Radiation biology and protection

For radiology and medical imaging department Students

Course plan and objectivesCourse plan and objectives

RSMI 352: RSMI 352: Radiation biology and protection, 2 Credits (2+0+0)Radiation biology and protection, 2 Credits (2+0+0) Prerequisites:Prerequisites: RSMI 244, CAMS 234. RSMI 244, CAMS 234.

Course outlinesCourse outlines Types of radiation and sources of our data on radiation Types of radiation and sources of our data on radiation

effects.effects. Dose response characteristics.Dose response characteristics. The direct and indirect action of radiation.The direct and indirect action of radiation. Radiation effects of tissue, bone, whole body.Radiation effects of tissue, bone, whole body. Radiation syndromes.Radiation syndromes. Acute and delayed effects of radiation.Acute and delayed effects of radiation. Radiation protection.Radiation protection.

Medical imaging physics fourth edition Medical imaging physics fourth edition William R. Hendee and E. RussellWilliam R. Hendee and E. Russell

The Essential physics of medical imaging The Essential physics of medical imaging second edition Bushberg et al. 2001second edition Bushberg et al. 2001

Herman Cember & Thomas A Johnson Herman Cember & Thomas A Johnson (2008) Introduction to Health Physics, 4th (2008) Introduction to Health Physics, 4th edition, McGraw-Hill Medicaledition, McGraw-Hill Medical. .

Amr A. Abd-Elghany Student lectures notes. Amr A. Abd-Elghany Student lectures notes.

ReferencesReferences

Learning activitiesLearning activities A) Lectures: the handouts for each lecture will be available to A) Lectures: the handouts for each lecture will be available to

you on the day of the lecture.you on the day of the lecture.

B) Study requirements: B) Study requirements: 1)1) Read the assigned material before class, Read the assigned material before class, 2)2) Attend all lectures and be on time, Attend all lectures and be on time, 3)3) Take notes and highlights as advised during the lecture, Take notes and highlights as advised during the lecture, 4)4) Review your notes within 4 hours to transfer information into Review your notes within 4 hours to transfer information into

long term memory,long term memory,5)5) Reread the text within 8-12 hours and add additional Reread the text within 8-12 hours and add additional

information to notebook, information to notebook, 6)6) Become a part of the group learning discussion, Become a part of the group learning discussion, 7)7) Come to my office hours for clarification of learning Come to my office hours for clarification of learning

difficulties.difficulties.

C) Evaluation: C) Evaluation: Research project 10%Research project 10% First mid term 20% Second mid term 20%First mid term 20% Second mid term 20% Final exam 50%Final exam 50%

The cellThe biological perspective

a mitochondrion

the membrane

a cytoskeletal filament

the endoplasmic reticulum

the nucleus

the Golgi apparatus

a lysosome

Types of RadiationsTypes of Radiations

Ionizing radiationα,β,γ

Non ionizing radiationEM waves

Sources of our data on Ionizing Radiation effects:

1 )Observations on the occupational exposure of workers: e.g.

Scientists

Medical personnel

Uranium miners

Atomic energy

workers

Industrial radiographers

2 )Patients who were exposed to radiation for diagnosis and therapy.

3 )The surviving population from nuclear bombing in Japan (270,000):

They received a wide range of doses depending on their location at the time of bombing.

•At 8.15 am on 6 August 1945, United States dropped the uranium atom bomb "Little Boy" on the city of Hiroshima. It had an explosive yield of around 15,000 tons of TNT. 90,000 were killed immediately and 145,000 within months.

•Three days later on 9 August 1945 at 11.02 am, the United States dropped the plutonium atom bomb "Fat Man" on Nagasaki. The plutonium bomb had an explosive yield of 21,000 tons of TNT. 45,000 were killed immediately and 75,000 more were dead by the end of 1945.

Hiroshima aftermath:

Nagasaki aftermath:

Hiroshima

Nagasaki

Japanese were able to stand up again:

4 )People exposed to fall out of:

(a )Nuclear weapons debris (b )Accidents involving nuclear reactors

e.g. Chernobyl in 1986The mushroom cloud full of radioactive debris will spread by winds and clouds. Rainfall will transfer radioactive pollution to distant places

Chernobyl is an abandoned city in northern Ukraine, in the Kiev province near the border with Belarus.

•On April 26, 1986, the fourth reactor of the Chernobyl Nuclear Power Plant, exploded at 01:23 AM local time. The workers were performing an experiment with the reactor's safety systems during which the computer-controlled safety systems were disabled.

5 )Numerous serious accidents from sealed sources:

•After the explosion, radioactive debris were flung several miles, and smoke containing radioactive contaminants from burning graphite traveled as far as Belarus.

•All permanent residents of Chernobyl and the Zone of alienation were evacuated because radiation levels in the area had become unsafe. Contaminated milk was blamed for childhood sicknesses across Europe.

•Radioactive sources, used widely throughout the world in medicine, industry, and agriculture, if lost or improperly discarded, increase the likelihood of a serious accident.

•Example: Meet-Halfa accident (5 May-3 July 2000, Qaluobiya, Egypt )

•Type of event: lost radiography source

Description:

Casualties resulted from a radiography source brought into a household in Meet Halfa. Four sources used for checking pipes were lost in or near Abu Rawash in late April 2000; the workers who lost the sources searched unsuccessfully for them but did not report the loss to authorities

• A total of 150 to 200 neighbors and friends each incurred estimated doses between 2.5 and 15 rem. Authorities began radiation surveys in the area on 25 June and recovered the source 26 June. Authorities found three more cylinders on 3 July (one in a warehouse), a day after arresting 4 for the loss of the cylinders.

•The family of Fadl Hassan Fadl found one source on 5 May and took it home, believing it to be precious metal. The rod contained 50 curies of iridium-192 (activity was reported as 31.5 curies on 5 May and 19.3 curies on 26 June).

•The 61-year old father, Fadl Hassan Fadl, died on 16 June from a dose of 550 rad. Five others (Hassan's wife and four more of their children) suffered radiation sickness from doses between 300 and 400 rad, and 76 neighbors were treated for minor symptoms of blood changes

•On 5 June Hassan Fadl Hassan, 9 years old, died of radiation sickness from a dose of 750 rad; the diagnosis was unclear at this point, but bone marrow failure and skin inflammations were evidence. On 12 June similar symptoms appeared in other family members who were hospitalized

6 )People living in environments with high natural background radiation

The home of Meet-Halfa family. The source was placed inside the closet in the utility room .

Why do we need to study the biological effects of Radiation?

Accumulation of dose -

response data

Health physicists

become able to specify

environmental radiation

control levels

Medical, scientific, and industrial applications of nuclear technology may

continue at low risk levels compared to other technologies accepted by

the society as safe

Dose Response Characteristics:Observed radiation effects are:

Stochastic Non-StochasticEffects that occur randomly

Deterministic effects*Most biological effects

are deterministic

Characteristics of Non-Stochastic (Threshold) Effects:

A certain minimum dose

must be exceeded before a

particular effect is observed

The magnitude of the effect increases non-linearly with size of the dose

A clear causal relationship exists between exposure to the radiation

source and observed effect

For example, the intensity of sound must exceed a certain limit before ear can hear it. After this stage, the effect of sound on ear will depend on sound intensity. Finally, if the ear suffered from rupture of the ear drum, there will be no doubt that this is the result of increased sound intensity.

Examples of non-stochastic effects:

Erythema (skin reddening)

Skin and tissue burns

Cataract formation Sterility

Radiation sickness & death.

Each of these effects differs from the others in that both its threshold dose and the time over which the dose was received cause the effect (i.e. acute vs. chronic exposure).

The 50% Dose:•It is the dose to which 50% of those who are exposed responded. It is statistically the most reliable.

The LD50 Dose:• It is the 50% dose when death is the biological end-point (LD: lethal dose). Example: If 30 rates out of 60 rats died within 20 days after exposure to a dose of radiation, we refer to LD50/20 days.

•The time required for the noxious agent to act is important.

Characteristics of Stochastic (linear, zero threshold) Effects:

They occur randomly

They occur among

unexposed as well as exposed

individuals

They are not certainly

related to a noxious agent

The dose response

relationship is linear (curve B)

In Stochastic effects, no pathologist can say with certainty that cancer would have not occurred if the person has not been exposed to a carcinogen (radiation or others).

To understand Stochastic effects, consider the following smoking facts:

•Lung cancer is present in cigarette smokers than among non-smokers.

•Lung cancer is present in heavy smokers than among light smokers.

•Most cigarette smokers do not develop lung cancer, while some non-smokers develop this disease.

Conclusion:

Even heavy smoking dose not ensure that the smoker will develop lung cancer; it merely increases the likelihood of developing the disease.

Examples of stochastic effects:

Carcinogenesis Mutagenesis

Initiated by damaging the chromosomes of a somatic cell.

Results from damage to the information stored in the chromosomes of a germ cell (a sperm or an ovum).

Since there is a zero threshold for stochastic effects, the smallest carcinogen or mutagen (e.g. single x-ray photon) can produce the effect if the photon should happen to interact with the appropriate base pair in DNA molecule.

The chemical structure of DNA:

The direct action:•It is the radiation effects at which ionizing radiation damage the biological molecule directly by ionization and excitation followed by the consequent dissociation of a molecule.

Example:

•Knowing that the LD50/30 day for a man = 4 Gy (400 rad), 1 Gy corresponds to energy absorption = 1J/kg or 6.25 x 1018 eV/kg and 34 eV produces a single ionization, then:

•The lethal dose produces the following amount of ionized atoms per kg:

kgatomsionizedioneV

GykgeVGy/1035.7

/34

1025.64 171118

Knowing that about 9 atoms are excited for each one ionized atom, we find that 7.35 x 1018 atoms/kg of tissue are directly affected by a lethal dose.

In soft tissue, there are about 9.5 x 1025 atoms/kg, thus the fraction of directly affected atoms is:

725

18

10105.9

1035.7 This means that only one atom is affected for

each 10 million atoms.

Point mutation:

It is an example of direct effect, in which mutation is due to a change in a single gene locus.

b) In a genetic cell

The information in the mutant cell is transferred to the next generation.

a) In Somatic cell

The information in the mutant cell is transferred only to the daughter cell.

Radiation dose due to point mutation:•For biological effects of radiation which depend on point mutation, the radiation dose is cumulative (every little dose may result in a change in the gene burden [load]).

•Reliable experimental data show that there is no genetic effect due to direct action of radiation in the range 0 up to 250 mGy (25 rad). i.e., the probability of occurrence of genetic changes in this region of doses is very little.

The indirect action:•It is the radiation effects caused indirectly by the production of free radicals and hydrogen peroxide in water of body fluids.

Free radicals: “are fragment of a compound or an element that contains unpaired electron which occupies an orbit by itself. They can be neutral or charged.”

Harmful free radicals are toxic molecules of oxygen that damage every area of our bodies. One free radical can initiate tens of thousands of chain reactions that cause tremendous harm (destroy cell membranes, disrupt crucial processes in the body, reprogram DNA, form mutant cells, etc. )

Interaction of radiation with water:•Most of the direct action of radiation is on water.

•The result of energy absorption by water is the production of highly reactive free radicals.

•These free radicals are highly toxic and may exert their toxicity on other molecules.

•Depending on the amount of energy transferred to the electron, the molecule can undergo:

Ionization (threshold in water ~

13 eV)

Excitation (threshold in

water ~ 7.4 eV)

Thermal transfer(vibration

, rotation & translation)

A dose of 104 Gy would be necessary before the thermal effects (a few degrees centigrade) became large enough to affect cellular biochemistry.

Initial Physical Events:The result of absorption of radiation by water in body fluids is the production of highly reactive free radicals that are highly toxic and may exert their toxicity on other molecules.

•Direct ionization of water produces a radical ion and a free sub excitation electron (E < 7.4 eV):

•Energy transfer can also produce a water molecule in an excited state:

The time scale for the creation of these species is on the order of 10-16 seconds.

•The electron is captured by water through dipolar interactions, becoming solvated, and referred to as an aqueous electron or a solvated electron surrounded by a cage of water:

Or it can react with H+ to form a radical.

• The radical ion of water can dissociate to produce a hydroxyl radical and a hydrogen ion.

• The excited water molecule can dissipate excess energy by bond breakage to produce hydroxyl and hydrogen radicals.

•In the last few steps we notice that, the three initial species: H2O*,

H2O·+ and e¯, react further to produce chemically reactive species:

HO·, H·, and , e-eq.

•These radicals are much more reactive than HO¯ or H+ from ionic dissociation of water

Oxidation: the loss of electrons. The electrons are transferred to the oxidizing agent, which becomes reduced.

Reduction: the addition of electrons. May involve the addition of electron only, or the addition of hydrogen together with an electron.

HO· is a powerful oxidizing agent, very reactive chemically.

After ~10-12 sec, the chemically reactive species HO·, H·, and , e¯eq are still located in the vicinity of the original H2O*, H2O·+ and e¯ species that caused their creation.

•These species now begin to migrate randomly about their initial positions. As this diffusion proceeds, individual pairs may come close enough together to react with each other.

A variety of reactions are possible :

•Most of these reactions remove chemically reactive species from the system.

•With time (by ~ 10-6

sec) all of the reactive species have diffused sufficiently far that further reactions are unlikely.

The Problem of produced Hydrogen Peroxide:

Except for hydrogen peroxide, most of the products of irradiation in water have very short lifetimes (microseconds). Hydrogen peroxide being a relatively stable compound and powerful oxidizing agent, persists long enough to diffuse points remote from point of origin. It can thus affect molecules which did not suffer from radiation damage directly.

G values represent the number of molecules altered per 100eV. These values vary based on the type of free radical.

Number of molecules damaged 100eV of Energy Absorbed

G =

The G Value:PRODUCPRODUC

TTG valueG value

HH..0.60.6

HH220.40.4

HH22OO220.70.7

Solvated Solvated ee--

2.62.6

HOHO..2.62.6

Radiation Effects on Organs and Tissues:

Acute (prompt) Effects:

•These are effects due to overexposure of the whole body of healthy adults to high dose of radiation within short periods of time.

•These effects will develop within hours, days or weeks, depending on the size of the dose. The larger the dose, the sooner a given effect will occur.

1. Common Effects:

Nausea

Vomiting

Fatigue

Increased Temperature

Blood changes

Death

(Adapted from NCRP Report No. 98 "Guidance on Radiation Received in Space Activities, NCRP, Bethesda, MD (1989)) * The LD50/60 is that dose at which 50%of the exposed population will die within 60 days.

Thresholds for Common Effects :

Remember:

•1Gy = 100 rad, 1 rem = 1 rad x QF, 1Sv = 100 rem

•The standard international unit is Gray (Gy) for Absorbed Dose and Sievert (Sv) for dose equivalent.

2. Hemopoietic Syndrome:

Syndrome: is a collection of signs and symptoms characteristic of a given disease state.

Hemopoietic syndrome:•Radiation effects are mainly on the blood-forming tissue.

•This tissue is very sensitive due to the presence of the highly undifferentiated stem cells (from which all blood cells arise).

Hemopoietic syndrome (continued):

Dose (mGy)Dose (mGy)Response on Hemopoietic Response on Hemopoietic systemsystem

140140Changes in the blood count Changes in the blood count may occur.may occur.

250-500 250-500 Changes in the blood count Changes in the blood count occurs in most cases.occurs in most cases.

Dose> 500Dose> 500Changes in the blood count Changes in the blood count are certain.are certain.

Dose > 2 GyDose > 2 GyThe hemopoietic syndrome The hemopoietic syndrome appears.appears.

Symptoms of Hemopoietic syndrome (continued):

Reticulocytes:

• They are immature red blood cells, typically composing about 1% of the red cells in the human body.

•They develop and mature in the red bone marrow and then circulate for about a day in the blood stream before developing into mature red blood cells.

•Like mature red blood cells, reticulocytes do not have a cell nucleus. They are called reticulocytes because of a reticular (mesh-like) network of ribosomal RNA that becomes visible under a microscope with certain stains such as new methylene blue.

Hematocrit: (or packed cell volume; PCV)

It is the proportion of blood volume that is occupied by red blood cells. It is normally about 46% for men and 38% for women.

Lymphocyte: is a type of white blood cell which play an important role in body defence.

Platelets (thrombocytes):

They are the cells circulating in the blood that are involved in the cellular mechanisms leading to the formation of blood clots.

Symptoms of Hemopoietic syndrome (continued):

Sharp increase in the number of granulocytes.

Within a day A decrease that reaches a minimum several weeks after exposure

After a period of several weeks to several months

1. Granulocytes:

Returns to normal

2. Lymphocytes:

Drop sharply after exposure.

Remain depressed for several months

3. Red blood cells count:

Does not reflect exposure until one week after exposure.

After one week Depression in RBC count starts.

A minimum is reached after one to two months.

A slow recovery over a period of weeks.

4. Platelets count:

Falls steadily until a minimum is reached one month after exposure.

Recovery is slow and may take several months.

In all cases the degree of change in blood counts as well as the rate of change is a function of radiation dose.

5. Epilation (loss of hair)

Appears during the second or third week after exposure.

7. Death

6. Bone marrow

DoseDoseEffectEffect

a) Above 2 Gya) Above 2 GyDepression of boneDepression of bone marrow marrow (reversible).(reversible).

b) 4-6 Gyb) 4-6 GyAblation of the marrow (spontaneous Ablation of the marrow (spontaneous re-growth is possible if the victim re-growth is possible if the victim survives).survives).

c) Above 7 c) Above 7 GyGy

Irreversible ablation of bone Irreversible ablation of bone marrow (this LDmarrow (this LD50/6050/60 for most for most mammals).mammals).

Gastrointestinal (GI) syndrome:

Central Nervous System (CNS) Syndrome:

Dose:>10 Gy

Cause:Occurs as a result of destruction of intestinal epithelium + complete destruction of bone marrow.

Symptoms:

All signs and symptoms of hemopoietic syndrome are seen.

•Sever nausea, vomiting and diarrhoea begin very soon after exposure

Death is the most likely outcome within weeks after exposure.

Dose:>20 Gy

Cause:Damage of the CNS + all other organ systems in the body

Symptoms:Unconsciousness within minutes of exposure.

Death in a matter or hours or several days

Case:

•A person exposed to 44 Gy in 200 μs burst of neutrons and gamma rays.

Symptoms:

1- Disoriented for 30 seconds.1- Disoriented for 30 seconds.

2- Unconscious and in shock for 10 minutes.2- Unconscious and in shock for 10 minutes.

3- An explosive water diarrhoea after 35 3- An explosive water diarrhoea after 35 minutes.minutes. This is found to be due to the This is found to be due to the passage of large amounts of fluids into the passage of large amounts of fluids into the gastrointestinal tract.gastrointestinal tract.

4- Died after 34.5 hours afters extensive 4- Died after 34.5 hours afters extensive medical treatment.medical treatment.

After death, the neural nuclei of the victim is After death, the neural nuclei of the victim is found to be 1/3 the diameter of normal found to be 1/3 the diameter of normal unirradiated brain.unirradiated brain.

Other Acute Effects:

a) Skin:

•It is subject to radiation exposure more than any other tissue.

•It is specially sensitive to low energy x-rays and beta rays (where maximum energy is deposited in the surface, i.e. skin, e.g. diagnostic x-rays).

•An exposure of 77mC/kg (300 R [Roentgen], ~300 rad, or 3Gy), of diagnostic x-rays results in erythema (skin becomes red in color).

•Higher doses may cause:

Changes in Pigmentation

Depilation (hair loss)

Blistering (local swelling of the skin that

contains watery fluid)

Necrosis (cell death) Ulcerations

Radiation burns

b) Gonads (testes & Ovaries):

•They are highly radiosensitive.

300 mGy 300 mGy (low (low dose)dose)

Temporary sterility among men.Temporary sterility among men.

3 Gy3 GyTemporary sterility among women (no Temporary sterility among women (no menstruation). Higher doses increase the menstruation). Higher doses increase the period of sterility.period of sterility.

4.4 Gy4.4 GySeveral years of temporary sterility in a man.Several years of temporary sterility in a man.

Treatment of acute exposure:

1 -Treatment is directed towards the alleviation (making it easy to bear) of symptoms.

2 -Leucopoenia (depression of white blood cells): This symptom affect the immune system. The patient is treated with antibodies and kept in an aseptic environment (sterile) in order to prevent infection.

3 -Thrombocytopenia (low platelets count).

4 -Anaemia (decrease in red blood cells):

Results in haemorrhage because blood clotting

is affected.

Results in decrease in haemoglobin.

Treatment

Blood Transfusion

5) Severe bone marrow depression:

TreatmentBone marrow transplant

Using human granulocyte macrophage colony stimulating factor (GM-CSF)

Stimulates bone marrow to produce granulocytes after severe depression of red marrow activity.

6) Vomiting and diarrhoea:

Dehydration Electrolyte imbalance

Treatment

Fluids and electrolytes are given through diet or intravenous infusion

7) Skin Symptoms: Treatment

Topical analgesics Antiseptics AntibioticsSkin lesions may be treated surgically

Hands and Feet

Usually, they are severely over-exposed

The arterioles (very small blood vessels) that supply the extremities may continue to compensate for and build up damaged arterioles until the entire lumen of the arteriole is solidly filled (overcompensation) .

Blood supply to tissue is cut-off.Gangrene (decay of parts of body)

Affected parts of hand or feet must be amputated

Effectiveness of Medical Treatment:

Dose < 10 Gy (range of Haemopoetic syndrome)

Medical treatment is usually successful

Dose > 10 Gy (range of Gastrointestinal syndrome)

There is no effective medical treatment that may prevent death

Delayed Effects of Radiation

These are radiation effects which are observed only after several years from exposure to radiation

Single large over-exposure Continuing low-level exposure

From external radiation fields

Inhalation or ingestion of radioisotope

Fixed in body by chemical reaction with tissue proteins

Fixed in body due to chemical similarity of radioisotope with body metabolites and thus it becomes absorbed by certain organs and tissues.

In both cases, internally deposited radioisotope will keep on irradiating body tissues for a long time

Cancer:

•A total dose of 1 Gy or more has a well documented carcinogenic effect.

•The most sensitive tissues to radiation-induced cancer are:

Hemopoietic system

The Thyroid gland

The Bone

The Skin

Skin cancer was the 1st type of malignancy associated with the exposure to x-rays.

Case: early x-ray workers were not aware with the risks of x-rays. In 1900, a physician using x-rays in his practice, in 9 years period showed the following effects:

Erythema & itching

Hyper-pigmentation Ulceration neoplasia Death due to

metastasis

Cancer of Fingers:

•It was reported for dentists who used to hold x-ray films by their hands during x-ray imaging of the teeth of their patients.

•Nowadays, each patient holds his own x-ray film.

Leukaemia:

• Early radiologists using x-rays showed significantly higher incident rate of leukaemia compared to their colleagues who did not work with x-rays.

• Doses associated with increased rate of leukaemia were in the order of 1 Gy/ year

• Increased rate of leukaemia was also seen among patients who had been treated with x-rays for “rheumatoid arthritis of spinal joints”

0

10

20

30

40

50

60

1945 1950 1955 1960 1965

YearIn

cid

ence

of

of

Leu

kem

ia/1

05 p

erso

n

per

yea

r

>1500 meter

0-1500 m

Leukaemia data from survivals of nuclear bombing (Japan 1945):

•Incidence was more for those who where within 1500 m from the centre of bombing.

• The 1st incidence of leukaemia was 3 years after bombing.

•It continued to increase until it peaked at 7 years after bombing.

• The number then decreased until it reached the same value of unexposed population.

• There was an increased rate of leukaemia mortality for those exposed to 0.4 Gy or more.

No radiation-induced mortality was found among people exposed in utero to radiation from the bombs.

• A study in UK, showed that children exposed to radiation in utero during medical x-ray examinations of mother had a statistically significant higher leukaemia rate than children who had not been irradiated in utero.

Conclusions about leukaemia

Only a dose greater than 0.4 Gy may induce leukaemia

Results about induction of leukaemia at lower doses is controversial and inconclusive

Low level exposures associated with diagnostic x-ray procedures, occupational exposure within recommended limits and natural background radiation are of extremely small risk of leukaemia

Bone cancer:

After the discovery of Radium by Pierre & Marie Curie (1902), Radium was used in many industrial applications. Among these are ---

1 .Manufacture of luminous paint:

+Ra powder Zn Sα-particle

absorption

glow

•This paint was used to paint instruments and clock dials.•Women working as dial painters used to point their brush between their lips in order to paint fine lines.

In early 1920s

•Several women who worked as dial painters suffered from:

Degeneration of jaw bones &

Died from anaemia

•Further investigations on dial painters revealed more cases of bone damage:

•Radium has been established as the etiologic agent.

2. Therapeutic Radium injections

•Despite the lack of clinical evidence, radium treatments were claimed to have benefit in the treatment of a range of conditions including arthritis, gout, neuralgia (painful disorder of nerves), lumbago (lower back pain), menstrual irregularities, and obesity!

Osteogenic sarcoma

Moreover, Radium was found to be retained in the bones and can still

be detected 25-30 years after administration

e.g. Osteogenic sarcoma

Bone-seeking radioisotopes:

•In addition to Radium, Experimental work on laboratory animals revealed a number of bone-seeking radioisotopes (e.g. Strontium and Barium) that produced the same damage as Radium.

They are chemically similar to Calcium and are therefore incorporated in the chemical structure of bone

Bone-seekers are very toxic because any small amount can damage the radiosensitive bone cells and hemopoietic tissue in the bone marrow

All bone seekers produced bone cancer when injected into laboratory animals in sufficient quantity

Lung Cancer:

•In the 16th century, a large number of miners working in a location in Carpathian mountains (Romania) died from a lung disease. About 100 years ago, it was realized that it was lung cancer.

•In 1924, the radioactive Radon gas was thought to be the etiological agent responsible for very high death rate from lung cancer among miners.

High radium content in soil

Radon Gas (radioactive daughter of Ra)

Diffuses into the air of the mine

• The concentration of radon in mine air in 1924 was about 10 μCi/m3 (3.7 x 105 Bq/m3).

• The International atomic energy authority (IAEA) recommended only 103 Bq/m3.

•Although radon is a gas, its radioactive daughters are particulate in nature and attach themselves to the dust particles that are suspended in air (e.g. 218Po, 214Pb, 214Bi, 214Po).

•The Committee for the Biological Effects of Ionizing Radiation (BEIR) estimated a relative risk of 1.25-1.8 per WLM (working level month)

WLM: it is a measure of the exposure to Radon gas and its daughters.

WL: it is a measure of atmospheric concentration of radon and its progeny (daughters).

One WL: is any combination of short-lived radon daughters in One litre of air that will result in the emission of 1.3 x 105 MeV of Alpha-particle energy.

This corresponds to an atmospheric concentration of 100PCi of 222Rn per litre (3700 Bq/m3) in equilibrium with its daughters.

One WLM: is thus, the exposure resulting from the inhalation of air with a one WL concentration for a period of one working month (170h).

An exposure to one WLM results in an alpha dose to lung of One rad (0.01Gy).

Airborne radioactivity may be inhaled as:

1- Inhaled gas Uniformly distributed in lung

2- Radioactive soluble particles

dissolved in lung Absorbed into body fluids

Translocated into a tissue or organ where it is deposited

Bind to a protein in the lung

3- Relatively insoluble Radioactive particles

Upper respiratory tract

Rapidly cleared and swallowed

Remain for a long period

Deep respiratory tract

May subject lung pulmonary tissue to severe radiation dose

Radiation dose from inhaled insoluble particulate can be expressed in three different ways:

By the quantitative relationship between dose rate and distance from the particle

By Tissue Mean Dose, which is the mean dose to the sphere of tissue whose radius is equal to the range of alphas of betas emitted from the radioactive particulate

By the Organ Mean Dose, which is the mean dose for the entire organ calculated on the basis of uniform distribution of the radioactivity throughout the lung instead of being concentrated in discrete foci

•Lung models used for setting radiation safety standards for inhaled radioactive materials, including particulate matter, are based on mean doses to the tissues of lung.

•Lung cancer was also associated with overexposure to external radiation, e.g.:

•Patients who had received x-ray therapy for the treatment of some diseases.

•Women who had undergone radiation therapy for cancer of uterine cervix.

•Japanese survivors of nuclear bombing who had received high doses of radiation.

•A dose of one Gy increases the likelihood of dying from lung cancer by about 50%.

Thyroid Cancer:

•Increased incidence rate of thyroid cancer has been reported among:

1- Children treated with x-rays for:

It is one of the largest endocrine glands in the body. It controls how quickly the body burns energy, makes proteins, and how sensitive the body should be to other hormones. The thyroid participates in these processes by producing thyroid hormones, principally thyroxine (T4) and triiodothyronine (T3).

The Thyroid gland:

•Ringworm of scalp: also known as "Tinea", is an infection of the skin, characterized by a reddish to brownish raised or bumpy patch of skin that may be lighter in the center, giving the appearance of a 'ring'. Contrary to its name, ringworm is not caused by a worm but by parasitic fungi.

•Enlarged thymus glands: In the two thymic lobes, lymphocyte precursors from the bone-marrow become thymocytes, and subsequently mature into T cells (immune role).

•Acne: is a skin disease caused by changes in the hair follicle and its associated sebaceous gland. It accompanies adolescence.

2- Children who had been exposed to:

•Internal radiation from inhaled radionuclides of Iodine.

•External Radiation from the BRAVO nuclear bomb test in Marshall Islands.

Castle Bravo was the code name given to the first U.S. test of a so-called dry fuel thermonuclear fusion device, detonated on March 1, 1954, Marshall Islands, by the United States. Fallout from the detonation—intended to be a secret test—poisoned the crew of a Japanese fishing boat (called lucky dragon), and created international concern about atmospheric thermonuclear testing.

•1954 Bravo test, there was a lot of wind shear, Radioactive fallout was spread eastward onto the inhabited Rongelap and Rongerik atolls, which were soon evacuated. Many of the Marshall Islands natives have since suffered from birth defects .

3-Japanese survivors of the nuclear bombing (1st of the observed solid tumours )

4- Young people in Ukraine following the Chernobyl nuclear power plant disaster in Aril 1986.

1986 1989 1992 1993

0

20

40

60

80

100

120

Nu

mb

er o

f ca

ses

Year

Thyroid cancer among Ukrainians 18 years or less at the time Chernoby accident 1986Delayed Effects (continued)

2-Life shortening:•It has been thought that radiation in high doses may cause life shortening by:

Developing different types

of cancer

Increasing the rate of

physiological aging

OR

This has only been demonstrated in animals. There is no clear-cut effect observed among irradiated populations (e.g. Japanese survivors)

3- Cataracts:A cataract is an opacity that develops in the crystalline lens of the eye or in its envelope.

Developed among:

Dose> 2GyAbnormal lens fibres on the anterior part of lens

Fibres disintegrate to form opaque

area

Preventing light from reaching

the retina

Increase in opacity with

time

Interfere with vision, i.e Cataract

a) Patients treated using therapeutic doses of x-ray

Cataractogenic (threshold) dose after x-ray therapy:

b) Physicists in cyclotron laboratories whose eyes had been exposed to mixed neutron, and gamma radiation for long periods

c) Nuclear bomb survivors whose eyes were exposed to single high radiation dose. Both acute and chronic exposures can cause cataracts

Neutrons are much more efficient in producing Cataracts than beta or gamma

The fast neutron threshold dose for producing Cataracts in humans lies between 0.15-0.45 Gy

They were exposed to mixed dose of neutron and gamma radiation

Cataracts in people exposed to doses between 0.6-1.5 Gy

Several years usually elapse between exposure to radiation and the appearance of Cataract.

4- Mental retardation:

•Children irradiated in utero and survived after the nuclear bombing of Japan have shown a dose related increase in mental retardation.

•This was more apparent for those exposed during the 8th to 17th week of pregnancy.

•During this period (gestation), the number of neurons in the developing brain increases rapidly and the neurons move into the specific parts of the brain where they will permanently reside.

•After the 17th week, the neurons do not undergo any further cell division.

•The high rate of mitotic activity during the 8th to 17th week is the basis of radio sensitivity.

5- Genetic Effects:

•No hereditary genetic effect of radiation have ever been observed in any human population irradiated at any dose ranging from natural background to that received by the Japanese survivors of the nuclear bombing.

•Genetic information can be altered by damaging one point on the gene (point mutation). Or by chromosomal aberrations (breaking chromosomes), where the broken pieces some times fail to reunit and one of the broken fragments may be lost when the cell divides

•Herman J Muller 1927 (Nobel prize) discovered the mutagenic properties of ionizing radiation (x-ray acting on fruit flies). Since then many studies proved the mutagenic effect of all forms of ionizing radiation.

•The biological model used to explain the genetic effects of radiation postulates a zero threshold for an effect to appear.

•Studies on dose –rate effects imply that there is a repair mechanism to correct genetic errors.

Radiation protection Units

ActivityActivityIt describes the amount of radiation coming It describes the amount of radiation coming out of the sourceout of the source..--------------------------------1Ci (Curie) =3.7x101Ci (Curie) =3.7x1010 10 disintegration/secdisintegration/sec

))This is the activity of 1g of RadiumThis is the activity of 1g of Radium.(.(--------------------------------1Bq (Becquerel) =1 dis/sec1Bq (Becquerel) =1 dis/secThus, 1Ci= 3.7x10Thus, 1Ci= 3.7x1010 10 BqBq

ExposureExposureIt describes the It describes the ionization of airionization of air due to the radiation coming out of due to the radiation coming out of the sourcethe source..

--------------------------------Roentgen (R) is the unit of exposure for x-rays and gamma raysRoentgen (R) is the unit of exposure for x-rays and gamma rays..1R = 2.58 x 101R = 2.58 x 104 4 Coulomb/kgCoulomb/kg

Absorbed Absorbed dosedose

It describes the amount of It describes the amount of energy absorbedenergy absorbed in the medium in the medium..----------------------------------------

11 Gray (Gy) = 1 Joule / kgGray (Gy) = 1 Joule / kg..11 Gy = 100 radGy = 100 rad

i.e., when one kg of tissue absorbs 1 joule, the tissue is said to have i.e., when one kg of tissue absorbs 1 joule, the tissue is said to have absorbed 1 Gyabsorbed 1 Gy..

Equivalent Equivalent dosedose

It accounts for the It accounts for the difference in the biological effectdifference in the biological effect caused by the caused by the absorbed dose from absorbed dose from different radiation sources compared to the different radiation sources compared to the effect caused by x-rays or gamma rayseffect caused by x-rays or gamma rays..

----------------------------------------------11 rem = 1 rad x Q.F. (The equivalent dose = absorbed dose x quality rem = 1 rad x Q.F. (The equivalent dose = absorbed dose x quality

factor)factor)Q.F. : is the quality factor of radiationQ.F. : is the quality factor of radiation

))Q.F. = 1 for x and gamma rays, electrons and positrons. Q.F. = 5-20 Q.F. = 1 for x and gamma rays, electrons and positrons. Q.F. = 5-20 for some neutrons, 20 for Alpha particles and 10 for protonsfor some neutrons, 20 for Alpha particles and 10 for protons.(.(

11 Sievert (Sv)= 100 remSievert (Sv)= 100 rem

Maximum permissible annual doses

a)a) Radiation Workers:Radiation Workers:

5 rem (50 mSv)/year5 rem (50 mSv)/yearb) b) Non-radiation Workers:Non-radiation Workers:

0.1 rem /year0.1 rem /year

Whole body:

a)a) Radiation Workers:Radiation Workers:

15 rem (150 mSv)/year15 rem (150 mSv)/yearb) b) Non-radiation Workers:Non-radiation Workers:

1.5 rem (15 mSv) 1.5 rem (15 mSv) /year/year

Lens of the eye:

a)a) Radiation Workers:Radiation Workers:

50 rem (500 mSv)/year50 rem (500 mSv)/yearb) b) Non-radiation Workers:Non-radiation Workers:

5 rem (50 mSv) /year5 rem (50 mSv) /year

Skin:

a)a) Radiation Workers:Radiation Workers:

50 rem (500 mSv)/year50 rem (500 mSv)/yearb) b) Non-radiation Workers:Non-radiation Workers:

5 rem (50 mSv) /year5 rem (50 mSv) /year

Hands and feet:

Radiation protection in radiation Radiation protection in radiation therapytherapy

To calculate the amount of shielding (e.g. To calculate the amount of shielding (e.g. concrete walls about 0.5m thick) to reduce concrete walls about 0.5m thick) to reduce γγ radiation from radiation from 6060Co source to safe level Co source to safe level we use the following steps:we use the following steps:

1.1. Calculate the radiation intensity ICalculate the radiation intensity Iγγ in in Rontgen/hr (initial intensity):Rontgen/hr (initial intensity):

IIγγ==ΓΓN/DN/D2 2 -------------- (1) -------------- (1)

Where D=distance from the source.Where D=distance from the source.

N=the activity of the source in MBq (mega N=the activity of the source in MBq (mega bequerels).bequerels).

ΓΓ=gamma constant for particular radionuclide =gamma constant for particular radionuclide in Rmin Rm22/Mbq.hr/Mbq.hr

2. The shielding thickness is calculated from:2. The shielding thickness is calculated from:

I=II=Iooee--µxµx ------------- (2) ------------- (2)

I=intensity transmitted from thickness (x)I=intensity transmitted from thickness (x)

IIoo=initial intensity=I=initial intensity=Iγγ

µ=linear absorption coefficient in cmµ=linear absorption coefficient in cm-1-1

X=thickness in cmX=thickness in cm

Half value thickness HVT:- is the thickness Half value thickness HVT:- is the thickness needed to reduce the initial intensity to its needed to reduce the initial intensity to its half value.half value.

HVT=0.693/µ ------------- (3)HVT=0.693/µ ------------- (3)

Calculate the radiation intensity at 1m from 185TBq 60Co source Calculate the radiation intensity at 1m from 185TBq 60Co source then calculate the shielding thickness of lead necessary to shield then calculate the shielding thickness of lead necessary to shield the source to a radiation level less than 2mR/hr at 1m? the source to a radiation level less than 2mR/hr at 1m?

(constants: (constants: ΓΓ for 60Co=3.5x10-5Rm2/MBq.hr&HVT=1.2cm) for 60Co=3.5x10-5Rm2/MBq.hr&HVT=1.2cm)

Given:-Given:- D=1m, N=185x10 D=1m, N=185x101212Bq=185x10Bq=185x1066MBq, I < 2mR/hrMBq, I < 2mR/hr

HVL=1.2cm=0.693/µHVL=1.2cm=0.693/µ

µ=0.693/1.2=0.58cmµ=0.693/1.2=0.58cm-1-1 ΓΓ=3.5x10-5Rm2/MBq.hr=3.5x10-5Rm2/MBq.hr

Required:Required: I Iγγ at 1m & x lead shield thickness at 1m & x lead shield thickness

Equations and calculationsEquations and calculations::

IIγγ = = ΓΓ N / D N / D22

IIγγ = (3.5x10 = (3.5x10-5-5x185x10x185x1066)/ (1))/ (1)22 = 6000 R/ hr = I = 6000 R/ hr = Ioo

I = II = Io o ee-µx-µx

2x102x10-3-3=6000 e =6000 e -(0.58)x-(0.58)x

6000/2x106000/2x10-3-3= e= e0.58x0.58x

ln (3x10ln (3x1066)= 0.58x)= 0.58x

x=25.7cmx=25.7cm

The shielding thickness must be higher than 25.7cm. The shielding thickness must be higher than 25.7cm.

Calculate the thickness of lead required to reduce x-Calculate the thickness of lead required to reduce x-ray beam intensity by 30%?ray beam intensity by 30%?

Given:Given: I = 70/100 Io, HVL=1.2cm I = 70/100 Io, HVL=1.2cm

Required:Required: x cm x cm

Equations and Calculations:Equations and Calculations:

I=70/100 II=70/100 Ioo I/I I/Ioo=70/100=70/100

70/100=e 70/100=e --µxµx and and µ=0.693/HVL=0.693/1.2=0.58cmµ=0.693/HVL=0.693/1.2=0.58cm-1-1

70/100=e70/100=e-0.58-0.58xx

ln 10/7 = 0.58xln 10/7 = 0.58x

x=ln (10/7) / 0.58 = 0.62cmx=ln (10/7) / 0.58 = 0.62cm

I = II = Ioo e e -µx-µx

Calculate the radiation intensity at 0.35m from an Calculate the radiation intensity at 0.35m from an unshielded 7.5GBq source of Au (unshielded 7.5GBq source of Au (ΓΓ=6.2x10-6Rm2/MBq), =6.2x10-6Rm2/MBq), Calculate the shielding thickness required to reduce the Calculate the shielding thickness required to reduce the radiation intensity of the source to its safe level radiation intensity of the source to its safe level (10mR/week) and µ=2.3cm-1. Assume that the employee (10mR/week) and µ=2.3cm-1. Assume that the employee must work at 1m from the source for 10hrs each week?must work at 1m from the source for 10hrs each week?

Golden Rules for Radiation Protection

Time Time (of exposure)(of exposure)

------------------------------The longer The longer the time of the time of exposure, the exposure, the higher the higher the radiation radiation dose. Do not dose. Do not spend spend unnecessary unnecessary time near time near radiation radiation sourcessources..

Distance Distance (from source)(from source)

--------------------------------The intensity of The intensity of radiation (I) is radiation (I) is inversely inversely proportional to proportional to the square of the square of the distance the distance from source from source (d(d22). So keep ). So keep away as much away as much as you can from as you can from sourcesource..

Activity Activity (of source)(of source)

------------------------------------Choose the Choose the lowest activity of lowest activity of source that is source that is sufficient for the sufficient for the needed jobneeded job..

ShieldingShielding

----------------------------Proper Proper shielding of shielding of source and source and Personnel Personnel will always will always reduce reduce radiation radiation dosedose..

Other Useful notices:

1- Don’t not use radiation when there are other means to get the same information.

2- Use a suitable radionuclide and a suitable amount of it

3- Do not mistake your patient for the correct radionuclide.

4- Wear laboratory coat and gloves when dealing with radio nuclides.

5- When working with volatile radioactive materials use an evacuated fume hood.

11- Do not eat drink or smoke in a radiation laboratory.

12- Do not pipette any radioactive solution using your mouth.

13- Radiation waste should be thrown only in the special containers prepared for it and having proper shielding.

14- Notify the radiation safety officer if any major spill or emergency took place.

7- Store and transport radioactive materials in lead containers.

8- Wear a radiation dosimeter (e.g. film page or TLD) while working near radiation sources in a radiation laboratory.

9- Survey work areas, using radiation detector, for contamination as frequently as possible.

10- Clean up spoils promptly and survey the area after cleaning.