SU-E-T-590: Procedure for Verification and Inter-Comparison of IMRT Beam Models.

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Planning

Background:

• Accurate beam modeling is essential for commissioning radiotherapy planning systems.
• Intensity-modulated radiation therapy (IMRT) beam models present unique challenges due to small field sizes and complex leaf effects.
• Evaluating and comparing different versions of IMRT beam models is critical for ensuring treatment accuracy.

Purpose of the Study:

• To develop and present a method for judging the quality of an IMRT beam model in comparison with other versions.
• To establish a procedure for the inter-comparison of IMRT beam models.
• To facilitate the evaluation and commissioning of IMRT beam models.

Main Methods:

• Distinguished between beam model evaluation and optimization routine evaluation.
• Utilized an H-shaped target suitable for small field sizes and common IMRT target dimensions.
• Generated IMRT plans using two beam models (old and new) with identical prescriptions, delivered on a solid water phantom for film and ionization chamber measurements.

Main Results:

• Performed four dose calculations per plan using each beam model.
• Compared calculated dose distributions with film measurements using gamma analysis.
• Assessed absolute dose accuracy and assigned a score to each beam model based on comparative results.

Conclusions:

• The presented procedure allows for the scoring and comparison of different IMRT beam model versions.
• A unified strategy for beam model inter-comparison can significantly aid in the evaluation and commissioning process.
• This method ensures the quality and reliability of IMRT beam models used in radiotherapy planning.