text: patient dose and computed tomography?   a ct examination with an effective dose of 10 millisieverts (abbreviated msv; 1 msv = 1 mgy in the case of x rays.) may be associated with an increase in the possibility of fatal cancer of approximately 1 chance in 2000. this increase in the possibility of a fatal cancer from radiation can be compared to the natural incidence of fatal cancer in the u.s. population, about 1 chance in 5. in other words, for any one person the risk of radiation-induced cancer is much smaller than the natural risk of cancer. nevertheless, this small increase in radiation-associated cancer risk for an individual can become a public health concern if large numbers of the population undergo increased numbers of ct screening procedures of uncertain benefit.  http://www.fda.gov/cdrh/ct/risks.html