SU-E-T-622: A Rapid Hybrid VMAT-IMRT Planning Method Using an Abbreviated Beam Angle Optimization Search.

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Planning

Background:

• Intensity-modulated radiation therapy (IMRT) offers high dose modulation.
• Volumetric Modulated Arc Therapy (VMAT) is an advanced radiotherapy technique.
• Combining VMAT and IMRT can potentially enhance treatment quality.

Purpose of the Study:

• To develop hybrid VMAT-IMRT treatment plans using an IMRT beam-angle-optimality (BAO) search.
• To achieve this within a standard treatment planning system (TPS) without specialized software or high-performance computing.
• To evaluate the efficacy of this novel planning approach.

Main Methods:

• A hybrid VMAT-IMRT plan was created by integrating a VMAT arc with selected IMRT segments.
• Beam-angle-optimality (BAO) was approximated by analyzing score penalties from a multi-beam IMRT plan ('poly-IMRT').
• The hybrid plan's BAO was compared to a rigorous method ('VMAT+1') and demonstrated on an SBRT lung patient case.

Main Results:

• Hybrid VMAT-IMRT plans demonstrated superior PTV coverage (87.7%) compared to VMAT (84.3%) and IMRT (85.6%).
• The hybrid plans achieved a better homogeneity index (1.32) than VMAT (1.38) and IMRT (1.41).
• Normal tissue doses remained within acceptable limits (within 0.5%).

Conclusions:

• The developed method successfully generates hybrid VMAT-IMRT plans.
• These plans combine the delivery efficiency of VMAT with the improved target coverage of IMRT.
• The entire planning process is achievable within approximately one hour using standard TPS.