To establish an organdosedatabase for pediatric and adolescent reference individuals undergoing computed tomography(CT) examinations by using Monte Carlo simulation. The data will permit rapid estimates of organ and effective doses for patients of different age, gender, examination type, and CTscanner model.Methods:
The Monte Carlo simulation model of a Siemens Sensation 16 CTscanner previously published was employed as a base CTscanner model. A set of absorbed doses for 33 organs/tissues normalized to the product of 100 mAs and CTDIvol (mGy/100 mAs mGy) was established by coupling the CTscanner model with age-dependent reference pediatric hybrid phantoms. A series of single axial scans from the top of head to the feet of the phantoms was performed at a slice thickness of 10 mm, and at tube potentials of 80, 100, and 120 kVp. Using the established CTDIvol− and 100 mAs-normalized dose matrix, organdoses for different pediatric phantoms undergoing head, chest, abdomen-pelvis, and chest-abdomen-pelvis (CAP) scans with the Siemens Sensation 16 scanner were estimated and analyzed. The results were then compared with the values obtained from three independent published methods: CT-Expo software, organdose for abdominal CT scan derived empirically from patient abdominal circumference, and effective dose per dose-length product (DLP).Results:
Organ and effective doses were calculated and normalized to 100 mAs and CTDIvol for different CT examinations. At the same technical setting, dose to the organs, which were entirely included in the CT beam coverage, were higher by from 40 to 80% for newborn phantoms compared to those of 15-year phantoms. An increase of tube potential from 80 to 120 kVp resulted in 2.5–2.9-fold greater braindose for head scans. The results from this study were compared with three different published studies and/or techniques. First, organdoses were compared to those given by CT-Expo which revealed dose differences up to several-fold when organs were partially included in the scan coverage. Second, selected organdoses from our calculations agreed to within 20% of values derived from empirical formulae based upon measured patient abdominal circumference. Third, the existing DLP-to-effective dose conversion coefficients tended to be smaller than values given in the present study for all examinations except head scans.Conclusions:
A comprehensive organ/effective dosedatabase was established to readily calculate doses for given patients undergoing different CT examinations. The comparisons of our results with the existing studies highlight that use of hybrid phantoms with realistic anatomy is important to improve the accuracy of CTorgandosimetry. The comprehensive pediatric dose data developed here are the first organ-specific pediatric CT scandatabase based on the realistic pediatric hybrid phantoms which are compliant with the reference data from the International Commission on Radiological Protection (ICRP). The organdosedatabase is being coupled with an adult organdosedatabase recently published as part of the development of a user-friendly computer program enabling rapid estimates of organ and effective dosedoses for patients of any age, gender, examination types, and CTscanner model.
This work was supported by Contract Nos. HHS-N2612-0090-0098P, HHS-N2612-0100-0692P, and HHS-N2612-0090-0177P with the Radiation Epidemiology Branch of the National Cancer Institute.
II. MATERIALS AND METHODS
II.A. CTscanner simulation
II.B. Reference pediatric male and female hybrid phantoms
II.C. Organdose matrix normalized by 100 mAs and CTDIvol
II.D. Organ and effective doses for major scan types and specific scanner
II.E. Comparison with other studies
III. RESULTS AND DISCUSSION
III.A. Organ and effective dose matrix for specific scan types
III.B. Scanner-specific organ and effective doses
III.C. Comparison of pediatric organdoses with other data
III.C.1. Comparison with CT-Expo
III.C.2. Comparison with organdoses derived from circumference
III.C.3. Comparison with the existing DLP-to-effective dose conversion coefficients
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