5,188 research outputs found
A supervised clustering approach for extracting predictive information from brain activation images
International audienceIt is a standard approach to consider that images encode some information such as face expression or biomarkers in medical images; decoding this information is particularly challenging in the case of medical imaging, because the whole image domain has to be considered a priori to avoid biasing image-based prediction and image interpretation. Feature selection is thus needed, but is often performed using mass-univariate procedures, that handle neither the spatial structure of the images, nor the multivariate nature of the signal. Here we propose a solution that computes a reduced set of high-level features which compress the image information while retaining its informative parts: first, we introduce a hierarchical clustering of the research domain that incorporates spatial connectivity constraints and reduces the complexity of the possible spatial configurations to a single tree of nested regions. Then we prune the tree in order to produce a parcellation (division of the image domain) such that parcel-based signal averages optimally predict the target information. We show the power of this approach with respect to reference techniques on simulated data and apply it to enhance the prediction of the subject's behaviour during functional Magnetic Resonance Imaging (fMRI) scanning sessions. Besides its superior performance, the method provides an interpretable weighting of the regions involved in the regression or classification task
A supervised clustering approach for fMRI-based inference of brain states
We propose a method that combines signals from many brain regions observed in
functional Magnetic Resonance Imaging (fMRI) to predict the subject's behavior
during a scanning session. Such predictions suffer from the huge number of
brain regions sampled on the voxel grid of standard fMRI data sets: the curse
of dimensionality. Dimensionality reduction is thus needed, but it is often
performed using a univariate feature selection procedure, that handles neither
the spatial structure of the images, nor the multivariate nature of the signal.
By introducing a hierarchical clustering of the brain volume that incorporates
connectivity constraints, we reduce the span of the possible spatial
configurations to a single tree of nested regions tailored to the signal. We
then prune the tree in a supervised setting, hence the name supervised
clustering, in order to extract a parcellation (division of the volume) such
that parcel-based signal averages best predict the target information.
Dimensionality reduction is thus achieved by feature agglomeration, and the
constructed features now provide a multi-scale representation of the signal.
Comparisons with reference methods on both simulated and real data show that
our approach yields higher prediction accuracy than standard voxel-based
approaches. Moreover, the method infers an explicit weighting of the regions
involved in the regression or classification task
Improving accuracy and power with transfer learning using a meta-analytic database
Typical cohorts in brain imaging studies are not large enough for systematic
testing of all the information contained in the images. To build testable
working hypotheses, investigators thus rely on analysis of previous work,
sometimes formalized in a so-called meta-analysis. In brain imaging, this
approach underlies the specification of regions of interest (ROIs) that are
usually selected on the basis of the coordinates of previously detected
effects. In this paper, we propose to use a database of images, rather than
coordinates, and frame the problem as transfer learning: learning a
discriminant model on a reference task to apply it to a different but related
new task. To facilitate statistical analysis of small cohorts, we use a sparse
discriminant model that selects predictive voxels on the reference task and
thus provides a principled procedure to define ROIs. The benefits of our
approach are twofold. First it uses the reference database for prediction, i.e.
to provide potential biomarkers in a clinical setting. Second it increases
statistical power on the new task. We demonstrate on a set of 18 pairs of
functional MRI experimental conditions that our approach gives good prediction.
In addition, on a specific transfer situation involving different scanners at
different locations, we show that voxel selection based on transfer learning
leads to higher detection power on small cohorts.Comment: MICCAI, Nice : France (2012
Prospects for Theranostics in Neurosurgical Imaging: Empowering Confocal Laser Endomicroscopy Diagnostics via Deep Learning
Confocal laser endomicroscopy (CLE) is an advanced optical fluorescence
imaging technology that has the potential to increase intraoperative precision,
extend resection, and tailor surgery for malignant invasive brain tumors
because of its subcellular dimension resolution. Despite its promising
diagnostic potential, interpreting the gray tone fluorescence images can be
difficult for untrained users. In this review, we provide a detailed
description of bioinformatical analysis methodology of CLE images that begins
to assist the neurosurgeon and pathologist to rapidly connect on-the-fly
intraoperative imaging, pathology, and surgical observation into a
conclusionary system within the concept of theranostics. We present an overview
and discuss deep learning models for automatic detection of the diagnostic CLE
images and discuss various training regimes and ensemble modeling effect on the
power of deep learning predictive models. Two major approaches reviewed in this
paper include the models that can automatically classify CLE images into
diagnostic/nondiagnostic, glioma/nonglioma, tumor/injury/normal categories and
models that can localize histological features on the CLE images using weakly
supervised methods. We also briefly review advances in the deep learning
approaches used for CLE image analysis in other organs. Significant advances in
speed and precision of automated diagnostic frame selection would augment the
diagnostic potential of CLE, improve operative workflow and integration into
brain tumor surgery. Such technology and bioinformatics analytics lend
themselves to improved precision, personalization, and theranostics in brain
tumor treatment.Comment: See the final version published in Frontiers in Oncology here:
https://www.frontiersin.org/articles/10.3389/fonc.2018.00240/ful
Learning and comparing functional connectomes across subjects
Functional connectomes capture brain interactions via synchronized
fluctuations in the functional magnetic resonance imaging signal. If measured
during rest, they map the intrinsic functional architecture of the brain. With
task-driven experiments they represent integration mechanisms between
specialized brain areas. Analyzing their variability across subjects and
conditions can reveal markers of brain pathologies and mechanisms underlying
cognition. Methods of estimating functional connectomes from the imaging signal
have undergone rapid developments and the literature is full of diverse
strategies for comparing them. This review aims to clarify links across
functional-connectivity methods as well as to expose different steps to perform
a group study of functional connectomes
Self-supervised learning methods and applications in medical imaging analysis: A survey
The scarcity of high-quality annotated medical imaging datasets is a major
problem that collides with machine learning applications in the field of
medical imaging analysis and impedes its advancement. Self-supervised learning
is a recent training paradigm that enables learning robust representations
without the need for human annotation which can be considered an effective
solution for the scarcity of annotated medical data. This article reviews the
state-of-the-art research directions in self-supervised learning approaches for
image data with a concentration on their applications in the field of medical
imaging analysis. The article covers a set of the most recent self-supervised
learning methods from the computer vision field as they are applicable to the
medical imaging analysis and categorize them as predictive, generative, and
contrastive approaches. Moreover, the article covers 40 of the most recent
research papers in the field of self-supervised learning in medical imaging
analysis aiming at shedding the light on the recent innovation in the field.
Finally, the article concludes with possible future research directions in the
field
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