MO-F-CAMPUS-T-02: Optimizing Orientations of Hundreds of Intensity-Modulated Beams to Treat Multiple Brain Targets

Authors

  • Ma L,

    1. University of California San Francisco, San Francisco, CA
    2. University of Oklahoma Health Science Center, Oklahoma City, OK
    3. University of Toronto, Toronto, ON
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  • Dong P,

    1. University of California San Francisco, San Francisco, CA
    2. University of Oklahoma Health Science Center, Oklahoma City, OK
    3. University of Toronto, Toronto, ON
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  • Keeling V,

    1. University of California San Francisco, San Francisco, CA
    2. University of Oklahoma Health Science Center, Oklahoma City, OK
    3. University of Toronto, Toronto, ON
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  • Hossain S,

    1. University of California San Francisco, San Francisco, CA
    2. University of Oklahoma Health Science Center, Oklahoma City, OK
    3. University of Toronto, Toronto, ON
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  • Ahmad S,

    1. University of California San Francisco, San Francisco, CA
    2. University of Oklahoma Health Science Center, Oklahoma City, OK
    3. University of Toronto, Toronto, ON
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  • Larson D,

    1. University of California San Francisco, San Francisco, CA
    2. University of Oklahoma Health Science Center, Oklahoma City, OK
    3. University of Toronto, Toronto, ON
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  • Sahgal A

    1. University of California San Francisco, San Francisco, CA
    2. University of Oklahoma Health Science Center, Oklahoma City, OK
    3. University of Toronto, Toronto, ON
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Abstract

Purpose:

To investigate a new modulated beam orientation optimization (MBOO) approach maximizing treatment planning quality for the state-of-the-art flattening filter free (FFF) beam that has enabled rapid treatments of multiple brain targets.

Methods:

MBOO selects and optimizes a large number of intensity-modulated beams (400 or more) from all accessible beam angles surrounding a patient's skull. The optimization algorithm was implemented on a standalone system that interfaced with the 3D Dicom images and structure sets. A standard published data set that consisted of 1 to 12 metastatic brain tumor combinations was selected for MBOO planning. The planning results from various coplanar and non-coplanar configurations via MBOO were then compared with the results obtained from a clinical volume modulated arc therapy (VMAT) delivery system (Truebeam RapidArc, Varian Oncology).

Results:

When planning a few number of targets (n<4), MBOO produced results equivalent to non-coplanar multi-arc VMAT planning in terms of target volume coverage and normal tissue sparing. For example, the 12-Gy and 4-Gy normal brain volumes for the 3-target plans differed by less than 1 mL ( 3.0 mLvs 3.8 mL; and 35.2 mL vs 36.3 mL, respectively) for MBOO versus VMAT. However, when planning a larger number of targets (n≥4), MBOO significantly reduced the dose to the normal brain as compared to VMAT, though the target volume coverage was equivalent. For example, the 12-Gy and 4-Gy normal brain volumes for the 12-target plans were 10.8 mL vs. 18.0 mL and 217.9 mL vs. 390.0 mL, respectively for the non-coplanar MBOO versus the non-coplanar VMAT treatment plans, yielding a reduction in volume of more than 60% for the case.

Conclusion:

MBOO is a unique approach for maximizing normal tissue sparing when treating a large number (n≥4) of brain tumors with FFF linear accelerators.

Dr Ma and Dr Sahgal are currently on the board of international society of stereotactic radiosurgery. Dr Sahgal has received support for educational presentations from Elekta company

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