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Publications (7)
Linh Tran, Cristina Oancea, Satoshi Kodaira, David Bolst, James Vohradsky, Carlos Granja, Jan Jakubek, Jaroslav Šolc, Elisabeth Bodenstein, Sebastian Gantz, Jörg Pawelke, Lukas Marek, Anatoly Rosenfeld
Fragments and neutrons produced by inelastic reactions in particle therapy can make a significant contribution to the Relative Biological Effectiveness (RBE) and as a consequence the biologically weighted-dose in the distal part of the Spread-out Bragg Peak (SOBP); this also make changes to the radiation quality and dose equivalent in surrounding organs near the target tumour. These mixed radiation fields of secondary fragments and neutrons are difficult to characterise which is why this paper reviews some solid state radiation detectors that can measure the radiation field produced out of primary field in particle therapy, and also assess the radiation quality and dose equivalent to normal organs located near the target volume. These detectors include active types such as the silicon on insulator (SOI) microdosimeter, the monolithic ΔE-E telescope, the pixel detectors TimePix3, and passive detectors such as CR-39 plastic charged particle track detector, and the fluorescent nuclear track detector (FNTD). This paper also reports on the microdosimetric measurements obtained with silicon-based microdosimeters, both laterally and downstream of the target volume, for proton and carbon ion beams. It also details the measurements taken by the TimePix3 detector, including a customised, miniaturized version with enhanced resolving power, for characterizing secondary radiation in proton therapy through single-particle tracking. The CR-39 and FNTD passive linear energy transfer (LET) detectors are also reviewed and the advantages and disadvantages of each type of detector are discussed. The SOI microdosimeter and ΔE-E telescope are suitable for characterising the typical mixed radiation field for out-of-field in particle therapy. An SOI microdosimeter can provide dose equivalent values to evaluate risk to normal organs, while the ΔE-E telescope can operate as a microdosimeter and distinguish the type of particles in the secondary radiation field. The TimePix3 chip can provide mixed field decomposition, particle flux, dose rate, and LET spectra while the CR-39 plastic detector could measure the LET spectra, absorbed dose, and dose equivalent from secondary particles of Carbon ion beam via nuclear targeted fragmentation reactions.
Paulina Stasica-Dudek, Cristina Oancea, Carlos Granja, Konrad Guguła, Jan Jakubek, Renata Kopeć, Dawid Krzempek, Michal Matous, Antoni Rucinski, Marzena Rydygier, Jan Gajewski
Purpose: With the increasing use of proton therapy, there is a growing emphasis on including radiation quality, often quantified by linear energy transfer, as a treatment plan optimization factor. The Timepix detectors offer energy-sensitive particle tracking useful for the characterization of proton linear energy transfer. To improve the detector's performance in mixed radiation fields produced in proton therapy, we customized the detector settings and performed the per-pixel energy calibration. Methods: The detection threshold and per-pixel signal shaping time (I krum current) were customized, and energy calibration was performed for MiniPIX Timepix3. The detector calibration was verified using α source and clinical proton beams, as well as Monte Carlo simulations. The effects on the detector's performance, in terms of spectral saturation and pixel occupancy, were evaluated. Results: Measurements with proton beams showed a good agreement with simulations. With the customized settings, the measurable energy range in the detector data-driven mode was extended, and the signal duration time was reduced by 80%, while the yield of pixel time occupancy reduction depends on the number of occupied pixels. For performed measurements with proton beams, the number of occupied pixels was further reduced up to 40% due to the increased threshold. Conclusions: Customized detector configuration of the Timepix3 detector allowed for reduced pixel occupancy and mitigation of signal saturation in a data-driven mode without significantly interfering with the energy deposition measurement. The presented approach enables the extension of the operational range, including higher intensities and mixed-radiation fields in particle radiotherapy environments.
L. Marek, C. Granja, J. Jakubek, J. Ingerle, D. Turecek, M. Vuolo, C. Oancea
Hybrid semiconductor pixelated detectors from the Timepix family are advanced detectors for online particle tracking, offering energy measurement and precise time stamping capabilities for particles of various types and energies. This inherent capability makes them highly suitable for various applications, including imaging, medical fields such as radiotherapy and particle therapy, space-based applications aboard satellites and the International Space Station, and industrial applications. The data generated by these detectors is complex, necessitating the development and deployment of various analytical techniques to extract essential information. For this purpose, and to aid the Timepix user community, the "Data Processing Engine" (DPE) was developed as an advanced tool for data processing designed explicitly for Timepix detectors. The DPE includes three processing levels: pre-processing (clusterization, calibrations, corrections), processing (particle classification using machine learning, radiation field recognition), and post-processing (directional and coincidence analysis, physics products generation). It is supported by a database of typical radiation field references and is accessible via command-line, API, and web interface.
C. Granja, J. Solc, J. Gajewski, A. Rucinski, P. Stasica, M. Rydygier, L. Marek, C. Oancea
Mixed radiation fields in environments such as particle radiotherapy and outer space exhibit large complexity in terms of composition and spectral distribution which are difficult to measure in detail. For this purpose, we present a high-sensitivity technique using the pixel detector Timepix3 to measure the composition and spectral-tracking characterization of secondary fields produced in proton radiotherapy. Particle-event classes are resolved into broad groups of high-energy transfer particles (HETP), such as protons, ions and neutrons, as well as low-energy transfer particles (LETP), such as electrons, X rays and, partly, low-energy gamma rays. The quantum-imaging capability of Timepix3 is exploited to enhance the resolving power for particle-type classification. The particle tracks are analyzed by spectral-sensitive pattern recognition algorithms. The response matrix for Timepix3 is newly derived based on experimental calibrations in well‑defined radiation fields including in‑beam rotational scans of protons performed at various energies and directions. Clinical proton beams of radiotherapeutic intensities and energies in the range 12–225 MeV were used in experimental configurations with and without a tissue‑equivalent phantom. Detailed results of radiation components can be used to produce total and partial particle fluxes, dose rate, absorbed dose, deposited energy and linear‑energy‑transfer (LET) spectra. Dedicated Monte Carlo (MC) simulations are compared with experimental results of field composition, particle fluence, and deposited energy. The numerical information aids the interpretation of experimental data which includes also secondary neutrons. The technique and developed methodology can be applied for research and routine measurements in environments of varying complexity.
Paulina Stasica, Hanh Nguyen, Carlos Granja, Renata Kopeć, Lukas Marek, Cristina Oancea, Łukasz Raczyński, Antoni Rucinski, Marzena Rydygier, Keith Schubert, Reinhard Schulte, Jan Gajewski
Protons have advantageous dose distributions and are increasingly used in cancer therapy. At the depth of the Bragg peak range, protons produce a mixed radiation field with low- and high-linear energy transfer (LET) components, where the high-LET is associated with increased biological effectiveness. LET prediction by Monte Carlo simulations is challenging to verify experimentally. This study presents measurements using the Timepix detector in a mixed radiation field produced by a therapeutic proton beam in water, validated by Monte Carlo simulations. The Timepix detector, with high-resolution particle tracking enhanced by artificial intelligence, identified particle types and measured deposited energy. Biologically relevant LET parameters, including single proton LET and dose-averaged LET, were computed. The neural network achieved over 95% accuracy in proton recognition. The LET spectra from measurements matched simulations with a mean dose-averaged LET difference of 17%. A wide LET range from sub-keV/μm to 10 keV/μm was observed. The proposed method offers accessible, experimental LET data for treatment planning validation and can be implemented in clinical proton therapy facilities.
Jaroslav Šolc, Jan Jakůbek, Lukáš Marek, Cristina Oancea, Jiří Pivec, Jana Šmoldasová, Jiří Tesař, Zdeněk Vykydal
The track structure of the signal measured by the semiconductor pixel detector Timepix3 was modelled in the Monte Carlo MCNP® code. A detailed model at the pixel-level (256 × 256 pixels, 55 × 55 µm² pixel size) was developed and used to generate and store clusters of adjacent hit pixels observed in the measured data because of particle energy deposition path, charge sharing, and drift processes. An analytical model of charge sharing effect and the detector energy resolution was applied to the simulated data. The method will help the user sort the measured clusters and distinguish radiation components of mixed fields by determining the response of Timepix3 detector to particular particle types, energies, and incidence angles that cannot be measured separately.
C. Granja, J. Jakubek, P. Soukup, M. Jakubek, D. Turecek, L. Marek, C. Oancea, S. Gohl, B. Bergmann, S. Pospisil, M. Malich, M. Vuolo, A. Owens, V. Zach, J. Stursa, D. Chvatil, V. Olsansky, A. Rucinski, J. Gajewski, P. Stasica, Z. Vykydal, J. Solc
The miniaturized radiation camera MiniPIX TPX3 is designed for detailed and wide-range measurements of mixed-radiation fields present in many applications such as radiotherapy and space radiation. The highly integrated instrumentation utilizes a single connector for control and readout for flexible measurements and quick deployment. The device features an option to process the registered data on the same device with limited resolution and basic particle-type resolving power. A novel readout and data processing technique exploits the detector's high granularity and dual per-pixel signal electronics to measure and characterize high-intensity radiation fields with basic particle-type discrimination.