[Physical characterizations for an integrated 160-leaf multi-leaf collimator with a new concept design]

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Technology

Context:

• The Elekta Agility™ system features 160 interdigitating multileaf collimators (MLCs), each 5 mm wide at the isocenter.
• Accurate characterization of MLC performance is crucial for precise radiation delivery.

Purpose:

• To conduct a comprehensive physical characterization of the Elekta Agility™ multileaf collimator system.
• To evaluate key performance parameters including leaf position accuracy, radiation leakage, field penumbra, and the tongue-and-groove (T&G) effect.

Summary:

• Leaf position accuracy was consistently within 0.5 mm across all gantry angles.
• Radiation leakage was notably low (average 0.44%), attributed to a novel tilted leaf design.
• The tongue-and-groove (T&G) effect averaged 20.8%, and penumbra width increased with field size, reaching 8.5 mm at 4 MV for a 20x20 cm field.

Impact:

• The Agility™ MLCs offer low leakage and increased head clearance, beneficial for stereotactic radiotherapy with non-coplanar beams.
• Understanding the trade-offs between leakage, penumbra, and T&G effect is vital for treatment planning and quality assurance.