Types of electromagnetic<unk> <unk>  is a moving form of energy, classified into ionizing and non-ionizing type. Ionizing<unk>  is further categorized into electromagnetic<unk>  (without matter) and particulate<unk>  (with matter). Electromagnetic<unk>  consists of photons, which can be thought of as energy packets, traveling in the form of a wave. Examples of electromagnetic<unk>  includes X-rays and gamma rays (see photo "Types of Electromagnetic<unk> "). These types of<unk>  can easily penetrate the human body because of high energy.<unk>  is a measure of the ionization of air due to ionizing<unk>  from photons. It is defined as the electric charge freed by such<unk>  in a specified volume of air divided by the mass of that air. Medical<unk>  is defined by the International Commission on Radiological Protection as<unk>  incurred by patients as part of their own medical or dental diagnosis or treatment; by persons, other than those occupationally exposed, knowingly, while voluntarily helping in the support and comfort of patients; and by volunteers in a programme of biomedical research involving their<unk> . Common medical tests and treatments involving<unk>  include X-rays, CT scans, mammography, lung ventilation and perfusion scans, bone scans, cardiac perfusion scan, angiography,<unk>  therapy, and more. Each type of test carries its own amount of<unk> . There are two general categories of adverse health effects caused by<unk> : deterministic effects and stochastic effects. Deterministic effects (harmful tissue reactions) are due to the killing/malfunction of cells following high doses; and stochastic effects involve either cancer development in exposed individuals caused by mutation of somatic cells, or heritable disease in their offspring from mutation of reproductive (germ) cells. Absorbed dose is a term used to describe how much energy that<unk>  deposits in a material. Common measurements for absorbed dose include rad, or<unk>  absorbed dose, and Gray, or Gy. Dose equivalent calculates the effect of<unk>  on human tissue. This is done using tissue weighting factor, which takes into account how each tissue in the body has different sensitivity to<unk> . The effective dose is the risk of<unk>  averaged over the entire body. Ionizing<unk>  is known to cause cancer in humans. We know this from the Life Span Study, which followed survivors of the atomic bombing in Japan during World War 2. Over 100,000 individuals were followed for 50 years. 1 in 10 of the cancers that formed during this time was due to<unk> . The study shows a linear dose response for all solid tumors. This means the relationship between dose and human body response is a straight line. The risk of low dose<unk>  in medical imaging is unproven. It is difficult to establish risk due to low dose<unk> . This is in part because there are other carcinogens in the environment, including smoking, chemicals, and pollutants. A common head CT has an effective dose of 2 mSv. This is comparable to the amount of background<unk>  a person is exposed to in 1 year. Background<unk>  is from naturally radioactive materials and cosmic<unk>  from space. The embryo and fetus are considered highly sensitive to<unk> . Complications from<unk>  include malformation of internal organs, reduction of IQ, and cancer formation. The SI unit of<unk>  is the coulomb per kilogram (C/kg), which has largely replaced the roentgen (R). One roentgen equals ; an<unk>  of one coulomb per kilogram is equivalent to 3876 roentgens.
Radiation exposure
Radiation damage
Occupational injury
Occupational noise
Human papillomavirus infection
Work accident
Drug use
Tobacco smoking