Current Issue : April - June Volume : 2017 Issue Number : 2 Articles : 5 Articles
Background: Metal artifacts appearing as streaks and shadows often compromise\nreadability of computed tomography (CT) images. Particularly in a dental CT in which\nhigh resolution imaging is crucial for precise preparation of dental implants or orthodontic\ndevices, reduction of metal artifacts is very important. However, metal artifact\nreduction algorithms developed for a general medical CT may not work well in a dental\nCT since teeth themselves also have high attenuation coefficients.\nMethods: To reduce metal artifacts in dental CT images, we made prior images by\nweighted summation of two images: one, a streak-reduced image reconstructed from\nthe metal-region-modified projection data, and the other a metal-free image reconstructed\nfrom the original projection data followed by metal region deletion. To make\nthe streak-reduced image, we precisely segmented the metal region based on adaptive\nlocal thresholding, and then, we modified the metal region on the projection data\nusing linear interpolation. We made forward projection of the prior image to make the\nprior projection data. We replaced the pixel values at the metal region in the original\nprojection data with the ones taken from the prior projection data, and then, we finally\nreconstructed images from the replaced projection data. To validate the proposed\nmethod, we made computational simulations and also we made experiments on teeth\nphantoms using a micro-CT. We compared the results with the ones obtained by the\nfusion prior-based metal artifact reduction (FP-MAR) method.\nResults: In the simulation studies using a bilateral prostheses phantom and a dental\nphantom, the proposed method showed a performance similar to the FP-MAR method\nin terms of the edge profile and the structural similarity index when an optimal global\nthreshold was chosen for the FP-MAR method. In the imaging studies of teeth phantoms,\nthe proposed method showed a better performance than the FP-MAR method in\nreducing the streak artifacts without introducing any contrast anomaly.\nConclusions: The simulation and experimental imaging studies suggest that the proposed\nmethod can be used for reducing metal artifacts in dental CT images....
Fluorescence molecular tomography (FMT) is an imaging technique that can localize and quantify fluorescent markers to resolve\nbiological processes at molecular and cellular levels. Owing to a limited number ofmeasurements and a large number of unknowns\nas well as the diffusive transport of photons in biological tissues, the inverse problem in FMT is usually highly ill-posed. In this\nwork, a sparsity-constrained preconditioned Kaczmarz (SCP-Kaczmarz) method is proposed to reconstruct the fluorescent target\nfor FMT.The SCP-Kaczmarz method uses the preconditioning strategy to minimize the correlation between the rows of the forward\nmatrix and constrains the Kaczmarz iteration results to be sparse.Numerical simulation and phantomand in vivo experiments were\nperformed to test the efficiency of the proposed method. The results demonstrate that both the convergence and accuracy of the\nproposed method are improved compared with the classical memory-efficient low-cost Kaczmarz method....
Background: The paper presents an automatic method for analysis and processing of\nimages from a camera operating in visible light. This analysis applies to images containing\nthe human facial area (body) and enables to measure the blood pulse rate. Special\nattention was paid to the limitations of this measurement method taking into account\nthe possibility of using consumer cameras in real conditions (different types of lighting,\ndifferent camera resolution, camera movement).\nMethods: The proposed new method of image analysis and processing was associated\nwith three stages: (1) image pre-processingââ?¬â?allowing for the image filtration\nand stabilization (object location tracking); (2) main image processingââ?¬â?allowing for\nsegmentation of human skin areas, acquisition of brightness changes; (3) signal analysisââ?¬â?\nfiltration, FFT (Fast Fourier Transformation) analysis, pulse calculation.\nResults and conclusions: The presented algorithm and method for measuring the\npulse rate has the following advantages: (1) it allows for non-contact and non-invasive\nmeasurement; (2) it can be carried out using almost any camera, including webcams;\n(3) it enables to track the object on the stage, which allows for the measurement of the\nheart rate when the patient is moving; (4) for a minimum of 40,000 pixels, it provides\na measurement error of less than Ã?±2 beats per minute for p < 0.01 and sunlight, or a\nslightly larger error (Ã?±3 beats per minute) for artificial lighting; (5) analysis of a single\nimage takes about 40 ms in Matlab Version 7.11.0.584 (R2010b) with Image Processing\nToolbox Version 7.1 (R2010b)....
Background: Coronary angiography (CAG) is widely used to assess lumen dimensions, and optical coherence\ntomography (OCT) is used to evaluate the characteristics of atherosclerotic plaque. This study was aimed to\ncompare coronary lumen dimensions using CAG and plaque characteristics using OCT and their changes during\nstatin therapy.\nMethods: We identified 97 lipid-rich plaques from 69 statin-na�¯ve patients, who received statin therapy in the\nfollowing 12 months. CAG and OCT examinations were conducted at baseline and 12-month follow-up period.\nResults: Lesion length, as measured by CAG, was closely correlated with lipid length by OCT (baseline: r = 0.754,\np < 0.001; follow-up: r = 0.639, p < 0.001). However, no significant correlations were found between the other\nfindings on OCT and data on CAG. With 12-month statin therapy, microstructures of lipid-rich plaques were\nsignificantly improved, but CAG-derived lumen dimensions were not improved. Moreover, we found no significant\nrelationship between changes in OCT measurements and changes in CAG data over time.\nConclusion: Lipid length on OCT and lesion length on CAG were closely correlated. However, plaque\nmicrostructural characteristics on OCT showed no significantly statistically correlations with lumen dimensions on\nCAG, neither did their evolutionary changes induced by statin over time....
Background: Early diastolic left ventricular (LV) filling can be accurately described using the same methods used in\nclassical mechanics to describe the motion of a loaded spring as it recoils, a validated method also referred to as\nthe Parameterized Diastolic Filling (PDF) formalism. With this method, each E-wave recorded by pulsed wave (PW)\nDoppler can be mathematically described in terms of three constants: LV stiffness (k), viscoelasticity (c), and\nload (x0). Also, additional parameters of physiological and diagnostic interest can be derived. An efficient\nsoftware application for PDF analysis has not been available. We aim to describe the structure, feasibility, time\nefficiency and intra-and interobserver variability for use of such a solution, implemented in Echo E-waves, a\nfreely available software application (www.echoewaves.org).\nResults: An application was developed, with the ability to open DICOM files from different vendors, as well as rapid\nsemi-automatic analysis and export of results. E-waves from 20 patients were analyzed by two investigators. Analysis\ntime for a median of 34 (interquartile range (IQR) 29ââ?¬â??42) E-waves per patient (representing 63 %, IQR 56ââ?¬â??79 % of the\nrecorded E-waves per patient) was 4.3 min (IQR 4.0ââ?¬â??4.6 min). Intra-and intraobserver variability was good or excellent\nfor 12 out of 14 parameters (coefficient of variation 2.5ââ?¬â??18.7 %, intraclass correlation coefficient 0.80ââ?¬â??0.99).\nConclusion: Kinematic analysis of diastolic function using the PDF method for Doppler echocardiography\nimplemented in freely available semiautomatic software is highly feasible, time efficient, and has good to\nexcellent intra-and interobserver variability....
Loading....