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Tyler Bradshaw – Spring 2009

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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Tyler Bradshaw – Spring 2009

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  1. Radiation and the Body Tyler Bradshaw – Spring 2009

  2. What is radiation? • There are three types of radiation: • -Alpha (α) particles • -Beta (β) particles • -Gamma (γ) rays

  3. Alpha (α) Particle -An α-particle is a high speed helium nucleus. -2 protons and 2 neutrons. + +

  4. Beta (β) Particle -A β-particle is a high speed electron

  5. Gamma (γ) Ray -A gamma ray is a high energy light ray (or photon)

  6. HOW ARE THESE TYPES OF RADIATION PRODUCED? γ α β

  7. ALPHA PARTICLE: Alpha Decay -An unstable atom emits an alpha particle. -The alpha particle is heavy compared to other forms of radiation. α particle

  8. 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

  9. 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).

  10. GAMMA RAYS -Produced by radioactive decay. - Cobalt-60 is commonly used to produce gamma rays. 60Co γ Rays

  11. So What Does Radiation Do To The Body?

  12. 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.

  13. β- and γ-radiation harm cells in two ways: -Direct Action -Indirect Action

  14. 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

  15. Direct Action (Target Theory) Gamma Ray DNA Molecule

  16. 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.

  17. INDIRECT ACTION Electron H o o H H H

  18. INDIRECT ACTION H o o H H H Free Radicals

  19. Free radicals can damage many parts of the cell… Membranes: Proteins: DNA: Enzymes:

  20. Radiation can be both dangerous and useful. So how much is too much?

  21. 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

  22. 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.

  23. 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

  24. So radiation kills our cells… • Chernobyl • Nuclear waste in Utah • Iran and a nuclear bomb But can we utilize it?

  25. 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).

  26. Types of radiation therapy: •Brachytherapy • External Beam (Teletherapy) • Unsealed Source

  27. Brachytherapy -Radioactive isotopes placed INSIDE the body. -Minimizes damage to surrounding tissue/organs. -Seed implants can be temporary or permanent. 125I 60Co 192Ir 137Cs

  28. -Hollow catheters are surgically placed -Seeds are pushed through the catheters -Seeds are inserted and removed by remote afterloading -Outpatient procedure

  29. Brachytherapy- Video Common method for treating breast, prostate, cervical, head and neck cancer.

  30. External beam (teletherapy) Radiation is administered from an external source (linear accelerator)

  31. Unsealed Source • Iodine-131 is swallowed to treat thyroid • cancer. • The thyroid gland absorbs the iodine.

  32. 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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