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

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

doi:10.3390/app11146459

Abstract

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.

Highlights

Hadron therapy is an advanced radiation therapy modality for treating cancer, which currently uses protons and carbon ions
Carlo simulation are included for resolution of the LaGEMPix, whose intrinsic spatial resolution is better than 9.70 ± 0.09 mm
We present for the first time the characterization of a Gas Electron Multiplier (GEM)-based detector with optical readout based on a matrix of organic photodiodes (OPDs) fabricated on top of a thin-film transistor (TFT) backplane using low energy X-rays

Summary

Introduction

Hadron therapy is an advanced radiation therapy modality for treating cancer, which currently uses protons and carbon ions. Hadrons have the unique feature of increasing energy deposition with penetration depth, with a maximum at the end of their range followed by a sharp decrease (Bragg peak). Hadron therapy offers considerable improvements to conventional radiation therapy treatments by. Hadron therapy offers considerable improvements to conventional radiation therapy treatments by allowing better conformity of the dose to the tumor [2], and requires allowing better conformity of A theprecise dose toverification the tumor [2], butdose delivered requires very accurate dose very accurate dose planning. A precise verification of be theguaranteed dose delivered to the patientquality is, mandatory and has to by appropriate assurance (QA). Appropriate quality assurance (QA) procedures with high procedures high spatial spatial resolution.

Results

Discussion

Conclusion