Answer to Question #5197 Submitted to "Ask the Experts"

1. Should the precautions of x rays and CT scans differ? Considering it was my neck area that was exposed to radiation, why was there a fuss and a contradiction of opinions from the technologists regarding the protection of my abdomen?
   
   
2. A change noticed after having been exposed to the radiation was that my following period came 17 days from the previous and  was filled with excess endometrial lining. My periods consistently come every 42 days. Could it be that the high dose of radiation caused my ovaries to dislodge many eggs all at once? I am a healthy 25-year-old.
   
   
3. Seeing as radiation technology has only been used in populations for half a century, how could there be sufficient data to have conclusive studies upon the concurrent health risks?

There are basically two reasons for differences in scattered radiation from conventional x ray and CT exams:

1. The quantity of scatter is proportional to the size of the x-ray beam and the volume of material (parts of the patient's body or inanimate material such as supporting apparatus) that the beam strikes. The beam for conventional x-ray diverges from the x-ray tube head to cover the film or electronic imaging element. Scatter arises from any of this material. It is quite low level, typically about 1 percent of the intensity of the primary x-ray beam. Some of this scatter arises from outside the patient's body, and some of that may strike the patient. Thus, use of leaded aprons or other shields may be a prudent practice.
   
   
2. In CT exams, the x-ray beam is a tiny pencil, all of which is contained and absorbed in the CT apparatus. Thus, there is very little scatter. Essentially all of the scatter arises from within the patient's body. Thus, shielding prevents the escape of this tiny amount of scatter, and may actually backscatter some of it back into the patient's body. Thus, in this case, the shield does no good and could actually increase the patient's radiation dose.

Your radiation dose to your abdomen from both of these procedures was very small, comparable to the dose you (and everyone else in the world) receive every year from natural environmental (background) radiation. It was not nearly enough to cause the symptoms you describe.

Medical x ray has been in widespread use for more than 100 years. Literally hundreds (perhaps thousands) of studies have been conducted in attempts to find effects, even long delayed, in exposed patients. In the early days of radiology, when little was known about radiation, a few patients were harmed, but rarely seriously. For example, the first report of injury was from a head x ray of the dean of Vanderbilt Medical School (where I work). Some three weeks after exposure, part of his hair began to fall out. The loss was only temporary, however. His x-ray exposure was one hour. With modern technology, there is no proof of any adverse effects.

S. Julian Gibbs, PhD, DDS