Are X-Rays Safe?
Uploaded by mmora12 on Apr 18, 2007
An occasional patient will ask: "Are x-rays safe?" Others will ask about the amount of radiation. As a radiologist you have a responsibility to give a reasonably honest and understandable answer to the patient. You can certainly explain that diagnostic x-rays are safe. There are no data to indicate otherwise. There is evidence that suggest that such low doses may actually reduce the chance of cancer.1 The question about amount is difficult to answer in an understandable way. First, because it is a rare x-ray unit that has a meter to measure the radiation to the patient and second, because scientific units for radiation dose are not understood. This article is to help you explain radiation to patients in words that they understand. In addition, I present evidence from various human studies to show that low level radiation, comparable to that from a radiograph, may be beneficial and even reduce cancer.
Explaining radiation dose to a patient using the BERT concept
Answering your patient's question about the amount of radiation would be easy if you knew the effective dose. However, it is unlikely the patient would be satisfied if your answer was "the mammogram will give you an effective dose of about 1 millisievert (mSv)." She probably would understand if you converted the effective dose into the amount of time it would take her to accumulate the same effective dose from background radiation. Since the average background rate in the U.S. is about 3 mSv per year, the answer in this case would be about four months. It is likely that she would understand and be satisfied with your answer.
This method of explaining radiation is called Background Equivalent Radiation Time or BERT.2,3 The idea is to convert the effective dose from the exposure to the time in days, weeks, months or years to obtain the same effective dose from background. This method has also been recommended by the U.S. National Council for Radiation Protection and Measurement (NCRP).4 To calculate BERT, I recommend using the average background in the U.S. including contributions to the lung from radon progeny. This is assumed to be 3 mSv/y (300 mrem/y). The background in different parts of the U.S. varies about ± 50% from this value. This uncertainty is unimportant for explaining radiation to patients. The effective dose from common diagnostic x-ray procedures are typically less than the amount of radiation you...