For Obese, Deep Organs Receive Lower Doses of Radiation

Phantom study shows less effect for shallow organs; increasing tube potential ups dose to organs

WEDNESDAY, April 11 (HealthDay News) -- For obese individuals, organs deep within the abdomen may receive lower doses of radiation than the organs of normal-weight individuals, with the same scanner operating parameters, according to a study published online April 5 in Physics in Medicine and Biology.

Aiping Ding, Ph.D., and colleagues from the Rensselaer Polytechnic Institute in Troy, N.Y., assessed radiation exposure in five male and five female phantoms with body mass indexes ranging from normal (23.5 kg/m²) to morbidly obese (46.4 kg/m²). The radiation doses to organs and tissues from computed tomography imaging were calculated.

The researchers found that, for obese individuals, radiation doses to organs deep in the abdomen, such as to the colon, may be 59 percent lower than those of normal-weight individuals, with the same scanner operating parameters. For shallow organs, this effect was less significant. When adjusting the tube potential from 120 to 140 kVp, the radiation dose to organs increased by 56 and 62 percent for organs within and outside the scan field, respectively. When the current was doubled for obese level-I, obese level-II, and morbidly-obese phantoms, there was an increase in the effective dose of 57, 42, and 23 percent, respectively, relative to that of the normal-weight phantom.

"This study has shown that the radiation dose to a patient can be greatly affected by his or her size and stature," the authors conclude.

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