In the past few months, much attention has been given to the increasing radiation exposure with CT. In the 14 December 2009 issue of Archives of Internal Medicine, two interesting papers (with three authors in common) investigated the association between radiation exposure from CT examinations and the risk of cancer.
In the first study entitled “Radiation dose associated with common computed tomography examinations and the associated lifetime attributable risk of cancer”, the authors evaluated the radiation dose associated with the 11 most common diagnostic CT examinations, using data from 1119 adult patients seen at 4 hospitals, and calculated the risk of developing cancer due to these examinations. The effective dose varied between 2 mSv (routine head CT) and 31 mSv (multiphase abdominal and pelvic CT). The risk of cancer depended on the type of examination and on the patient’s demographic characteristics. For example, approximately 1 in 270 women and 1 in 595 men who undergo CT coronary angiography at the age of 40 years will develop CT-associated cancer later in their lifetimes. For all CT protocols, the lifetime risk of cancer was substantially higher for examinations performed on patients aged 20 years, while it was substantially lower for examinations performed on 60-year-old patients. The authors concluded that there is a need for greater standardization of CT protocols worldwide to reduce the variation in radiation exposure among institutions, considering that doses from the diagnostic CT examinations investigated here were higher than what has previously been reported.