Scatter dose fears unfounded for pregnant women undergoing screening mammography

Women in early pregnancy need not put off clinically indicated screening mammography over concerns about scatter radiation affecting internal or fetal health, according to a study running in the February edition of the American Journal of Roentgenology.

The researchers behind the study, all of Penn State, arrived at their conclusion by quantifying scatter radiation dose in 207 population-representative women with varied body mass indexes who underwent annual screening mammography.

Prior to the exam, the women were fitted with six optically stimulated luminescence dosimeters. These were placed to assess scatter radiation dose to the skin overlying various internal structures.

The Penn State team found average scatter radiation doses to the structures as follows: 

  1. Left lobe of the thyroid: 0.25 mGy
  2. Right lobe of the thyroid: 0.24 mGy
  3. Salivary gland: 0.2 mGy
  4. Sternum: 0.87 mGy
  5. Bridge of the nose: 0.025 mGy
  6. Umbilicus: 0.011 mGy

Lead author Alison Chetlen, DO, and team noted that the bottom two measurements were so low as to prevent measuring with statistical confidence.

They also found that radiation dose increased with increasing body mass index and increasing breast compression thickness.

In their study discussion, Chetlen et al. pointed out that the National Council on Radiation Protection and Measurements considers the risk of fetal abnormality from doses below 50 mGy to be negligible.

The authors further remind that radiation dose to a fetus from naturally occurring background radiation is approximately 0.5 to 1 mSv for the entire period of gestation, while people receive an average annual dose of 3 mSv just from the environment.

“The low levels of scatter radiation measured in our study do not support delaying mammography during early pregnancy when clinically indicated,” they wrote.

The authors close by stating that the insights they gleaned are “valuable in counseling patients, who may be concerned about the effects of radiation exposure from an annual screening study, or for women who may be pregnant (recognized or unrecognized) during the mammographic examination.”