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Technique for Differentially Weighted, Mixed Energy, Forward Planned, MLC-Based Compensator Planning for Breast and Chestwall

B Rasmussen*, X Du , UP Health System Marquette General Hospital, Marquette, MI


(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: To demonstrate a technique for creating deferentially weighted, mixed energy, MLC-based compensator plans for breast and chestwall.

Methods: The irregular surface compensator technique in the Eclipse planning system (version 13.7, Varian Medical Systems, Palo Alto, CA) was used to create initial fluences for breast/chestwall tangent fields for both 6 MV and 15 MV photon beams. The fluence for each field was manually adjusted to provide a transition from a more heavily weighted 15 MV fluence in the large separation regions of the treatment volume into a more 6 MV weighted fluence in the superficial regions of the treatment volume. The methodology described above was created and tested on multiple patient and phantom datasets. Comparisons to mixed energy field-in-field (FinF) planning were made for validation. Robust quality assurance tests were performed to ensure accuracy and deliverability.

Results: The method described in this work was successful at creating clinically acceptable treatment plans. Delivery accuracy was confirmed to meet typical IMRT gamma criteria. The freedom in iteratively editing fluence-based plans was found to be advantageous in achieving target coverage and dose homogeneity. Potential pitfalls of the planning technique were identified and methods for preventing them were developed.

Conclusion: Mixed energy MLC-based compensator planning provides the ability to tailor the balance of beam energy to patient anatomy, maximizing the benefits of the physical properties of high and low energy photon beams in appropriate regions of the treatment volume. The method described in this work produces plans with desirable isodose distributions. However, it can be considerably more time consuming than traditional field-in-field planning and utilizes modulated high energy fields, making it most advantageous in cases of challenging patient anatomy.


Breast, Treatment Planning, Compensators


TH- External beam- photons: treatment planning/virtual clinical studies

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