User:Doc James/CT

Adverse effects
the benefits are typically greater than the risks when used for appropriate reasons. , especially in children, the benefits that stem from their use outweigh the risk in many cases.

Cancer
There is a small increase risk of cancer with CT scans with this risk being slightly larger in children. CT scans involve the use of 10 to 100 times more ionizing radiation than plain X-rays. It is estimated that 0.4% of current cancers in the United States are due to CTs performed in the past and that this may increase to as high as 1.5-2% with 2007 rates of CT usage; however, this estimate is disputed.

These estimates are partly based on similar radiation exposures experienced by those present during the atomic bomb explosions in Japan during the second world war and nuclear industry works. Estimated lifetime cancer mortality risks attributable to the radiation exposure from a CT in a 1-year-old are 0.18% (abdominal) and 0.07% (head) — an order of magnitude higher than for adults — although those figures still represent a small increase in cancer mortality over the background rate. In the United States, of approximately 600,000 abdominal and head CT examinations annually performed in children under the age of 15 years, a rough estimate is that 500 of these individuals might ultimately die from cancer attributable to the CT radiation. The additional risk is still low: 0.35% compared to the background risk of dying from cancer of 23%. Furthermore, certain conditions can require children to be exposed to multiple CT scans.

One study indicated that radiation by CT scans is often higher and more variable than cited, and each of the 19,500 CT scans that are daily performed in the US is equivalent to 30 to 442 chest X-rays in radiation. It has been estimated that CT radiation exposure will result in 29,000 new cancer cases just from the CT scans performed in 2007. The most common cancers caused by CT are thought to be lung cancer, colon cancer and leukemia, with younger people and women more at risk. These conclusions, however, are criticized by the American College of Radiology (ACR), which maintains that the life expectancy of CT scanned patients is not that of the general population and that the model of calculating cancer is based on total-body radiation exposure and thus faulty.

CT scans can be performed with different settings for lower exposure in children, although these techniques are often not employed. Studies support informing parents of the risks of pediatric CT scanning.

Contrast
The old radiocontrast agents caused reactions in 1% of cases while the newer lower osmolar agents cause reactions in 0.04% of cases.

The contrast agent may induce contrast-induced nephropathy. This occurs in 2 – 7% of people who receives these agents with greater risk in those who have preexisting renal insufficiency, preexisting diabetes, or reduced intravascular volume. People with mild kidney impairment are usually advised to ensure full hydration for several hours before and after the injection. For moderate kidney failure, the use of iodinated contrast should be avoided; this may mean using an alternative technique instead of CT. Those with severe renal failure requiring dialysis do not require special precautions, as their kidneys have so little function remaining that any further damage would not be noticeable and the dialysis will remove the contrast agent.

Hair loss
A few cases of temporary hair lose following multiple CTs in a short period of time have been reported.