SU-E-T-723: Testing Critical Structure Avoidance: End-To-End Verification Using the MAX-HD Phantom

Authors

  • Shay K,

    1. St. Francis Millennium Cancer Center, Greenville, SC
    2. Gibbs Cancer Center and Research Institute - Pelham, Greer, SC
    3. Spectrum Medical Physics, LLC, Greenville, SC
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  • Myers D,

    1. St. Francis Millennium Cancer Center, Greenville, SC
    2. Gibbs Cancer Center and Research Institute - Pelham, Greer, SC
    3. Spectrum Medical Physics, LLC, Greenville, SC
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  • Gersh J

    1. St. Francis Millennium Cancer Center, Greenville, SC
    2. Gibbs Cancer Center and Research Institute - Pelham, Greer, SC
    3. Spectrum Medical Physics, LLC, Greenville, SC
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Abstract

Purpose:

End-to-end tests should be performed prior to implementation of any major component in the treatment workflow. Each facet of the workflow should be tested; simulation, planning, image-guided alignment, and delivery. This study demonstrates the use of the MAX-HD Phantom (Integrated Medical Technologies, Troy, NY) for multi-system QA prior to clinical implementation of a new LINAC. This anthropomorphic cranial phantom contains multiple targets which can be localized during simulation and planning. During delivery, the dose to these targets can be measured using detectors and dose distribution measured using radiochromic film. While dose to the PTV is an important test, as-important is the verification of critical structure avoidance. This phantom allows for placement of detectors in several critical structure regions, yielding a subsequent verification of the fidelity of avoidance algorithms.

Methods:

The described end-to-end tests evaluate cranial RapidArc treatments planned using Eclipse (AAA and Acuros) delivered using a Varian TrueBeam (Varian Medical Systems, Palo Alto, CA). A 2.5cm-diameter spherical volume serves as the PTV while a peripherally-located region (3cm-offset) serves as the avoidance structure. The planning CT was performed with an “imaging insert,” which is identical to the “detector insert,” however lacks detector bore holes. Prior to delivery, CBCT is used for alignment. Two deliveries were performed for each plan; one with the detector placed within the PTV and the other within the avoidance structure.

Results:

Ten plans were tested; varying the energy, fluence mode, and algorithm. The dose to the PTV differed on average by 0.66% while the dose to the avoidance structure differed by 0.27%.

Conclusion:

The MAX-HD allowed for the verification of treatment workflow (simulation, treatment planning, image-guided alignment, and delivery), concentrating not only on absolute dose to the PTV, but the dose to an avoidance structure.

Presenting author is the President/Owner of Spectrum Medical Physics, LLC, a company which maintains contracts with Siemens Healthcare and Standard Imaging, Inc.

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