Abstract Book

S1196

ESTRO 37

Conclusion In patients with heart failure, guarantee VAD functionality for any type of dose is crucial. In this work, we showed that the pump continued its proper work after irradiation under high-energy photon beams. Future measurements will involve in vitro investigation of the system by simulating some typical radiotherapy treatments using 18MV energy photon beams where the influence of the neutron activation on the components can become important. EP-2166 Halcyon clinical performance evaluation for Head and Neck treatments compared to Truebeam D. Mihailidis 1 , R. Scheuermann 1 , C. Kennedy 1 , L. Brady 1 , L. Dong 1 , J. Metz 1 1 PENN-Perelman Center for Advanced Med, Radiation Oncology, Philadelphia, USA Purpose or Objective Evaluate the dosimetric performance and delivery of the Varian Halcyon TM (H) system and compare it with that of the Varian Truebeam TM (TB). Halcyon is the new radiotherapy platform that offers a single 6X-FFF straight-through linac with a new jawless fast dual level stacked MLC system, all optimized for rapid intensity modulated deliveries. This is our initial clinical experience for Head and Neck (H&N) treatments compared to the Truebeam platform. Material and Methods The dosimetric and delivery performance of the first clinical H system was studied at UPenn for a number of H&N patients. Based on our experience with the prototype system, fast IMRT delivery resulted in superior dosimetric results than VMAT (RapidArc) delivery for the H 1 . For our clinical implementation, H&N cases were planned for IMRT on the H and were compared with the TB VMAT plans and delivery times. For our first seven H&N patients, the comparison was based on dose distributions, plan verification and quality assurance accuracy, and the overall delivery times of the two systems. Our institutional prescriptions and optimization objectives were used for the plan optimization and the plans were reviewed and evaluated by the same clinician. The MVCBCT image dose is part of the H workflow and is included in the plan optimization for the H. Results In six cases, IMRT plans on the H were dosimetrically superior to the VMAT plans on the TB in that the OARs received lower mean doses. In 1 case, the TB VMAT plan was superior. DVHs between H and TB plans for OARs, with most OARs for the H plan receiving lower doses for the complex H&N cases, are shown in Fig. 1. The dose differences for various OARs range from ~1 to ~5 Gy with 95% CI for the mean. The H plan QA results gave passing rates of 90% or higher for γ: 3%, 3mm (global) with the H IMRT delivery time being comparable to the RA TB delivery time.

made blood flow, through the anastomized effusion into the descending thoracic aorta with Hemashield 16mm discharge prosthesis and ensured the perfusion of the organs. All this was possible thanks to the alternation of the two operating states: S1 (high speed in 64sec.) and S2 (low speed in 8sec). The device was connected to an external FlowMaker controller delivering power via a tun- nelled driveline from a lithium ion battery. The controller allowed manual adjustments of pump speed. All measur- ements were performed with the full charged battery. The in vitro setting (Fig.1) consisted of a RW3 phantom with Plexiglas siliconized box filled by deionized water where the pump was immersed and connected to Flow- Maker, 1.5m away from pump. The pump was located and irradiated at the isocenter of a Synergy Agility (Elekta, Crawley) using 10MV photon beam (to minimize neutron activation), 1000 M.U. and 20x20cm 2 field. Voltage, current and frequency, parameters of VAD alternating power supply, were initially measured to establish reference values in the BaseLine session. These values were then compared to those obtained immediately before (PreRad session), during and immediately after irradiation (Irradiation and PostRad sessions, respectively). The same parameters were also measured two months later (Final verification session). After each session, the pump was left running till battery life. The whole set of measurements took six months.

Results No changes were recorded in the registered parameters, i.e. after each session, the VAD system worked stably. These results are collected in Fig.2. This figure shows the behaviour of the voltage (mV), the current (mA) and the frequencies (Hz) in S1 and S2 operating states during BaseLine session (a). The same figure displays the behaviour of the voltage (b), the current (c) and the frequency (d) measured in the five sessions during S1 state, respectively.

Fig. 1: DVH for OARs, with H lower mean doses compared to the TB