Relative optimized linearization for radiochromic film dosimetry with non-uniformity correction

Area of Science:

• Medical Physics
• Radiation Oncology
• Dosimetry

Background:

• Traditional radiochromic film dosimetry necessitates time-consuming batch-specific dose-response curve measurements.
• Existing relative dosimetry techniques often overlook film non-uniformities, compromising accuracy.
• Clinical workflows are burdened by the complexity and time demands of conventional film dosimetry.

Purpose of the Study:

• To develop and validate a relative optimized linearization (ROL) method for radiochromic film dosimetry.
• To eliminate the need for dose-response curve measurements in film dosimetry.
• To enhance accuracy by incorporating non-uniformity corrections into the linearization process.

Main Methods:

• Simulations evaluated an initial linearization method using EBT4 film data (1-10 Gy).
• The linearization was refined with an optimized power function for improved accuracy across dose ranges.
• The optimized linearization was integrated into the multichannel dosimetry (MCD) framework, creating the ROL method.
• ROL was validated against MCD using measured data from various radiation therapy plans (open, wedge, VMAT).
• Robustness was assessed via induced positional and dose delivery errors, and sensitivity to treatment planning modeling errors was examined.

Main Results:

• ROL reduced average errors to below 1% across all channels and dose ranges, outperforming previous methods.
• Dose distributions generated by ROL were comparable to MCD (within 1%) for open and VMAT fields.
• Small discrepancies (<1.5%) were observed in the wedge field's toe region.
• ROL demonstrated robustness against spatial errors and subtle treatment planning variations (MLC modeling).
• Gamma analysis using ROL successfully detected induced partial plan delivery errors.

Conclusions:

• The ROL method offers an efficient and accurate alternative to traditional radiochromic film dosimetry.
• It removes the need for calibration curves and incorporates non-uniformity corrections for high-fidelity results.
• The streamlined workflow of ROL is particularly beneficial for routine clinical quality assurance in radiation therapy.