Inverse-optimized 3D conformal planning: minimizing complexity while achieving equivalence with beamlet IMRT in...

Area of Science:

• Radiation Oncology
• Medical Physics
• Computational Biology

Background:

• Intensity modulated radiation therapy (IMRT) uses beamlet-based inverse planning for conformal treatments.
• Direct comparisons between IMRT and 3D conformal radiation therapy (3DCRT) are challenging due to differing planning methods (inverse vs. forward).
• This study introduces inverse-optimized 3D (IO-3D) conformal planning to enable direct comparisons.

Purpose of the Study:

• To compare simple, optimized IO-3D plans with non-constrained beamlet IMRT.
• To evaluate the effectiveness of optimization versus modulation in IMRT.
• To assess the dosimetric equivalence and complexity of IO-3D plans.

Main Methods:

• Integrated IO-3D dose calculation and optimization into an existing planning system.
• Developed features for dose calculation distributions, cost functions, DVH analysis, and optimization strategies.
• Optimized 3DCRT plans with one to two segments per beam without beamlet approximations, using identical cost functions and evaluation metrics as IMRT.

Main Results:

• IO-3D plans achieved high-quality results comparable to beamlet IMRT for several sites.
• Dosimetric equivalence was observed between IO-3D plans (1-2 segments/beam) and beamlet IMRT plans.
• IO-3D significantly reduced plan complexity, with 22%-84% fewer monitor units per fraction compared to beamlet IMRT.

Conclusions:

• Inverse planning with IO-3D can generate high-quality 3DCRT plans equivalent to beamlet IMRT.
• IO-3D facilitates the optimization of simple, few-segment 3DCRT plans, enhancing efficiency and ease of delivery.
• The reduced complexity of IO-3D plans offers operational advantages for adaptive replanning and motion management.