Experimental validation of an analytical microdosimetric model based on Geant4-DNA simulations by using a silicon-based microdosimeter

Bertolet, Alejandro; Grilj, Veljko; Guardiola, Consuelo; Harken, Andrew; Cortés‐Giraldo, M. A.; Baratto-Roldan, Anna; Fleta, C.; Lozano, M.; Cárabe, Alejandro

doi:10.1016/j.radphyschem.2020.109060

Cited by 6 publications

(5 citation statements)

References 51 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Third, we have customized a low-noise multi-channel readout electronics system to work at therapeutic fluence rates. Fourth, both the experimental and are in good agreement with the expected trends in the literature in the Bragg peak and distal edge (with energy values equivalent to those used herein) in clinical proton beams 29 , 58 and radiology accelerator platforms 59 with solid-state microdosimeters, and in a low-energy proton cyclotron 60 with mini-TEPCs. For example, Pan et al 60 obtained an average value of 6.4 keV/ (water-equivalent) irradiating with a 15 MeV proton beam at 50 mm from the cyclotron beam exit to the mini-TEPC (close to our 51 mm distance from the kapton layer in the beam exit to our microsensors).…”

Section: Discussionsupporting

confidence: 87%

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

Bachiller‐Perea

Zhang

Fleta

et al. 2022

Sci Rep

View full text Add to dashboard Cite

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.

show abstract

Section: Discussionsupporting

confidence: 87%

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

Bachiller‐Perea

Zhang

Fleta

et al. 2022

Sci Rep

View full text Add to dashboard Cite

show abstract

“…Third, we have customized a low-noise multi-channel readout electronics system to work at therapeutic fluence rates. Fourth, both the experimental ȳF and ȳD are in good agreement with the expected trends in the literature in the Bragg peak and distal edge (with energy values equivalent to those used herein) in clinical proton beams 21,45 and radiology accelerator platforms 46 with solid-state microdosimeters, and in a low-energy proton cyclotron 47 with mini-TEPCs. For example, Pan et al 47 obtained an average ȳD value of 6.4 keV/µm (water-equivalent) irradiating with a 15 MeV proton beam at 50 mm from the cyclotron beam exit to the mini-TEPC (close to our 51 mm distance from the kapton layer in the beam exit to our microsensors).…”

Section: Discussionsupporting

confidence: 87%

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

Bachiller‐Perea

Zhang

Fleta

et al. 2021

Preprint

View full text Add to dashboard Cite

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

“…Spectra shifts were also found in other microdosimetry works, for example, Debrot and Bertolet et al 48,49 . Interestingly, this discrepancy is generally unnoticed in the literature as it is not the pulse‐height spectra that is usually shown, but the microdosimetry spectra, which are in logarithm scale and where the shifts of the peaks are less evident.…”

Section: Resultsmentioning

confidence: 75%

“…Spectra shifts were also found in other microdosimetry works, for example, Debrot and Bertolet et al 48,49 Interestingly, this discrepancy is generally unnoticed in the literature as it is not the pulse-height spectra that is usually shown, but the microdosimetry spectra, which are in logarithm scale and where the shifts of the peaks are less evident. Likewise, Figure 6(right) shows the experimental dose-averaged lineal energy, y D , being 2.17 ± 0.05 keV µm −1 in the entrance, 3.08 ± 0.06 keV µm −1 in the proximal zone, 6.69 ± 0.11 keV µm −1 close to the Bragg peak, and 11.60 ± 0.13 keV µm −1 in the distal edge.…”

Section: Average Pulse-height Spectramentioning

confidence: 77%

First experimental measurements of 2D microdosimetry maps in proton therapy

et al. 2022

View full text Add to dashboard Cite

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.

show abstract

Experimental validation of an analytical microdosimetric model based on Geant4-DNA simulations by using a silicon-based microdosimeter

Cited by 6 publications

References 51 publications

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

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

Contact Info

Product

Resources

About