Students training on virtual medical linear accelerator

Abstract

At the Czech Technical University in Prague, we have installed virtual software environment simulating a radiotherapy treatment room with a medical linear accelerator (software VERT and VERT Physics by Vertual Ltd., United Kingdom). It is possible to simulate patient treatment and physics QA (quality assurance) measurements in virtual reality. This is beneficial for our students and teachers because there is no radiation present while doing the exercises and it is accessible at any time, unlike medical linear accelerators at hospitals. For our department, we have chosen the TrueBeam model by Varian Medical Systems, USA. The linear accelerator can be operated by the user in the same way as at the hospital, including the hardware pendant. There is a selection of patient treatment plans, CT images and RT structures, all of which can be visualised inside the treatment room, also during beam on, simulating the situation inside the patient while irradiating the tumour. Any DICOM files, even from another manufacturer’s linac (linear accelerator) or treatment planning system, can be imported into VERT. Apart from this, there is also an imaging interface and cone-beam CT interface showing options for patient setup. Another part of the software is a physics module with various phantoms and detectors for dosimetry as well as geometry tests. For example, a large water tank can be used for relative dosimetry of photon beams (percent depth doses and profiles), a smaller water phantom can be used for reference dosimetry or chamber cross calibration according to the TRS 398 (1) or IPEM (2) protocol. The results of measurements are based on look-up tables coming from real beam data, so dependence on the depth of measurement, field size, temperature and pressure and other parameters can be demonstrated. Moreover, it is possible to introduce many types of errors into the linac, such as jaw position, laser, or collimator miscalibration, and show how these errors propagate to patient irradiation and how they can be detected by QA tools. This paper is a short report on how this system has been used at our university and how it might be used in modern learning, pointing out its advantages and drawbacks. At the 16th Workshop on European Collaboration in Higher Education on Radiological and Nuclear Engineering and Radiation Protection (CHERNE) it was proposed that this virtual system could be used for an international student training course on medical physics in radiotherapy within the CHERNE network. This course might contain theoretical lectures with demonstrations on the virtual linac, practical exercises on the virtual linac and visits to hospitals (a photon radiotherapy centre, the Thomayer University Hospital in particular, and a proton therapy centre).