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Radiation and the Body. Tyler Bradshaw – Spring 2009. What is radiation?. There are three types of radiation: -Alpha ( α ) particles -Beta ( β ) particles -Gamma ( γ ) rays. Alpha ( α ) Particle. -An α -particle is a high speed helium nucleus. -2 protons and 2 neutrons. +. +.

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Radiation and the Body

Tyler Bradshaw – Spring 2009


What is radiation?

  • There are three types of radiation:

  • -Alpha (α) particles

  • -Beta (β) particles

  • -Gamma (γ) rays


Alpha (α) Particle

-An α-particle is a high speed helium nucleus.

-2 protons and 2 neutrons.

+

+


Beta (β) Particle

-A β-particle is a high speed electron


Gamma (γ) Ray

-A gamma ray is a high energy light ray

(or photon)



ALPHA PARTICLE: Alpha Decay

-An unstable atom emits an alpha particle.

-The alpha particle is heavy compared to other forms of radiation.

α particle


BETA PARTICLE:

1st- Beta Decay

-An unstable atom decays and emits an electron and a neutrino.

-Only the electron (or beta particle) interacts with the body.

Electron

Neutrino


BETA PARTICLE:

2nd- Particle Accelerator

-Particles are pushed forward by alternating electric fields.

-Can reach speeds close to that of light (180,000 miles per second).


GAMMA RAYS

-Produced by radioactive decay.

- Cobalt-60 is commonly used to produce gamma rays.

60Co

γ Rays



Radiation Penetration

α-particles are heavy enough to be stopped by a piece of paper. Easily stopped by the skin.

β- and γ-radiation pass into the body and can damage tissue.


β- and γ-radiation harm cells in two ways:

-Direct Action

-Indirect Action


Direct Action (Target Theory)

- Radiation directly hits important molecules in the cell.

  • The damage done to a cell depends on what part of the cell the radiation hits (i.e. membrane, proteins, RNA, etc)

- Damage to a cell’s DNA can cause cancer.

Beta particle

Membrane


Direct action target theory
Direct Action (Target Theory)

Gamma Ray

DNA Molecule


INDIRECT ACTION

  • Most of the body is water.

  • H20 is more likely to be hit by the radiation.

  • When H20 absorbs radiation, it can turn toxic.


INDIRECT ACTION

Electron

H

o

o

H

H

H


INDIRECT ACTION

H

o

o

H

H

H

Free Radicals


Free radicals can damage many parts of the cell…

Membranes:

Proteins:

DNA:

Enzymes:



Measuring radiation

•There are many units for measuring radiation. (Currie, becquerel, rad, gray, roentgen, REM, sievert, LET, RBE)

•They can be split into two categories:

Biological

Non-biological


non-biological

Roentgen (R): Measures actual exposure to x-rays and

gamma rays.

Linear Energy Transfer (LET): Energy loss per unit travelled.

biological

Sievert (Sv) : Energy transferred from radiation to tissue.

Specific to the type of tissue involved.

Gray (Gy): Equal to 100 Rads. Amount of energy absorbed

per kilogram of matter.


BRAIN: Mostly resistant.

SKIN: Erythema and edema early on. Atrophy

and skin cancer up to years later.

How do the different

parts of the body react

to radiation?

LUNGS: Edema, adult respiratory distress syndrome.

GI TRACT: Mucosal injury, ulceration.

GONADS: Destruction of sperm in testes and

germ cells in ovaries.

BLOOD/BONE : Thrombocytopenia, anemia, and

granulocytopenia


So radiation kills our cells…

  • Chernobyl

  • Nuclear waste in Utah

  • Iran and a nuclear bomb

But can we utilize it?


CANCER

-Cancer is characterized by uncontrolled cell

growth.

-Tumors can harm adjacent healthy tissues.

-Cancer cells aren’t as efficient at repairing

themselves from damage.

-This makes them vulnerable to

certain treatments (radiation).


Types of radiation therapy:

•Brachytherapy

• External Beam (Teletherapy)

• Unsealed Source


Brachytherapy

-Radioactive isotopes placed INSIDE the body.

-Minimizes damage to surrounding tissue/organs.

-Seed implants can be temporary or permanent.

125I 60Co 192Ir 137Cs


-Hollow catheters are surgically placed

-Seeds are pushed through the catheters

-Seeds are inserted and removed by remote afterloading

-Outpatient procedure


Brachytherapy- Video

Common method for treating breast, prostate, cervical, head and neck cancer.


External beam (teletherapy)

Radiation is administered from an external source (linear accelerator)


Unsealed Source

  • Iodine-131 is swallowed to treat thyroid

  • cancer.

  • The thyroid gland absorbs the iodine.


Cancers Treated with Radiation

About 50-60% of cancer patients will at some point receive radiation therapy

Brachytherapy

Breast, Prostate, Cervical, Breast, Lung, Head and Neck, Ovary, Uterus, Gallbladder

External Beam

Skin, Lung, Brain, Colon, Bladder, Prostate, Larynx, Head and Neck, Rectal, and more

Unsealed Source

Thyroid Cancer


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