An open-source motion platform that replicates time synchronised internal and external patient motion for real-time image-guided radiotherapy

Real-time Image-guided Radiotherapy (IGRT) technologies aim to track intra-fractional tumour motion during delivery of high radiation doses to tumours. For the development and safe implementation of real-time IGRT technologies into the clinic, there is a need for robust and repeatable quality assurance (QA) devices. Motivated by this need, this work presents the development and characterisation of a novel time-synchronised motion platform designed for QA purposes of real-time IGRT technologies that perform combined internal and external patient motion monitoring. The Internal-External Robotic Actuator (IntERAct) QA device was developed to integrate a 6-degree-of-freedom (6DoF) robotic arm with a 1-degree-of-freedom (1DoF) motion actuator, which replicate 6DoF internal tumour and 1DoF external surface movements, respectively. The IntERAct device was validated by performing tests which replicated patient-measured lung and liver motion traces on the 6DoF and 1DoF platforms. The device synchronised the internal and external motions to within 0.1 s with under two-millimetre geometric accuracy. The full details of the IntERAct device have been compiled into an open-source repository on GitHub for the medical physics community to use: https://github.com/Image-X-Institute/IntERAct .