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 (IKrum 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.

• MeSH
• kalibrace MeSH
• lineární přenos energie MeSH
• metoda Monte Carlo * MeSH
• protonová terapie * přístrojové vybavení   MeSH
• Publikační typ
• časopisecké články MeSH

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.

• Publikační typ
• časopisecké články MeSH

Inspired by the standard computed tomography, a new method of 3D X-ray imaging embedded in FIB-SEM microscope is proposed. The unique combination of TEM-like specimen stage enabling in lens STEM detection (referred to as CompuStage), nanomanipulator (referred to as EasyLift) facilitating in-situ sample transfer from bulk sample to TEM-like stage and pixelated in-situ Timepix X-ray detector in Helios G4 FX FIB-SEM system offers an unprecedented workflow. Motivated by common circular CT scan known from microCT world, the object under study is placed on CompuStage rod which enables two possible rotation (in TEM/SEM terminology called tilt) movements - α-tilt - rotation of the CompuStage rod around its axis, and β-tilt - rotation around axis perpendicular to CompuStage rod. β-tilt rotation enables a circular movement of the sample while α-tilt sets the correct position of sample with respect to target and detector. Thin metal lamella of suitable material welded to EasyLift manipulator needle is used as an X-ray target. The final target-sample geometry - position, distance - can be fine-tuned using position control of CompuStage and EasyLift and in-situ monitored by SEM. Both sample and target can also be easily prepared in-situ. Radiographs are recorded by Timepix detector with inherent noise-free operation and energy filtration. For the 3D reconstruction standard microCT reconstruction algorithm is used with the procedure adjusted for the format and quality of nanoCT images. The experiments were carried out on Helios G4 FX DualBeam using titanium and tungsten targets and various semiconductor samples. The ultimate resolution of the proposed method in orders of tens of nanometers was achieved both by the possibility of close target to sample positioning and of adjustment of primary beam energy down to low energies reducing the interaction volume in the target. Since the lower energy radiation is well suited for life-science, the method was also tested on several bio-samples using silver target. The silver target, thanks to its massive low energy Lα line, allowed to distinguish subtle structures in the resin embedded stained mouse brain and also to observe and reconstruct canaliculi in the mouse bone (earlier reported by Dierolf et al. 2010, Nature 467 436).

• MeSH
• algoritmy MeSH
• fantomy radiodiagnostické MeSH
• femur ultrastruktura   MeSH
• mikroskopie elektronová rastrovací * přístrojové vybavení   metody   MeSH
• myši MeSH
• počítačové zpracování obrazu metody   MeSH
• rentgenová mikrotomografie * přístrojové vybavení   metody   MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

PURPOSE: Non-invasive methods for monitoring of the therapeutic ion beam extension in the patient are desired in order to handle deteriorations of the dose distribution related to changes of the patient geometry. In carbon ion radiotherapy, secondary light ions represent one of potential sources of information about the dose distribution in the irradiated target. The capability to detect range-changing inhomogeneities inside of an otherwise homogeneous phantom, based on single track measurements, is addressed in this paper. METHODS: Air and stainless steel inhomogeneities, with PMMA equivalent thickness of 10mm and 4.8mm respectively, were inserted into a PMMA-phantom at different positions in depth. Irradiations of the phantom with therapeutic carbon ion pencil beams were performed at the Heidelberg Ion Beam Therapy Center. Tracks of single secondary ions escaping the phantom under irradiation were detected with a pixelized semiconductor detector Timepix. The statistical relevance of the found differences between the track distributions with and without inhomogeneities was evaluated. RESULTS: Measured shifts of the distal edge and changes in the fragmentation probability make the presence of inhomogeneities inserted into the traversed medium detectable for both, 10mm air cavities and 1mm thick stainless steel. Moreover, the method was shown to be sensitive also on their position in the observed body, even when localized behind the Bragg-peak. CONCLUSIONS: The presented results demonstrate experimentally, that the method using distributions of single secondary ion tracks is sensitive to the changes of homogeneity of the traversed material for the studied geometries of the target.

• MeSH
• celková dávka radioterapie MeSH
• fantomy radiodiagnostické * MeSH
• ionty MeSH
• kovy * MeSH
• lidé MeSH
• radiometrie metody   MeSH
• radioterapie těžkými ionty * MeSH
• uhlík MeSH
• vzduch * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

PURPOSE: BrachyView is a novel in-body imaging system which aims to provide LDR brachytherapy seeds position reconstruction within the prostate in real-time. The first prototype is presented in this study: the probe consists of a gamma camera featuring three single cone pinhole collimators embedded in a tungsten tube, above three, high resolution pixelated detectors (Timepix). METHODS: The prostate was imaged with a TRUS system using a sagittal crystal with a 2.5mm slice thickness. Eleven needles containing a total of thirty 0.508U(125)I seeds were implanted under ultrasound guidance. A CT scan was used to localise the seed positions, as well as provide a reference when performing the image co-registration between the BrachyView coordinate system and the TRUS coordinate system. An in-house visualisation software interface was developed to provide a quantitative 3D reconstructed prostate based on the TRUS images and co-registered with the LDR seeds in situ. A rigid body image registration was performed between the BrachyView and TRUS systems, with the BrachyView and CT-derived source locations compared. RESULTS: The reconstructed seed positions determined by the BrachyView probe showed a maximum discrepancy of 1.78mm, with 75% of the seeds reconstructed within 1mm of their nominal location. An accurate co-registration between the BrachyView and TRUS coordinate system was established. CONCLUSIONS: The BrachyView system has shown its ability to reconstruct all implanted LDR seeds within a tissue equivalent prostate gel phantom, providing both anatomical and seed position information in a single interface.

• MeSH
• brachyterapie přístrojové vybavení   MeSH
• celková dávka radioterapie MeSH
• dávka záření * MeSH
• fantomy radiodiagnostické * MeSH
• gely MeSH
• lidé MeSH
• nádory prostaty diagnostické zobrazování   radioterapie   MeSH
• počítačové zpracování obrazu MeSH
• prostata diagnostické zobrazování   účinky záření   MeSH
• radioterapie řízená obrazem přístrojové vybavení   MeSH
• rektum * MeSH
• ultrasonografie přístrojové vybavení   MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH

Progress in the development of high-performance semiconductor radiation imaging pixel detectors based on technologies developed for use in high-energy physics applications has enabled the development of a completely new generation of compact low-power active dosimeters and area monitors for use in space radiation environments. Such detectors can provide real-time information concerning radiation exposure, along with detailed analysis of the individual particles incident on the active medium. Recent results from the deployment of detectors based on the Timepix from the CERN-based Medipix2 Collaboration on the International Space Station (ISS) are reviewed, along with a glimpse of developments to come. Preliminary results from Orion MPCV Exploration Flight Test 1 are also presented.

• MeSH
• dávka záření MeSH
• design vybavení MeSH
• kosmická loď MeSH
• kosmické záření * MeSH
• kosmický let MeSH
• monitorování radiace přístrojové vybavení   metody   MeSH
• radiometrie metody   MeSH
• termoluminiscenční dozimetrie metody   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH

On the Earth, protection from cosmic radiation is provided by the magnetosphere and the atmosphere, but the radiation exposure increases with increasing altitude. Aircrew and especially space crew members are therefore exposed to an increased level of ionising radiation. Dosimetry onboard aircraft and spacecraft is however complicated by the presence of neutrons and high linear energy transfer particles. Film and thermoluminescent dosimeters, routinely used for ground-based personnel, do not reliably cover the range of particle types and energies found in cosmic radiation. Further, the radiation field onboard aircraft and spacecraft is not constant; its intensity and composition change mainly with altitude, geomagnetic position and solar activity (marginally also with the aircraft/spacecraft type, number of people aboard, amount of fuel etc.). The European Union Council directive 96/29/Euroatom of 1996 specifies that aircrews that could receive dose of >1 mSv y(-1) must be evaluated. The dose evaluation is routinely performed by computer programs, e.g. CARI-6, EPCARD, SIEVERT, PCAire, JISCARD and AVIDOS. Such calculations should however be carefully verified and validated. Measurements of the radiation field in aircraft are thus of a great importance. A promising option is the long-term deployment of active detectors, e.g. silicon spectrometer Liulin, TEPC Hawk and pixel detector Timepix. Outside the Earth's protective atmosphere and magnetosphere, the environment is much harsher than at aviation altitudes. In addition to the exposure to high energetic ionising cosmic radiation, there are microgravity, lack of atmosphere, psychological and psychosocial components etc. The milieu is therefore very unfriendly for any living organism. In case of solar flares, exposures of spacecraft crews may even be lethal. In this paper, long-term measurements of the radiation environment onboard Czech aircraft performed with the Liulin since 2001, as well as measurements and simulations of dose rates on and outside the International Space Station were presented. The measured and simulated results are discussed in the context of health impact.

• MeSH
• atmosféra MeSH
• dávka záření * MeSH
• fantomy radiodiagnostické MeSH
• kosmická loď MeSH
• kosmické záření * MeSH
• kosmický let * MeSH
• letadla MeSH
• letecké a kosmické lékařství * MeSH
• lidé MeSH
• lineární přenos energie MeSH
• neutrony MeSH
• pracovní expozice * MeSH
• radiační expozice * MeSH
• radiometrie přístrojové vybavení   metody   MeSH
• sluneční aktivita MeSH
• software MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Aircrew members and passengers are exposed to increased rates of cosmic radiation on-board commercial jet aircraft. The annual effective doses of crew members often exceed limits for public, thus it is recommended to monitor them. In general, the doses are estimated via various computer codes and in some countries also verified by measurements. This paper describes a comparison of three cosmic rays detectors, namely of the (a) HAWK Tissue Equivalent Proportional Counter; (b) Liulin semiconductor energy deposit spectrometer and (c) TIMEPIX silicon semiconductor pixel detector, exposed to radiation fields on-board commercial Czech Airlines company jet aircraft. Measurements were performed during passenger flights from Prague to Madrid, Oslo, Tbilisi, Yekaterinburg and Almaty, and back in July and August 2011. For all flights, energy deposit spectra and absorbed doses are presented. Measured absorbed dose and dose equivalent are compared with the EPCARD code calculations. Finally, the advantages and disadvantages of all detectors are discussed.

• MeSH
• absorpce radiace MeSH
• design vybavení MeSH
• kosmické záření * MeSH
• letadla přístrojové vybavení   MeSH
• lidé MeSH
• monitorování radiace přístrojové vybavení   MeSH
• polovodiče MeSH
• pracovní expozice analýza   normy   MeSH
• radiační expozice MeSH
• sluneční aktivita MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH

A Timepix detector covered with polyethylene convertors of different thicknesses is presented as a fast neutron real-time dosemeter. The application of different weighting factors in connection with the position of a signal in a Timepix detector enables one to obtain an energy-dependent signal equal to neutron dose equivalents. A simulation of a Timepix detector covered with polyethylene convertors using monoenergetic neutrons is presented. The experimental set-up of a dosemeter was also produced. The first results of detector response using different fast neutron sources are presented.

• MeSH
• algoritmy MeSH
• americium MeSH
• beryllium MeSH
• dávka záření MeSH
• design vybavení MeSH
• kalifornium MeSH
• neutrony MeSH
• počítačová simulace MeSH
• polyethylen MeSH
• pravděpodobnost MeSH
• protony MeSH
• radiační ochrana metody   MeSH
• radiační rozptyl MeSH
• radiometrie přístrojové vybavení   metody   MeSH
• rychlé neutrony * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH