OBJECTIVES:To (1) establish the feasibility of texture analysis for the in vivo assessment of biochemical changes in meniscal tissue on delayed gadolinium-enhanced magnetic resonance imaging of ...cartilage (dGEMRIC), and (2) compare textural with conventional T1 relaxation time measurements calculated from dGEMRIC data (“T1(Gd) relaxation times”).
MATERIALS AND METHODS:We enrolled 10 asymptomatic volunteers (7 men and 3 women; mean age, 27.2 ± 4.5 years), without a history of meniscus damage, in our study. MRI of the right knee was performed at 3.0 T. An isotropic, 3-dimensional (3D), double-echo steady-state sequences was used for morphologic evaluation, and a dual flip angle 3D gradient echo sequence was used for T1(Gd) mapping. All MRI scans were performed 90 minutes after injection of 0.2 mmol/kg of Gd-diethylenetriamine pentaacetic acid (DTPA), and subsequently, during application of a compressive force (50% of the body weight) in the axial direction. Regions of interest, covering the central portions of the posterior horn of the medial meniscus, were defined on 3 adjacent sagittal sections. Based on the relaxation time maps, mean T1(Gd), as well as the T1(Gd) texture features derived from the co-occurrence matrix (COCAngular Second Moment, Entropy, Inverse Difference Moment) and wavelet transform (WAVWavEnLL, WavEnHL, WavEnHH, WavEnLH), were calculated. Paired t tests were used to assess differences between baseline and compression, and intraclass correlation coefficients (ICC) were calculated to establish the intrarater reliability of the measurements.
RESULTS:Mean T1(Gd) (−67.3 ms, P = 0.011), Angular Second Moment (−0.0002, P = 0.009), Entropy (+0.033, P = 0.025), WavEnLL (+1011.16, P = 0.002), WavEnHL (+18.64, P = 0.012), and WavEnLH (+72.74, P = 0.035) differed significantly between baseline and compression. Intrarater reliability was substantial for mean T1(Gd) relaxation times (ICC = 0.99–1.0), and also for T1(Gd) co-occurrence matrix (ICC = 0.63–0.92) and WAV (ICC = 0.86–0.98) features.
CONCLUSIONS:Texture features extracted from T1 maps calculated from dGEMRIC data are feasible for the in vivo assessment of biochemical changes in the menisci, such as might be induced by mechanical loading. Thus, T1(Gd) texture features complement conventional relaxation time measurements. Further studies are necessary to determine whether the mechanical compression, or a prolonged Gd-DTPA uptake, or both, are responsible for the observed decrease in mean T1(Gd) relaxation times in the menisci.
With the great progress in magnetic resonance imaging of the last decades, computerized image texture analysis has become an appealing approach to image quantification - for more objective medical ...diagnosis and therapy outcome evaluation. The number of research papers on TA applications to MRI of the bone, brain, breast, liver, myocardium and prostate continues to increase. MRI texture descriptors are computed to characterize spatial patterns of the image intensity that originate in the structure of tissues. This is a rich source of information, not available through standard quantification, based on single-voxel intensity only. However, the large number of texture descriptors depend not only on the texture, but also on local average image intensity. Since variations of intensity, known as image nonuniformity (inhomogeneity) artifacts, often occur in MRI, their presence may severely interfere with texture analysis and, consequently, lead to errors in tissue description. The origin of this unwanted effect is explained using the popular gray-level-cooccurrence matrix texture description. The intensity-caused errors are discussed and illustrated using MRI slices of a normal and fibrotic liver. To reduce those errors, correction of image spatial nonuniformity prior to texture analysis is recommended as an image preprocessing step, especially for large-volume regions of interest, featuring homogeneous texture.
Purpose - This paper presents an IT system - Student Connectivity Module (SCM) - designed to support administration of student exchange between universities in different countries, developed under ...the EU seventh Framework Program. The purpose of this paper is to share the acquired knowledge on existing difficulties in mobility management, propose solutions to those problems, and present results of system validation using its prototype deployed at two universities. Design/methodology/approach - Prior to the system design, the needs, plans and expectations concerning the academic IT services were surveyed among 100 universities. On this basis, in close with prospective system users, an original peer-to-peer system was developed using top-down model-driven and agile software development techniques. Findings - The barriers to effective interoperation of academic information systems (AIS) were revealed: first, diversity and heterogeneity of campus IT solutions; second, differences in patterns of international student mobility flow; third, diversity in national personal data protection policies; and fourth, lack of standards for e-data exchange. The SCM system overcomes these problems by adopting platform-independent IT solutions, web-services, a network of trusted authority servers, and a novel "quasi-standard" solution for e-data exchange, with the use of home university campus cards to access facilities at host institutions. Originality/value - The management of foreign student exchange is a complicated process. It involves students, faculty, administrative staff and external institutions. To the authors knowledge, there is no other comprehensive networked IT system available to facilitate administration of student mobility, make it better controlled, less laborious and faster, in a secure way. The IT solution contributes to overcoming the current barriers to academic mobility within Europe and elsewhere.
This paper describes an automatic method for classification and segmentation of different intracardiac masses in tumor echocardiograms. Identification of mass type is highly desirable, since to ...different treatment options for cardiac tumors (surgical resection) and thrombi (effective anticoagulant treatment) are possible. Correct diagnosis of the character of intracardiac mass in a living patient is a true challenge for a cardiologist; therefore, an objective image analysis method may be useful in heart diseases diagnosis.
Image texture analysis is used to distinguish various types of masses. The presented methods assume that image texture encodes important histological features of masses and, therefore, texture numerical parameters enable the discrimination and segmentation of a mass. The recently developed technique based on the network of synchronized oscillators is proposed for the image segmentation. This technique is based on a ‘temporary correlation’ theory, which attempts to explain scene recognition as it would be performed by a human brain. This theory assumes that different groups of neural cells encode different properties of homogeneous image regions (e.g. shape, color, texture). Monitoring of temporal activity of cell groups leads to scene segmentation. A network of synchronized oscillators was successfully used for segmentation of Brodatz textures and medical textured images. The advantage of this network is its ability to detect texture boundaries. It can be also manufactured as a VLSI chip, for a very fast image segmentation.
The accuracy of locating of analyzed tissues in the image should be assessed to evaluate a segmentation technique. The new evaluation method based on measurement of physical textured test objects was proposed. Firstly, a series of object images was obtained by the use of different devices (scanner, digital camera and TV camera). Secondly, the images were segmented using oscillator network and feedforward artificial neural network. Thirdly, geometrical test object parameters were estimated and compared to its true values. The experiment was repeated also for ultrasound images, which represented rectangular cross-section of synthetic sponge submerged in water.
In addition, classification and segmentation of selected benign tumor echocardiograms were performed. Oscillator network was used with network weights defined for both whole texture region and texture boundary detection for the tumor segmentation. The latter method provides much faster segmentation with the similar accuracy. The obtained segmentation results were discussed and compared to the artificial neural network classifier.
Finally, it was demonstrated that the network of synchronized oscillators is a reliable tool for the segmentation of the selected intracardiac masses, since it gives a relatively accurate location of analyzed tissues. The advantage of the proposed method is its resistance to changes of the visual information in the analyzed image and to noise and artifacts, often present in echocardiograms.
Accurate modeling of the human vascular tree from 3D computed tomography (CTA) or magnetic resonance (MRA) angiograms is required for visualization, diagnosis of vascular diseases, and computational ...fluid dynamic (CFD) blood flow simulations. This work describes an automated algorithm for constructing the polygonal mesh of blood vessels from such images. Each vascular segment is modeled as a tubular object, and a thin plate spline transform is used to generate the corresponding surface from its centerline-radius representation. A novel approach for generating the polygonal mesh of bifurcating vessels based on conformal mapping is presented. A mathematical description of the methodology is also provided. The model is improved by computing local intensity features with subvoxel accuracy, to slightly deform the mesh of the vascular tree for fine-tuning. The proposed algorithm was successfully tested on a 3D synthetic image containing randomly generated vascular branches. Experiment results, confirmed by real-world Time of Flight MRA, demonstrate that our methodology is consistent and capable of generating high quality triangulated meshes of vascular trees, suitable for further CFD simulations. Compared to common techniques, conformal mapping proved to be a simple and effective mathematical approach for polygonal mesh modeling of bifurcating vessels.
In this paper, we propose a method for denoising diffusion-weighted images (DWI) of the brain using a convolutional neural network trained on realistic, synthetic MR data. We compare our results to ...averaging of repeated scans, a widespread method used in clinics to improve signal-to-noise ratio of MR images. To obtain training data for transfer learning, we model, in a data-driven fashion, the effects of echo-planar imaging (EPI): Nyquist ghosting and ramp sampling. We introduce these effects to the digital phantom of brain anatomy (BrainWeb). Instead of simulating pseudo-random noise with a defined probability distribution, we perform noise scans with a brain-DWI-designed protocol to obtain realistic noise maps. We combine them with the simulated, noise-free EPI images. We also measure the Point Spread Function in a DW image of an AJR-approved geometrical phantom and inter-scan movement in a brain scan of a healthy volunteer. Their influence on image denoising and averaging of repeated images is investigated at different signal-to-noise ratio levels. Denoising performance is evaluated quantitatively using the simulated EPI images and qualitatively in real EPI DWI of the brain. We show that the application of our method allows for a significant reduction in scan time by lowering the number of repeated scans. Visual comparisons made in the acquired brain images indicate that the denoised single-repetition images are less noisy than multi-repetition averaged images. We also analyse the convolutional neural network denoiser and point out the challenges accompanying this denoising method.
The real bone structure can be completely described by histomorphometric analysis; however, it needs bone biopsy. The development of imaging techniques and mathematical methods of texture parameters ...extraction from radiographs make it possible to reveal the characteristic bone features in non-invasive manner. The aim of this study was to formulate a mathematical description of image texture for finding out whether there exist any structural differences (run-length matrix) in jaw bone depended on gender. Parameters derived from a run-length matrix are used to characterize the texture in quantity.
319 digital, standardized, intra-oral, plain radiographs of patients qualifying to dental implantations were included into this study. Straight-line series (runs) of pixels of similar gray level were searched and analyzed in radiographs.
Exploring the local bone structure at particular fragments of the jaws, in females significantly more frequent the presence of short series of pixels in lower alveolar ridge than in upper alveolar ridge are observed. Only later aspects of maxillary alveolar ridge have the radiomicroarchitecture depending on patient's gender in respect to the investigated feature. In females, much more number of short series of the pixels is revealed at lateral aspect of alveolar ridge of mandible than at frontal aspect.
Quantitative description of short series of pixels is useful for evaluation of radiotexture in images of alveolar ridge.
Nonuniformities in illumination of a scene and/or in imaging device response can deteriorate texture analysis results since some texture parameters depend not only on the properties of visualized ...structure but also on local mean and variance of the image. This work is an attempt to discuss the sensitivity of texture parameters to image inhomogeneities (nonuniformities) - to select those which do not alter their values significantly. The properties of widely used texture parameters, i.e. based on gray level co-occurrence matrix, run length matrix and wavelet transform are taken into account. Two nonuniformity models are considered: smooth variations of image intensity and of its contrast, respectively. The discussion is illustrated by classification examples performed for natural textures from the Brodatz album. In conclusion, some features are identified, which represent certain immunity to the discussed image inhomogeneities.
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