Computer-Assisted Segmentation of Videocapsule Images Using Alpha-Divergence-Based Active Contour in the Framework of Intestinal Pathologies Detection

Visualization of the entire length of the gastrointestinal tract through natural orifices is a challenge for endoscopists. Videoendoscopy is currently the “gold standard” technique for diagnosis of different pathologies of the intestinal tract. Wireless Capsule Endoscopy (WCE) has been developed in the 1990's as an alternative to videoendoscopy to allow direct examination of the gastrointestinal tract without any need for sedation. Nevertheless, the systematic post-examination by the specialist of the 50,000 (for the small bowel) to 150,000 images (for the colon) of a complete acquisition using WCE remains time-consuming and challenging due to the poor quality of WCE images. In this article, a semiautomatic segmentation for analysis of WCE images is proposed. Based on active contour segmentation, the proposed method introduces alpha-divergences, a flexible statistical similarity measure that gives a real flexibility to different types of gastrointestinal pathologies. Results of segmentation using the proposed approach are shown on different types of real-case examinations, from (multi-) polyp(s) segmentation, to radiation enteritis delineation

Light Bullets in Nonlinear Periodically Curved Waveguide Arrays

We predict that stable mobile spatio-temporal solitons can exist in arrays of periodically curved optical waveguides. We find two-dimensional light bullets in one-dimensional arrays with harmonic waveguide bending and three-dimensional bullets in square lattices with helical waveguide bending using variational formalism. Stability of the light bullet solutions is confirmed by the direct numerical simulations which show that the light bullets can freely move across the curved arrays. This mobility property is a distinguishing characteristic compared to previously considered discrete light bullets which were trapped to a specific lattice site. These results suggest new possibilities for flexible spatio-temporal manipulation of optical pulses in photonic lattices.Comment: 7 pages, 4 figure

Kontrastmittelgestützte Magnetresonanzangiographie mit Eisenoxidpartikeln

Das superparamagnetische T2-Kontrastmittel (KM) Resovist zeigt unter T1-gewichteten Sequenzen niedrig dosiert ein positives und hoch dosiert ein negatives Signalverhalten. In der mit Resovist durchgeführten T1-gewichteten MRA konnte zwar ein intravasaler Signalanstieg, jedoch keine nutzbare Verlängerung der Bluthalbwertszeit (BHWZ) erzielt werden. Daraufhin wurde experimentell getestet, bei welchem Partikel-Durchmesser (DM) von Resovist (65-21nm), bei welcher Konzentration und welchen Sequenzen sich der T1-Effekt der KM diagnostisch nutzen lassen könnte. Unter Berücksichtigung dieser Ergebnisse wurde in der Tierstudie der Einfluss von Partikel-DM und Dosis für die T1-gewichtete MRA ermittelt. Abnehmender Partikel-DM und zunehmende KM-Dosis zeigten eine Signalverstärkung und eine verlängerte BHWZ. Die kleinste Resovist-Fraktion (21nm) erzielte neben der stärksten Signalerhöhung auch die längste BHWZ, sodass aussagekräftige MRA bis über 25 Minuten nach KM-Gabe angefertigt werden konnten

Nonlinear directional coupler for polychromatic light

We demonstrate that nonlinear directional coupler with special bending of waveguide axes can be used for all-optical switching of polychromatic light with very broad spectrum covering all visible region. The bandwidth of suggested device is enhanced five times compared to conventional couplers. Our results suggest novel opportunities for creation of all-optical logical gates and switches for polychromatic light with white-light and super-continuum spectrum.Comment: 3 pages, 3 figure

Biomechanical evaluation of combined short segment fixation and augmentation of incomplete osteoporotic burst fractures

Background: Treating traumatic fractures in osteoporosis is challenging. Multiple clinical treatment options are found in literature. Augmentation techniques are promising to reduce treatment-related morbidity. In recent years, there have been an increasing number of reports about extended indication for augmentation techniques. However, biomechanical evaluations of these techniques are limited. Methods: Nine thoracolumbar osteoporotic spinal samples (4 FSU) were harvested from postmortem donors and immediately frozen. Biomechanical testing was performed by a robotic-based spine tester. Standardized incomplete burst fractures were created by a combination of osteotomy-like weakening and high velocity compression using a hydraulic material testing apparatus. Biomechanical measurements were performed on specimens in the following conditions: 1) intact, 2) fractured, 3) bisegmental instrumented, 4) bisegmental instrumented with vertebroplasty (hybrid augmentation, HA) and 5) stand-alone vertebroplasty (VP). The range of motion (RoM), neutral zone (NZ), elastic zone (EZ) and stiffness parameters were determined. Statistical evaluation was performed using Wilcoxon signed-rank test for paired samples (p = 0.05). Results: Significant increases in RoM and in the NZ and EZ (p < 0.005) were observed after fracture production. The RoM was decreased significantly by applying the dorsal bisegmental instrumentation to the fractured specimens (p < 0.005). VP reduced fractured RoM in flexion but was still increased significantly (p < 0.05) above intact kinematic values. NZ stiffness (p < 0.05) and EZ stiffness (p < 0.01) was increased by VP but remained lower than prefracture values. The combination of short segment instrumentation and vertebroplasty (HA) showed no significant changes in RoM and stiffness in NZ in comparison to the instrumented group, except for significant increase of EZ stiffness in flexion (p < 0.05). Conclusions: Stand-alone vertebroplasty (VP) showed some degree of support of the anterior column but was accompanied by persistent traumatic instability. Therefore, we would advocate against using VP as a stand-alone procedure in traumatic fractures. HA did not increase primary stability of short segment instrumentation. Some additional support of anterior column and changes of kinematic values of the EZ may lead one to suppose that additive augmentation may reduce the load of dorsal implants and possibly reduce the risk of implant failure.<br

Andromeda's Parachute: A Bright Quadruply Lensed Quasar at z=2.377

We present Keck Cosmic Web Imager spectroscopy of the four putative images of the lensed quasar candidate J014709+463037 recently discovered by Berghea et al. (2017). The data verify the source as a quadruply lensed, broad absorption-line quasar having z_S = 2.377 +/- 0.007. We detect intervening absorption in the FeII 2586, 2600, MgII 2796, 2803, and/or CIV 1548, 1550 transitions in eight foreground systems, three of which have redshifts consistent with the photometric-redshift estimate reported for the lensing galaxy (z_L ~ 0.57). By virtue of their positions on the sky, the source images probe these absorbers over transverse physical scales of ~0.3-21 kpc, permitting assessment of the variation in metal-line equivalent width W_r as a function of sight-line separation. We measure differences in W_r,2796 of <40% across all sight-line pairs subtending 7-21 kpc, suggestive of a high degree of spatial coherence for MgII-absorbing material. W_r,2600 is observed to vary by >50% over the same scales across the majority of sight-line pairs, while CIV absorption exhibits a wide range in W_r,1548 differences of ~5-80% within transverse distances less than ~3 kpc. J014709+463037 is one of only a handful of z > 2 quadruply lensed systems for which all four source images are very bright (r = 15.4-17.7 mag) and are easily separated in ground-based seeing conditions. As such, it is an ideal candidate for higher-resolution spectroscopy probing the spatial variation in the kinematic structure and physical state of intervening absorbers.Comment: Submitted to ApJL. 9 pages, 3 figures. Uses aastex61 forma

Organizacja pracy poczty. Przegląd Zagadnień Łączności, 1963, nr 9 (24)

Opracowania na podstawie artykułó