That statement that introduces this post is one I have often heard from patients and even doctors to justify doing a test that is likely to yield very little useful information. An article in this week's New England Journal of Medicine actually spells out the real risk of diagnositc imaging exams.
The Cumulative Effect of Radiation
Radiation effects on the body are cumulative. That is why we require health professionals who deal with this modality regularly to monitor their radiation exposure. More than 100 mSv in a five year period, or more than 50 mSv in a single year is considered dangerous. This article looked at records of almost 1 million people and found that, just from diagnostic studies, more than 4 million Americans each year have diagnostic radiology exams exceeding 20mSv per year, putting them on a path to having more than 100 mSv in five years if that dose is continued.
The Worst Offenders
Myocardial Perfusion Studies are the greatest contributors to these high radiation doses that create risk for patients. Abdominal Pelvic and Chest CTs also are major culprits and many of these exams are routinely encouraged "just to be safe" when the safest course may be to avoid these tests.
Understanding the Danger
The accompanying Perspective in the New England Journal points out that most doctors do not know of this danger. Only 9% of ER doctos knew that CT scans delivered high radiation doses that could be dangerous. It is estimated that diagnostic studies may cause 2% of all cancers each year. People should know that these tests aren't harmless and should only be done if they are likely to give results that will impact treament.