An orthogonal moment-based method for automatic verification of radiation field shape

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Image Analysis

Background:

• Accurate verification of radiotherapy treatment fields is crucial for patient safety.
• Current methods for on-line verification can be time-consuming and less precise.
• Automated, real-time verification systems are needed to improve radiotherapy quality assurance.

Purpose of the Study:

• To develop and validate a new automated method for on-line verification of radiotherapy treatment field shape.
• To enable precise comparison of portal field boundaries against reference shapes.
• To enhance the efficiency and accuracy of radiotherapy quality control.

Main Methods:

• Extracting treatment field boundaries from digital portal images and approximating them as polygons.
• Utilizing an orthogonal moment-based method for aligning field boundaries, correcting for translational shifts, scaling, and rotation.
• Developing a fast Legendre moment computation method to reduce processing time.

Main Results:

• The alignment procedure demonstrated high accuracy: 0.5 mm for translational shift, 0.004 for magnification, and <0.3 degrees for rotation.
• The automated alignment process can be completed within 2 seconds on a standard personal computer.
• Simulated cases confirmed the method's effectiveness in precise shape verification.

Conclusions:

• The proposed automated method offers a fast and accurate solution for on-line radiotherapy treatment field shape verification.
• This technique has the potential to significantly improve real-time quality assurance in radiotherapy.
• The developed method can enhance patient safety through reliable and efficient treatment field monitoring.