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Advanced template matching method for estimation of intervertebral kinematics of lumbar spine.
No full textDiagnosis of low back pain and other degenerative spinal pathologies can be extremely difficult and,
so far, there are not accepted standards. In general, such pathologies are associated with alteration of
mechanical properties of spine and, in particular, with the instability of spinal motion. Intervertebral
kinematics can be a valuable, objective method to assess the functionality of spinal segments. Fluoroscopic
imaging system can provide continuous screening of lumbar tracts during patient’s motion, with
an acceptable low X-ray dose. Estimation of intervertebral kinematics relies on accurate recognition of
vertebrae positions throughout the fluoroscopic sequence: specific vertebrae features are identified and
tracked either by manual selection or by automated methods. This study presents a new method of vertebra
tracking, based on image template matching of the contour of the vertebral body for an accurate
intervertebral kinematics analysis. An image gradient operator was utilized to obtain the vertebral contours;
it operates after an edge-preserving smoothing filter designed to reduce low dose X-ray image
noise. Once a template is defined for each vertebra, this is used to determine the best vertebral location
in each image throughout the fluoroscopic sequence. Accuracy of the proposed method was tested using
images of a calibration model. Average error achieved for the intervertebral angle is of the order of 0.4◦
and approximately 2 mm for the intervertebral centre of rotation. Five fluoroscopic lumbar sequences
of healthy volunteers undergoing passive flexion–extension motion were processed. The intervertebral
kinematics was compared with other methods (automated and manual) by an estimation of measurement
error. Results showed that the current method provides a better representation of the evolution over
time of kinematic parameters. In particular, root mean square differences between the current method
and a manual selection procedure performed by an experienced and trained clinician resulted 1.3◦ for
the intervertebral angles and 0.9 mm for the intervertebral trajectory. The proposed method provides an
effective, automated and objective technique for estimation of intervertebral kinematics of lumbar spine
Changes of serum hydroxybutyrate and lactate concentrations diet dependent in overweight blood donors
No full textA comparison of denoising methods for X-ray fluoroscopic images
No full textFluoroscopic images exhibit severe signal-dependent quantum noise, due to the reduced X-ray dose involved in image formation, that is generally modelled as Poisson-distributed. However, image gray-level transformations, commonly applied by fluoroscopic device to enhance contrast, modify the noise statistics and the relationship between image noise variance and expected pixel intensity. Image denoising is essential to improve quality of fluoroscopic images and their clinical information content. Simple average filters are commonly employed in real-time processing, but they tend to blur edges and details. An extensive comparison of advanced denoising algorithms specifically designed for both signal-dependent noise (AAS, BM3Dc, HHM, TLS) and independent additive noise (AV, BM3D, K-SVD) was presented. Simulated test images degraded by various levels of Poisson quantum noise and real clinical fluoroscopic images were considered. Typical gray-level transformations (e.g. white compression) were also applied in order to evaluate their effect on the denoising algorithms. Performances of the algorithms were evaluated in terms of peak-signal-to-noise ratio (PSNR), signal-to-noise ratio (SNR), mean square error (MSE), structural similarity index (SSIM) and computational time. On average, the filters designed for signal-dependent noise provided better image restorations than those assuming additive white Gaussian noise (AWGN). Collaborative denoising strategy was found to be the most effective in denoising of both simulated and real data, also in the presence of image gray-level transformations. White compression, by inherently reducing the greater noise variance of brighter pixels, appeared to support denoising algorithms in performing more effectively. © 2012 Elsevier Ltd. All rights reserve
Impaired insulin secretion in human diabetes mellitus III. The effect of the serotonin antagonist metergoline
No full text
Impaired insuIin secretion in human diabetes mellitus. III. The effect of the serotonin antagonist metergoline.
No full textInfluence of the hypocaloric diet on serum free fatty acids and glycerol in blood donors in overweight
No full textA continuous description of intervertebral motion by means of spline interpolation of kinematic data extracted by videofluoroscopy
No full textIn vivo analysis of intervertebral kinematics provides useful information about spinal disorders and performance of disk prostheses. Diagnosis of intervertebral instability is based on measurement of abnormal range of segmental motion in sagittal plane through functional flexion-extension radiography; however, this concise measure does not take into account the progression of segmental motion in between flexion and extension extremes. Fluoroscopy can support analysis of intervertebral kinematics during patient's motion with an acceptable X-ray dose. A spline-based method designed for a continuous-time description of intervertebral motion extracted by videofluoroscopy is proposed. Fluoroscopic sagittal sequences of lumbar spine were processed by an automated method based on template matching to track vertebrae. A smoothing spline interpolation of the estimated intervertebral kinematic data was performed and a continuous-time description of segmental rotation and translation was obtained; the smoothing parameter was chosen both to preserve motion and to reduce noise. Concise measurements were extracted by the continuous-time kinematics and compared with standard clinical measurements of intervertebral sagittal rotation and translation. The trajectory of instantaneous center of rotation, never presented before for in vivo spinal segments, was provided and compared with standard measurements of the finite center of rotation. Results showed a good agreement with standard clinical measurements: on average, absolute differences resulted 0.74. degree for sagittal rotation, 0.59. mm for translation and 1.02. mm for the x- and y-position of center of rotation. The proposed method offers an effective technique for the continuous-time description of intervertebral motion, maintaining standard clinical measurements for diagnosis of lumbar instability
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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