Journal of X-Ray Science and Technology - Volume 19, 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: X-ray imaging dose from serial Cone-beam CT (CBCT) scans raises a clinical concern in most image guided radiation therapy procedures. The goal of this paper is to develop a fast GPU-based algorithm to reconstruct high quality CBCT images from undersampled and noisy projection data so as to lower the imaging dose. The CBCT is reconstructed by minimizing an energy functional consisting of a data fidelity term and a total variation regularization term. We develop a GPU-friendly…version of a forward-backward splitting algorithm to solve this problem. A multi-grid technique is also employed. We test our CBCT reconstruction algorithm on a digital phantom and a head-and-neck patient case. The performance under low mAs is also validated using physical phantoms. It is found that 40 x-ray projections are sufficient to reconstruct CBCT images with satisfactory quality for clinical purposes. Phantom experiments indicate that CBCT images can be successfully reconstructed under 0.1 mAs/projection. Comparing with the widely used head-and-neck scanning protocol of about 360 projections with 0.4 mAs/projection, an overall 36 times dose reduction has been achieved. The reconstruction time is about 130 sec on an NVIDIA Tesla C1060 GPU card, which is estimated ∼ 100 times faster than similar regularized iterative reconstruction approaches.
Abstract: In computer tomography (CT), truncated projections are produced due to scanning large objects with a detector that is limited in width. Applying filtered back-projection(FBP) method directly to truncated projections, the reconstructed image will contain truncation artifacts – bright rings on the boundary of region of interest (ROI). Extrapolation algorithms can be used to reduce the truncation artifacts; however extrapolations are usually double the length of the projection data; resulting in an increased calculation time. This…paper introduces mixed extrapolation, which is a combination of exponential and quadratic extrapolation. It is proven that doubling the length of the projection data for the mixed extrapolation can be avoided. The projections were extrapolated according to the boundary values and their derivatives. The algorithm achieves equivalence to the extrapolation approach with negligible increased calculation time. Supplementary functions are introduced in order to simplify the calculations. These functions can be calculated prior to extrapolation process, hence the calculation time is significantly reduced. The calculation times are compared between fast extrapolation introduced in this paper and normal extrapolation with doubling the length of projection data.
Keywords: Extrapolation, truncation artifacts, truncated projections, local tomography, limit field of view, reconstruction, incomplete projections, quadratic, exponential
Abstract: An algorithm is proposed to directly reconstruct a CT gradient image in a region of interest(ROI). First, the central slice theorem is generalized and a differential constraint condition (DCC) is introduced in parallel-beam geometry. Then, an algorithm is developed to reconstruct the gradient images in both Cartesian and polar coordinate systems based on a two-step Hilbert transform method. Finally, the reconstruction algorithm is extended into the equi-distant fan-beam geometry. Meanwhile, a conditional truncation for…projection data acquisition is permitted by using a one-dimensional(1-D) finite Hilbert transform in image domain. Because the reconstructed gradient image is in terms of local operator, it have a better performance in CT image analysis and other CT applications compared to the global Calderon operator in Lambda Tomography.
Keywords: Computed tomography, region of interest, hilbert transform, lambda tomography
Abstract: A questionnaire survey was performed to investigate the different knowledge of radiation exposure, awareness and expectation for O-arm imaging system between the users (orthopaedic surgeons) and the developers (engineers). A total of 93 orthopaedic surgeons and 19 engineers participated and answered the questionnaire consisting of 18 items designed for this study. The items were focused on knowlege, awareness, and expectation. Orthopaedic surgeons had higher scores for items of knowledge domains regarding radiation exposure than…the engineers while the engineers were more sensitive to radiation hazards and adopted higher levels of radiation protection than orthopaedic surgeons in the awareness domain. Most engineers and orthopaedic surgeons answered that the requirements of diagnostic and intraoperative imaging systems differ. Image resolution, a low radiation exposure, and the time required for image acquisition was the top three requirements of O-arm selected by engineers. On the other hand, the top three requirements according to orthopaedic surgeons were; image resolution, expediency, and spatial occupancy. User requirements need to be reflected in developing O-arm along with basic requirements such as image resolution and low radiation exposure.
Keywords: O-arm, questionnaire, different perspective, user, developer
Abstract: Previous lumbar motion analyses suggest the usefulness of quantitatively characterizing spine motion. However, the application of such measurements is still limited by the lack of user-friendly automatic spine motion analysis systems. This paper describes an automatic analysis system to measure lumbar spine disorders that consists of a spine motion guidance device, an X-ray imaging modality to acquire digitized video fluoroscopy (DVF) sequences and an automated tracking module with a graphical user interface…(GUI). DVF sequences of the lumbar spine are recorded during flexion-extension under a guidance device. The automatic tracking software utilizing a particle filter locates the vertebra-of-interest in every frame of the sequence, and the tracking result is displayed on the GUI. Kinematic parameters are also extracted from the tracking results for motion analysis. We observed that, in a bone model test, the maximum fiducial error was 3.7%, and the maximum repeatability error in translation and rotation was 1.2% and 2.6%, respectively. In our simulated DVF sequence study, the automatic tracking was not successful when the noise intensity was greater than 0.50. In a noisy situation, the maximal difference was 1.3 mm in translation and 1° in the rotation angle. The errors were calculated in translation (fiducial error: 2.4%, repeatability error: 0.5%) and in the rotation angle (fiducial error: 1.0%, repeatability error: 0.7%). However, the automatic tracking software could successfully track simulated sequences contaminated by noise at a density ⩽ 0.5 with very high accuracy, providing good reliability and robustness. A clinical trial with 10 healthy subjects and 2 lumbar spondylolisthesis patients were enrolled in this study. The measurement with auto-tacking of DVF provided some information not seen in the conventional X-ray. The results proposed the potential use of the proposed system for clinical applications.
Keywords: Auto-tracking, digitized video fluoroscopy, spine motion, particle filter, lumbar spine, vertebral body
Abstract: The conventional attenuation contrast imaging does not yield satisfactory sensitivity and specificity for weakly absorbing media, such as biological soft tissues. The x-ray scattering offer an important contrast mechanism to reveal structural features and density fluctuation within an object. This scattering signal carries information at the molecular and supra-molecular level, and has a tremendous implication for biomedical and other applications. In this paper, we develop a scattering imaging approach to reconstruct the…electron density distribution of an object and demonstrate its feasibility in the numerical simulation.
Keywords: X-ray scattering tomography, single scattering, electron density, compressive sensing
Abstract: We propose a multiresolution X-ray imaging method designed for non-destructive testing/evaluation (NDT/NDE) applications which can also be used for small animal imaging studies. Two sets of projections taken at different magnifications are combined and a multiresolution image is reconstructed. A geometrical relation is introduced in order to combine properly the two sets of data and the processing using wavelet transforms is described. The accuracy of the reconstruction procedure is verified through a…comparison to the standard filtered backprojection (FBP) algorithm on simulated data.
Abstract: XANES spectra of biomacromolecules such as histone, hemoglobin or bovine serum albumin (BSA) were measured in transmission at the S-K absorption edge for comparison with those of sulfur containing low-molecular weight biomolecules with special reference to the dependence on the chemical environment of sulfur. The spectra of dry histone and hemoglobin exhibited a prominent peak at the same energy as that of cysteine and glutathione (GSH), while the BSA spectrum showed an additional peak at a…lower energy, which coincided with that of cystine and glutathione disulfide (GSSG). XANES peaks were found at the same energy even in a mammalian cell dry pellet. Spectra in the hydrated state exhibited similar profiles except for a very slight shift of resonance peaks to the lower energy. These results indicate that XANES profiles could be applicable to the mapping of S-C and S-S bonds in dry/hydrated biological systems using a spectromicroscopic technique. In addition, mass absorption coefficients of GSH and GSSG were determined.
Abstract: This paper presents an image processing approach to process incomplete penetration type flaws in radiographic images of the weld specimens considering morphological aspects of the image. In the present approach, radiographic weld image is processed to get the image with good contrast and reduced noise using image enhancement techniques like histogram equalization and noise filtering. This is followed by an effective edge detector such as Canny operator to find the edges of flaws, which are further…used to segment the image to fix the boundaries. Image segmentation is performed using morphological approach implemented through dilation of similar boundaries and erosion of dissimilar and irrelevant boundaries decided on the basis of pixel characteristics. The incomplete penetration type flaws are clearly identifiable in the finally processed image, which is obtained by superimposing the segmented image over the original enhanced image. The experimental results proved that proposed approach can be used as a reliable method for automatic detection of incomplete penetration types of flaws in radiographic weld images.
Keywords: Radiographic images, flaw detection, incomplete penetration type of flaw, edge detection, dilation, erosion
Abstract: Indocyanine green (ICG) is a functional dye with a variety of unique photomechanical, photochemical and photobiological properties. Single-walled carbon nanotubes (SWNTs) are promising new materials being used in biological and medical fields. In this paper, we reveal that ICG can directly dissolve SWNTs without covalent chemical functionalization of the tubes or the use of surfactants in aqueous solution. The ICG-SWNT complexes have been characterized with absorption, fluorescence and Raman spectroscopy. It is demonstrated that…ICG molecules that affect nanotubes properties are also altered by the presence of the SWNTs. These results provide an important evidence to better understand the π–π interactions between aromatic molecules and sidewalls of nanotubes. The broad absorption spectrum of ICG-SWNT complexes ranging from the UV to the near-infrared (NIR) regions opens this novel nanosystem to potential applications in the cancer photothermal therapy.