Using collimator rotation to retain conformal dose distributions with thicker MLC leaves

Area of Science:

• Medical Physics
• Radiation Oncology
• Biomedical Engineering

Background:

• Multi-leaf collimators (MLCs) are crucial for conformal radiotherapy but are sensitive and prone to failure.
• Increasing MLC leaf count improves beam shaping but reduces robustness, a critical issue in low- and middle-income countries (LMICs).
• Limited linac availability and high downtime in LMICs necessitate more robust radiotherapy components.

Purpose of the Study:

• To investigate a novel method for achieving conformal dose distribution using simplified, robust MLCs with thicker leaves.
• To assess the feasibility of using multiple collimator angles to compensate for reduced MLC complexity.
• To evaluate the impact of MLC leaf thickness and collimator angles on dose conformity and homogeneity.

Main Methods:

• Utilized open-source treatment planning software (matRad) to generate treatment plans.
• Simulated radiotherapy plans with varying MLC leaf thicknesses (up to 1.5 cm) and multiple collimator angles.
• Compared dose conformity (CI), homogeneity (HI), and mean dose for circular and crescent-shaped targets.

Main Results:

• Achieved increased dose conformity (CI > 0.6) for crescent-shaped targets using 2 to 6 collimator angles with thicker MLCs.
• Demonstrated that simplified MLCs with thicker leaves can still produce excellent conformal dose distributions.
• The multi-angle delivery technique shows promise for improving treatment capacity and robustness in radiotherapy.

Conclusions:

• A simplified MLC design with thicker leaves, combined with multi-angle beam delivery, can achieve excellent conformal dose distributions.
• This approach enhances MLC robustness, making it suitable for resource-limited settings.
• The technique holds potential for improving conformal dose delivery in intensity-modulated radiotherapy (IMRT).