Radiation

Radiation

Prepared by: Timothy John D. Matoy

Radiation is energy that comes from a source and travels through some material or through space.

Energy emitted and transferred through space.

The transfer of energy.

Radiation

Non-ionizing radiationIonizing radiation

2 types of radiation

Capable of removing an electron from an atom

Ionizing Radiation

Natural Environmental Radiation

Man-made Radiation

2 Sources of Ionizing Radiation

Annual dose of approximately 300 millirem (mrem) (3 millisievert [mSv])

Cosmic rays, terrestrial radiation, internally deposited radionuclides

Natural Environmental Radiation

Approximately 60 mrem (0.6 mSv) annually

Medical imaging, nuclear power generation, research application, industrial sources, consumer items

Man-made Radiation

Diagnostic x-rays constitute the largest man-made source of ionizing radiation (39 mrem/year) (0.39 mSv/yr)

Man-made Radiation

Particulate radiationElectromagnetic radiation

Two Types of Ionizing Radiation

Particle radiation is the radiation of energy by means of fast-moving subatomic particles.

Particulate radiation

Alpha ParticlesBeta Particles

Particulate radiation

Alpha particles are high energy, large subatomic structures of protons and neutrons.

They can travel only a short distance and are stopped by a piece of paper or skin.

Alpha Particles

Beta particles are fast moving electrons. They are a fraction of the size of alpha particles, but can travel farther and are more penetrating.

Beta Particles

This kind of radiation is pure energy with no mass and is like vibrating or pulsating waves of electrical and magnetic energy. Electromagnetic waves are produced by a vibrating electric charge and as such, they consist of both an electric and a magnetic component.

Electromagnetic Radiation

Gamma raysX-rays

Electromagnetic Radiation

Quantities and Units

The inverse square law can be applied to distances greater than seven times the longest dimension of the source

Inverse Square Law

Inverse Square Law

Where:

I1 = Intensity at distance 1 I2 = Intensity at distance 2

d1 = distance 1 d2 = distance 2

Inverse Square Law

The intensity of light from a reading lamp is 100 millilumens (mlm), I2, at a distance of 1 m, d2. What is the intensity, I1, of this light at 3 m?

Sample Problem

For a given technique, the x-ray intensity at 1 m is 450 mR. What is the intensity at the edge of the control booth, at a distance of 3 m, if the useful beam is directed at the booth?

Sample problem

For a given technique, the x-ray intensity at 2 m is 170 mR. What is the intensity at a distance of 1 m?

Practice problem

A temporary chest radiographic imaging system is to be set up in a large hall. The technique used results in an exposure of 25 mR at 180 cm. The area behind the chest stand in which the exposure intensity exceeds 1 mR is to be cordoned off. How far from the x-ray tube will this area be extend?

A temporary chest radiographic imaging system is to be set up in a large hall. The technique used results in an exposure of 15 mR at 230 cm. The area behind the chest stand in which the exposure intensity exceeds 1 mR is to be cordoned off. How far from the x-ray tube will this area be extend?