The radiation dose is measured in terms of Roentgen, - It is the quantity of X-Rays or gamma radiation which produces one electrostatic unit in one C.C. of dry air after its ionization at 0 degree centigrade and 760 mm Hg pressure..

RADIATION ABSORBED DOSE

RADIATION ABSORBED DOSE

• This is a measure of the amount of energy absorbed from the radiation beam per unit mass of tissue.

Units of measurement:• SI unit : Gray, (Gy) measured in joules/kg• original unit : rad, measured in ergs/gm• 1 Gray = 100 rad

WEIGHING FACTOR (W)

• Measures the radiosensitivity, i.e. the risk of the tissue being damaged by radiation.

• The higher the damage, the higher is W

EQUIVALENT DOSE

• A measure which allows comparison between different types of radiation in regard to their absorbed doses in the body (RBE radiobiological effectiveness)

• Unit of measurement (SI unit) : Sievert (Sv)• subunits : millisievert (mSv) ( 1/1 000Sv) : microsievert ( µSv) ( 1/1 000 000)• original unit : rem• 1 Sievert = 100 rem

EFFECTIVE DOSE

• IT IS THE TISSUE WEIGHTED SUM OF THE EQUIVALENT DOSE IN ALL SPECIFIED TISSUES AND ORGAN OF THE HUMAN BODY AND REPRESENTS THE STOCHASTIC HEALTH RISK TO THE WHOLE BODY WHICH IS THE PROBABILITY OF CANCER INDUCTION AND GENETICS EFFECTS OF LOW LEVELS OF IONISING RADIATION.

• EFFECTIVE DOSE =ABSORBED DOSE x WR

Effective doses in different diagnostic proceduresDiagnostic procedure

Typical effective dose (mSv)

No. of chest X rays leading to comparable exposures

Chest X ray 0.02 1-

Extremities 0.01 0.5

Skull 0.07 3.5

Thoracic and vertebrae

0.7 35

Lumbar vertebrae 1.3 65

Hip 0.3 15

Pelvis 0.7 35

Effective doses in different diagnostic proceduresDiagnostic procedure

Typical effective dose (mSv)

No. of chest X rays leading to comparable exposures

Mammography 0.5 25

IVU 2.5 125

Head CT 2.3 115

Chest CT 8 00

Abdomen & Pelvis CT

10 500

PET 7.2 360

Abdomen 1.0 50

DOSE LIMITS (ATOMIC ENERGY REGULATORY COMITTEE)

Doses Occupational workers Apprentices and trainees

For public

Effective dose 20mSv (for 5 consecutive years) - -

Effective dose 30mSv 6mSv 1mSv

Equivalent dose (lens)

150mSv 50mSv 15mSv

Equivalent dose(extremities)

500mSV 150mSv -

Equivalent dose (skin)

500mSv 150mSv 50mSv

Equivalent dose(embryo & fetus)

1mSv - -

Radiation Weighting Factors for various types of radiations

Types of radiation Radiation Weighting Factors

X ray, gamma, beta and electrons

1

Protons 2

Neutrons (energy dependent) 2.5-20

Alpha particles and other multiple – charged particles

20

Tissue weighing factor assigned by the international commission on radiological protection

Organ / tissue W1 % of total determinant

Gonads 0.08 8Bladder 0.04

16Esophagus 0.04

Liver 0.04

Thyroid 0.04



Breast 0.12

72

Bone marrow 0.12

Colon 0.12

Lung 0.12

Stomach 0.12

Remainder 0.12



Bone surface 0.01

4Brain 0.01

Salivary glands 0.01

Skin 0.01

Total 1.0 100

What is ‘radiation’?-Electromagnetic energy-Spectrum

SOURCES OF RADIATION

• Natural background radiation- cosmic rays - gamma rays from rocks & soil 87%- ingested radioisotopes in certain foods- radon decay products (granite )• Artificial background radiation- fallout from nuclear explosions > 1% - radioactive waste • Medical and dental diagnostic radiation 12% • Occupational exposure > 1%

RADON

• Produced from radium in decay chain of uranium

• Escapes into air – short lived decay products emit alpha particles – stick to dust, inhaled, deposit in lung – high but localised radiation

• Second most important cause lung cancer

BIOLOGICAL EFFECTS OF RADIATON

• Deterministic effects (>100mSv)– Threshold– Increased dose = increased damage

• Stochastic (probabilistic) effects (no safe threshold)– Increased dose = increased probability of damage

but not severity

After exposure to a high radiation dose, humans can experience a response within a few days to a few weeks called deterministic effect and such early effects are deterministic because the severity of response is dose related.

Stochastic Effect :

• are the result of low doses delivered over a long period.•Radiation exposures experienced by personnel in diagnostic imaging are low dose and low linear energy transfer (LET) delivered intermittently over long periods.

Deterministic Effect

IRRADIATION

Prodromal (0-48hrs)

Latent (hrs-21d) Manifest Illness (hrs-30d)

Death/Recovery (hrs-60+d)

Anorexia Prodromata absent or diminished

Vascular Damage With Increase dose first three phases shorten in time.

Nausea InfectionVomiting Bone marrow

depressionDiarrhea LeukopeniaFever Thrombocytopenia

Lymphopenia GI SymptomsGranulocytosis

ACUTE RADIATION SYNDROMEGastro Intestinal System• food intake Poor Nutrition• absorption• Diarrhoea Fluid Loss• Ulceration• Electrolyte LossHematopoietic System • lymphocytes • granulocytes Infection• Platelets • Erythrocytes Haemorrhage

• Anaemia• • Anoxia • • More resistant tissues damage

VASCULAR SYSTEM• Capillary permeability • Vascular fragility Fluid Loss

• Obstruction of vessels Electrolyte Loss

• • Hemorrhage• • Anemia

• Anoxia

Damage to more resistant tissues

BIOLOGICAL EFFECTS

Ind irec t D irec t

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N o e f fec t on o f fsp ring

G ene ticD o no t a f fec t in d iv idu ia l

O ffspr in g is a f fec ted

R ad ia tion d am ag e

RADIATION HAZARDSDirect damage.

Radiation

• DNA /RNA molecule nuclear acid breakdown • Nuclear acid breakdown Somatic cells Radiation induced malignancy Genetic cells Radiation induced congenital abnormality

• INDIRECT EFFECTS• 80% of the biological tissue is water • Most of the incident radiation energy is absorbed by the

water molecules• It is broken into very unstable H and OH radicals which then

react with body molecules and cause the cell damage. • subsequent to many series of reactions hydrogen peroxide is

formed which is highly reactive oxidizing compound and break chemical bonds in macromolecules of the body such as proteins, lipids and other nucleic acids etc causing cellular damage, cell death and mutations.

• The biological effects are enhanced by the presence of oxygen which is always present in the cells.

1. Radiation decomposition i.e. splitting of water into H+ and OH- and also splitting of other solvents of the body.

2. kinetic energy of the incident photons heats up the molecules of the living tissues

3. Incident radiation when traveling through the body tissues knock out the bound electrons free from their parent atoms or molecules. These free electrons are highly unstable and interact with other atoms and molecules within the irradiated system.

DELAYED SOMATIC EFFECTS

1. Cancer: solid tumors– Increased risk– Latency period: 10+ yr

2. Cancer: leukemia– Increased risk– Latency period: 5+ yr

3. Degenerative effects (LSS, not sure at low doses)– Life shortening (not sure)– Heart disease, stroke; digestive, respiratory, haemopoietic

systems

CANCER RISKS

• Increased risk of cancer mortality about half those :• Solid cancer deaths: about 1 in 20,000Infancy 3-4x

increased risk cf 20-50y.

• Female infants 2x risk of male infants.

• Female risk of cancer is 37.5% greater than males– 50% greater risk of solid tumours– Less risk leukaemia.

FETAL RADIATION RISK

• There are radiation-related risks throughout pregnancy that are related to the stage of pregnancy and absorbed dose.

• Radiation risks are most significant during organogenesis and in the early fetal period, somewhat less in 2nd trimester, and least in 3rd trimester.

•

Less LeastMost risk

FETAL GROWTH

• No significant impact on fetal growth and development < 50 mGy

• Fetal growth retardation > 200 mGy

• Childhood cancer, growth retardation and abnormality of nervous system > 1 Gy

• Pre-implantation- Either fetal death or fetal risk

• Organogenesis- Death decreases but congenital malformation of various organ system may occur.

Spermatogonia- Most sensitive leading to reduced infertility.

Temporary sterility and permanent sterility. (Azoospermia) – Acute exposure 500mGy to 6Gy.

Recovery beginning-1year for 1 Gy for temporary sterility and 3-5 years for 2Gy.

REPRODUCTIVE ORGAN

SKINAcute Radiation - Reduction and impairment of functional stemcells, endothelial cells and epidermal cells via apoptosis and necrosis > 1Gy.

Epilation – Can occur in 3 weeks after exposure to 3-6Gy.Regrowth beginning after 2 months and gets completed within 6-12 months.

Reepithelialization – Within 6-8 weeks and healing with atrophic, hypo or hyper pigmentation. Which might get infected after physical trauma in future.

LEUKEMIAThe relative risk may be as high as 1.4 (40% increase over normal incidence) due to a fetal dose of 10 mSv.

For an individual exposed in utero to 10 mSv, the absolute risk of cancer at ages 0-15 is about 1 excess cancer death per 1,700.

Leukemia (with exception of CLL and viral induced Leukemia.Detected 1 to 2 years after exposure with a maximum 12 years of peak time after exposure.Youngest affected more.

THYROID CANCER

• Most common- Well differentiated Papillary Adenocarcinoma.

• Most common in women than men (2-3 times) because of hormonal influence.

• Lower percentage of follicular form.

• Time taken for malignancy, from 10-35 years.

• Through internally radio nuclides it is 60%-100% causing Thyroid Cancer ( I-131, I-125)

GASTRO INTESTINAL

• GI Syndrome-10-50Gy

• Normally GI cells are replaced in 3-5days.

• Radiation Exposure kills the most sensitive cells, stem cells.

• Intestinal lining is completely denuded of functional cells, fluid pass uncontrollably across the intestinal membrane, electrolyte balance is destroyed and conditions promote infections.

• Cells most sensitive to radiation during mitosis (M phase)and G2 phase (Pre mitosis or RNA synthesis).

• cells are least sensitive to radiation during S-phase (DNA synthesis).

• Cell transformation behave as a cancer cell.• The x ray energy used in the diagnostic radiology

varies from 25 to 125 KVp. They deposit these energy in a very small volume and are sufficient to produce ionization inside the human body.

Types of DNA damage

• Single and double strand breaks. • Damage in sugar and base• Denaturation(sepration of the two strands).• DNA-DNA cross links.• DNA protein cross links.• These damage can lead to-• Slow down cell synthesis,delay in repair will delay cell cycle

progression,cell proliferation,death of the cell and mutation of the cell.

TOP FIVE DISASTER DUE TO RADIATION1-Atomic Bombings of Hiroshima and Nagasaki – World War II, 1945

2-Fukushima Disaster – March 11, 2011

TOP FIVE DISASTER DUE TO RADIATION3-Chernobyl Disaster – April 26, 1986

4-Mayak Nuclear Plant – September 29, 1957

TOP FIVE DISASTER DUE TO RADIATION

5-Soviet Submarine K-431 Accident –August 10, 1985

Q1. Prodromal period appears with radiation dose delivered to the whole body is:

• A) more than 1 Gy• B) less than 1Gy• C) more than 0.5Gy• D) less than 0.5Gy

Ans : A) more than 1 Gy [Bushong 10th edi, pg-505 yr 2013

• Q2. During interaction of radiation with tissue, the electrons transfer their kinetic energy to their environment via ;

• A) Ionization and thermal heating• B) Excitation and ionization• C) Thermal heating and excitation • D) All of the above

Ans : D) [bushberg, pg-752.] 3rd edi 2012

• Q3. Most radio sensitive cell? • A. spermatogonia.• B. lymphocytes• C. oocytes• D. hair follicles

Ans A (Bushberg 3rd edi , pg769 yr 2012)

• Q4) The gastro intestinal syndrome is induced by a total body absorbed dose of :

• A) more than 100 Gy of gamma rays• B) more than 10 Gy of gamma rays• C) 3-8 Gy of gamma rays• D) 8-10 Gy of gamma rays

Ans : B [Bushong 10th edi, pg-506 yr 2013]

• Q5. The most sensitive stage for lethal effects of radiation is :A) Pre implantation

• B) Early organogenesis• C) Late organogenesis• D) The fetal period

Ans : A) [Bushberg 3rd edi, pg-831 yr 2012]

• Q6. Recommendation of therapeutic abortion for fetal doses in diagnostic imaging, regardless of gestational age would be:

• A.< 25 mGy• B.< 50mGy• C.< 75mGy• D. >100mGy

Ans D Bushberg 3rd edi pg 826 yr 2012]

Q7. The main effects on children irradiated in utero in Hiroshima and Nagasaki are:

A.Fetal loss and mental retardationB. Infant mortality and microcephalyC. Microcephaly and mental retardationD. Growth retardation and teratogenesis

Ans C Bushberg 3rd edi pg 829 yr 2012

• Q8. Radiation induced teratogenesis effects are less common in human than in animals because of the following, except:

• A. Development of the CNS in humans takes place over a much longer gestational intervals.

• B. Small fraction of the gestational period is taken up by organogenesis

• C. Some anomalies may have more than one critical period• D. The response of each organ to the induction of radiation

induced malformation is not unique.

Ans D (Bushberg 3rd edi, pg 824 2012)

Q9.Permanent sterility for radiation exposure in human is:A.1-2 GyB.2-3 GyC.4-5 GyD.5-6 Gy

Ans D (Bushong 10th edi, pg 510 yr 2013)

• Q10. All of following are true except: A. Thyroid cancer accounts for only approx. 2% of the yearly total cancer incidence.

B. Well differentiated follicular carcinoma is commonC. More common in women than menD.I -123 and Tc 99m are equally effective ( per unit thyroid

dose) as external radiation in causing thyroid cancer.

Ans Q10: B(Bushberg 3rd edi, , pg 818)

Ppt. on Radiation Hazards by Dr. Brajesh K. Ben

Health & Medicine

Transcript of Ppt. on Radiation Hazards by Dr. Brajesh K. Ben