Determining Safe Radiation Doses for Spine and Extremities

While many studies have documented effective radiation dose (ED) delivered by CT scans of the head, neck, chest, abdomen, and pelvis, a new study from Yale set out to quantify ED by CT imaging to the spine and extremities. The study is published in the December issue of the American volume of The Journal of Bone and Joint Surgery.

Reviewing data from 20 imaging studies, the researchers estimated ED based on absorbed radiation dose and tissue-weighting factors. To check their accuracy, the study authors used the same methods to estimate ED for the chest, abdomen, and pelvis, then compared their results to previous studies. Findings showed that CT scans of the thoracic and lumbar spine delivered the highest ED, equivalent to 225 and 240 chest X-rays, respectively. ED to the extremities was highest from scans of the hips and shoulders (locations closest to the torso), delivering roughly the same amount as annual exposure to the public from background radiation. CT scans of wrist or ankle joints delivered less radiation than a posteroanterior chest X-ray.

“Regardless of the study’s limitations, [the researchers'] estimations of ED to the thoracolumbar spine and proximal joints are astounding,” said Rahul Pawar, MD, who reviewed the study. “Research of this nature serves to add a necessary transparency to our profession.”

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