Applied Sciences (Jul 2021)

Characterization with X-rays of a Large-Area GEMPix Detector with Optical Readout for QA in Hadron Therapy

  • Andreia Maia Oliveira,
  • Hylke B. Akkerman,
  • Saverio Braccini,
  • Albert J. J. M. van Breemen,
  • Lucia Gallego Manzano,
  • Natalie Heracleous,
  • Ilias Katsouras,
  • Johannes Leidner,
  • Fabrizio Murtas,
  • Bart Peeters,
  • Marco Silari

DOI
https://doi.org/10.3390/app11146459
Journal volume & issue
Vol. 11, no. 14
p. 6459

Abstract

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Quality Assurance (QA) in hadron therapy is crucial to ensure safe and accurate dose delivery to patients. This can be achieved with fast, reliable and high-resolution detectors. In this paper, we present a novel solution that combines a triple Gas Electron Multiplier (GEM) and a highly pixelated readout based on a matrix of organic photodiodes fabricated on top of an oxide-based thin-film transistor backplane. The first LaGEMPix prototype with an active area of 60 × 80 mm2 was developed and characterized using low energy X-rays. The detector comprises a drift gap of 3.5 mm, a triple-GEM stack for electron amplification, and a readout featuring 480 × 640 pixels at a 126 µm pitch. Here, we describe the measurements and results in terms of spatial resolution for various experimental configurations. A comparison with GAFCHROMIC® films and the GEMPix detector used in the charge readout mode was performed to better understand the contribution to the spatial resolution from both the electron diffusion and the isotropic emission of photons. The measurements were compared to Monte Carlo simulations, using the FLUKA code. The simulation predictions are in good agreement with the GEMPix results. Future plans with respect to applications in hadron therapy are discussed.

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