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Estimating thyroid dose in pediatric CT exams from surface dose measurement.
Rani Al-Senan1, Deborah L Mueller, Mustapha R Hatab
1Department of Radiology, University of Alabama at Birmingham, Birmingham, AL, USA. ralsenan@uab.edu
Physics in Medicine and Biology
|June 12, 2012
Summary
Pediatric thyroid radiation doses from CT scans can be estimated using neck surface doses. This method provides an acceptable prediction, with a thyroid-to-surface dose ratio of 1.1, aiding in radiation protection for children.
Area of Science:
- Medical Physics
- Radiology
- Pediatric Imaging
Background:
- Accurate estimation of pediatric thyroid radiation dose from CT is crucial for minimizing long-term risks.
- Surface dose measurements offer a potentially simpler alternative to complex internal dose calculations.
Purpose of the Study:
- To investigate the feasibility of estimating pediatric thyroid doses from CT scans using measured neck surface doses.
- To establish a reliable conversion factor between surface dose and actual thyroid dose in young children.
Main Methods:
- Utilized optically stimulated luminescence dosimeters to measure neck surface doses in 25 children (1-3 years old).
- Employed acrylic phantoms to simulate varying pediatric neck anatomies and depths.
- Correlated surface doses with thyroid doses calculated using ImPACT software and age-specific correction factors.
Main Results:
- A consistent thyroid-to-surface dose ratio of 1.1 was determined.
- Pediatric thyroid doses ranged from 20 to 80 mGy.
- No statistically significant difference was found between the proposed method and ImPACT calculations (p = 0.18).
- Surface dose variation along the z-axis ranged from 5% to 8% depending on scan parameters.
Conclusions:
- Neck surface dose is a viable and acceptable predictor of pediatric thyroid dose from CT.
- Optimizing CT parameters, such as using narrower collimation and a pitch factor near 1.0, can reduce dose uncertainty.
- Thyroid depth did not significantly influence the measured dose in this study.
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