Radiation

 

What is radiation?   

Radiation is electromagnetic energy moving through space. It can take several different forms, including visible light, x-rays, gamma rays, microwaves, and radio waves. Physicians use low-dose radiation from x-rays to create images on film or computer. High-dose radiation can be used to treat certain cancers.

Where does radiation come from?

Radiation is all around us. Natural background radiation mostly comes from the Earth (mostly Radon) and the Sun (Cosmic Radiation). Natural background radiation produces about 3.1 mSv (“millisievert”) each year, depending upon where you live. Medical exposure, mostly from x-rays  and CT cans, accounts for another important source of ionizing radiation to which we are exposed.

What is an x-ray?

X-rays are a type of radiation often used for medical imaging. X-rays create an image on film (or computer) depending upon how many get absorbed in the body and how many passed through.

What is the risk of x-rays?

In most cases, in a properly performed medical x-ray test, the benefits outweigh the risks of x-ray radiation exposure. There are data, particularly from atomic bombs and radiation spills, that high doses can lead to cancer. There is no proof that low doses of radiation, such as used with common x-rays or CT scans, cause cancer. Nevertheless, radiation exposure can be cumulative, so unnecessary x-rays, especially CT scans, should be avoided. There is no exposure to ionizing radiation from MRIs or ultrasound.

How much radiation am I getting?

  • Natural background radiation = average 3.1 mSv/year
  • Medical sources = average 3.0 mSv/year (mostly CT scans)
  •  Standard two-view chest x-ray = 0.10 mSv
  •  Standard chest CT = 7 mSv
  •  Routine bitewing dental exam = 0.005 mSv
  •  Panoramic dental exam = 0.010 mSv
  • Mammogram (unilateral) = 0.40 mSv
  • Cardiac Thallium Stress Test = 40.70 mSv
  •  Coast-to Coast round-trip commercial flight = 0.03 mSv

The standard two-view chest x-ray is equivalent to approximately 10-12 days of natural background radiation. The standard chest CT is equivalent to approximately 2.25 years of background radiation.

How much radiation to airport security scanners use?

There are two types of body scanners. The Millimeter Wave Scanners use radio waves and do not expose you to any ionizing radiation. The Backscatter Wave Scanners use very weak x-rays, with a dose of 0.0001 mSv.

In other words, 80 airport scans are equivalent to approximately one day of natural background radiation and 1000 airport scans are roughly the equivalent radiation of a standard chest x-ray.

How can I calculate my risk?

As noted above, the risk of cancer from medical x-ray imaging is extremely small. There are websites that can help you with the numerical risk, depending upon your age, sex, and type of examination.