137 research outputs found
Unsupervised Clustering of Quantitative Imaging Phenotypes using Autoencoder and Gaussian Mixture Model
Quantitative medical image computing (radiomics) has been widely applied to
build prediction models from medical images. However, overfitting is a
significant issue in conventional radiomics, where a large number of radiomic
features are directly used to train and test models that predict genotypes or
clinical outcomes. In order to tackle this problem, we propose an unsupervised
learning pipeline composed of an autoencoder for representation learning of
radiomic features and a Gaussian mixture model based on minimum message length
criterion for clustering. By incorporating probabilistic modeling, disease
heterogeneity has been taken into account. The performance of the proposed
pipeline was evaluated on an institutional MRI cohort of 108 patients with
colorectal cancer liver metastases. Our approach is capable of automatically
selecting the optimal number of clusters and assigns patients into clusters
(imaging subtypes) with significantly different survival rates. Our method
outperforms other unsupervised clustering methods that have been used for
radiomics analysis and has comparable performance to a state-of-the-art imaging
biomarker.Comment: Accepted at MICCAI 201
Single-shot compressed ultrafast photography at one hundred billion frames per second
The capture of transient scenes at high imaging speed has been long sought by photographers, with early examples being the well known recording in 1878 of a horse in motion and the 1887 photograph of a supersonic bullet. However, not until the late twentieth century were breakthroughs achieved in demonstrating ultrahigh-speed imaging (more than 10^5 frames per second). In particular, the introduction of electronic imaging sensors based on the charge-coupled device (CCD) or complementary metalâoxideâsemiconductor (CMOS) technology revolutionized high-speed photography, enabling acquisition rates of up to 10^7 frames per second. Despite these sensorsâ widespread impact, further increasing frame rates using CCD or CMOS technology is fundamentally limited by their on-chip storage and electronic readout speed. Here we demonstrate a two-dimensional dynamic imaging technique, compressed ultrafast photography (CUP), which can capture non-repetitive time-evolving events at up to 10^(11) frames per second. Compared with existing ultrafast imaging techniques, CUP has the prominent advantage of measuring an xâyât (x, y, spatial coordinates; t, time) scene with a single camera snapshot, thereby allowing observation of transient events with temporal resolution as tens of picoseconds. Furthermore, akin to traditional photography, CUP is receive-only, and so does not need the specialized active illumination required by other single-shot ultrafast imagers. As a result, CUP can image a variety of luminescentâsuch as fluorescent or bioluminescentâobjects. Using CUP, we visualize four fundamental physical phenomena with single laser shots only: laser pulse reflection and refraction, photon racing in two media, and faster-than-light propagation of non-information (that is, motion that appears faster than the speed of light but cannot convey information). Given CUPâs capability, we expect it to find widespread applications in both fundamental and applied sciences, including biomedical research
Perceptual Compressive Sensing
Compressive sensing (CS) works to acquire measurements at sub-Nyquist rate
and recover the scene images. Existing CS methods always recover the scene
images in pixel level. This causes the smoothness of recovered images and lack
of structure information, especially at a low measurement rate. To overcome
this drawback, in this paper, we propose perceptual CS to obtain high-level
structured recovery. Our task no longer focuses on pixel level. Instead, we
work to make a better visual effect. In detail, we employ perceptual loss,
defined on feature level, to enhance the structure information of the recovered
images. Experiments show that our method achieves better visual results with
stronger structure information than existing CS methods at the same measurement
rate.Comment: Accepted by The First Chinese Conference on Pattern Recognition and
Computer Vision (PRCV 2018). This is a pre-print version (not final version
SMART: Unique splitting-while-merging framework for gene clustering
Copyright @ 2014 Fa et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted
use, distribution, and reproduction in any medium, provided the original author and source are credited.Successful clustering algorithms are highly dependent on parameter settings. The clustering performance degrades significantly unless parameters are properly set, and yet, it is difficult to set these parameters a priori. To address this issue, in this paper, we propose a unique splitting-while-merging clustering framework, named âsplitting merging awareness tacticsâ (SMART), which does not require any a priori knowledge of either the number of clusters or even the possible range of this number. Unlike existing self-splitting algorithms, which over-cluster the dataset to a large number of clusters and then merge some similar clusters, our framework has the ability to split and merge clusters automatically during the process and produces the the most reliable clustering results, by intrinsically integrating many clustering techniques and tasks. The SMART framework is implemented with two distinct clustering paradigms in two algorithms: competitive learning and finite mixture model. Nevertheless, within the proposed SMART framework, many other algorithms can be derived for different clustering paradigms. The minimum message length algorithm is integrated into the framework as the clustering selection criterion. The usefulness of the SMART framework and its algorithms is tested in demonstration datasets and simulated gene expression datasets. Moreover, two real microarray gene expression datasets are studied using this approach. Based on the performance of many metrics, all numerical results show that SMART is superior to compared existing self-splitting algorithms and traditional algorithms. Three main properties of the proposed SMART framework are summarized as: (1) needing no parameters dependent on the respective dataset or a priori knowledge about the datasets, (2) extendible to many different applications, (3) offering superior performance compared with counterpart algorithms.National Institute for Health Researc
Fully Trainable and Interpretable Non-Local Sparse Models for Image Restoration
Non-local self-similarity and sparsity principles have proven to be powerful
priors for natural image modeling. We propose a novel differentiable relaxation
of joint sparsity that exploits both principles and leads to a general
framework for image restoration which is (1) trainable end to end, (2) fully
interpretable, and (3) much more compact than competing deep learning
architectures. We apply this approach to denoising, jpeg deblocking, and
demosaicking, and show that, with as few as 100K parameters, its performance on
several standard benchmarks is on par or better than state-of-the-art methods
that may have an order of magnitude or more parameters.Comment: ECCV 202
An Integrated Model of Multiple-Condition ChIP-Seq Data Reveals Predeterminants of Cdx2 Binding
Regulatory proteins can bind to different sets of genomic targets in various cell types or conditions. To reliably characterize such condition-specific regulatory binding we introduce MultiGPS, an integrated machine learning approach for the analysis of multiple related ChIP-seq experiments. MultiGPS is based on a generalized Expectation Maximization framework that shares information across multiple experiments for binding event discovery. We demonstrate that our framework enables the simultaneous modeling of sparse condition-specific binding changes, sequence dependence, and replicate-specific noise sources. MultiGPS encourages consistency in reported binding event locations across multiple-condition ChIP-seq datasets and provides accurate estimation of ChIP enrichment levels at each event. MultiGPS's multi-experiment modeling approach thus provides a reliable platform for detecting differential binding enrichment across experimental conditions. We demonstrate the advantages of MultiGPS with an analysis of Cdx2 binding in three distinct developmental contexts. By accurately characterizing condition-specific Cdx2 binding, MultiGPS enables novel insight into the mechanistic basis of Cdx2 site selectivity. Specifically, the condition-specific Cdx2 sites characterized by MultiGPS are highly associated with pre-existing genomic context, suggesting that such sites are pre-determined by cell-specific regulatory architecture. However, MultiGPS-defined condition-independent sites are not predicted by pre-existing regulatory signals, suggesting that Cdx2 can bind to a subset of locations regardless of genomic environment. A summary of this paper appears in the proceedings of the RECOMB 2014 conference, April 2â5.National Science Foundation (U.S.) (Graduate Research Fellowship under Grant 0645960)National Institutes of Health (U.S.) (grant P01 NS055923)Pennsylvania State University. Center for Eukaryotic Gene Regulatio
An investigation of supervector regression for forensic voice comparison on small data
International audienceThe present paper deals with an observer design for a nonlinear lateral vehicle model. The nonlinear model is represented by an exact Takagi-Sugeno (TS) model via the sector nonlinearity transformation. A proportional multiple integral observer (PMIO) based on the TS model is designed to estimate simultaneously the state vector and the unknown input (road curvature). The convergence conditions of the estimation error are expressed under LMI formulation using the Lyapunov theory which guaranties bounded error. Simulations are carried out and experimental results are provided to illustrate the proposed observer
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