Weight Can Be Used to Calculate Pediatric CT Dose

January 7, 2015

Dose for CT examination of children can be calculated by the children’s weight rather than torso diameter measurement.

Dose estimation for children undergoing CT examinations may be based on body weight instead of body diameter, according to a study published in the American Journal of Roentgenology.

Researchers from Harvard Medical School sought to determine if size-specific dose estimates (SSDEs) needed for children undergoing CT examinations, which require manual measurement of torso diameters, could be replaced by using individual body weights.

The study involved 483 children who had undergone 522 CT examinations (187 of the chest and 335 of the abdomen-pelvis). The SSDEs were anteroposterior (DAP), lateral (DLAT) and effective (DE). The children ranged in age from 6 to 20 years.

The effective diameter (DE1) was calculated as the square root of the product of DAP and DLAT. A second measurement of effective diameter (DE2) was obtained using automated software.

Results showed that the median body weight was 51 kg.

  Correlation with Diameter
Mean DAP207.1±50.8 mm0.88
Mean DLAT289.8 ±72.6 mm0.85
Mean DE1243.3±62.0 mm0.86
Mean DE2233.6±55.4 mm0.93


The researchers found that the SSDE measured using body weight was not statistically different than SSDE measured using effective diameters. “Children weighing less than 27 kg and between 46 and 100 kg had statistically significant correlations with torso diameters, whereas only anteroposterior and effective diameters were correlated with children weighing between 27 and 45 kg,” the authors wrote. “Children less than 4 years old had strong correlation with all diameters. Adolescents (15–18 years) did not have statistically significant correlation with any of the diameters.”

The researchers concluded that clinicians could use the simpler method of calculating size-specific dose based on the body weight of children who are undergoing CT examination.