Radiation Effective Doses to Patients Undergoing Abdominal CT Examinations

Purpose: To determine the radiation effective dose to adult and pediatric patients undergoing abdominal computed tomographic (CT) examinations.

Materials And Methods: Technique factors were obtained for three groups of randomly selected patients undergoing abdominal CT examinations: 31 children aged 10 years or younger; 32 young adults aged 11-18 years; and 36 adults older than 18 years. The radiographic techniques, together with the measured cross sections of patients, were used to estimate the total energy imparted to each patient. Each value of energy imparted was subsequently converted into the corresponding effective dose to the patient, taking into account the mass of the patient.

Results: All abdominal CT examinations were performed at 120 kVp with a section thickness of approximately 7 mm for all sizes of patients. The mean number of CT sections increased from 22.0 for children to 31.5 for adults, and the mean quantity of x radiation in milliampere-seconds increased from 220 mAs for children to 290 mAs for adults. The mean values (+/- SD) of energy imparted were 72.1 mJ +/- 24.4 for children, 183.5 mJ +/- 44.8 for young adults, and 234.7 mJ +/- 89.4 for adults. The corresponding mean values of patient effective dose were 6.1 mSv +/- 1.4 for children, 4.4 mSv +/- 1.0 for young adults, and 3.9 mSv +/- 1.1 for adults.

Conclusion: Values of energy imparted to patients undergoing abdominal CT examinations were a factor of three higher in adults than in children, but the corresponding patient effective doses were 50% higher in children than in adults.