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Cone-beam CT (CBCT) imaging is heavily being utilized in radiotherapy treatment as means of treating cancer patients. One of the platforms is the Varian On-Board Imager (oBI) where kilo-volts (kV) CBCT imaging is used. In this study, a model of the OBI is developed to simulate the two scan modes that are available, namely: Full-Fan (FF) and Half-Fan (HF) modes. By shifting the same set of 1024×768...
This paper presents a low-cost silicon-based terahertz computed tomography system for industrial volumetric imaging. The THz-CT scanner comprises a single radiator and detector at 490 GHz and a PTFE-lens based optical train that is fixed inside a portable cage system. It features a 2.5 mm resolution limited by the effective lens aperture and offers up to 62 dB SNR in chopped and 38 dB in a continuous-wave...
We have evaluated the performance of the InP double heterojunction bipolar transistor and InP-based varactors as a room temperature sensitive detectors for THz computed tomography applications. They were used in transmission mode for the 350 GHz and 650 GHz atmospheric windows.
Spectral computed tomography (SCT) makes use of the spectral dependence of X-ray attenuation in tissues and contrast agents to separate the attenuation data into more than two energy bins. Current SCT detectors are costly and the measured data have low signal to noise ratio due to the detector's narrow bin bandwidth and quantum noise. A new approach called coded aperture compressive X-ray SCT that...
Although the classic TLD (tracking-learning-detection) target tracking algorithm can track a single target robustly in a long period, its real-time performance is poor. CT (Compressing Tracking) real-time tracking algorithm is real-time and efficient, but it cannot accurately track the scale-changing targets. Aiming at handling both methods' shortcomings, this paper proposes an improved TLD tracking...
Bowtie filter, as a beam shaping attenuator placed between X-ray source and scanned object in computed tomography system, can effectively reduce radiation dose. In addition, the bowtie filter is expected to be able to compress the dynamic range which could limit the application of some detectors. In this paper, we propose a methodology for dynamic bowtie which can balance the photon flux on a detector...
We propose a stable and fast reconstruction technique for parallel-beam (PB) tomographic X-Ray imaging, relying on the discrete pseudo-polar (PP) Radon and PP Fourier transforms. Our main contribution is a resampling method, based on modern sampling theory, that transforms the PB measurements to a PP grid. The resampling process is both fast and accurate, and in addition, simultaneously denoises the...
A Computed Tomography scan employs various combinations of X-ray images taken from different angles to create cross sectional images of specific portions of a scanned object. It allows the user to view the interior regions of the object without dismantling or cutting. This process is complex and involves a lot of parameters. Peak voltage of X-ray source, total number of scans needed, source to iso...
For investigations of rapidly moving structures in opaque technical devices ultrafast electron beam X-ray computed tomography (CT) scanners are available at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). Currently, measurement data must be initially downloaded after each CT scan from the scanner to a data processing machine. Afterwards, cross-sectional images are reconstructed. This limits the application...
Customs continue to use a wide range of technology in protecting against terrorism and the movement of illicit trade and prohibited imports. The throughput of scanned vehicles and cargo increases and just keeps on growing. Therefore, the need of automated algorithms to help screening officers in inspection, examination or surveillance of vehicles and containers is crucial. In this context, the successful...
It is advantageous to combine information about geometry and inner structure of historical artefacts with information about element composition of the decorative layers, typically covering historical wooden sculptures. X-ray computed tomography describing artifact structure is quite common and easy. Standard X-ray fluorescence (XRF) analysis of decorative layers is typically done for several selected...
We present the implementation of the CT iterative reconstruction strategy developed within the SYRMA-CT project for in vivo phase contrast CT of the uncompressed breast, ongoing at the ELETTRA synchrotron radiation facility (Trieste, Italy). Propagation-based phase-contrast imaging exploited the high spatial coherence of the monoenergetic laminar X-ray beam (3-mm high along the chest-wall-to-nipple...
Flat-Panel C-arm Computed Tomography (CT) suffers from pixel saturation due to the detector's limited dynamic range. We describe a novel approach of analog, non-linear tone mapping (TM) for preventing detector saturation. An analog TM operator (TMO) applies a non-linear transformation in a CMOS (complementary metal-oxide semiconductor) sensor and its inverse TMO based on 14-bit digital raw data. This...
By utilizing finely pitched scintillator arrays where the scintillator has high atomic number and density, fast decay time, and high light output, realizing a scintillator-based Photon Counting Detector (PCD) is conceptually feasible. Fabrication of fine-pitched scintillator arrays however, has been the bottleneck for realizing such detectors. Combining the novel scintillator fabrication technique...
In this work we perform a preliminary investigation of a discretized natural pixel expansion set for image representation in optimization-based image reconstruction for X-ray computed tomography. In particular, we focus our attention on total variation regularized image reconstruction in pixel and discrete natural pixel expansion sets. The work is motivated by two observations: (1) under certain conditions,...
A direct-conversion photon-counting detector has great potential in CT imaging and has been intensively studied in recently years. However, the optimization of the detector configuration based on clinically-relevant metrics is still lacking. In this study, we developed an optimization scheme for CZT-based photon-counting detector design. The spectral response functions characterizing different detector...
The availability of synchrotron-generated high-flux and high-energy x-rays has significantly reduced the acquisition time a tomographic scan which allows following dynamic processes in 4D (3D space + time). In the ultra-fast endstation usually a scintillator is used to convert X-ray to visible photons that can be detected by the camera. However, this conversion is not ideal and the scintillator decays...
The sensitivity of ion therapy to inaccuracies in treatment planning and delivery procedures demands the development of imaging techniques capable of accurate assessment of the Relative (to water) ion Stopping Power (RSP). The investigated tomographic carbon ion CT (iCT) imaging setup consists of a prototype integration-mode detector working as range telescope using active scanning ion beam delivery...
In practical CBCT imaging such as that in interventional procedures, data collected are truncated due to the limited detector size that cannot cover the imaged subject and especially the involved interventional devices. We study optimization-based image reconstruction directly from truncated data, with an aim to reduce truncation artifacts observed in practical or clinical reconstructions. In the...
Measurement and visualization of the fracture process zone (FPZ) in the silicate composites is essential for understanding how the crack is formed and how it is propagating through the material. Although several time-lapse radiography and tomography experiments during the three-point bending of silicate composites with conventional imaging techniques have been already realized, the crack initiation...
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