A silicon strip detector array for energy verification and quality assurance in heavy ion therapy

Purpose: The measurement of depth dose profiles for range and energy verification of heavy ionbeams is an important aspect of quality assurance procedures for heavy ion therapy facilities. Thesteep dose gradients in the Bragg peak region of these profiles require the use of detectors with highspatial resolution. The aim of this work is to characterize a one dimensional monolithic silicon detec-tor array called the “serial Dos e Magnifying Glass” (sDMG) as an independent ion beam energy andrange verificat ion system used for quality assurance conducted for ion beams used in heavy iontherapy.Methods: The sDMG detector consists of two linear arrays of 128 silicon sensitive volumes eachwith an effective size of 2mm 9 50lm 9 100lm fabricated on a p-type substrate at a pitch of200 lm along a single axis of detection. The detector was characterized for beam energy and rangeverification by measuring the response of the detector when irradiated with a 290 MeV/u12C ionbroad beam incident along the single axis of the detector embedded in a PMMA phanto m. Theenergy of the12C ion beam incident on the detector and the residual energy of an ion beam incidenton the phantom was determined from the measured Bragg peak position in the sDMG. Ad hoc MonteCarlo simulations of the experimental setup were also performed to give further insight into thedetector response.Results: The relative response profiles along the single axis measured with the sDMG detector werefound to have good agreement between experiment and simulation with the position of the Braggpeak determined to fall withi n 0.2 mm or 1.1% of the range in the detector for the two cases. Theenergy of the beam incident on the detector was found to vary less than 1% between experiment andsimulation. The beam energy incident on the phantom was determined to be (280.9 0.8) MeV/ufrom the experimental and (280.9 0.2) MeV/u from the simulated profiles. These values coincidewith the expected energy of 281 MeV/u.Conclusions: The sDMG detector response was studied experimentally and characterized using aMonte Carlo simulation. The sDMG detector was found to accurat ely determine the12C beam energyand is suited for fast energy and range verif ication quality assurance. It is proposed that the sDMG isalso applicable for verification of treatment planning systems that rely on particle range