Radiation Quantities and Units

When did Roentgen announce the discovery of X-rays?

December 28, 1895

Who designed the first film badge?

Dr. William Rollins in 1904

British X-Ray and Radium Protection Committee (1921)

Formed to investigate methods for reducing radiation exposure

What did the British X-Ray and Radium Protection Committee develop?

Dosage unit known as the skin erythema dose (SED)

What is the skin erythema dose (SED)?

Quantity of radiation that can cause diffused redness over an area of skin after irradiation

Special units:

Roentgen, Rad, Rem, and Curie

SI units:

Coulomb/kg, Gray (Gy), Sievert (Sv), and Becquerel (Bq)

What does exposure/intensity measure?

X-rays and gamma rays in air, up to 3 MeV

The exposure rate from an X-ray machine is often measured in ______ or _____

R/min or Air kerma

What 4 factors is exposure rate affected by?

mAs - directly proportional

kVp - exponentially related

SID - inverse square relationship

Filtration - will decrease exposure rate

1 C/kg =

3.88 x 10^3 R or 3876 R

Acronym for KERMA

Kinetic energy released in matter

What does Air Kerma measure?

Amount of kinetic energy transferred into charged particles (such as electrons) by X-rays or gamma rays

What is Air Kerma expressed in?

Joule per kilogram (J/kg) or Gray

What does absorbed dose measure?

Amount of energy that is transferred into matter by radiation

1 Gy =

1 joule/kilogram

What is the absorbed dose equivalent?

A method with which to calculate the effective absorbed dose into human tissue for all types of radiation

Absorbed dose equivalent (H) =

Absorbed dose x Quality Factor (QF) or Radiation Weighting Factor (W)

What does the Sievert (Sv) measure?

Dose equivalent

What is effective dose?

The sum of the weighted equivalent doses for all irradiated tissues and organs

What is effective dose measured in?

Sieverts

What is background radiation?

Type of exposure that the general population as a whole are exposed to and cannot be avoided

What are the 2 types of background radiation?

Natural and artificial

What is natural radiation?

Radiation received from natural source and averages 310 mrem (3.10 mSv) per year

Source of natural radiation:

Cosmic radiation

Terrestrial radiation

Internal radiation

What is cosmic radiation?

High energy particles that originate in the sun (solar) and outside the solar system (galactic) that crash into the outer layers of the earth's atmosphere where they lose kinetic energy and release radiation

What 2 factors does cosmic radiation depend on?

Latitude and altitude

Why does cosmic radiation depend on latitude?

Cosmic radiation is greatest at the poles because the earth's magnetic field is strongest and attracts more of the high energy particles

Why does cosmic radiation depend on altitude?

Higher altitudes result in greater exposure to cosmic radiation because you are closer to the source and because there is less atmosphere to possibly absorb them

What is terrestrial radiation?

Radiation coming from the earth

Sources of terrestrial radiation:

Radon

Earth's crust

Building materials

Air

Food and drinking water

What is radon?

An alpha emitter that decays into other radioactive substances and can contribute greatly to the total lifetime dose of radiation

What is the 2nd leading cause of lung cancer?

Radon

What radioactive materials are present in the earth's crust?

Potassium

Uranium

Radium

Thorium

What radioactive materials are present in the building materials?

Brick

Concrete

Gypsum materials

What radioactive materials are present in the air?

Carbon, polonium and other radioactive materials exist as a gas

What is internal radiation?

Radioactive materials normally found in body tissues such as carbon, hydrogen, and potassium, all emit ionizing radiation that expose body tissue

What is the most common radioactive material deposited in human body tissue?

Potassium

Artificial (manmade) radiation:

Airport surveillance systems

Consumer products

Nuclear reactors

Atmospheric fallout

Transport of nuclear material