Four-dimensional intensity-modulated radiation therapy planning for dynamic tracking using a direct aperture...

Area of Science:

• Radiation Oncology
• Medical Physics
• Image-Guided Therapy

Background:

• Accurate radiation therapy planning for moving targets is essential for treatment efficacy.
• Four-dimensional (4D) intensity-modulated radiation therapy (IMRT) planning addresses respiration-induced motion.
• Existing methods for 4D IMRT planning often simplify or ignore nonrigid target motion.

Purpose of the Study:

• To develop and evaluate a simplified method for 4D IMRT planning that incorporates both rigid and nonrigid target motion.
• To compare the proposed method against traditional approaches for planning IMRT for moving targets.

Main Methods:

• A novel aperture deformation technique was developed using 4D computed tomography (4DCT) data.
• The method optimizes apertures on a reference phase and deforms them to other phases based on target contour changes.
• Three planning schemes were evaluated: individual phase optimization (gold standard), rigid registration, and the proposed deformation method.

Main Results:

• The proposed direct aperture deformation scheme achieved plan quality comparable to the gold standard (individual phase optimization).
• Compared to rigid-body registration, the new method demonstrated improved target coverage and conformity.
• Normal tissue dose remained similar across the evaluated schemes.

Conclusions:

• Direct aperture deformation is an effective strategy for 4D IMRT planning.
• This method enhances plan quality by accurately addressing nonrigid target motion during respiration.
• The technique offers a practical improvement over methods solely considering rigid-body motion.