Computing effective doses to pediatric patients undergoing body CT examinations

Background The computation of patient effective doses to children is of particular interest given the relatively high doses received from this imaging modality, as well as the increased utilization of CT in all areas of medicine. Current methods for computing effective doses to children are relatively complex, and it would be useful to develop a simple method of computing pediatric effective doses for clinical purposes that could be used by radiologists and technologists. Objective To obtain pediatric effective doses for body CT examinations by the use of adult effective doses obtained from effective dose (E) per unit dose length product (DLP) coefficients, and energy imparted to a child relative to an adult. Materials and methods Adult E/DLP coefficients were obtained at 120 kV using the ImPACT CT dosimetry spreadsheet. Patients were modeled as cylinders of water, and values of energy imparted to cylinders of varying radii were generated using Monte Carlo modeling. The amounts of energy imparted to the chest and abdomen of children relative to adults (R-en) were obtained. Pediatric effective doses were obtained using scaling factors that accounted for scan length, mAs, patient weight, and relative energy imparted (R-en). Results E/DLP values were about 16 mu Sv/mGy cm for males and about 19 mu Sv/mGy cm for females. R-en at 120 kV for newborns was 0.35 for the chest and 0.49 for the abdomen. At constant mAs, the effective dose to 6-month-old patients undergoing chest CT examinations was found to be about 50% higher than that to adults, and for abdominal examinations about 100% higher. Conclusion Adult effective doses can be obtained using DLP data and can be scaled to provide corresponding pediatric effective doses from body examinations on the same CT scanner.