Preliminary results of the Gas Electron Multiplier (GEM) as real-time beam monitor in hadron therapy

Aza, E.; Ciocca, Mario; Murtas, F.; Puddu, S.; Pullia, M.; Silari, M.

doi:10.1016/j.nima.2016.10.029

Cited by 7 publications

(5 citation statements)

References 17 publications

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“…Therefore, it provides new information such as 2D images and 3D data representation. As a first step, a triple-GEM detector coupled to an earlier, coarser readout was irradiated with protons and carbon ions in air [44]. Lateral beam profiles of the GEMPix for one carbon ion beam energy were found in agreement with those obtained by radiochromic EBT3 films.…”

Section: Hadron Therapysupporting

confidence: 52%

Medical Applications of the GEMPix

2021

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The GEMPix is a small gaseous detector with a highly pixelated readout, consisting of a drift region, three Gas Electron Multipliers (GEMs) for signal amplification, and four Timepix ASICs with 55 µm pixel pitch and a total of 262,144 pixels. A continuous flow of a gas mixture such as Ar:CO2:CF4, Ar:CO2 or propane-based tissue equivalent gas is supplied externally at a rate of 5 L/h. This article reviews the medical applications of the GEMPix. These include relative dose measurements in conventional photon radiation therapy and in carbon ion beams, by which on-line 2D dose images provided a similar or better performance compared to gafchromic films. Depth scans in a water phantom with 12C ions allowed measuring the 3D energy deposition and reconstructing the Bragg curve of a pencil beam. Microdosimetric measurements performed in neutron and photon fields allowed comparing dose spectra with those from Tissue Equivalent Proportional Counters and, additionally, to obtain particle track images. Some preliminary measurements performed to check the capabilities as the detector in proton tomography are also illustrated. The most important on-going developments are: (1) a new, larger area readout to cover the typical maximum field size in radiation therapy of 20 × 20 cm2; (2) a sealed and low-pressure version to facilitate measurements and to increase the equivalent spatial resolution for microdosimetry; (3) 3D particle track reconstruction when operating the GEMPix as a Time Projection Chamber.

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Section: Hadron Therapysupporting

confidence: 52%

Medical Applications of the GEMPix

2021

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“…A triple-GEM detector coupled to an earlier, coarser readout was compared to radiochromic film measurements for irradiation with protons and carbon ions in Ref. [20]. In that work, lateral beam profiles of the GEMPix for one carbon ion beam energy are compared to those obtained by radiochromic EBT3 films and found in very good agreement.…”

Section: A Experimentalmentioning

confidence: 98%

A GEMPix‐based integrated system for measurements of 3D dose distributions in water for carbon ion scanning beam radiotherapy

et al. 2020

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Purpose: Commercially available systems for ion beam reference dosimetry in water are mainly based on ionization chambers. In those systems, a large number of small detectors are typically arranged in a two-dimensional (2D) array or matrix to achieve high spatial resolution (order of several millimeters) and large field coverage at the same time. The goal of this work was to investigate the reliability of a detector of superior spatial resolution to perform three-dimensional (3D) ionization measurements in carbon ion pencil beams. Methods: The GEMPix is a small gaseous detector with a highly pixelated readout, consisting of a drift region (with 2.8 cm 3 9 2.8 cm 3 9 0.3 cm 3 volume), three gas electron multipliers (GEMs) for signal amplification and four Timepix ASICs with 55 µm pixel pitch and a total of 262,144 pixels. An integrated system was designed and built, which consists of a commercial water phantom with a three-axis motorized arm, a reference large-area ionization chamber for signal normalization to the beam output and the GEMPix itself. Measurements at different depths in water have been performed at the Italian National Centre for Oncological Hadrontherapy (CNAO) with three carbon ion beam energies. Lateral beam profiles measured with the GEMPix at the shallowest depth were compared to those measured with radiochromic EBT3 films in air in the position of the reference ionization chamber. The Timepix readout was calibrated in energy by using one independent depth scan with carbon ions of 150 mm range. Bragg peak curves were also simulated using the Monte Carlo FLUKA code as a reference. Results: Beam profiles measured with the GEMPix were smooth and showed similar shape and full width at half maximum when compared to those measured with radiochromic EBT3 films. Smooth, reproducible Bragg curves were obtained with statistical uncertainties of about 2%, matching FLUKA simulations of the Bragg curves within 15% for most data points. This difference is partially explained for the measurement with carbon ions of 150 mm range by a saturation effect in the GEMs. The high granularity of the readout allowed to produce 2D images of the deposited dose at different depths, as well as 3D data distributions. Conclusions: This paper demonstrates the capability of the GEMPix detector to measure the 3D dose distribution of carbon ions in water for a clinical pencil beam reliably. In the future, the detector area will be increased to cover fields of scanned beams. Measurements at higher beam intensities and with protons are planned.

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“…Very preliminary results have been actually published about this topic [23] but they seems to be very promising, and the possibility to use them as substitutes of the strip chambers has to be investigated.…”

Section: Gas Electron Multipliermentioning

confidence: 99%

Control Of The Dose Distribution In Charged Particle Therapy

Manganaro¹,

Attili²,

Dalmasso³

et al. 2017

Proceedings of the 26th International Nuclear Physics Conference — PoS(INPC2016)

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The use of ions in radiation therapy aims at improving the selectivity of the irradiation thanks to a favourable depth-dose profile and, in case of heavy ions, to their enhanced radiobiological effect. The treatment modality employing actively scanned pencil beams provides highly conformal dose distributions but is sensitive to uncertainties in the dose calculation, delivery and measurement. During the treatment, the delivery of the beam has to be controlled in real time and monitored with high accuracy, including any effect due to patient positioning and motion. Based on the experience gained in the collaboration with the CNAO (Centro Nazionale di Adroterapia Oncologica, Pavia, Italy), this paper is intended to give an overview of recent techniques and trends for the delivery, measurement and verification of the dose distribution in charged particle therapy with scanned ion beams, focusing in particular on real time and online techniques.

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Preliminary results of the Gas Electron Multiplier (GEM) as real-time beam monitor in hadron therapy

Cited by 7 publications

References 17 publications

Medical Applications of the GEMPix

Medical Applications of the GEMPix

A GEMPix‐based integrated system for measurements of 3D dose distributions in water for carbon ion scanning beam radiotherapy

Control Of The Dose Distribution In Charged Particle Therapy

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