Radiation Sources, Doses, and Regulations

What is radiation?

Energy that passes from one location to another in the form of waves or particles.

What are the two main types of radiation?

Ionizing radiation and Non-ionizing radiation.

What is ionizing radiation?

Radiation with enough energy to remove electrons from atoms (x-rays, gamma rays, high-energy UV).

What is non-ionizing radiation?

Radiation that cannot remove electrons (visible light, microwaves, radio waves).

What is particulate radiation?

Radiation made of particles like alpha, beta, protons, and neutrons.

What is an alpha particle?

Helium nucleus (2 protons, 2 neutrons); stopped by paper but harmful if inhaled.

What is a beta particle?

High-speed electron; more penetrating than alpha, stopped by aluminum or wood.

What is a proton?

Positively charged particle in nucleus; defines atomic number.

What is a neutron?

Neutral particle in nucleus; contributes to isotopes.

What is absorbed dose (D)?

Energy deposited per unit mass, measured in Gray (Gy).

What is equivalent dose (EqD)?

Absorbed dose adjusted for radiation type, measured in Sievert (Sv).

What is effective dose (EfD)?

Dose adjusted for radiation type AND organ sensitivity; best overall measure of harm.

What does BERT stand for?

Background Equivalent Radiation Time.

What does BERT do?

Compares medical radiation dose to natural background exposure over time.

What is terrestrial radiation?

From radioactive elements in the Earth’s crust (uranium, radium, thorium).

What is cosmic radiation?

From the sun and space; higher at altitude.

What is internal radiation?

From radionuclides in the body (K-40, C-14).

What gas is the largest natural radiation source?

Radon.

What is the EPA action level for radon in homes?

4 picocuries per liter (pCi/L).

What are the main human-made radiation sources?

Consumer products, nuclear power, fallout, medical imaging.

What is the largest artificial source of radiation?

Medical imaging.

How much does medical imaging contribute annually?

About 2.3 mSv per year.

Name examples of consumer products with radiation.

Smoke detectors, airport scanners, electron microscopes.

How much radiation does air travel give?

About 0.005–0.01 mSv per flight hour.

What was the Three Mile Island accident?

1979 partial meltdown in Pennsylvania; very low public dose.

What was the Chernobyl accident?

1986 explosion in Ukraine; large radiation release, thyroid cancers.

What was the Fukushima accident?

2011 earthquake/tsunami in Japan caused reactor meltdown.

What is the average annual U.S. radiation dose (2016)?

5.5 mSv total.

How much comes from natural sources?

About 3.1 mSv.

How much comes from medical imaging?

About 2.3 mSv.

How much comes from other human-made sources?

About 0.1 mSv.

Chest X-ray dose

0.08 mSv (≈10 days background radiation).

Lumbar spine x-ray dose

3.0 mSv (≈1 year background radiation).

CT brain dose

2.0 mSv (≈1 year background radiation).

CT chest dose

8.0 mSv (≈3.6 years background radiation).

CT abdomen/pelvis dose

10 mSv (≈4.5 years background radiation).

What does ALARA stand for?

As Low As Reasonably Achievable.

What are the three cardinal rules of radiation protection?

Time, Distance, and Shielding.

What is diagnostic efficacy?

Accuracy of an imaging study to show disease while keeping dose low.

What is a Radiation Safety Program?

Written plan to ensure ALARA and safe practices in imaging facilities.

What is a Radiation Safety Committee (RSC)?

Group that guides safety programs; NRC requires it.

What is a Radiation Safety Officer (RSO)?

Qualified person overseeing daily safety and monitoring staff.

What was the Radiation Control for Health and Safety Act of 1968?

U.S. law to protect public from unnecessary radiation from electronic products.

What is the Center for Devices and Radiological Health (CDRH)?

FDA branch created to regulate x-ray equipment standards.

What did the 1974 Code of Standards require?

PBL, filtration, reproducibility, linearity, beam limits, “beam on” indicators, AEC backup timers.

What is ICRP?

International Commission on Radiological Protection; sets international safety guidelines.

What is NCRP?

National Council on Radiation Protection and Measurements; sets U.S. standards and reports.

What is UNSCEAR?

UN committee that evaluates global radiation exposures.

What is NAS/NRC-BEIR?

Committee reviewing biologic effects of radiation and risk assessment.

What is the Image Gently Campaign?

Started 2008; promotes pediatric radiation dose reduction.

What is Pause and Pulse?

Part of Image Gently; recommends pulsed fluoroscopy and child-sized techniques.

What is the Image Wisely Campaign?

Started 2009; promotes dose reduction and elimination of unnecessary procedures in adults.