82 research outputs found
Development of Unsupervised methods for medical Image Segmentation
Image segmentation is the process of partitioning an image into meaningful parts. Image segmentation is used to locate objects and boundaries in images. It is the process of assigning a label to every pixel in an image such that pixels with the same label share certain visual characteristics.
The need for accurate segmentation tools in medical applications is driven by the increased capacity of the imaging devices. Due to high resolutions and a large number of image slices CT and MRI generated images cannot be examined manually. Furthermore, it is very difficult to visualize complex structures in three-dimensional image volumes without cutting away large portions of, perhaps important, data. Tools, such as segmentation, can aid the medical staff in browsing through such large images by highlighting objects of particular importance. In addition, segmentation in particular can output models of organs, tumors, and other structures for further analysis, quantification or simulation. We have used k means, fuzzy c means for better performance we map the input space onto a self-organising map and then the low dimensional input is clustered using the above methods.
A self-organising map (SOM) is a type of artificial neural network that is trained using unsupervised learning to produce a low-dimensional (typically two-dimensional), discretized representation of the input space of the training samples, called a map. This thesis is devoted to medical image segmentation techniques and their applications in clinical and research settings
Sulfonylurea Receptor 1 in Central Nervous System Injury: An Updated Review
Hinchazón celular; Edema; Traumatismo cerebralCellular swelling; Edema; Traumatic brain injuryInflor cel·lular; Edema; Traumatisme cerebralSulfonylurea receptor 1 (SUR1) is a member of the adenosine triphosphate (ATP)-binding cassette (ABC) protein superfamily, encoded by Abcc8, and is recognized as a key mediator of central nervous system (CNS) cellular swelling via the transient receptor potential melastatin 4 (TRPM4) channel. Discovered approximately 20 years ago, this channel is normally absent in the CNS but is transcriptionally upregulated after CNS injury. A comprehensive review on the pathophysiology and role of SUR1 in the CNS was published in 2012. Since then, the breadth and depth of understanding of the involvement of this channel in secondary injury has undergone exponential growth: SUR1-TRPM4 inhibition has been shown to decrease cerebral edema and hemorrhage progression in multiple preclinical models as well as in early clinical studies across a range of CNS diseases including ischemic stroke, traumatic brain injury, cardiac arrest, subarachnoid hemorrhage, spinal cord injury, intracerebral hemorrhage, multiple sclerosis, encephalitis, neuromalignancies, pain, liver failure, status epilepticus, retinopathies and HIV-associated neurocognitive disorder. Given these substantial developments, combined with the timeliness of ongoing clinical trials of SUR1 inhibition, now, another decade later, we review advances pertaining to SUR1-TRPM4 pathobiology in this spectrum of CNS disease—providing an overview of the journey from patch-clamp experiments to phase III trials.No funding directly supported the writing of this review. R.M.J. is supported by grants from the National Institute of Neurological Disorders and Stroke (NINDS) (K23NS101036; R01NS115815), and the Barrow Neurological Foundation. J.M.S. is supported by grants from the Department of Veterans Affairs (I01RX003060; 1I01BX004652), the Department of Defense (SC170199), the National Heart, Lung and Blood Institute (R01HL082517) and the NINDS (R01NS102589; R01NS105633)
Type Ia supernova SN 2003du: optical observations
UBVRI photometry and optical spectra of type Ia supernova SN 2003du obtained
at the Indian Astronomical Observatory for nearly a year since discovery are
presented.
The apparent magnitude at maximum was B=13.53 +/- 0.02 mag, and the colour
(B-V) = -0.08 +/- 0.03 mag. The luminosity decline rate, Delta(m_{15}(B)) =
1.04 +/- 0.04 mag indicates an absolute B magnitude at maximum of M_B = -19.34
+/- 0.3 mag and the distance modulus to the parent galaxy as mu=32.89 +/-
0.4.The light curve shapes are similar, though not identical, to those of SNe
1998bu and 1990N, both of which had luminosity decline rates similar to that of
SN 2003du and occurred in spiral galaxies. The peak bolometric luminosity
indicates that 0.9 Msun mass of 56Ni was ejected by the supernova. The spectral
evolution and the evolution of the Si II and Ca II absorption velocities
closely follows that of SN 1998bu, and in general, is within the scatter of the
velocities observed in normal type Ia supernovae.
The spectroscopic and photometric behaviour of SN 2003du is quite typical for
SNe Ia in spirals.
A high velocity absorption component in the Ca II (H & K) and IR-triplet
features, with absorption velocities of ~20,000 km/s and ~22,000 km/s
respectively, is detected in the pre-maximum spectra of days -11 and -7.Comment: 10 pages, 10 figures; Accepted for publication in A&
Dermoscopic Features of Actinic Cheilitis and Other Common Inflammatory Cheilitis: A Multicentric Retrospective Observational Study by the International Dermoscopy Society
Background: Clinical differentiation between different cheilitis variants may be difficult. Application of mucoscopy, in addition to clinical background, could provide additional diagnostic clues facilitating initial patient management. Objectives: To determine mucoscopic clues differentiating actinic cheilitis from the main forms of inflammatory cheilitis, including eczematous cheilitis, discoid lupus erythematosus, and lichen planus of the lips. Methods: This was a retrospective, multicenter study being a part of an ongoing project "Mucoscopy - an upcoming tool for oral mucosal disorders" under the aegis of the International Dermoscopy Society. Cases included in the current study were collected via an online call published on the IDS website (www.dermoscopy-ids.org) between January 2019 and December 2020. Results: Whitish-red background was found in actinic cheilitis as well as in cheilitis due to discoid lupus erythematous and lichen planus. Polymorphous vessels were more likely to be seen in actinic cheilitis compared to other causes of cheilitis. White scales, ulceration, and blood spots predominated in actinic cheilitis and lichen planus, whereas yellowish scales typified eczematous and discoid lupus erythematous cheilitis. Radiating white lines although most common in lichen planus patients were also seen in actinic cheilitis. Conclusion: Despite differences in the frequency of mucoscopic structures, we have not found pathognomonic features allowing for differentiation between analyzed variants of cheilitis
Diversity of supernovae Ia determined using equivalent widths of Si II 4000
Spectroscopic and photometric properties of low and high-z supernovae Ia (SNe
Ia) have been analyzed in order to achieve a better understanding of their
diversity and to identify possible SN Ia sub-types. We use wavelet transformed
spectra in which one can easily measure spectral features. We investigate the
\ion{Si}{II} 4000 equivalent width (EW_w\lbrace\ion{Si}{II}\rbrace). The
ability and, especially, the ease in extending the method to SNe at high- is
demonstrated. We applied the method to 110 SNe Ia and found correlations
between EW_w\lbrace\ion{Si}{II}\rbrace and parameters related to the
light-curve shape for 88 supernovae with available photometry. No evidence for
evolution of EW_w\lbrace\ion{Si}{II}\rbrace with redshift is seen. Three
sub-classes of SNe Ia were confirmed using an independent cluster analysis with
only light-curve shape, colour, and EW_w\lbrace\ion{Si}{II}\rbrace. SNe from
high- samples seem to follow a similar grouping to nearby objects. The
EW_w\lbrace\ion{Si}{II}\rbrace value measured on a single spectrum may point
towards SN Ia sub-classification, avoiding the need for expansion velocity
gradient calculations.Comment: 12 pages, 5 figure
Supernova Legacy Survey: Using Spectral Signatures To Improve Type Ia Supernovae As Distance Indicators
GMOS optical long-slit spectroscopy at the Gemini-North telescope was used to
classify targets from the Supernova Legacy Survey (SNLS) from July 2005 and May
2006 - May 2008. During this time, 95 objects were observed. Where possible the
objects' redshifts (z) were measured from narrow emission or absorption
features in the host galaxy spectrum, otherwise they were measured from the
broader supernova features. We present spectra of 68 confirmed or probable SNe
Ia from SNLS with redshifts in the range 0.17 \leq z \leq 1.02. In combination
with earlier SNLS Gemini and VLT spectra, we used these new observations to
measure pseudo-equivalent widths (EWs) of three spectral features - CaII H&K,
SiII and MgII - in 144 objects and compared them to the EWs of low-redshift SNe
Ia from a sample drawn from the literature. No signs of changes with z are seen
for the CaII H&K and MgII features. Systematically lower EW SiII is seen at
high redshift, but this can be explained by a change in demographics of the SNe
Ia population within a two-component model combined with an observed
correlation between EW SiII and photometric lightcurve stretch.Comment: 49 pages including 2 online-only appendices, accepted for publication
in MNRA
SALT2: using distant supernovae to improve the use of Type Ia supernovae as distance indicators
We present an empirical model of Type Ia supernovae spectro-photometric
evolution with time. The model is built using a large data set including
light-curves and spectra of both nearby and distant supernovae, the latter
being observed by the SNLS collaboration. We derive the average spectral
sequence of Type Ia supernovae and their main variability components including
a color variation law. The model allows us to measure distance moduli in the
spectral range 2500-8000 A with calculable uncertainties, including those
arising from variability of spectral features. Thanks to the use of
high-redshift SNe to model the rest-frame UV spectral energy distribution, we
are able to derive improved distance estimates for SNe Ia in the redshift range
0.8<z<1.1. The model can also be used to improve spectroscopic identification
algorithms, and derive photometric redshifts of distant Type Ia supernovae.Comment: Accepted for publication in A&A. Data and source code available at :
http://supernovae.in2p3.fr/~guy/salt
Spectroscopic observations of eight supernovae at intermediate redshift
We present spectra of six Type Ia and two Type II supernovae obtained in June
2002 at the William Herschel Telescope during a search for Type Ia supernovae
(SNIa) at intermediate redshift. Supernova type identification and phase
determination are performed using a fitting technique based on a Xi2
minimization against a series of model templates. The spectra range from
z=0.033 to z=0.328, including one spectroscopically underluminous SNIa at
z=0.033. This set of spectra significantly increases the sample of
well-observed type SNIa supernovae available in the range 0.15< z <0.35.
Together with the twelve supernovae observed by our team in 1999 in the same
redshift range, they form an homogeneous sample of seventeen type Ia supernovae
with comparable signal-to-noise ratio and regular phase sampling in a still
largely unexplored region of the redshift space.Comment: 30 pages, 15 figures. Published in A&
Discovery and Rapid Follow-up Observations of the Unusual Type II SN 2018ivc in NGC 1068
We present the discovery and high-cadence follow-up observations of SN 2018ivc, an unusual SNe II that exploded in NGC 1068 (D = 10.1 Mpc). The light curve of SN 2018ivc declines piecewise-linearly, changing slope frequently, with four clear slope changes in the first 30 days of evolution. This rapidly changing light curve indicates that interaction between the circumstellar material and ejecta plays a significant role in the evolution. Circumstellar interaction is further supported by a strong X-ray detection. The spectra are rapidly evolving and dominated by hydrogen, helium, and calcium emission lines. We identify a rare high-velocity emission-line feature blueshifted at ~7800 km s⁻¹ (in Hα, Hβ, Pβ, Pγ, He I, and Ca II), which is visible from day 18 until at least day 78 and could be evidence of an asymmetric progenitor or explosion. From the overall similarity between SN 2018ivc and SN 1996al, the Hα equivalent width of its parent H II region, and constraints from pre-explosion archival Hubble Space Telescope images, we find that the progenitor of SN 2018ivc could be as massive as 52 M⊙ but is more likely <12 M⊙. SN 2018ivc demonstrates the importance of the early discovery and rapid follow-up observations of nearby supernovae to study the physics and progenitors of these cosmic explosions
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