Microdosimetry in low energy proton beam at therapeutic-equivalent fluence rate with silicon 3D-cylindrical microdetectors

Guardiola, Consuelo; Bachiller‐Perea, Diana; Prieto-Pena, Juan; Jiménez-Ramos, M.C.; López, J. Garcı́a; Esnault, Cécile; Fleta, C.; Quirion, D.; Gómez, F.

doi:10.1088/1361-6560/abf811

Cited by 9 publications

(12 citation statements)

References 41 publications

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“…Additionally, the well delimited and truly isolated radiation sensitive volume (SV) of the 3D cylindrical architecture are able to mimic the microscopic sizes of mammalian cells. The sensors have already shown a good performance in microdosimetry at both carbon therapy 44 and low energy protons facilities 45 . Details about the fabrication processes, electrical simulations and charge collection efficiency studies of the devices are described somewhere else 42 , 43 , 46 , 47 .…”

Section: Introductionmentioning

confidence: 99%

Microdosimetry performance of the first multi-arrays of 3D-cylindrical microdetectors

Bachiller‐Perea

Zhang

Fleta

et al. 2022

Sci Rep

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The present work reports on the microdosimetry measurements performed with the two first multi-arrays of microdosimeters with the highest radiation sensitive surface covered so far. The sensors are based on new silicon-based radiation detectors with a novel 3D cylindrical architecture. Each system consists of arrays of independent microdetectors covering 2 mm$$\times$$ × 2 mm and 0.4 mm$$\times$$ × 12 cm radiation sensitive areas, the sensor distributions are arranged in layouts of 11$$\times$$ × 11 microdetectors and 3$$\times$$ × 3 multi-arrays, respectively. We have performed proton irradiations at several energies to compare the microdosimetry performance of the two systems, which have different spatial resolution and detection surface. The unitcell of both arrays is a 3D cylindrical diode with a 25 $$\mu$$ μ m diameter and a 20 $$\mu$$ μ m depth that results in a welldefined and isolated radiation sensitive micro-volume etched inside a silicon wafer. Measurements were carried out at the Accélérateur Linéaire et Tandem à Orsay (ALTO) facility by irradiating the two detection systems with monoenergetic proton beams from 6 to 20 MeV at clinical-equivalent fluence rates. The microdosimetry quantities were obtained with a spatial resolution of 200 $$\mu$$ μ m and 600 $$\mu$$ μ m for the 11$$\times$$ × 11 system and for the 3$$\times$$ × 3 multi-array system, respectively. Experimental results were compared with Monte Carlo simulations and an overall good agreement was found. The good performance of both microdetector arrays demonstrates that this architecture and both configurations can be used clinically as microdosimeters for measuring the lineal energy distributions and, thus, for RBE optimization of hadron therapy treatments. Likewise, the results have shown that the devices can be also employed as a multipurpose device for beam monitoring in particle accelerators.

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Section: Introductionmentioning

confidence: 99%

Microdosimetry performance of the first multi-arrays of 3D-cylindrical microdetectors

Bachiller‐Perea

Zhang

Fleta

et al. 2022

Sci Rep

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“…In our first work, 31 the in‐house electronics consisted of a charge‐sensitive preamplifier, a spectroscopy shaping amplifier, and an Amptek MCA8000D to digitize the pulse height. In a second version, 32 another electronics was created for increasing the signal‐to‐noise ratio, which allowed us to reduce the low‐level discrimination one order of magnitude, from 36.4 to 2.5 keV µm −1 (in silicon). In both cases, the single microdetector was irradiated at average fluence rates of 10 7 s −1 cm −2 .…”

Section: Introductionmentioning

confidence: 99%

“…In both cases, the single microdetector was irradiated at average fluence rates of 10 7 s −1 cm −2 . The silicon sensors belonged to the first 31 and second 32 generations of 3D‐cylindrical microdetectors manufactured at the Instituto de Microelectronica de Barcelona (IMB‐CNM (CSIC)). In the first prototype generation, the CCE was not fully optimized, which affected the reconstruction of the probability distributions and momenta of the stochastic quantities related to microdosimetry, as discussed in Ref.…”

Section: Introductionmentioning

confidence: 99%

“…27,28 To improve the performance of silicon-based microdosimeters and overcome some of those limitations, in 2013-2015, we proposed and created a new 3D-cylindrical architecture. 29,30 The sensors have already shown a good performance in microdosimetry in both carbon therapy 31 and low-energy proton 32 facilities. In these proof -of -concept works, we had only one individual 3D-cylindrical sensor (one pixel) connected to a singlechannel readout electronics.…”

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First experimental measurements of 2D microdosimetry maps in proton therapy

et al. 2022

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Background Empirical data in proton therapy indicate that relative biological effectiveness (RBE) is not constant, and it is directly related to the linear energy transfer (LET). The experimental assessment of LET with high resolution would be a powerful tool for minimizing the LET hot spots in intensity‐modulated proton therapy, RBE‐ or LET‐guided evaluation and optimization to achieve biologically optimized proton plans, verifying the theoretical predictions of variable proton RBE models, and so on. This could impact clinical outcomes by reducing toxicities in organs at risk. Purpose The present work shows the first 2D LET maps obtained at a proton therapy facility using the double scattering delivery mode in clinical conditions by means of new silicon 3D‐cylindrical microdetectors. Methods The device consists of a matrix of 121 independent silicon‐based detectors that have 3D‐cylindrical electrodes of 25‐µm diameter and 20‐µm depth, resulting each one of them in a well‐defined micrometric radiation sensitive volume etched inside the silicon. They have been specifically designed for a hadron therapy, improving the performance of current silicon‐based microdosimeters. Microdosimetry spectra were obtained at different positions of the Bragg curve by using a water‐equivalent phantom along an 89‐MeV pristine proton beam generated in the Y1 proton passive scattering beamline of the Orsay Proton Therapy Centre (Institut Curie, France). Results Microdosimetry 2D‐maps showing the variation of the lineal energy with depth in the three dimensions were obtained in situ during irradiation at clinical fluence rates (∼108 s−1 cm−2) for the first time with a spatial resolution of 200 µm, the highest achieved in the transverse plane so far. The experimental results were cross‐checked with Monte Carlo simulations and a good agreement between the spectra shapes was found. The experimental frequency‐mean lineal energy values in silicon were 1.858 ± 0.019 keV µm−1 at the entrance, 2.61 ± 0.03 keV µm−1 at the proximal distance, 4.97 ± 0.05 keV µm−1 close to the Bragg peak, and 8.6 ± 0.1 keV µm−1 at the distal edge. They are in good agreement with the expected trends in the literature in clinical proton beams. Conclusions We present the first 2D microdosimetry maps obtained in situ during irradiation at clinical fluence rates in proton therapy. Our results show that the arrays of 3D‐cylindrical microdetectors are a reliable microdosimeter to evaluate LET maps not only in the longitudinal axis of the beam, but also in the transverse plane allowing for LET characterization in three dimensions. This work is a proof of principle showing the capacity of our system to deliver LET 2D maps. This kind of experimental data is needed to validate variable proton RBE models and to optimize LET‐guided plans.

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“…Additionally, the well delimited and truly isolated radiation sensitive volume (SV) of the 3D cylindrical architecture are able to mimic the microscopic sizes of mammalian cells. The sensors have already shown a good performance in microdosimetry at both carbon therapy 31 and low energy protons facilities 32 . Details about the fabrication processes, electrical simulations and charge collection efficiency studies of the devices are described somewhere else 29,30,33,34 .…”

Section: Introductionmentioning

confidence: 99%

Microdosimetry Performance of The First Multi-Arrays of 3D-Cylindrical Microdetectors

Bachiller‐Perea

Zhang

Fleta

et al. 2021

Preprint

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Purpose: The present work reports on the microdosimetry measurements performed with the two first multi-arrays of microdosimeters with the highest radiation sensitive surface covered so far. The sensors are based on new silicon-based radiation detectors with a novel 3D cylindrical architecture. Methodology: Each system consists of arrays of independent microdetectors covering 2 mm×2 mm and 0.4 mm×12 cm radiation sensitive areas, the sensor distributions are arranged in layouts of 11×11 microdetectors and 3×3 multi-arrays, respectively. We have performed proton irradiations at several energies to compare the microdosimetry performance of the two systems, which have different spatial resolution and detection surface. The unit-cell of both arrays is a new type of 3D cylindrical diode with a 25 µm diameter and a 20 µm depth that results in a well-defined and isolated radiation sensitive micro-volume etched inside a silicon wafer. Measurements were carried out at the Accélérateur Linéaire et Tandem à Orsay (ALTO) facility by irradiating the two detection systems with monoenergetic proton beams from 6 to 18 MeV at clinical-equivalent fluence rates. Results: The microdosimetry quantities were obtained with a spatial resolution of 200 µm and 600 µm for the 11×11 system and for the 3×3 multi-array system, respectively. Experimental results were compared with Monte Carlo simulations and an overall good agreement was found. Conclusion: We have studied the microdosimetry response under clinical equivalent fluence rate of the first multi-arrays of 3D cylindrical microdetectors covering several centimeters of sensitive area. The good performance of both microdetector arrays demonstrates that this architecture and both configurations can be used clinically as microdosimeters for measuring the lineal energy distributions and, thus, for RBE optimization of hadron therapy treatments. Likewise, the results have shown that the devices can be also employed as a multipurpose device for beam monitoring in particle accelerators.

show abstract

Microdosimetry in low energy proton beam at therapeutic-equivalent fluence rate with silicon 3D-cylindrical microdetectors

Cited by 9 publications

References 41 publications

Microdosimetry performance of the first multi-arrays of 3D-cylindrical microdetectors

Microdosimetry performance of the first multi-arrays of 3D-cylindrical microdetectors

First experimental measurements of 2D microdosimetry maps in proton therapy

Microdosimetry Performance of The First Multi-Arrays of 3D-Cylindrical Microdetectors

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