Sci—Thur PM: Planning & Delivery — 03: Automated delivery and quality assurance of a modulated electron radiation therapy plan

Authors

  • Connell T,

    1. Medical Physics Unit, McGill University, Montreal General Hospital, Montreal, Québec, Canada
    2. Medical Physics Department, Saskatoon Cancer Center, Saskatoon, Saskatchewan, Canada
    3. Medical Physics Department, McGill University Health Center, Montreal, Québec, Canada
    4. Department of Radiation Oncology, Jewish General Hospital, Montréal, Québec, Canada
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  • Alexander A,

    1. Medical Physics Unit, McGill University, Montreal General Hospital, Montreal, Québec, Canada
    2. Medical Physics Department, Saskatoon Cancer Center, Saskatoon, Saskatchewan, Canada
    3. Medical Physics Department, McGill University Health Center, Montreal, Québec, Canada
    4. Department of Radiation Oncology, Jewish General Hospital, Montréal, Québec, Canada
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  • Papaconstadopoulos P,

    1. Medical Physics Unit, McGill University, Montreal General Hospital, Montreal, Québec, Canada
    2. Medical Physics Department, Saskatoon Cancer Center, Saskatoon, Saskatchewan, Canada
    3. Medical Physics Department, McGill University Health Center, Montreal, Québec, Canada
    4. Department of Radiation Oncology, Jewish General Hospital, Montréal, Québec, Canada
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  • Serban M,

    1. Medical Physics Unit, McGill University, Montreal General Hospital, Montreal, Québec, Canada
    2. Medical Physics Department, Saskatoon Cancer Center, Saskatoon, Saskatchewan, Canada
    3. Medical Physics Department, McGill University Health Center, Montreal, Québec, Canada
    4. Department of Radiation Oncology, Jewish General Hospital, Montréal, Québec, Canada
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  • Devic S,

    1. Medical Physics Unit, McGill University, Montreal General Hospital, Montreal, Québec, Canada
    2. Medical Physics Department, Saskatoon Cancer Center, Saskatoon, Saskatchewan, Canada
    3. Medical Physics Department, McGill University Health Center, Montreal, Québec, Canada
    4. Department of Radiation Oncology, Jewish General Hospital, Montréal, Québec, Canada
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  • Seuntjens J

    1. Medical Physics Unit, McGill University, Montreal General Hospital, Montreal, Québec, Canada
    2. Medical Physics Department, Saskatoon Cancer Center, Saskatoon, Saskatchewan, Canada
    3. Medical Physics Department, McGill University Health Center, Montreal, Québec, Canada
    4. Department of Radiation Oncology, Jewish General Hospital, Montréal, Québec, Canada
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Abstract

Modulated electron radiation therapy (MERT) offers the potential to improve healthy tissue sparing through increased dose conformity. Challenges remain, however, in accurate beamlet dose calculation, plan optimization, collimation method and delivery accuracy. In this work, we investigate the accuracy and efficiency of an end-to-end MERT plan and automated-delivery workflow for the electron boost portion of a previously treated whole breast irradiation case. Dose calculations were performed using Monte Carlo methods and beam weights were determined using a research-based treatment planning system capable of inverse optimization. The plan was delivered to radiochromic film placed in a water equivalent phantom for verification, using an automated motorized tertiary collimator. The automated delivery, which covered 4 electron energies, 196 subfields and 6183 total MU was completed in 25.8 minutes, including 6.2 minutes of beam-on time with the remainder of the delivery time spent on collimator leaf motion and the automated interfacing with the accelerator in service mode. The delivery time could be reduced by 5.3 minutes with minor electron collimator modifications and the beam-on time could be reduced by and estimated factor of 2–3 through redesign of the scattering foils. Comparison of the planned and delivered film dose gave 3%/3 mm gamma pass rates of 62.1, 99.8, 97.8, 98.3, and 98.7 percent for the 9, 12, 16, 20 MeV, and combined energy deliveries respectively. Good results were also seen in the delivery verification performed with a MapCHECK 2 device. The results showed that accurate and efficient MERT delivery is possible with current technologies.

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