Microdosimetry with a sealed mini-TEPC and a silicon telescope at a clinical proton SOBP of CATANA

Bianchi, A.; Selva, A. Della; Colautti, P.; Bortot, D.; Mazzucconi, D.; Pola, A.; Agosteo, S.; Petringa, Giada; Cirrone, Giuseppe Antonio Pablo; Reniers, Brigitte; Parisi, Amilcare; Struelens, Lara; Vanhavere, F.; Conte, V.

doi:10.1016/j.radphyschem.2020.108730

Cited by 35 publications

(29 citation statements)

References 21 publications

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“…47 Such value is much lower than that reported for ΔE-E monolithic 2 µm thick silicon microdosimeter (corresponding to a water equivalent thickness of approximately 4.5 µm) tested in the same condition measurement. 20 Indeed, this low noise value is comparable with that of a silicon-on-insulator diode array-based microdosimeter 21,48 characterized by a water equivalent SV thickness very similar to that of our device (i.e., about 22 µm). It is worth to point out that the limit of lineal energy detection, obtained in this work, is more than a factor two lower than that estimated in reference 47 for 6 µm thick diamond detector (axial incidence).…”

Section: A Microdosimetric Spectrasupporting

confidence: 75%

“…Such a peak was also observed and reported in literature for other solid-state detector. 20,49 It was found to be related to the geometry of the SV of the detectors. 50 In a microdosimeter of generic shape and for isotropic radiation, the edge is formed by those lowenergy particles which cross the sensitive volume along the maximum chord lengths and stop immediately after.…”

Section: A Microdosimetric Spectramentioning

confidence: 99%

“…This is found to be consistent with that observed in literature for mini TEPC and silicon detector, tested in similar therapeutic proton beam. 10,17,20,48 In the plateau and in the flat region of the SOBP (positions A-H) as well as the plateau of the BP of unmodulated proton beam (positions A-C), the main part of the distribution is less of 10 keV/µm, due to protons of energy above 4 MeV. However, at water depths in the distal fall-off region of the BP (positions E and F) and SOBP (positions I and L), a greater portion of the microdosimetric spectrum falls in the range of lineal energy larger than 10 keV/μm, reaching the "proton edge" at about 43 keV/μm, In this region, where the primary proton beam is quickly vanishing, the spectrum is comprised of secondary particles including recoil protons and ion recoils.…”

Section: A Microdosimetric Spectramentioning

confidence: 99%

“…These have been employed for the characterization of both proton and carbon therapeutic beams. [20][21][22][23] Silicon detectors are not tissue-equivalent or radiation hard detectors but have high resolution and are user-friendly to operate.…”

Section: Introductionmentioning

confidence: 99%

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Microdosimetric measurements of a monoenergetic and modulated Bragg Peaks of 62 MeV therapeutic proton beam with a synthetic single crystal diamond microdosimeter

et al. 2020

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Purpose The purpose of this study was to investigate for the first time the performance of a synthetic single crystal diamond detector for the microdosimetric characterization of clinical 62 MeV ocular therapy proton beams. Methods A novel diamond microdosimeter with a well‐defined sensitive volume was fabricated and tested with a monoenergetic and spread‐out Bragg peak (SOBP) of the CATANA therapeutic proton beam in Catania, Italy. The whole sensitive volume of the detector has an active planar‐sectional area of 100 µm × 100 µm and a thickness of approximately 6.3 um. Microdosimetric measurements were performed at several water equivalent depths, corresponding to positions of clinical relevance. From the measured spectra, microdosimetric quantities such as the frequency mean lineal energy (y¯F), dose mean lineal energy (y¯D) as well as microdosimetric relative biological effectiveness (RBEµ) values were derived for each depth along both a pristine Bragg curve and SOBP. Finally, Geant4 Monte Carlo simulations were performed modeling the detector geometry and CATANA beamline in order to calculate the average linear energy transfer (LET) values in the diamond active layer and water. Results The microdosimetric spectra acquired by the diamond microdosimeter show different shapes as a function of the water equivalent depths. No spectral distortion, due to pile‐up events and polarization effects, was observed. The experimental spectra have a very low detection threshold due to the electronic noise during the irradiation of about 1 keV/μm. The y¯F and y¯D values were in agreement with expected trends, showing a sharp increase in mean lineal energy at the distal edge of the Bragg peak. In addition, a good agreement between the mean lineal energy values and the calculated average LET ones was also observed. Finally, the RBE values evaluated with the diamond microdosimeter were in excellent agreement with those obtained with a mini tissue equivalent proportional counter as well as with radiobiological measurements in the same proton beam field. Conclusions The microdosimetric performance of the tested synthetic single crystal diamond microdosimeter clearly indicates its suitability for quality assurance in clinical proton therapy beam.

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Section: A Microdosimetric Spectrasupporting

confidence: 75%

Section: A Microdosimetric Spectramentioning

confidence: 99%

Section: A Microdosimetric Spectramentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Microdosimetric measurements of a monoenergetic and modulated Bragg Peaks of 62 MeV therapeutic proton beam with a synthetic single crystal diamond microdosimeter

et al. 2020

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“…Due to the limitations of silicon-based microdosimeters, further developments in the portability and efficiency of the TEPCs are also being considered. Some compelling work is that of Conte [ 14 ] and Bianchi [ 15 ] on the use of sealed mini TEPC for proton beam therapy. Bianchi et al observed similar microdosimetry spectra for mini TEPC and a

silicon microdosimeters at linear energies higher than 8 (keV/μm ) with discrepancies observed at lower LET values.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous Measurements of Dose and Microdosimetric Spectra in a Clinical Proton Beam Using a scCVD Diamond Membrane Microdosimeter

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et al. 2021

Sensors

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A single crystal chemical vapor deposition (scCVD) diamond membrane-based microdosimetric system was used to perform simultaneous measurements of dose profile and microdosimetric spectra with the Y1 proton passive scattering beamline of the Center of Proton Therapy, Institute Curie in Orsay, France. To qualify the performance of the set-up in clinical conditions of hadrontherapy, the dose, dose rate and energy loss pulse-height spectra in a diamond microdosimeter were recorded at multiple points along depth of a water-equivalent plastic phantom. The dose-mean lineal energy (y¯D) values were computed from experimental data and compared to silicon on insulator (SOI) microdosimeter literature results. In addition, the measured dose profile, pulse height spectra and y¯D values were benchmarked with a numerical simulation using TOPAS and Geant4 toolkits. These first clinical tests of a novel system confirm that diamond is a promising candidate for a tissue equivalent, radiation hard, high spatial resolution microdosimeter in beam quality assurance of proton therapy.

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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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Microdosimetry with a sealed mini-TEPC and a silicon telescope at a clinical proton SOBP of CATANA

Cited by 35 publications

References 21 publications

Microdosimetric measurements of a monoenergetic and modulated Bragg Peaks of 62 MeV therapeutic proton beam with a synthetic single crystal diamond microdosimeter

Microdosimetric measurements of a monoenergetic and modulated Bragg Peaks of 62 MeV therapeutic proton beam with a synthetic single crystal diamond microdosimeter

Simultaneous Measurements of Dose and Microdosimetric Spectra in a Clinical Proton Beam Using a scCVD Diamond Membrane Microdosimeter

First experimental measurements of 2D microdosimetry maps in proton therapy

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