Abdominal radiograph of a pregnant woman, a procedure that should be performed only after proper assessment of benefit versus risk Diagnostic<unk> s (primarily from CT scans due to the large dose used) increase the risk of developmental problems and cancer in those exposed.<unk> s are classified as a carcinogen by both the World Health Organization's International Agency for Research on Cancer and the U.S. government. It is estimated that 0.4% of current cancers in the United States are due to computed tomography (CT scans) performed in the past and that this may increase to as high as 1.5–2% with 2007 rates of CT usage. Experimental and epidemiological data currently do not support the proposition that there is a threshold dose of radiation below which there is no increased risk of cancer. However, this is under increasing doubt. It is estimated that the additional radiation from diagnostic<unk> s will increase the average person's cumulative risk of getting cancer by age 75 by 0.6–3.0%. The amount of absorbed radiation depends upon the type of<unk>  test and the body part involved. CT and fluoroscopy entail higher doses of radiation than do plain<unk> s. To place the increased risk in perspective, a plain chest<unk>  will expose a person to the same amount from background radiation that people are exposed to (depending upon location) every day over 10 days, while exposure from a dental<unk>  is approximately equivalent to 1 day of environmental background radiation. Each such<unk>  would add less than 1 per 1,000,000 to the lifetime cancer risk. An abdominal or chest CT would be the equivalent to 2–3 years of background radiation to the whole body, or 4–5 years to the abdomen or chest, increasing the lifetime cancer risk between 1 per 1,000 to 1 per 10,000. This is compared to the roughly 40% chance of a US citizen developing cancer during their lifetime. For instance, the effective dose to the torso from a CT scan of the chest is about 5 mSv, and the absorbed dose is about 14 mGy. A head CT scan (1.5 mSv, 64 mGy) that is performed once with and once without contrast agent, would be equivalent to 40 years of background radiation to the head. Accurate estimation of effective doses due to CT is difficult with the estimation uncertainty range of about ±19% to ±32% for adult head scans depending upon the method used. The risk of radiation is greater to a fetus, so in pregnant patients, the benefits of the investigation<unk>  should be balanced with the potential hazards to the fetus. In the US, there are an estimated 62 million CT scans performed annually, including more than 4 million on children. Avoiding unnecessary<unk> s (especially CT scans) reduces radiation dose and any associated cancer risk. Medical<unk> s are a significant source of human-made radiation exposure. In 1987, they accounted for 58% of exposure from human-made sources in the United States. Since human-made sources accounted for only 18% of the total radiation exposure, most of which came from natural sources (82%), medical<unk> s only accounted for 10% of total American radiation exposure; medical procedures as a whole (including nuclear medicine) accounted for 14% of total radiation exposure. By 2006, however, medical procedures in the United States were contributing much more ionizing radiation than was the case in the early 1980s. In 2006, medical exposure constituted nearly half of the total radiation exposure of the U.S. population from all sources. The increase is traceable to the growth in the use of medical imaging procedures, in particular computed tomography (CT), and to the growth in the use of nuclear medicine. Dosage due to dental<unk> s varies significantly depending on the procedure and the technology (film or digital). Depending on the procedure and the technology, a single dental<unk>  of a human results in an exposure of 0.5 to 4 mrem. A full mouth series of<unk> s may result in an exposure of up to 6 (digital) to 18 (film) mrem, for a yearly average of up to 40 mrem. Financial incentives have been shown to have a significant impact on<unk>  use with doctors who are paid a separate fee for each<unk>  providing more<unk> s. Early photon tomography or EPT (as of 2015) along with other techniques are being researched as potential alternatives to<unk> s for imaging applications.
X-ray
Scan
Medicine chest 
Medicine chest
Radiography
Radiochemistry
Hip examination
Radiology