Three-dimensional Patient-specific Quality Assurance Using Beam Delivery Log Data for Pencil Beam Scanning Carbon-ion...

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Quality Assurance

Background:

• Pencil beam scanning in carbon-ion radiotherapy requires precise 3D spot positioning.
• Spot position errors can lead to dose deviations within the target region.
• Current 3D patient-specific quality assurance (PSQA) methods are complex and lack established measurement techniques.

Purpose of the Study:

• To establish a simplified 3D dose verification method for PSQA in carbon-ion radiotherapy.
• To utilize beam delivery log data for dose distribution calculations.
• To develop a clinically applicable method for routine PSQA.

Main Methods:

• Monte Carlo (MC) calculations generated pencil beam dose distributions.
• Semi-MC (SMC) calculations superimposed dose distributions based on log data.
• Gamma analysis (GA) was performed using SMC dose distributions, comparing 2D and 3D analyses against measured data.

Main Results:

• SMC dose curves showed good agreement with measured doses (<5% deviation).
• The proposed 3D GA method, with criteria of 3%-3 mm and 3%-2 mm, demonstrated comparable capabilities to measurement-based methods.
• The 3D GA approach proved effective for clinical application.

Conclusions:

• A 3D dose verification method using beam log data for PSQA in carbon-ion radiotherapy has been successfully developed.
• The method is clinically applicable, offering a simplified approach to quality assurance.
• The proposed method, utilizing specific gamma analysis criteria, ensures reliable dose verification.