45 research outputs found
DeepSleepNet-Lite: A Simplified Automatic Sleep Stage Scoring Model with Uncertainty Estimates
Deep learning is widely used in the most recent
automatic sleep scoring algorithms. Its popularity stems from its
excellent performance and from its ability to process raw signals
and to learn feature directly from the data. Most of the existing scoring algorithms exploit very computationally demanding
architectures, due to their high number of training parameters,
and process lengthy time sequences in input (up to 12 minutes).
Only few of these architectures provide an estimate of the
model uncertainty. In this study we propose DeepSleepNet-Lite,
a simplified and lightweight scoring architecture, processing only
90-seconds EEG input sequences. We exploit, for the first time in
sleep scoring, the Monte Carlo dropout technique to enhance the
performance of the architecture and to also detect the uncertain
instances. The evaluation is performed on a single-channel EEG
Fpz-Cz from the open source Sleep-EDF expanded database.
DeepSleepNet-Lite achieves slightly lower performance, if not
on par, compared to the existing state-of-the-art architectures,
in overall accuracy, macro F1-score and Cohenβs kappa (on
Sleep-EDF v1-2013 Β±30mins: 84.0%, 78.0%, 0.78; on Sleep-EDF
v2-2018 Β±30mins: 80.3%, 75.2%, 0.73). Monte Carlo dropout
enables the estimate of the uncertain predictions. By rejecting the
uncertain instances, the model achieves higher performance on
both versions of the database (on Sleep-EDF v1-2013 Β±30mins:
86.1.0%, 79.6%, 0.81; on Sleep-EDF v2-2018 Β±30mins: 82.3%,
76.7%, 0.76). Our lighter sleep scoring approach paves the way
to the application of scoring algorithms for sleep analysis in realtime
Multi-Scored Sleep Databases: How to Exploit the Multiple-Labels in Automated Sleep Scoring.
STUDY OBJECTIVES
Inter-scorer variability in scoring polysomnograms is a well-known problem. Most of the existing automated sleep scoring systems are trained using labels annotated by a single scorer, whose subjective evaluation is transferred to the model. When annotations from two or more scorers are available, the scoring models are usually trained on the scorer consensus. The averaged scorer's subjectivity is transferred into the model, losing information about the internal variability among different scorers. In this study, we aim to insert the multiple-knowledge of the different physicians into the training procedure. The goal is to optimize a model training, exploiting the full information that can be extracted from the consensus of a group of scorers.
METHODS
We train two lightweight deep learning based models on three different multi-scored databases. We exploit the label smoothing technique together with a soft-consensus (LSSC) distribution to insert the multiple-knowledge in the training procedure of the model. We introduce the averaged cosine similarity metric (ACS) to quantify the similarity between the hypnodensity-graph generated by the models with-LSSC and the hypnodensity-graph generated by the scorer consensus.
RESULTS
The performance of the models improves on all the databases when we train the models with our LSSC. We found an increase in ACS (up to 6.4%) between the hypnodensity-graph generated by the models trained with-LSSC and the hypnodensity-graph generated by the consensus.
CONCLUSION
Our approach definitely enables a model to better adapt to the consensus of the group of scorers. Future work will focus on further investigations on different scoring architectures and hopefully large-scale-heterogeneous multi-scored datasets
Precision measurements of Linear Scattering Density using Muon Tomography
We demonstrate that muon tomography can be used to precisely measure the
properties of various materials. The materials which have been considered have
been extracted from an experimental blast furnace, including carbon (coke) and
iron oxides, for which measurements of the linear scattering density relative
to the mass density have been performed with an absolute precision of 10%. We
report the procedures that are used in order to obtain such precision, and a
discussion is presented to address the expected performance of the technique
when applied to heavier materials. The results we obtain do not depend on the
specific type of material considered and therefore they can be extended to any
application.Comment: 16 pages, 4 figure
U-Sleep's resilience to AASM guidelines
AASM guidelines are the result of decades of efforts aiming at standardizing
sleep scoring procedure, with the final goal of sharing a worldwide common
methodology. The guidelines cover several aspects from the technical/digital
specifications,e.g., recommended EEG derivations, to detailed sleep scoring
rules accordingly to age. Automated sleep scoring systems have always largely
exploited the standards as fundamental guidelines. In this context, deep
learning has demonstrated better performance compared to classical machine
learning. Our present work shows that a deep learning based sleep scoring
algorithm may not need to fully exploit the clinical knowledge or to strictly
adhere to the AASM guidelines. Specifically, we demonstrate that U-Sleep, a
state-of-the-art sleep scoring algorithm, can be strong enough to solve the
scoring task even using clinically non-recommended or non-conventional
derivations, and with no need to exploit information about the chronological
age of the subjects. We finally strengthen a well-known finding that using data
from multiple data centers always results in a better performing model compared
with training on a single cohort. Indeed, we show that this latter statement is
still valid even by increasing the size and the heterogeneity of the single
data cohort. In all our experiments we used 28528 polysomnography studies from
13 different clinical studies
Delirium symptoms duration and mortality in SARS-COV2 elderly: results of a multicenter retrospective cohort study
BACKGROUND: Since the occurrence of the SARS-COV2 pandemic, there has been an increasing interest in investigating the epidemiology of delirium. Delirium is frequent in SARS-COV2 patients and it is associated with increased mortality; however, no information is available on the association between delirium duration in SARS-COV2 patients and related outcomes. AIMS: The aim of this study is to investigate the association between the duration of delirium symptoms and in-hospital mortality in older patients with SARS-COV2 infection. METHODS: Retrospective cohort study of patients 65Β years of age and older with SARS-CoV 2 infection admitted to two acute geriatric wards and one rehabilitation ward. Delirium symptoms duration was assessed retrospectively with a chart-based validated method. In-hospital mortality was ascertained via medical records. RESULTS: A total of 241 patients were included. The prevalence of delirium on admission was 16%. The median number of days with delirium symptoms was 4 (IQR 2β6.5) vs. 0 (IQR 0β2) in patients with and without delirium on admission. In the multivariable Cox regression model, each day with a delirium symptom in a patient with the same length of stay was associated with a 10% increase in in-hospital mortality (Hazard ratio 1.1, 95% Confidence interval 1.01β1.2; pβ=β0.03). Other variables associated with increased risk of in-hospital death were age, comorbidity, CPAP, CRP levels and total number of drugs on admission. CONCLUSIONS: The study supports the necessity to establish protocols for the monitoring and management of delirium during emergency conditions to allow an appropriate care for older patients. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40520-021-01899-8
Late mortality and causes of death among 5-year survivors of childhood cancer diagnosed in the period 1960β1999 and registered in the Italian Off-Therapy Registry
The longitudinal changes of BOLD response and cerebral hemodynamics from acute to subacute stroke. A fMRI and TCD study
<p>Abstract</p> <p>Background</p> <p>By mapping the dynamics of brain reorganization, functional magnetic resonance imaging MRI (fMRI) has allowed for significant progress in understanding cerebral plasticity phenomena after a stroke. However, cerebro-vascular diseases can affect blood oxygen level dependent (BOLD) signal. Cerebral autoregulation is a primary function of cerebral hemodynamics, which allows to maintain a relatively constant blood flow despite changes in arterial blood pressure and perfusion pressure. Cerebral autoregulation is reported to become less effective in the early phases post-stroke.</p> <p>This study investigated whether any impairment of cerebral hemodynamics that occurs during the acute and the subacute phases of ischemic stroke is related to changes in BOLD response.</p> <p>We enrolled six aphasic patients affected by acute stroke. All patients underwent a Transcranial Doppler to assess cerebral autoregulation (Mx index) and fMRI to evaluate the amplitude and the peak latency (time to peak-TTP) of BOLD response in the acute (i.e., within four days of stroke occurrence) and the subacute (i.e., between five and twelve days after stroke onset) stroke phases.</p> <p>Results</p> <p>As patients advanced from the acute to subacute stroke phase, the affected hemisphere presented a BOLD TTP increase (p = 0.04) and a deterioration of cerebral autoregulation (Mx index increase, p = 0.046). A similar but not significant trend was observed also in the unaffected hemisphere. When the two hemispheres were grouped together, BOLD TTP delay was significantly related to worsening cerebral autoregulation (Mx index increase) (Spearman's rho = 0.734; p = 0.01).</p> <p>Conclusions</p> <p>The hemodynamic response function subtending BOLD signal may present a delay in peak latency that arises as patients advance from the acute to the subacute stroke phase. This delay is related to the deterioration of cerebral hemodynamics. These findings suggest that remodeling the fMRI hemodynamic response function in the different phases of stroke may optimize the detection of BOLD signal changes.</p
KRIT1 Regulates the Homeostasis of Intracellular Reactive Oxygen Species
KRIT1 is a gene responsible for Cerebral Cavernous Malformations (CCM), a major cerebrovascular disease characterized by abnormally enlarged and leaky capillaries that predispose to seizures, focal neurological deficits, and fatal intracerebral hemorrhage. Comprehensive analysis of the KRIT1 gene in CCM patients has suggested that KRIT1 functions need to be severely impaired for pathogenesis. However, the molecular and cellular functions of KRIT1 as well as CCM pathogenesis mechanisms are still research challenges. We found that KRIT1 plays an important role in molecular mechanisms involved in the maintenance of the intracellular Reactive Oxygen Species (ROS) homeostasis to prevent oxidative cellular damage. In particular, we demonstrate that KRIT1 loss/down-regulation is associated with a significant increase in intracellular ROS levels. Conversely, ROS levels in KRIT1β/β cells are significantly and dose-dependently reduced after restoration of KRIT1 expression. Moreover, we show that the modulation of intracellular ROS levels by KRIT1 loss/restoration is strictly correlated with the modulation of the expression of the antioxidant protein SOD2 as well as of the transcriptional factor FoxO1, a master regulator of cell responses to oxidative stress and a modulator of SOD2 levels. Furthermore, we show that the KRIT1-dependent maintenance of low ROS levels facilitates the downregulation of cyclin D1 expression required for cell transition from proliferative growth to quiescence. Finally, we demonstrate that the enhanced ROS levels in KRIT1β/β cells are associated with an increased cell susceptibility to oxidative DNA damage and a marked induction of the DNA damage sensor and repair gene Gadd45Ξ±, as well as with a decline of mitochondrial energy metabolism. Taken together, our results point to a new model where KRIT1 limits the accumulation of intracellular oxidants and prevents oxidative stress-mediated cellular dysfunction and DNA damage by enhancing the cell capacity to scavenge intracellular ROS through an antioxidant pathway involving FoxO1 and SOD2, thus providing novel and useful insights into the understanding of KRIT1 molecular and cellular functions
Understanding Factors Associated With Psychomotor Subtypes of Delirium in Older Inpatients With Dementia
Steady Streaming Induced by Asymmetric Oscillatory Flows over a Rippled Bed
The flow induced by progressive water waves propagating over a rippled bed is reproduced by means of the numerical solution of momentum and continuity equations to gain insights on the steady streaming induced in the bottom boundary layer. When the pressure gradient that drives the flow is given by the sum of two harmonic components an offshore steady streaming is generated within the boundary layer which persists in the irrotational region. This steady streaming depends on the Reynolds number and on the geometrical characteristics of the ripples. Nothwithstanding the presence of a steady velocity component, the time-average of the force on the ripples vanishes