RAD 315 RADIATION BIOLOGY AND PROTECTION INTRODUCTION

Radiation Protection The promotion of practices that limit exposure to ionizing radiation to a minimum. Applies radiation physics and radiation biology in a clinical setting

Goal of Radiation Protection Maximize the benefit of an examination or procedure while minimizing the risk to the patient. ALARA- “as low as reasonably achievable” It is assumed that radiation causes harm and any exposure should be kept to a minimum.

Radiation Biology Branch of science that looks at the effects of ionizing radiation on living matter. Most effects are on cellular level

Radiation Units

Radiation Units To express radiation units there are two types of measurement Traditional- typically used in the United States SI- Systeme International- universally used around the world

EXPOSURE IN AIR SI Unit- coulombs per kilogram (C/kg) Traditional- Roentgen (R) Measures the ionization of air produced by x-radiation and gamma radiation below 3 million electron volts (3 MeV)

Coulombs / kg SI expression of exposure in air The coulomb is the SI unit of electric charge and represents a given number of electrons. The kilogram measures the quantity of air Hence the amount of electric charge in a quantity of air.

Roentgen Named after Wilhelm Conrad Roentgen (discovered x-rays) Measure of the amount of ionization produced by x-radiation or gamma radiation in air.

ABSORBED DOSE SI Unit- Gray (Gy) Traditional- rad (radiation absorbed dose)

Gray and rad 1 rad= 1cGy =1/100 Gray = 0.01 Gy Rad- an energy transfer of 100 ergs (energy unit) per gram of absorbing material Patient dose is usually expressed Gray.

Occupational Exposure SI Unit- Sievert Traditional- rem (radiation equivalent man) Units of biological effect

Rems and Sieverts Rems – the quantity of ionizing radiation that has the same biologic effect of 1 rad of x-ray. 1 rad= 1 rem 1 Sievert = 100 rem

RADIOACTIVITY SI Unit- Becquerel- Bq Traditional- Curie- Ci Measures the rate of radioactive decay of a material.

Curies & Becquerels Curie- 3.7x1010 disinergrations per second of any radioactive substances. Becquerels- one decay per second of any radioactive substance The curie is a larger unit that the becquerel.

Half Life The time it takes a radioactive material to decay 50% of its original activity is known as the HALF LIFE. Ex: If you had 100 atoms of radioactive material and it takes 3 hours for 50 of them to decay. What is the half life of this material?

CONVERSIONS 1 Gy=_______mrads 1 Gy= 100 rad= 100,000 mrads 100 rem= 1 Sievert

Think About It! The prescription says that the patient is to receive 1.8 Gy of radiation. How many cGy of radiation will the patient receive? Which is a larger? Becquerel or curie? 10,000 mrems or 1 Sievert 1 Gray or 1000 rads

THE END Any Questions?