ALARA, not Alarm
Nice post over at Scan Man's Notes. He has an excerpt from an editorial in Applied Radiology by the Chief of Rads at Maryland, Dr. Mezrich.
The editorial comes as a response to recent fears that diagnostic tests such as CT scans may increase the likelihood of cancer. This can be of particular concern for tests performed in children, who will presumably have a longer time to accumulate radiation doses from subsequent radiological studies. At our institution we recently had a discussion regarding the doses of radiation used for tests such as CT scans and others that involve radiation exposure. ALARA is an acronym for "as low as reasonably achievable," in reference to the amount of radiation used for a particular diagnostic test. There are some excellent standards available that take into account a patient's weight (mass) and adjust the doses of radiation accordingly.
The crux of the editorial speaks to the way cells repair damage due to radiation. There are excellent mechanisms for this, as we have evolved in an environment with a substantial amount of radiation. The real question is determining the level of radiation in both time and intensity that will overwhelm our ability to repair damage. Dr. Mezrich makes a good argument for thinking that our bodies can deal with the level of radiation from most tests rather well, and that total radiation dose stretched out over a lifespan does not necessarily increase the risk of cancer. The excerpt concludes by mentioning the need for research to find this specific level of harmful radiation. I suspect that there isn't a single dosage point, but rather as with most other functions of our complex physiology, we will narrow it down to a range of radiation that, in most people, would be sufficient to increase the risk of cancer.
A good read on the subject, for those interested.