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Development and Commissioning of a Prototype Compact Fixed-Beam Radiotherapy System

P Liu1*, R O'Brien1 , S Downes2 , S Heng2 , M Newall2 , S Corde2 , P Keall1 , (1) The University of Sydney, Camperdown, NSW, (2) Prince of Wales Hospital, Randwick, NSW


(Monday, 7/30/2018) 1:15 PM - 1:45 PM

Room: Exhibit Hall | Forum 3

Purpose: Compared to conventional rotating gantry linacs, a fixed-beam radiotherapy system would be smaller, more robust and more cost effective, potentially improving global treatment access. In this work, we developed and commissioned a prototype radiotherapy system utilizing a fixed vertical radiation beam and horizontal patient rotation.

Methods: The prototype system consists of two parts: an Elekta Synergy linac with gantry fixed at 0° and a custom-built patient rotation system (PRS). The PRS is designed to safely immobilize a patient and rotate about the superior-inferior axis to the angle required by the treatment plan. The control, interlock and safety systems of both the PRS and linac were integrated and custom software was developed to control PRS motion, monitor interlocks and gate the radiation beam. The prototype system was commissioned based on guidelines specified in AAPM TG-142, with modifications for the fixed beam geometry made where necessary.

Results: The prototype system meets all TG-142 specifications. Motion of the PRS was within 0.1 ± 0.3 mm and 0.10° ± 0.07° of input values for translation and rotation respectively. The axis of rotation was coincident with the radiation isocenter to within 1 mm. Attenuation of 6 MV X-ray beams by the PRS couch was measured at different angles to be input into the treatment planning system and found to be up to 16.6%. The control software was tested in a variety of machine states and executed motion, stop and beam gating commands as expected. Interlocks and emergency stops of the linac and PRS were successfully integrated and correctly stopped PRS motion and the radiation beam when triggered.

Conclusion: In this work, we have developed and commissioned a prototype system that will serve as a testbed for real-time image-guided treatments with a fixed-radiation beam and horizontal target rotation.

Funding Support, Disclosures, and Conflict of Interest: Co-author Keall is an inventor on several pending patents Nano-X technology and is a founder and shareholder of Nano-X Pty Ltd, which is developing a fixed beam radiotherapy system.


Patient Positioning, Commissioning, Image-guided Therapy


TH- External beam- photons: Development (new technology and techniques)

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