chapter introduction to radiobiology - · pdf file ·...

HDR 112

CHAPTER 1

RADIATION BIOLOGY AND RADIATION PROTECTION

INTRODUCTION

TO

RADIOBIOLOGY

PREPARED BY:MR KAMARUL AMIN BIN ABDULLAH

SCHOOL OF MEDICAL IMAGINGFACULTY OF HEALTH SCIENCE

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CHAPTER 1: Introduction to Radiobiology

LEARNING OUTCOMES

At the end of the lesson, the student should be able to:-

Explain the history of radiation injury.

Describe the firstly discovered of radiation injury.

Explain the types ionizing radiation.

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TOPIC OUTLINES

INTRODUCTION

1.1 Significant Discoveries

1.2 New Dangers Come with Discoveries

1.3 Meeting the Need for Radiation Protection

1.4 Ionization

1.5 Types or Products of Ionizing Radiation

1.6 References

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INTRODUCTION

Since ancient times, philosophers and scientists have been interested

in the basic building blocks of our physical universe.

In fact the ancient Greeks were the first to believe that all matter in

the universe must be made of tiny building blocks or atoms.

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INTRODUCTION

Beginning with the earliest scholars of science throughout history and

into this century, scientists have been driven to learn more about the

atom and how to control it.

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It wasn't until the latter part of the 19th century that scientists truly

began to make advances in the study of atomic structure and

radiation.

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During the 1600s, Sir Isaac Newton had proven his theories on gravity.

Marie and Pierre Curie had begun their studies in chemistry and

physics, and Dmitri Mendeleev had introduced the periodic system of

elements.

Just before the turn of the century, Wilhelm Conrad Roentgen

discovered the basic properties of X-Rays; the properties of ionizing

radiation and the possibility of using radiation in medicine.

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Finally, in 1896, Henri Becquerel announced the discovery of

radioactivity to the Academy of Sciences in Paris.

By the early 1900s the study of radiation was a widely accepted

scientific endeavor.

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But, these discoveries did not come without a price.

Scientists learned that radiation was not only a source of energy and

medicine, it could also be a potential threat to human health if not

handled properly.

In fact, early pioneers in radiation research died from radiation-

induced illnesses (too much exposure).

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For instance, Thomas Edison's assistant died from a radiation-induced

tumor as a result of too much x-Ray exposure.

As new uses for radioactive elements were discovered, potentially

fatal incidents of overexposure increased.

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Example 1: Radium Paint

During World War I, radium paint (a mixture of radium and phosphor)

was used on military aircraft instruments to make them glow in the

dark so they would be more visible to pilots flying at night.

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Example 2: Luminous Dial Painters

After the war was over, the industry that supported this technology

changed their business to paint glow-in-the-dark clocks and watch

faces.

The young women who were employed in this vocation would form a

fine point on their paint brushes by pulling the freshly-dipped brushes

between their lips before applying the paint onto the watch faces.

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Unknowingly, they were swallowing small amounts of radium and

damaging their bodies.

Over a two-year period, nine women who had worked as dial

painters died of severe and unexplained anemia, accompanied by

destructive lesions of the mouth and jawbones.

A dentist who had treated one of these women finally made the

connection between inflammation of the jawbone marrow, and the

radium dial painting.

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Example 3: Radium Miners

Radium is chemically similar to

calcium.

Incorporated to bone tissue.

Caused: osteoporosis, osteogenic

carcinoma, carcinoma of

epithelial cells.

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Example 4: Atomic Warfare

Is a military conflict or political strategy in which nuclear weaponry is

used to inflict damage on an opponent.

Could have severe long-term effects, primarily from radiation release.

Could last for decades, centuries, or even millennia after the initial

attack.

Only two nuclear weapons have been used in the course of warfare,

both by the United States near the end of World War II.

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Example 5: Power Plant Accidents

Nuclear power plants - they have various kinds of accidents have

occurred, from the mundane to the catastrophic.

E.g: Employees have mishaps and equipment breaks down.

When accidents occur, they usually result in a minor release of

radioactive steam or water.

The incident at Chernobyl was the most extreme nuclear accident in history,

resulting in deaths from radiation, destruction of the plant and widely-dispersed

radioactivity.

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The Three Mile Island nuclear power plant

accident March 28, 1979.

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Year Events

1895 Discovery of x- ray

1896

a) Becquerel discover radiations emitted by

uranium compounds.

b) First biological effects e.g.: skin burns,

epilation.

1897 Discoveries of alpha-ray and beta-ray.

1903 Law of Bergonie and Tribondeau.

1911 Leukemia in five radiation workers reported.

1915British Roentgen Society introduces proposals for

radiation protection.

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Year Events

1927First observation of mutations by x- rays in

Drosophila.

1928First international recommendations on radiation

protection.

1930 First survival curve for bacteria.

1945 Atomic bomb in Hiroshima & Nagasaki.

1951 Hereditary effects of radiation in mice reported.

1956First in- vitro radiation survival curve for

mammalian cells.

1986 Chernobyl nuclear reactor meltdown.

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By 1915, the British Roentgen Society had adopted a resolution to

protect people from overexposure to X-rays.

This was probably the first organized effort at Radiation Protection.

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By 1922, American organizations had adopted the British protection

rules.

Awareness and education grew, and throughout the 1920s and 30s,

more guidelines were developed and various organizations were

formed to address radiation protection in the United States and

overseas.

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Radiation protection was primarily a non-governmental function until

the late 1940s.

After World War II, the development of the atomic bomb, and nuclear

reactors caused the federal government to establish policies dealing

with human exposure to radiation.

In 1959, the Federal Radiation Council was established.

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The FDR Council was responsible for three things:

1. advising the President of the United States on radiological issues

that affected public health

2. providing guidance to all federal agencies in setting radiation

protection standards

3. working with the States on radiation issues.

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In 1970, Congress created the Environmental Protection Agency

(EPA) and radiation protection became a part of EPA's responsibility.

Today, EPA's Radiation Protection Division (RPD) is responsible for

protecting the public's health and the environment from undue

exposure to radiation.

This is accomplished by setting safety standards and guidelines.

Now, organizations that deal with ionizing radiation must meet these

standards to comply with the law.

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The Radiation Protection Program is responsible for other protection

activities too.

For example, there is a team of experts that respond to emergencies

involving radioactivity.

There is also a laboratory that monitors the environment to determine

how much radiation is in the air.

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In Malaysia, there is MARPA (Malaysian Radiation Protection

Association/Persatuan Perlindungan Sinaran Malaysia) – is a non-

governmental organization that was established on 15 September

2002.

Visit http://www.marpa.org.my/ for more info.

http://www.marpa.org.my/

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It represents a pool of professionals of highest skill in radiation

protection and safety.

MARPA can be considered a national asset and a resource for experts

and specialists in radiation protection and safety.

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1.4 Ionization

Ionizing radiation is produced by unstable atoms. Unstable atoms

differ from stable atoms because they have an excess of energy or

mass or both.

Unstable atoms are said to be radioactive. In order to reach stability,

these atoms give off, or emit, the excess energy or mass. These

emissions are called radiation.

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1. Alpha particles

2. Beta particles

3. Gamma rays (or photons)

4. X-Rays (or photons)

5. Neutrons

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or X-rayneutron

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Alpha Particles: 2 neutrons and 2 protons

They travel short distances, have large mass

Only a hazard when inhaled

1.5 Types of Ionizing Radiation:Alpha Particles

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1.5 Types of Ionizing Radiation:Beta Particles

Beta Particles: Electrons or positrons having small mass and variable

energy. Electrons form when a neutron transforms into a proton

and/or an electron.

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1.5 Types of Ionizing Radiation:Gamma Rays

Gamma Rays (or photons): Result when the nucleus releases

energy, usually after an alpha, beta or positron transition.

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1.5 Types of Ionizing Radiation:X-rays

X-Rays: Occur whenever an inner shell orbital electron is removed and

rearrangement of the atomic electrons results with the release of the

elements characteristic X-Ray energy.

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1.5 Types of Ionizing Radiation:Neutrons

Neutrons are usually produced when a nuclear transformation is induced (that

is, is made to happen, rather than through occurring naturally), for example by

taking an atomic nucleus and firing another nuclear particle at it, or when

radioactive fission occurs (the breaking up of a large unstable nucleus into two

roughly equal nuclei, each around half the size of the original and with the

liberation of considerable amounts of energy) .

Most neutron sources occur in the laboratory (or nuclear reactor) under special

conditions

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Nuclear fission is fundamental to the operation of many types of nuclear

reactor. During the fission process, large amount of energy are released from

the nucleus that undergoes fission, and this energy can be used to provide

electrical power by heating water.

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1.6 References

Bushong, S.C. (2008). Radiologic science for technologist. 9th ed. Mosby

Elsevier

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