Quantitative analysis of patient-specific dosimetric IMRT verification

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Dosimetry

Background:

• Current patient-specific dosimetric verification for intensity-modulated radiation therapy (IMRT) is often qualitative, time-consuming, and hinders evidence-based reductions.
• There is a need for more efficient and quantitative methods to assess the accuracy and reliability of IMRT delivery.

Purpose of the Study:

• To apply a quantitative analysis parameter to IMRT dosimetric verification.
• To determine the most suitable verification plane for IMRT prostate patients.
• To assess the long-term accuracy, reproducibility, and stability of the planning and delivery system to propose a reduction in verification frequency.

Main Methods:

• Acquired film measurements in different planes for ten IMRT prostate patients.
• Analyzed film and ion chamber verification results for 61 patients to assess long-term accuracy and reproducibility.
• Studied the reproducibility of the measurement and analysis system.

Main Results:

• Verification results are significantly dependent on the chosen plane; the coronal plane showed insensitivity to delivery errors.
• No correlation was found between error levels in different verification planes.
• Long-term verification data demonstrated consistent patterns, supporting the potential for safely reducing patient-specific verification.

Conclusions:

• An evidence-based model for reducing IMRT verification is proposed, emphasizing the use of quantitative parameters like dose/distance to agreement (e.g., 3%/3 mm) as acceptability criteria.
• Quantitative parameters and discrepancy displays are recommended for effective verification.
• Planning and delivery systems must meet stringent accuracy, reproducibility, and stability standards to enable reduced verification.