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Session: SBRT Planning and Dose Delivery [Return to Session]

IMRT and SBRT Treatment Planning Study for the First Clinical Installation of Biology-Guided Radiotherapy System

D Pham1*, E Simiele2, D Breitkreutz3, D Capaldi4, O Oderinde5, B Han1, M Surucu1, L Vitzthum1, M Gensheimer1, H Bagshaw1, A Chin1, D Chang1, N Kovalchuk1, (1) Stanford University, Palo Alto, ,(2) Rutgers University, New Brunswick, NJ, (3) Sunnybrook Health Sciences Centre, North York, ON, CA, (4) University of California, San Francisco, San Francisco, CA, (5) RefleXion Medical, Hayward, CA


TU-F115-IePD-F7-1 (Tuesday, 7/12/2022) 1:15 PM - 1:45 PM [Eastern Time (GMT-4)]

Exhibit Hall | Forum 7

Purpose: The first clinical biology-guided radiation therapy (BgRT) system – RefleXion™ X1 - was installed and commissioned for clinical use at our institution. This study aimed at evaluating the treatment plan quality and delivery efficiency for IMRT/SBRT cases without PET-guidance.

Methods: Forty-two patient plans across six cancer sites (conventionally-fractionated lung, head and neck, anus, prostate, brain, and lung SBRT) planned with the Eclipse™ treatment planning system (TPS) and treated with either a TrueBeam® or Trilogy® were selected for this retrospective study. For each Eclipse VMAT plan, two corresponding plans were generated on the X1 TPS with 10 mm jaws (X1-10mm) and 20 mm jaws (X1-20mm) using our institutional planning constraints. All clinically relevant metrics in this study, including PTV D95%, PTV D2%, Conformity Index (CI), R50, organs-at-risk (OAR) constraints, and beam-on time were analyzed and compared between 126 VMAT and RefleXion plans using paired t-tests.

Results: All but three planning metrics were either equivalent or superior for the 15 X1-10mm plans as compared to the Eclipse VMAT plans across all planning sites investigated. The Eclipse VMAT and X1-10mm plans generally achieved superior plan quality and sharper dose fall-off superior/inferior to targets as compared to the X1-20mm plans, however, the X1-20mm plans were still considered acceptable for treatment. Strong correlation was observed between the TPS-calculated beam-on time and PTV length in the superior-inferior direction for the X1-10mm (R2 = 0.87) and X1-20mm (R2 = 0.85) plans. On average, the required beam-on time increased by a factor of 1.6 across all sites for X1-10mm compared to X1-20mm plans.

Conclusion: Clinically acceptable IMRT/SBRT treatment plans were generated with the X1 TPS for both the 10 mm and 20 mm jaw settings. The X1-10mm plans were equivalent or superior to the Eclipse VMAT plans, however the beam-on times were longer.


Treatment Planning, PET


TH- External Beam- Photons: treatment planning/virtual clinical studies

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