The Compton camera concept is based on reconstruction of recorded Compton scattering events for incoming gamma rays. The camera usually consist of two or more position (2D) and energy sensitive ...detectors. The Compton scattering of the incoming gamma ray recoiling an electron occurs in the first detector. The position and energy of recoiled electron is recorded. The scattered gamma ray continues to the next detector where it is absorbed and its energy and position is recorded too. Knowing both positions and energies the scattering angle can be calculated using the Compton equation. By detecting multiple events the position and image of the gamma source can be reconstructed. The Compton scattering and absorption of the scattered gamma can occur within a single detector too. Such events can be used for reconstruction only if the detector provides information on 3D positions of both events along with their energies. The Timepix3, a hybrid single photon counting pixel detector, is perfect device for such measurements. It can record time-of-arrival (ToA) and energy of incident gamma rays simultaneously in each pixel. In this article we present a concept of miniaturized single layer Compton camera consisting of a single Timepix3 detector with a thick 2 mm CdTe sensor. Thanks to Timepix3 high resolution ToA measurement (1.6 ns), it is possible to measure the drift time of charge transport within the sensor and thus determine the vertical position (depth) of both interactions. By knowing both energy and position of the events in the sensor, we can reconstruct the image of the gamma source. The angular resolution of the presented Compton camera depends on the detected energy and reaches the order of a few degrees.
The semiconductor pixel detectors Medipix2, Timepix and Medipix3 (256x256 square pixels, 55x55 mu m each) are superior imaging devices in terms of spatial resolution, linearity and dynamic range. ...This makes them suitable for various applications such as radiography, neutronography, micro-tomography and X-ray dynamic defectoscopy. In order to control and manage such complex measurements a multi-platform software package for acquisition and data processing with a Java graphical user interface has been developed. The functionality of the original version of Pixelman package has been upgraded and extended to include the new medipix devices. The software package can be run on Microsoft Windows, Linux and Mac OS X operating systems. The architecture is very flexible and the functionality can be extended by plugins in C++, Java or combinations of both. The software package may be used as a distributed acquisition system using computers with different operating systems over a local network or the Internet.
The Compton camera concept is based on the reconstruction of recorded Compton scattering events of incoming gamma rays. The scattering of primary gamma ray occurs in the first detector (called ...scattering detector—usually thin) recording the position and energy of the recoiled electron. The scattered gamma quantum continues towards the second detector (called absorption detector - usually thick) where it is absorbed. The second detector records the energy and the position of this scattered gamma. Using the Compton scattering equation it is possible to determine the scattering angle, and estimate possible directions of the original gamma ray as a surface of a cone. When the Compton camera records the number of such events, the location and the shape of the gamma source can be reconstructed. Timepix3, a hybrid single photon counting imaging pixel detector, is a perfect device for creation of a compact Compton camera. Timepix3 is an event based readout chip (every hit pixel is immediately sent to a readout) and can record the time-of-arrival (ToA) and energy of an incident gamma simultaneously in each pixel. The chip offers high energy resolution (1 keV at 60 keV, 7 keV at 356 keV), as well as time resolution (1.6 ns). The Timepix3 readout chip can be combined with different sensor materials (Si, CdTe, CZT). In this contribution, we present a very compact detector system for imaging with gamma-rays using the Compton camera principle. The system consists of at least two layers of hybrid pixel detectors Timepix3 with the sensors being optimized for gamma-ray tracking. The front detector layer (scattering) is made of silicon of 1 mm thickness, while the last layer (absorbing) is equipped with thick CdTe or CZT sensors up to 2 mm in thickness. The total absorption of the whole detector can be very high if several CdTe or CZT layers are used. The maximal number of layers is not limited, but the practical evaluation was performed with 2 layers. Thanks to Timepix3 simultaneous measurement of ToA and energy, it is possible to precisely detect coincidence events in the detector layers. Based on the energy and position of these events, it is possible to estimate the possible direction of the original gamma. The angular resolution of the presented Compton camera depends on the detected energy, and it is in the order of 1 degree.
Abstract 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, it was designed and developed the “Data Processing Engine” (DPE) as an advanced tool for data processing designed explicitly for Timepix detectors. The functionality of the DPE is structured into three distinct processing levels: i) Pre-processing: this phase involves clusterization and the application of necessary calibrations and corrections. ii) Processing: this stage includes particle classification, employing machine learning algorithms, and the recognition of radiation fields. iii) Post-processing: involves various analyses, such as directional analysis, coincidence analysis, frame analysis, Compton directional analysis, and the generation of physics products, are performed. The core of the DPE is supported by an extensive experimental database containing calibrations and referential radiation fields of typical environments, including protons, ions, electrons, gamma rays and X rays, as well as thermal and fast neutrons. To enhance accessibility, the DPE is implemented into various user interface platforms such as a command-line tool, an application programming interface, and as a graphical user interface in the form of a web portal. The DPE's broad utility is exemplified through its integration into various applications and developments.
The Timepix2 ASIC (application-specific integrated circuit) is the upgraded successor to the Timepix 1 hybrid pixel detector readout chip. Like the original, Timepix2 contains a matrix of 65k square ...pixels of 55 μm pitch that can be coupled to a similarly segmented semiconductor sensor, or integrated in an ionising gas detector. The pixels are programmable, with several operation modes and selectable counter depths (up to 18 bits for time-of-arrival, ToA, and up to 14 bits for time-over-threshold, ToT). In ToT and ToA mode, each pixel records the arrival time and energy deposited by particles interacting with the corresponding sensor segment, with an optional separation of timing resolution for ToT and ToA: down to 10 ns each. The gain of the frontend circuit can be programmed to adapt to the quantity of energy deposited in the sensor, yielding a large dynamic range of 0.38 ke− to 950 ke−. The frontend noise in adaptive gain mode is 380 e− rms. The design also introduces some power optimisation features to the Timepix portfolio, such as power masking on selectable parts of the pixel matrix. With all pixels powered on, using 100 MHz for both ToT and ToA clock frequencies, and assuming a sparse particle interaction with the pixels, the matrix is estimated to consume less than 900 mW based on simulation.
We present software for interfacing FITPix and USB Lite compatible readout electronics using Robot Operating System (ROS). ROS is widely adopted middleware for integration of sensors, processing ...algorithms and logic to autonomous systems such as robots, unmanned helicopters, and robotic payloads. Thanks to ROS, Timepix detectors can be deployed in automated experiments on platforms spanning from traditional desktop computers to small ARM devices such as Raspberry Pi and Odroid. Acquisition and detector settings can be controlled in Linux shell allowing deployment on headless devices. Using ROS networking capabilities, captured frames and detector control can be transmitted via a network, which allows building distributed processing pipelines. The proposed software is a lightweight package, easily connectable to existing visualization, logging, and processing software in ROS. It offers simple bindings to custom Python and C++ programs for real-time control of the acquisition or processing of the captured frames. Rospix was deployed on NASA suborbital rocket, which was successfully launched on April 4, 2018, from Kwajalein Atoll by Pennsylvania State University. Rospix provides reliable solution for mobile robots where the collected data are used in real time to guide the robot through an environment. We release Rospix using the GitHub platform and welcome the community to contribute on the first project connecting the fields of ionizing radiation imaging and mobile robotics.
The dose conformation and the sparing of neighboring critical healthy structures are improved in carbon-ion beam radiotherapy in comparison to conventional photon radiotherapy. Inter and ...intrafractional plan adaptation strategies may preclude the quality assurance (QA) of the actually applied treatment plan before the treatment starts. Therefore, independent measurements of the positions of scanned pencil 12C ion beams are of interest in order to monitor the beam application during the treatment and the beam in the isocenter. In this work, secondary ions outgoing from a patient-like phantom are exploited for the assessment of the lateral pencil beam position in a clinic-like 12C treatment fraction. The experiment was performed at the Heidelberg Ion-Beam Therapy Center (HIT) in Germany. A carbon-ion treatment plan was used to treat a 100 cm3 tumor volume in the center of an Alderson head phantom. Two silicon pixel detectors based on the Timepix3 technology developed at CERN were operated in synchronization to detect and to track outgoing secondary ions. We established an analysis of the measured secondary ion track distribution which enabled us to follow the beam scanning movement of the carbon-ion pencil beam by assessing the lateral position of the single beam spots. The precision of the developed method was found to range from 0.84 mm to 2.59 mm. For beam energies greater than 197.58 MeV/n, the mean of absolute distances of the measured lateral pencil beam positions with respect to the pencil beam positions measured by the beam application system (averaged over each energy layer) were smaller than 2 mm. We conclude that the presented method has shown capabilities of monitoring the lateral pencil beam positions by means of secondary ions with precision and sensitivity of clinical interest.
The superior properties of the single particle counting semiconductor pixel detectors in radiation imaging are well known. They are namely: very high dynamic range due to digital counting, absence of ...integration and read-out noise, high spatial resolution and energy sensitivity. The major disadvantage of current pixel devices preventing their broad exploitation has been their relatively small sensitive area of few cm super(2). This disadvantage is often solved using tiling method placing many detector units side by side forming a large matrix. The current tiling techniques require rather large gaps of few millimeters between tiles. These gaps stand as areas insensitive to radiation which is acceptable only in some applications such as diffraction imaging. However standard transmission radiography requires fully continuous area sensitivity. In this article we present the new large area device WIDEPIX composed of a matrix of 10 x 10 tiles of silicon pixel detectors Timepix (each of 256 x 256 pixels with pitch of 55 mu m) having fully sensitive area of 14.3 x 14.3 cm super(2) without any gaps between the tiles. The device contains a total of 6.5 mega pixels. This achievement was reached thanks to new technology of edgeless semiconductor sensors together with precise alignment technique and multilevel architecture of readout electronics. The mechanical construction of the device is fully modular and scalable. This concept allows replacing any single detector tile which significantly improves production yield. The first results in the field of X-ray radiography and material sensitive X-ray radiography are presented in this article.
Abstract
The semiconductor pixel detector Timepix2 is operated with highly integrated readout electronics as a miniaturized and portable MiniPIX TPX2 radiation camera for radiation imaging and ...spectral-sensitive particle tracking in wide field-of-view. The device provides room-temperature operation, ease of use (single USB 2.0 port), online response with single track visualization, fast frame readout (up to 60 fps) and double per-pixel response for detailed measurements with per-pixel energy and counting or energy and timing sensitivity. We evaluate the response and applicability of a MiniPIX TPX2 camera with the Timepix2 ASIC chip equipped with a 300 µm thick silicon sensor for wide-range composition and spectral characterization of mixed-radiation fields. Measurements were performed in high-energy proton radiotherapy environments with protons of selected energies in the range 225–70 MeV and water-equivalent targets of varying configuration (size, dimension, geometry). High-resolution pattern recognition and spectral-tracking analysis of the single particle tracks in the pixelated detector enable to resolve and classify all detected signals according particle species, direction and energy loss. Based on the experimental calibrations performed with well-defined radiation fields together with quantum imaging visualization of single particle tracks, ten broad-range particle-event classes are resolved. Mixed-radiation fields are thus analyzed according particle-event types in wide range of deposited energy, linear-energy-transfer LET, particle fluxes and dose rates. The spatial distribution over the detector sensor matrix of the distinguished groups can be visualized as well as the directional mapping of energetic charged particles.
Abstract
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 in outer orbit. 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 high granularity and double per-pixel signal electronics to measure and characterize radiation fields of high intensity over a wide range with basic particle-type discrimination.
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