It turns out that the CT scan radiation exposure risk is much more dangerous than was previously thought. This is really scary considering how freely CT scans are ordered these days. Come the the ER with a headache shortness of breath or belly pain and your doctor is likely going to have a low threshold to order a CT scan as a rule out test. A while back the FDA published a report titled: What Are the Radiation Risks of CT? See the table below.
Now it appears these numbers relating to radiation exposure risk have been severely underestimated due in large part to the higher doses of radiation being given to patients. The average CT scan radiation exposure for an abdomen and pelvis exam was not the 8 mSv reported by the FDA, but rather 31millsieverts, with a range of 6 to 90. Ninety millisieverts is equivalent to many thousands of chest X-rays, or the equivalent background radiation of living over a 30 year period. And you get it all from one CT.
Thirty years of background radiation from one exposure to a CT scan of the abdomen? That's scary. With America's obesity epidemic expanding as we speak, higher and higher doses of radiation will be necessary to obtain good looking films. This can only mean increasing exposure and risk for potential cancer causing CT scan radiation.
|Chest x ray (PA film)|
|Skull x ray|
|Upper G.I. exam|
1.Average effective dose in millisieverts (mSv) as compiled by Fred A. Mettler, Jr., et al., "Effective Doses in Radiology and Diagnostic Nuclear Medicine: A Catalog," Radiology Vol. 248, No. 1, pp. 254-263, July 2008.
How many cancers are CT scans causing? Great question. According to the article "Projected Cancer Risks from Computed Tomographic Scans Performed in the United States in 2007," abstract, Archives of Internal Medicine, Dec. 14/28, 2009, 29,000 cancers will be caused by CT scans performed in 2007 alone, with CT scans of the abdomen and pelvis accounting for just under half of those future cancers. The younger the patient is the greater their risk of getting cancer as they have more years to develop cancer after CT radiation exposure. Women were disproportionately affected by the risk (2/3) due to the larger number of scans being performed on them.
Here's one scary figure. The study authors calculate that a one out of every 270 forty year old women undergoing CT coronary angiography will develop cancer. These numbers are shocking and leave physicians in a catch 22. With more and more data now coming out suggesting that CT scan radiation exposure may significantly increase one's lifetime risk of cancer, physicians are left in a no win situation. To this data I say wow!
But why? Why do physicians continue to order so many CT scans? Some reasons are fear, uncertainty, defensive medicine, easy access and a substitute for good history and physical exam, as this original Happy Hospitalist ecard so eloquently describes below.