Variable transformation of calibration equations for radiation dosimetry

Area of Science:

• Medical Physics
• Radiation Detection and Measurement

Background:

• Calibration is essential for accurate radiation dosimetry, relating absorbed dose to measurable quantities.
• Calibration equations introduce uncertainties, affecting dose estimation accuracy.
• Some dosimeters exhibit linear responses with dose-offset or nonlinear behavior.

Purpose of the Study:

• To develop mathematical formulations for calibration, including uncertainty analysis.
• To propose variable transformation methods (linear and log) for dosimeter calibration.
• To reduce the uncertainty of estimated doses in radiation dosimetry.

Main Methods:

• Mathematical formulation of linear and nonlinear calibration relationships.
• Derivation of equations for dose uncertainty based on parameter uncertainties.
• Application of linear and log variable transformations to measured physical quantities.
• Testing methods with Kodak X-Omat V film and BANG polymer gel dosimeters.

Main Results:

• Demonstrated that linear calibration with zero dose-offset allows relative dosimetry without calibration data.
• Showcased variable transformations leading to linear equations with zero dose-offset.
• Reduced the uncertainty of the estimated dose using the proposed transformation methods.

Conclusions:

• Variable transformation methods effectively linearize dosimeter responses, simplifying dosimetry.
• These methods reduce dose estimation uncertainty, improving accuracy.
• The findings support enhanced data manipulation for comparing dose distributions in radiation therapy.