Smoothing intensity-modulated treatment delivery under hardware constraints

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Imaging

Background:

• Intensity-modulated radiation therapy (IMRT) enables precise dose delivery but can result in complex beam sequences.
• Hardware limitations in linear accelerators can affect the fidelity of IMRT delivery.
• Optimizing IMRT plans often involves a trade-off between plan complexity and deliverability.

Purpose of the Study:

• To develop and validate a method for smoothing IMRT beam delivery that accounts for hardware constraints.
• To assess the impact of this smoothing method on leaf segment reduction and treatment plan quality.
• To evaluate the method's performance across different cancer types and intensity distributions.

Main Methods:

• Utilized matrix algebra to model multi-leaf collimator (MLC) leaf motion and hardware constraints (interleaf digitization, synchronization, field abutment).
• Implemented and tested the smoothing method on simulated IMRT cases with varying dimensions and intensity levels.
• Applied the method to clinical IMRT cases for prostate, head and neck, lung, and esophageal cancers.

Main Results:

• Achieved a significant reduction in leaf segment numbers through the smoothing approach.
• The reduction in segments was more pronounced in unconstrained delivery scenarios compared to constrained ones.
• The method's sensitivity to intensity distribution complexity was higher for head and neck cases than for prostate cases.

Conclusions:

• The developed method effectively smooths IMRT treatments while respecting hardware limitations.
• It allows for the maintenance of inversely optimized treatment plans within acceptable tolerance levels.
• This approach enhances the clinical feasibility of delivering complex IMRT plans.