Reconstruction Of Cross-sectional Images Research Articles

Feasibility study of implementing gamma-ray computed tomography on measuring aggregate distribution and radiation shielding properties of concrete samples

Aggregate segregation is one of the key defects that impair the performance of concrete at fresh and hardened stages. This study aims to assess the feasibility of using an advanced technique to identify/scan/determine the aggregate segregation of concrete elements and determine radiation shielding properties of the concrete. The gamma-ray computed tomography (γ-CT) technique was employed to study aggregate distribution/dispersion in self-consolidating concrete (SCC). Accordingly, two SCC mixtures with moderate segregation (MS) and high segregation (HS) levels were cast and compared with highly stable SCC with no segregation (NS). The γ-CT scans were located on three different levels of concrete specimens located at the top-level (L1), middle-level (L2), and bottom-level (L3). A Cs-137 (660 keV emission) was used as a gamma-ray source to measure the linear attenuation coefficient per unit chord length at each level. Alternating minimization (AM) algorithm was utilized for cross-sectional image reconstruction based on the attenuation coefficient of the material density and the elements atomic number that represent the materials. A phantom of three Plexiglas layers was used to pre-validate the technique’s ability to identify aggregate locations. Moreover, the γ-CT scans of the concrete samples were compared with selected sections using the image processing method. The findings confirmed that the γ-CT technique can determine the level of segregation in the investigated samples. Further, it has been found that the presence of the aggregate enhanced the radiation shielding properties by up to ∼25%. The linear attenuation values were used to quantify the aggregate distribution of the concrete samples.

Automatic measurement of mandibular cortical bone width on cone-beam computed tomography images

The computed tomography cortical index (CTCI), computed tomography mandibular index (CTMI), and computed tomography index (inferior) [CTI(I)] are indexes obtained from cone-beam computed tomography images for the assessment of the mandibular cortex quality for implant planning or osteoporosis. However, cross-sectional image reconstruction for the measurements is labor-intensive. This study aimed to develop and evaluate a method to automatically reconstruct cross-sectional images and measure the cortex width in all areas inferior to the mental foramen (MF). Seventy-one women (mean age: 52.4years; range: 20-78years) were enrolled. They were divided into four age and CTCI groups, including females younger (FY) and females older (FO) than 50years (C1: normal, C2: mild/moderate erosion, and C3: severe porosity). Automatic and manual measurements of CTMI and CTI(I) were compared, and the inter- and intraobserver agreements were assessed using the intraclass correlation coefficient (ICC). The relationships between CTMI or CTI(I) and CTCI were also assessed. The mean processing times for reconstruction and measurements were 31.9s and 1.22s, respectively. ICCs for the comparison of automatic and manual measurements were 0.932 and 0.993 in the C1 and C2/C3 groups, respectively. Significant differences in CTMI and CTI(I) were observed between the FY or the FO-C1 and FO-C3 groups (p < 0.05). The automatic and manual measurements showed a strong agreement. The new method could drastically reduce routine clinical workload. Additionally, our method enables the measurement of the cortex width in all the mandibular bones inferior to the MF.

Optical coherence refraction tomography.

Optical coherence tomography (OCT) is a cross-sectional, micron-scale imaging modality with widespread clinical application. Typical OCT systems sacrifice lateral resolution to achieve long depths of focus for bulk tissue imaging, and hence tend to have better axial than lateral resolution. Such anisotropic resolution can obscure fine ultrastructural features. Furthermore, conventional OCT suffers from refraction-induced image distortions. Here, we introduce optical coherence refraction tomography (OCRT), which extends the superior axial resolution to the lateral dimension, synthesising undistorted cross-sectional image reconstructions from multiple conventional images acquired with angular diversity. In correcting refraction-induced distortions to register the OCT images, OCRT also achieves spatially resolved refractive index imaging. We demonstrate >3-fold improvement in lateral resolution as well as speckle reduction in imaging tissue ultrastructure, consistent with histology. With further optimisation in optical designs to incorporate angular diversity into clinical instruments, OCRT could be widely applied as an enhancement over conventional OCT.

PEMBELAJARAN SIMULASI PENCITRAAN CT DENGAN MENGGUNAKAN PRINSIP REKONSTRUKSI CITRA DALAM SOFTWARE MATLAB

This research was conducted as a learning alternatives for study of CT (computed tomograpghy) imaging using image reconstruction technique which are inversion matrix, back projection and filtered back projection. CT imaging can produce images of objects that do not overlap. Objects more easily distinguishable although given the relatively low contrast. The image is generated on CT imaging is the result of reconstruction of the original object. Matlab allows us to create and write imaging algorithms easily, easy to undersand and gives applied and exciting other imaging features. In this study, an example cross-sectional image recon-struction performed on the body of prostate tumors using. With these methods, medical prac-titioner (such as oncology clinician, radiographer and medical physicist) allows to simulate the reconstruction of CT images which almost resembles the actual CT visualization techniques.Keywords : computed tomography (CT), image reconstruction, Matlab

The Uro Dyna-CT Enables Three-dimensional Planned Laser-guided Complex Punctures

BackgroundUltrasound and fluoroscopy are the standard imaging techniques used to perform punctures in urology. Cross-sectional and three-dimensional (3D) imaging may enable safer procedures, especially in complex cases. ObjectivesTo assess the feasibility of 3D planned laser-guided punctures in urology performed with the Uro Dyna-CT (Siemens Healthcare Solutions, Erlangen, Germany). Design, setting, and participantsA total of 27 punctures using the laser-guided system syngo iGuide (Artis Zee Ceiling; Siemens Healthcare Solutions, Erlangen, Germany) for the Uro Dyna-CT have been performed to date. Patients with complex puncture indications due to unclear ultrasound findings or a suspicion of surrounding bowel were included. Surgical procedureImage acquisition was performed using a customized 8s syngo iGuide protocol of the Uro Dyna-CT. The puncture tract was planned after 3D and cross-sectional image reconstruction. The puncture was performed supported by the laser-guiding system. Outcome measurements and statistical analysisThe primary end point of our assessment was accuracy and applicability of the system in a clinical setting. Secondary end points were planning time, puncture time, and radiation exposure of the patient. Results and limitationsOverall, 24 of 27 punctures were successful. No severe complications occurred. Median radiation dose of the Uro Dyna-CT scan was 6113.1 micrograys meter squared (μGym2; range: 1081.6–7957.2μGym2). The small patient cohort is the major limitation of our study. ConclusionsWe believe the Uro Dyna-CT–based puncture technique is an excellent additional instrument that allows the urologist to handle complex punctures. Image acquisition leads to higher radiation doses than standard fluoroscopy but does not exceed the radiation exposure of alternative procedures such as computed tomography (CT)–guided punctures with multidetector CT, which is used mainly for complex cases. Patient summaryWe report our experience with a three-dimensional planning and laser-guiding tool to perform complex punctures for urologic indications. The technique is feasible in the endourologic intervention suite.

Triple Rule-out Computed Tomographic Angiography for Chest Pain: A Diagnostic Systematic Review and Meta-Analysis

The objective was to compare the image quality, diagnostic accuracy, radiation exposure, and contrast volume of "triple rule-out" (TRO) computed tomography (CT) to other diagnostic modalities commonly used to evaluate patients with nontraumatic chest pain (dedicated coronary, pulmonary embolism [PE], and aortic dissection CT; invasive coronary angiography; and nuclear stress testing). Four electronic databases were searched, along with reference lists and contacted content experts, for relevant studies from inception until October 2012. Eligible studies enrolled patients with nontraumatic chest pain, shortness of breath, suspected acute coronary syndrome (ACS), PE, or aortic dissection; used at least 64-slice CT technology; and compared TRO CT to another diagnostic modality. Eleven studies enrolling 3,539 patients (791 TRO and 2,748 non-TRO) were included (one randomized controlled trial and 10 observational). There was no significant difference in image quality between TRO and dedicated CT scans. TRO CT had the following pooled diagnostic accuracy estimates for coronary artery disease: sensitivity of 94.3% (95% confidence interval [CI] = 89.1% to 97.5%), specificity of 97.4% (95% CI = 96.1% to 98.4%), positive likelihood ratio (LR+) of 17.71 (95% CI = 3.92 to 79.96), and negative likelihood ratio (LR-) of 0.08 (95% CI = 0.02 to 0.27). There were insufficient numbers of patients with PE or aortic dissection to generate diagnostic accuracy estimates for these conditions. Use of TRO CT involved greater radiation exposure (mean difference [MD] = 4.84 mSv, 95% CI = 1.65 to 8.04 mSv) and contrast exposure (MD = 38.0 mL, 95% CI = 28.1 to 48.0 mL) compared to non-TRO CT patients. Triple rule-out CT is highly accurate for detecting coronary artery disease. Given the low (<1%) prevalence of PE and aortic dissection in the included studies, and the increased radiation and contrast exposure, there are insufficient data to recommend use of TRO CT in the diagnosis of these conditions.

Electromagnetic Tissue Properties Imaging for Biomedical Applications

Recently, imaging techniques in science, engineering, and medicine have evolved to expand our ability to visualize a property of an object such as the human body. In particular, there has been marked progress in electromagnetic property imaging techniques, where cross sectional image reconstructions of electric conductivity, permittivity, and magnetic susceptibility distributions inside the human body are pursued. These techniques also have wider application to imaging methods in medicine, biotechnology, nondestructive testing, monitoring of industrial process, and others. This special issue focuses on imaging methodologies, mathematical models, and computational algorithms for imaging electrical tissue properties for biomedical applications. The imaging problems in this topic can be formulated as inverse problems that are intrinsically nonlinear. Finding solutions with practical significance and value requires in-depth understanding of the underlying physical phenomena and data acquisition systems as well as implementation details of image reconstruction algorithms. Experience over the last three decades has shown that the symbiotic interplay between theoretical mathematics, computational mathematics, and experiments is crucial for understanding and solving these nonlinear problems in practice. With this special issue, we hope to give an opportunity for this scientific community to consolidate knowledge in the field and to identify the new challenges and the most promising directions for future progress. Jin Keun Seo William Lionheart Ulrich Katscher EungJe Woo

Magnetic resonance electrical impedance tomography (MREIT): conductivity and current density imaging

This paper reviews the latest impedance imaging technique called Magnetic Resonance Electrical Impedance Tomography (MREIT) providing information on electrical conductivity and current density distributions inside an electrically conducting domain such as the human body. The motivation for this research is explained by discussing conductivity changes related with physiological and pathological events, electromagnetic source imaging and electromagnetic stimulations. We briefly summarize the related technique of Electrical Impedance Tomography (EIT) that deals with cross-sectional image reconstructions of conductivity distributions from boundary measurements of current-voltage data. Noting that EIT suffers from the ill-posed nature of the corresponding inverse problem, we introduce MREIT as a new conductivity imaging modality providing images with better spatial resolution and accuracy. MREIT utilizes internal information on the induced magnetic field in addition to the boundary current-voltage measurements to produce three-dimensional images of conductivity and current density distributions. Mathematical theory, algorithms, and experimental methods of current MREIT research are described. With numerous potential applications in mind, future research directions in MREIT are proposed.

Evaluation of regional systolic function in hypertrophic cardiomyopathy and hypertensive heart disease: A three-dimensional echocardiographic study

Assessment of regional left ventricular (LV) function in patients with asymmetric LV hypertrophy is difficult with two-dimensional echocardiography mainly because of factors such as LV geometry, structure, regional wall stress, and ischemia. Multiplane transesophageal echocardiography with three-dimensional reconstruction of cross-sectional images was used for quantitative evaluation of regional wall thickness and fractional thickening. Fifteen patients (56 ± 13 years old) with hypertrophic cardiomyopathy (LV ejection fraction 71% ± 4%), 15 (62 ± 13 years) with hypertensive heart disease (ejection fraction 66% ± 8%) and 15 (53 ± 11 years) healthy control subjects (ejection fraction 61% ± 5%) were included in the analysis. Regional function was studied in four parallel equidistant short-axis cross sections from base to apex of the reconstructed left ventricle. In 15 degree intervals, 24 wall thickness measurements in each cross section were made at end-diastole and end-systole after endocardial and epicardial border tracing. A total of 192 measurements were obtained in each patient, and absolute wall thickening and fractional thickening were calculated. Absolute and fractional wall thickening showed a significant inverse relation to end-diastolic wall thickness in all heart conditions ( r = 0.71, p < 0.0001). Regions of normal wall thickness in diseased patients were not hyperdynamic when compared with normal control subjects. Significant impairment in fractional thickening at identical end-diastolic thickness was observed in the septum compared with the lateral free wall in both hypertrophic cardiomyopathy and hypertensive heart disease. Thus regional systolic function is inversely related to end-diastolic wall thickness. The decrease in regional systolic function with increasing LV hypertrophy was similar in idiopathic and hypertensive cardiomyopathy. In both types of hypertrophy, significant differences in systolic function were observed in septal and lateral wall segments of similar wall thickness. This indicates that factors other than end-diastolic wall thickness influence myocardial thickening in patients with hypertrophy and preserved global function. (J Am Soc Echocardiogr 1998;11:778-86.)

A unified approach to statistical tomography using coordinate descent optimization

Over the past years there has been considerable interest in statistically optimal reconstruction of cross-sectional images from tomographic data. In particular, a variety of such algorithms have been proposed for maximum a posteriori (MAP) reconstruction from emission tomographic data. While MAP estimation requires the solution of an optimization problem, most existing reconstruction algorithms take an indirect approach based on the expectation maximization (EM) algorithm. We propose a new approach to statistically optimal image reconstruction based on direct optimization of the MAP criterion. The key to this direct optimization approach is greedy pixel-wise computations known as iterative coordinate decent (ICD). We propose a novel method for computing the ICD updates, which we call ICD/Newton-Raphson. We show that ICD/Newton-Raphson requires approximately the same amount of computation per iteration as EM-based approaches, but the new method converges much more rapidly (in our experiments, typically five to ten iterations). Other advantages of the ICD/Newton-Raphson method are that it is easily applied to MAP estimation of transmission tomograms, and typical convex constraints, such as positivity, are easily incorporated.

Recent progress in quantitative echocardiography.

Substantial progress has been made recently in quantitating a variety of functional or morphologic parameters with echocardiography. Doppler techniques for measuring regurgitant flow rate and regurgitant orifice area in mitral and tricuspid regurgitation have become well established, along with other Doppler measures of regurgitation severity, such as proximal jet width. Doppler measurement of diastolic flow propagation in the left ventricle is emerging as a promising, albeit fascinatingly complex way of looking at diastolic function. Doppler velocimetry has been extended to wall motion, yielding color maps of tissue, an entirely new tool for assessing myocardial function and its timing. In the field of two-dimensional data processing, automatic on-line boundary detection based on integrated ultrasound backscatter has been used for volume and cardiac output calculations. Finally, three-dimensional reconstruction of cross-sectional images now has been well validated for in vivo measurements of heart cavity volumes and masses.

Image reconstruction by a Hopfield neural network

The reconstruction of cross-sectional images from projections involves the solution of a large system of simultaneous equations in which the unknowns are attentuation coefficients associated with the cells consti tuting the image. As an alternative to iterative methodssuch as the algebraic reconstruction technique (ART), a modified linear form of the Hopfield neural network with a summation layer to significantly decrease the number of interconnections is proposed. Higher speed and improved SNR, compared to ART, have been obtained on the Shepp and Logan ‘head phantom’ divided into 100 × 100 cells.

Assessment of Body Composition of Poultry by Nuclear Magnetic Resonance Imaging and Spectroscopy

Nuclear magnetic resonance (NMR) imaging and spectroscopy were used to assess body composition of the chicken and turkey poult. The NMR imaging was performed using a clinical, whole-body imaging system operating at 1.5 tesla (T; 63 MHz). Three-dimensional reconstruction of cross-sectional images made along the transaxial plane was used to estimate mass of the Pectoralis muscle of chickens ranging in weight from 140 to 2,760 g. Results indicate that NMR imaging can be used to determine size of the Pectoralis muscle (R2 = .99) in the bird, thus permitting repetitive measurements during the growth and development of the bird. The NMR spectroscopy was performed using an imaging spectrometer operating at 4.7 T (200 MHz). Integral areas of the water and lipid proton peaks of the spectra were compared with the water and lipid content of the whole body as determined by chemical analysis. Regression analysis of measurements made on turkey poults, ranging in weight from 115 to 630 g (n = 6), resulted in R2 values of .94 for NMR water proton peak area and total body water, .93 for NMR lipid proton peak area and total body lipid, and .96 for NMR water proton peak area and total body protein. From NMR spectroscopy of chickens weighing 528 ± 18 g (n = 6), the relative area of the lipid peak correlated with whole-body lipid (R2 = .97). Thus, whole-body spectroscopy of smaller birds can be used to measure total body water, protein, and lipid content.

Cross-Sectional Reconstructions of Sickle Cell Hemoglobin Macrofibers.

We have succeeded in performing two-dimensional cross sectional image reconstructions of sickle cell hemoglobin (HbS) macrofibers. Macrofibers are long helical structures which are intermediates in the crystallization of deoxygenated sickle cell hemoglobin at low pH. Earlier work has established that macrofibers are aggregates of Wishner-Love double strands which consist of 2 half-staggered HbS molecules repeating every 64 A in the axial direction. Thin sections of embedded aggregating macrofiber cross sections reveal a dumbbell like pattern of double strands (Figure 2a,b) that is similar to the a-axis projection of the crystal structure. Approximately 5 rows with 10 double strands per row were identified in the cross section, but structural features in the thin sections were obscured by an approximately 15 degree rotational blur due to the finite thickness (400 A) of the helical section, the ill defined boundaries of the section due to uneven staining, and apparent particle damage. These structural features have now been resolved in reconstructed cross sections obtained using a real space filtered back projection algorithm.

Data Collection for Cross-Sectional Image Reconstruction by a Moving Ring of Positron Annihilation Detectors

A ring of positron annihilation detectors capable of two independent motions in the plane of the ring is considered. It can rotate around its center, and the whole ring may move so that its center traces a circular path. Provided certain parameters are chosen according to given formulas, data collected by such a detector ring can be reorganized (rebinned), in a computationally very inexpensive fashion, so that the data items in each bin are measurements along parallel lines spaced at small equal intervals. Efficient high resolution reconstruction algorithms that assume such data organization can therefore be applied to data collected collected by a moving positron ring detector. The method is demonstrated on a realistic example.