[MLC positioning checks and calibration with a portal imaging system]

Area of Science:

• Medical Physics
• Radiation Oncology
• Image Analysis

Context:

• Accurate positioning of radiation therapy beams is crucial for treatment efficacy and patient safety.
• Current methods for verifying Multi Leaf Collimator (MLC) positioning may require specialized equipment or complex procedures.
• The need for efficient and accessible quality assurance tools in radiation oncology is paramount.

Purpose:

• To develop and validate a cost-effective method for precisely verifying the leaf positions of a Multi Leaf Collimator (MLC).
• To implement an in-house image analysis program utilizing Electronic Portal Imaging Device (EPID) images for MLC leaf position checks.
• To establish a reliable technique for transforming image coordinates to radiation field coordinates for accurate leaf tip determination.

Summary:

• The developed method uses EPID images with a marker plate containing known metal marker positions.
• Image analysis determines marker positions, enabling transformation to the radiation field coordinate system.
• This allows for exact determination of MLC leaf tip positions relative to the radiation field for arbitrary field shapes.

Impact:

• Provides a simple, cost-effective, and easily adaptable quality assurance tool for radiation therapy centers.
• Enhances the accuracy and reliability of radiation beam delivery by ensuring correct MLC positioning.
• Facilitates routine quality control of MLC performance, contributing to improved patient safety in radiotherapy.