1,538 research outputs found
Use of Optical Coherence Tomography to Detect Retinal Nerve Fiber Loss in Children With Optic Pathway Glioma
Optic pathway glioma (OPG) presents in childhood and can cause significant morbidity and visual loss. Magnetic resonance imaging (MRI) is the current imaging modality of choice for evaluation of OPG progression, but it is a relatively limited resource often requiring sedation in the pediatric age group. Additionally, OPG progression on MRI does not always correlate with clinical progression. As a result, several other modalities for evaluating OPG are being investigated, including optical coherence tomography (OCT), a readily available imaging technique in ophthalmic practice. The purpose of the present study was to examine the association between retinal nerve fiber layer (RNFL) thickness measured using OCT and optic nerve function in children with OPG with and without neurofibromatosis-1 (NF-1). A retrospective chart review was conducted to identify children diagnosed with OPG from 2001 to 2015 at a tertiary pediatric medical center. The correlation between OCT measurements and clinical visual parameters was statistically analyzed. Included were 23 children with imaging-confirmed OPG and spectral domain OCT: 10 with NF-1 (mean age at diagnosis 5.8 years) and 13 without (mean age at diagnosis 5.9 years). The glioma involved the chiasma-hypothalamus in 19 patients, optic nerve in 11, and optic tract in 7; more than one anatomic site was affected in 15. Symptoms were reported in 2 patients with NF-1 and most patients without NF-1. Visual field defects included monocular, bitemporal, nasal, and homonymous hemianopia. Initial mean RNFL was 85.4 μm in the NF-1 group and 65 μm in the non-NF-1 group. Visual acuity deteriorated in 1/10 patients and 5/13 patients, respectively. Repeated OCT showed continued RNFL thinning in 3 patients (5 eyes) in the NF-1 group and in 8 patients (11 eyes) in the non-NF-1 group, often associated with a decrease in optic nerve function. In conclusion, visual function in children with OPG is correlated with repeated OCT measurements and weakly with neuroimaging. Children without NF-1 are usually symptomatic and have a worse clinical outcome. These findings may have important implications when considering initiating, continuing or stopping chemotherapy for OPG. The application of OCT in the assessment of OPG and the correlation of the findings to clinical progression can have a significant impact on OPG patient management
Unbounded autocatalytic growth on diffusive substrate: the extinction transition
The effect of diffusively correlated spatial fluctuations on the
proliferation-extinction transition of autocatalytic agents is investigated
numerically. Reactants adaptation to spatio-temporal active regions is shown to
lead to proliferation even if the mean field rate equations predict extinction,
in agreement with previous theoretical predictions. While in the proliferation
phase the system admits a typical time scale that dictates the exponential
growth, the extinction times distribution obeys a power law at the parameter
region considered
Imitation, mirror neurons and autism
Various deficits in the cognitive functioning of people with autism have been documented in recent years but these provide only partial explanations for the condition. We focus instead on an imitative disturbance involving difficulties both in copying actions and in inhibiting more stereotyped mimicking, such as echolalia. A candidate for the neural basis of this disturbance may be found in a recently discovered class of neurons in frontal cortex, 'mirror neurons' (MNs). These neurons show activity in relation both to specific actions performed by self and matching actions performed by others, providing a potential bridge between minds. MN systems exist in primates without imitative and ‘theory of mind’ abilities and we suggest that in order for them to have become utilized to perform social cognitive functions, sophisticated cortical neuronal systems have evolved in which MNs function as key elements. Early developmental failures of MN systems are likely to result in a consequent cascade of developmental impairments characterised by the clinical syndrome of autism
Quantum key distribution without alternative measurements
Entanglement swapping between Einstein-Podolsky-Rosen (EPR) pairs can be used
to generate the same sequence of random bits in two remote places. A quantum
key distribution protocol based on this idea is described. The scheme exhibits
the following features. (a) It does not require that Alice and Bob choose
between alternative measurements, therefore improving the rate of generated
bits by transmitted qubit. (b) It allows Alice and Bob to generate a key of
arbitrary length using a single quantum system (three EPR pairs), instead of a
long sequence of them. (c) Detecting Eve requires the comparison of fewer bits.
(d) Entanglement is an essential ingredient. The scheme assumes reliable
measurements of the Bell operator.Comment: REVTeX, 5 pages, 2 figures. Published version with some comment
Self-Supervised Learning for Endoscopic Video Analysis
Self-supervised learning (SSL) has led to important breakthroughs in computer
vision by allowing learning from large amounts of unlabeled data. As such, it
might have a pivotal role to play in biomedicine where annotating data requires
a highly specialized expertise. Yet, there are many healthcare domains for
which SSL has not been extensively explored. One such domain is endoscopy,
minimally invasive procedures which are commonly used to detect and treat
infections, chronic inflammatory diseases or cancer. In this work, we study the
use of a leading SSL framework, namely Masked Siamese Networks (MSNs), for
endoscopic video analysis such as colonoscopy and laparoscopy. To fully exploit
the power of SSL, we create sizable unlabeled endoscopic video datasets for
training MSNs. These strong image representations serve as a foundation for
secondary training with limited annotated datasets, resulting in
state-of-the-art performance in endoscopic benchmarks like surgical phase
recognition during laparoscopy and colonoscopic polyp characterization.
Additionally, we achieve a 50% reduction in annotated data size without
sacrificing performance. Thus, our work provides evidence that SSL can
dramatically reduce the need of annotated data in endoscopy.Comment: Accepted to MICCAI 202
The Role of RASSF1A in Uveal Melanoma
1, 5, 6 PURPOSE. RASSF1A inactivation in uveal melanoma (UM) is common and methylation-induced. We investigated the effect of RASSF1A re-expression on the UM phenotype in vivo and in vitro. METHODS. The phenotypic effect of methylation-induced inactivation of RASSF1A in UM was explored using a stable RASSF1A-expressing UM-15 clone. RASSF1A expression was assessed using QRT-PCR. Proliferation was evaluated in vitro using MTT assays. Additionally, athymic NOD/SCID mice were injected subcutaneously or intraocularly with RASSF1A-expressing and -non-expressing UM-15 clones, and euthanized when tumors reached a volume of 1500 mm 3 , or at 56 or 46 days, respectively. Tumor tissues, eyes, and livers were analyzed histologically. RESULTS. In vitro analysis confirmed the lack of RASSF1A expression and full methylation of the RASSF1A promoter region in the UM-15 cell line, which was reversible following treatment with 5-Aza-2-deoxycytidine. Cells expressing exogenous RASSF1A showed slower proliferation than controls and regained sensitivity to cisplatin. Compared to mice injected with control cells, mice treated with UM-15 cells expressing exogenous RASSF1A did not acquire intraocular tumors, and their subcutaneous tumors were relatively delayed and small. Neither group had liver metastases. CONCLUSIONS. UM cells reduced tumorigenicity in the presence of activated RASSF1A. RASSF1A apparently has an important role in the development of UM, and its reactivation might be applied in the development of new treatments. (Invest Ophthalmol Vis Sci. 2012;53:2611-2619) DOI:10.1167/ iovs.11-7730 U veal melanoma (UM) is the most common form of primary eye cancer in adults, with an annual incidence of 6-7 cases per million per year. 1 It accounts for 80% of all noncutaneous melanomas and 13% of all deaths caused by melanoma. The tumor carries up to 50% 5-year mortality from metastasis. 3,4 However, their biological and clinical behaviors differ. 2 Additionally, although alterations of chromosomes 1 and 6 are common to both tumors, aberrations, such as monosomy of chromosome 3 and gain of 8q, in addition to other aberrations, typically are found only in UM. 9 Studies revealed that a mutation in the alpha subunit of the heterotrimeric G gene (GNAQ) was present in almost half of all UMs examined, 9-15 and that UM metastatic spread was related to mutations in the BRCA associated protein 1 (BAP1) gene on chromosome 3. 9 Aberrant promoter hypermethylation of CpG islands is thought to have an important role in the inactivation of tumor suppressor genes (TSGs) in cancer. 21 From th
A Statistical Social Network Model for Consumption Data in Food Webs
We adapt existing statistical modeling techniques for social networks to
study consumption data observed in trophic food webs. These data describe the
feeding volume (non-negative) among organisms grouped into nodes, called
trophic species, that form the food web. Model complexity arises due to the
extensive amount of zeros in the data, as each node in the web is predator/prey
to only a small number of other trophic species. Many of the zeros are regarded
as structural (non-random) in the context of feeding behavior. The presence of
basal prey and top predator nodes (those who never consume and those who are
never consumed, with probability 1) creates additional complexity to the
statistical modeling. We develop a special statistical social network model to
account for such network features. The model is applied to two empirical food
webs; focus is on the web for which the population size of seals is of concern
to various commercial fisheries.Comment: On 2013-09-05, a revised version entitled "A Statistical Social
Network Model for Consumption Data in Trophic Food Webs" was accepted for
publication in the upcoming Special Issue "Statistical Methods for Ecology"
in the journal Statistical Methodolog
- …