Inverse planning for four-dimensional (4D) volumetric modulated arc therapy

Area of Science:

• Radiation Oncology
• Medical Physics
• Cancer Treatment

Background:

• Organ motion during radiation therapy, particularly due to breathing, poses challenges for accurate dose delivery.
• Traditional 3D VMAT planning may not adequately account for the dynamic nature of tumor motion during treatment.
• Gated VMAT strategies exist but may limit treatment efficiency or the ability to optimize dose distribution across all phases.

Purpose of the Study:

• To develop and present a novel 4D volumetric modulated arc therapy (VMAT) inverse planning framework.
• To integrate the temporal dimension (breathing phase) into VMAT planning for improved accuracy.
• To demonstrate the potential of this framework in optimizing dose distribution and target coverage.

Main Methods:

• Developed a 4D VMAT inverse planning framework that synchronizes gantry rotation with patient breathing phases.
• Utilized registration of phased CT images to compute dose contributions from different respiratory phases.
• Iteratively optimized aperture shape and beam weights by minimizing a planning objective function.
• Compared the proposed 4D VMAT approach with traditional 3D VMAT plans.

Main Results:

• Successfully developed a functional framework for 4D VMAT inverse planning.
• Incorporating the time dimension in VMAT allows for tighter target margins.
• Achieved a full duty cycle optimization, which is superior to 3D VMAT or gated VMAT alone.

Conclusions:

• The proposed 4D VMAT planning framework offers a method to leverage the 'time' dimension in rotational arc therapy.
• This approach provides significant insights into compensating for intrafraction organ motion.
• Exploiting the temporal dimension can lead to more precise and effective radiation treatments.