Double-Stacked MLC Layout for Low-Penumbra Radiation Therapy
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Solution Overview
Problem
Existing radiation therapy systems face challenges in achieving precise beam shaping and delivery, particularly in ensuring minimal penumbra and inter-leaf leakage, while also accommodating patient positioning and imaging requirements for accurate treatment planning.
Innovation Solution
The system employs a double-stacked multileaf collimator design with independently movable leaves, offset and focused to minimize penumbra, and a gantry configuration allowing coplanar therapy, integrated with a diagnostic-quality CT scanner for precise imaging and on-table adaptive therapy planning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single multileaf collimator is used for beam shaping, then the device complexity is reduced, but the penumbra and inter-leaf leakage increase
Solution Approach 1:
The collimation system is divided into two separate multileaf collimators (first MLC and second MLC) positioned at different locations in the beam path. Each MLC independently shapes the beam, with the first MLC closer to the source and the second MLC closer to the patient. This segmentation allows each collimator to work at its optimal position, reducing penumbra and inter-leaf leakage while maintaining manageable device complexity through modular design
Solution Approach 2:
The invention adds a spatial dimension to the collimation system by positioning two MLCs at different longitudinal locations rather than using a single MLC. This dual-plane arrangement creates overlapping collimation fields that reduce penumbra effects and minimize inter-leaf leakage by addressing beam shaping from two different spatial perspectives
2Device complexity
If the focus points of the first and second multileaf collimators are the same, then the system is simpler to align, but the penumbra match between collimators is degraded
Solution Approach 1:
Each multileaf collimator is configured with its own optimized focus point tailored to its specific position in the beam path. The first MLC has a focus point optimized for its location closer to the source, while the second MLC has a focus point optimized for its location closer to the patient. This localized optimization at each position improves penumbra matching and reduces inter-leaf leakage, with the control system managing the additional alignment parameters
3Manufacturing precision
If a ring gantry configuration is used for coplanar therapy, then the system achieves precise beam delivery, but the adaptability for non-coplanar therapy is reduced
Solution Approach 1:
The ring gantry is configured to enable coplanar therapy with high precision, while the system maintains adaptability through dynamic treatment planning and couch positioning capabilities. The dual MLC system can be repositioned and reconfigured for different treatment scenarios, and the control system can adapt the coplanar beam delivery to approximate non-coplanar dose distributions through sophisticated treatment planning, balancing precision with operational flexibility
4Device complexity
If the leaves of the multileaf collimators are made wider to reduce the number of leaves, then the device complexity is reduced, but the beam shaping precision and inter-leaf leakage are worsened
Solution Approach 1:
The beam shaping task is segmented between two MLCs rather than requiring a single MLC with excessive precision. Each MLC can use moderately sized leaves since the combined effect of both collimators achieves the required beam shaping precision. This segmentation allows each individual MLC to have fewer, wider leaves while maintaining overall system precision through the layered collimation approach
Data Source
AI summary
A system including a diagnostic-quality CT scanner for imaging a patient, the diagnostic-quality CT scanner having an imaging isocenter and a radiation therapy device positioned adjacent the diagnostic-quality CT scanner, the radiation therapy device including a gantry carrying a radiation therapy beam source and having a radiation therapy isocenter separate from the imaging isocenter of the diagnostic-quality CT scanner. The system including a couch configured to position the patient for imaging and for radiation therapy by translating the patient between the diagnostic quality CT scanner and the radiation therapy device.