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. +. +.
Tyler Bradshaw – Spring 2009
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
-An unstable atom emits an alpha particle.
-The alpha particle is heavy compared to other forms of radiation.
1st- Beta Decay
-An unstable atom decays and emits an electron and a neutrino.
-Only the electron (or beta particle) interacts with the body.
2nd- Particle Accelerator
-Particles are pushed forward by alternating electric fields.
-Can reach speeds close to that of light (180,000 miles per second).
-Produced by radioactive decay.
- Cobalt-60 is commonly used to produce gamma rays.
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 (Target Theory)
- Radiation directly hits important molecules in the cell.
- Damage to a cell’s DNA can cause cancer.
So how much is too much?
•There are many units for measuring radiation. (Currie, becquerel, rad, gray, roentgen, REM, sievert, LET, RBE)
•They can be split into two categories:
Roentgen (R): Measures actual exposure to x-rays and
Linear Energy Transfer (LET): Energy loss per unit travelled.
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
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
But can we utilize it?
-Cancer is characterized by uncontrolled cell
-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).
• External Beam (Teletherapy)
• Unsealed Source
-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
Common method for treating breast, prostate, cervical, head and neck cancer.
External beam (teletherapy)
Radiation is administered from an external source (linear accelerator)
About 50-60% of cancer patients will at some point receive radiation therapy
Breast, Prostate, Cervical, Breast, Lung, Head and Neck, Ovary, Uterus, Gallbladder
Skin, Lung, Brain, Colon, Bladder, Prostate, Larynx, Head and Neck, Rectal, and more