Journal of X-Ray Science and Technology - Volume 20, issue 2
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Journal of X-Ray Science and Technology is an international journal designed for the diverse community (biomedical, industrial and academic) of users and developers of novel x-ray imaging techniques. The purpose of the journal is to provide clear and full coverage of new developments and applications in the field.
Areas such as x-ray microlithography, x-ray astronomy and medical x-ray imaging as well as new technologies arising from fields traditionally considered unrelated to x rays (semiconductor processing, accelerator technology, ionizing and non-ionizing medical diagnostic and therapeutic modalities, etc.) present opportunities for research that can meet new challenges as they arise.
Abstract: In computed tomography (CT) systems, it is desirable to know the X-ray energy spectra for various applications, including medical CT imaging, and diagnostic field and heavy ion therapy. However, because of the restricted space, the only practical solution is to use Compton spectroscopy, where the incident spectrum is inferred from the scattered spectrum. The geometry of the scatterer and its position within the CT can affect the spectrum of the secondary beam, making it difficult to…determine the primary spectrum during operation of the CT system. A modified Compton spectrometer is described that allows measurement of the X-ray energy spectra during operation, and most importantly, in rotation mode. The geometry of the scatterer was optimized to reduce the energy broadening of the secondary beam. The performance of the system was evaluated by comparing the reconstructed exposure to that measured directly using an ion chamber.
Abstract: Head motion during Computer Tomographic (CT) studies can adversely affects the reconstructed image through distortion and other artifacts such as blurring and doubling, thereby contributing to misdiagnosis of diseases. In this paper, we propose a method to detect and mitigate motion artifacts in three-dimensional (3D) cone-beam CT system. Motion detection is achieved by comparing the correlation coefficient between the adjacent x-ray projections. Artifacts, caused by motion, are mitigated either by replacing motion corrupted…projections with their counterpart 180° apart projections under certain conditions, or by estimating motion corrupted projections using Least Square Support Vector Machine (LS-SVM) based time series prediction. The method has been evaluated on 3D Shepp-Logan phantom. In this research, Feldkamp-David-Kress (FDK) based back-projection algorithm is used for 3D reconstruction process. Computer simulation validates the motion detection and artifacts elimination mechanism.
Abstract: Using the reverse motion of the treatment couch, this study offset the organ displacement generated by respiratory motion to solve the current clinical problem of increasing field sizes and safety margin expansions. This study used the self-designed simulated respiratory system (SRS) coupled with radiochromic EBT film to verify the self-developed respiratory compensation system. Pressure signals were generated from SRS to simulate abdomen movements during respiratory motion. The respiratory compensation system takes the phase…of the pressure signals as the respiratory motion phase and adjusts the pressure signal gain to make the compensation signal amplitude close to the displacement of the target region. A linear accelerator is used to irradiate a 300 cGy dose on the EBT film. The experimental results suggested that the average dose percentage in the target region for the sine-wave amplitudes of 5, 10 and 15 mm with compensation improved by 6.9 ∼ 20.3% over the cases without compensation. The 80% isodose area with compensation improved by 22.8 ∼ 77.2% over the cases without compensation. The average dose percentage in the target region with compensation for respiratory motion distances of 5, 10 and 15 mm improved by 10.3 ∼ 18.7%. The 80% isodose area improved by 22.4 ∼ 55.1% after compensation. The average dose percentage of the compensated target region indicates that the proposed respiratory compensation system could improve the issue of the inability to constantly irradiate the target region caused by respiratory motion.
Keywords: Real-time tracking, compensated respiratory motion, GafChromic film
Abstract: Kidney stones are a very frequent finding in southern Italy, but stone analysis is not routinely performed. However, it is an important requirement not only for a successful treatment of this disease, but also for the prophylaxis to prevent any recurrence. We therefore set out to analyze 80 kidney stones collected from Basilicata Region (Southern, Italy). X-ray powder diffraction as well as optical and scanning electron microscopy and petrographic thin section analysis have been…applied in order to determine the mineralogical and morphological compositions. The internal structure and the relation between major and minor components have facilitated the classification of the kidney stones according to a detailed scheme. As it is known from other country, calcium oxalate stones were the most frequent (59%) [39% mainly composed of whewellite, CaC_2 O_4 *H_2 O and 29% is mainly made of weddellite, CaC_2 O_4 *2H_2 O]. Uric acid stones were abundant too (18%). Calcium phosphate and cystine stone were less. The results of the observations of kidney stones in thin petrographic sections led to the identification of more cores in the same whewellite kidney stones. In some kidney stones the core is not situated in the central zone, which represents the point of attachment on kidney wall. Basilicata kidney stone prevalence is different from the average prevalence determined in other Mediterranean areas. The comparison showed that calcium oxalate stones seem to be more frequent, and there is a high prevalence of uric acid kidney stones and a lower prevalence of phosphate kidney stones, especially hydroxyapatite. The relative increase frequency of uric acid stones in the northern part of the Region may be due to high-purine diets and softness water consumption.
Keywords: Kidney stone, mineralogical composition, type of stones, medical geology, geographical distribution
Abstract: As a whole process, we present a concept that the complete reconstruction of CT image should include the computation part on GPUs and the data storage part on hard disks. From this point of view, we propose a Multi-Thread Scheduling (MTS) method to implement the 3D CT image reconstruction such as using FDK algorithm, to trade off the computing and storage time. In this method we use Multi-Threads to control GPUs and a separate thread to…accomplish data storage, so that we make the calculation and data storage simultaneously. In addition, we use the 4-channel texture to maintain symmetrical projection data in CUDA framework, which can reduce the calculation time significantly. Numerical experiment shows that the time for the whole process with our method is almost the same as the data storage time.
Keywords: FDK algorithm, complete reconstruction, Multi-Thread Scheduling, multi-GPU, large data
Abstract: The Medipix All Resolution System (MARS) system is a commercial spectral/multi-energy micro-CT scanner designed and assembled by the MARS Bioimaging, Ltd. in New Zealand. This system utilizes the state-of-the-art Medipix photon-counting, energy-discriminating detector technology developed by a collaboration at European Organization for Nuclear Research (CERN). In this paper, we report our preliminary experimental results using this system, including geometrical alignment, photon energy characterization, protocol optimization, and spectral image reconstruction. We produced our…scan datasets with a multi-material phantom, and then applied ordered subset-simultaneous algebraic reconstruction technique (OS-SART) to reconstruct images in different energy ranges and principal component analysis (PCA) to evaluate spectral deviation among the energy ranges.
Abstract: Material detection is a vital need in dual energy X-ray luggage inspection systems at security of airport and strategic places. In this paper, a novel material detection algorithm based on statistical trainable models using 2-Dimensional power density function (PDF) of three material categories in dual energy X-ray images is proposed. In this algorithm, the PDF of each material category as a statistical model is estimated from transmission measurement values of low and high energy X-ray images…by Gaussian Mixture Models (GMM). Material label of each pixel of object is determined based on dependency probability of its transmission measurement values in the low and high energy to PDF of three material categories (metallic, organic and mixed materials). The performance of material detection algorithm is improved by a maximum voting scheme in a neighborhood of image as a post-processing stage. Using two background removing and denoising stages, high and low energy X-ray images are enhanced as a pre-processing procedure. For improving the discrimination capability of the proposed material detection algorithm, the details of the low and high energy X-ray images are added to constructed color image which includes three colors (orange, blue and green) for representing the organic, metallic and mixed materials. The proposed algorithm is evaluated on real images that had been captured from a commercial dual energy X-ray luggage inspection system. The obtained results show that the proposed algorithm is effective and operative in detection of the metallic, organic and mixed materials with acceptable accuracy.
Keywords: Material detection, 2D GMM-based power density function, pre-processing, maximum voting scheme, dual energy X-ray image.
Abstract: For finite detector and focal spot sizes, here we propose a projection model for high spatial resolution. First, for a given x-ray source point, a projection datum is modeled as an area integral over a narrow fan-beam connecting the detector elemental borders and the x-ray source point. Then, the final projection value is expressed as the integral obtained in the first step over the whole focal spot support. An ordered-subset simultaneous algebraic reconstruction technique (OS-SART)…is developed using the proposed projection model. In the numerical simulation, our method produces improved spatial resolution and suppresses high-frequency artifacts.
Keywords: Finite detector size, area integral model, line integral model, iterative reconstruction, high spatial resolution
Abstract: Training on micro- and nano- computed tomography (CT) scanners has been traditionally conducted via extensive practice on the instrument. This entails presence of an instructor to guide through the training procedure, until reasonable experience is attained. Modern tomographic instruments being expensive to maintain, the operational costs escalates with increasing number of training conducted. In a pioneering approach, the technical know-how to operate such equipment has been partly imparted via virtual reality environment…running on the Second Life grid. The experimentation has indicated a reduction of the total training time. The authors hope that in the long run, such techniques will aid in significant reduction of instruction time and costs associated with training.
Keywords: Virtual world, micro-CT, nano-CT, simulation, Second Life, CT (computed tomography), training
Abstract: Port wine stains are categorized as a benign capillary vascular malformation, which is hard to cure. In this paper, a photoacoustic microscopy system, which integrated a two-dimensional scanning galvanometer, an objective lens and a focused ultrasound transducer, was designed for noninvasive imaging of blood vessels of port wine stains model in vivo. Cock comb was chosen as the port wine stains model in the experiment. The blood vessels in x-y plane and x-z plane were imaged…clearly. Experimental results demonstrate that photoacoustic microscopy can image the blood vessels of port wine stains model in vivo with high contrast and high resolution. It has the potential for clinical applications in detecting the blood vessels in port wine stains skin.