Simultaneous measurement of the spectral and temporal properties of a LINAC pulse from outside the treatment room

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A detection system composed of a CeBr3 scintillating crystal coupled with a photomultiplier tube and connected to a digital oscilloscope was installed in the control room of a Cyberknife™ clinical accelerator during normal irradiation in order to infer the temporal characteristics of the beam and spectral characteristics of the low-intensity scattered radiation present outside the treatment room. Three batches of 20,000 pulses were measured at three different gantry angles. After digitalization and post-processing of the signals, the time profile of the beam pulses was determined with an accuracy of 14 ns with respect to the gating signal, while the energy spectrum of the measured radiation field could be acquired with a resolution of 5.5%. The proposed device makes it possible, thanks to the increased sensitivity of the scintillating crystals and the digital signal processing techniques in place, to monitor the properties of the radiation present outside the bunker produced by the treatment beam, minimizing interference with patient treatment, QA or research activitie
Work supported by the Spanish Government (FPA2015-65035-P, RTC-2015-3772-1), Comunidad de Madrid (S2013/MIT-3024 TOPUS-CM) and European Regional Funds. This is a Contribution for the Moncloa Campus of International Excellence, “Grupo de Física Nuclear-UCM”, Ref. 910059. The authors acknowledge partial support by EU's H2020 under MediNet: a Networking Activity of ENSAR-2 (grant agreement 654002).
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