Plastic scintillation dosimeter with a conical mirror for measuring 3D dose distribution

Area of Science:

• Medical Physics
• Radiation Dosimetry
• Radiotherapy Technology

Background:

• Accurate measurement of three-dimensional (3D) dose distribution is crucial for effective radiotherapy.
• Existing techniques may have limitations in precision and real-time monitoring.
• Plastic scintillators offer potential for high-resolution dose detection.

Purpose of the Study:

• To evaluate a novel measurement technique for 3D dose distribution using a plastic scintillator system.
• To assess the accuracy and reliability of scintillation light capture for dose mapping.
• To validate the system's performance against established dosimetry methods.

Main Methods:

• A system comprising a plastic scintillator, scintillating screen, conical mirror, and CCD camera was employed.
• Irradiation was performed using 6 MV photon beams with static and conformal arc plans.
• Monte Carlo simulations provided reference 3D dose distributions for comparison.
• Gamma analysis with criteria of 3% dose difference and 2 mm distance-to-agreement was used for evaluation.

Main Results:

• The system exhibited linear dose response and dose rate independence (<0.5% variation from 100-600 MU/min).
• Deconvolution processing effectively corrected light blurring in measured images.
• High 3D gamma passing rates (3D GPR) were achieved: 99.3% for 10x10 mm², 98.8% for 16x16 mm², and 97.8% for 20x20 mm² fields.
• Excellent reproducibility was confirmed, with 3D GPR of 99.7% for 2F plans and 100% for CA plans.

Conclusions:

• The developed plastic scintillation dosimeter is a suitable technique for measuring 3D dose distributions.
• The system's performance, validated by gamma analysis, indicates its potential for clinical applications.
• Future work will focus on extending the technique to 4D dose distribution measurements for VMAT-SBRT plans.