The purpose of this study is to develop a method for estimating patient-specific dose from
abdomen-pelvis CT examinations and to investigate dose variation across patients in the
same weight group. Our study consisted of seven pediatric patients in the same
weight/protocol group, for whom full-body computer models were previously created
based on the patients' CT data obtained for clinical indications. Organ and effective dose
of these patients from an abdomen-pelvis scan protocol (LightSpeed VCT scanner,
120-kVp, 85-90 mA, 0.4-s gantry rotation period, 1.375-pitch, 40-mm beam collimation, and
small body scan field-of-view) was calculated using a Monte Carlo program previously
developed and validated for the same CT system. The seven patients had effective dose
of 2.4-2.8 mSv, corresponding to normalized effective dose of
(coefficient of variation: 7.6%). Dose variations across the patients were small for large
organs in the scan coverage (mean: 6.6%; range: 4.9%-9.2%), larger for small organs in
the scan coverage (mean: 10.3%; range: 1.4%-15.6%), and the largest for organs partially
or completely outside the scan coverage (mean: 14.8%; range:
effective dose correlated strongly with body weight (correlation coefficient: r = -0.94).
Normalized dose to the kidney and the adrenal gland correlated strongly with mid-liver
equivalent diameter (kidney: r = -0.97; adrenal glands:
r = -0.98). Normalized dose to the
small intestine correlated strongly with mid-intestine equivalent diameter (r = -0.97).
These strong correlations suggest that patient-specific dose may be estimated for any
other child in the same size group who undergoes the abdomen-pelvis scan.