104 research outputs found
Spinal cord gray matter segmentation using deep dilated convolutions
Gray matter (GM) tissue changes have been associated with a wide range of
neurological disorders and was also recently found relevant as a biomarker for
disability in amyotrophic lateral sclerosis. The ability to automatically
segment the GM is, therefore, an important task for modern studies of the
spinal cord. In this work, we devise a modern, simple and end-to-end fully
automated human spinal cord gray matter segmentation method using Deep
Learning, that works both on in vivo and ex vivo MRI acquisitions. We evaluate
our method against six independently developed methods on a GM segmentation
challenge and report state-of-the-art results in 8 out of 10 different
evaluation metrics as well as major network parameter reduction when compared
to the traditional medical imaging architectures such as U-Nets.Comment: 13 pages, 8 figure
Deep Learning Methods for MRI Spinal Cord Gray Matter Segmentation
La moelle Ă©piniĂšre humaine, qui fait partie du systĂšme nerveux central, est la principale
voie responsable de la connexion du cerveau et du systÚme nerveux périphérique. On sait
que la matiÚre grise présente dans la moelle épiniÚre est associée à de nombreux troubles
neurologiques tels que la sclérose en plaques et la sclérose latérale amyotrophique.
LâIRM est souvent utilisĂ©e pour Ă©tudier les maladies neurologiques et surveiller leur Ă©volution.
à cette fin, la morphométrie extraite de la substance grise de la moelle épiniÚre, telle que le
volume de la substance grise, peut ĂȘtre utilisĂ©e pour identifier et comprendre les modifications
tissulaires associées aux troubles neurologiques comme ceux mentionnés précédemment.
Pour extraire des mesures morphométriques de la matiÚre grise de la moelle épiniÚre, une
annotation (label) par voxel est requise pour chaque tranche du volume IRM. Lâannotation
manuelle ne peut donc pas ĂȘtre facilement implĂ©mentĂ© dans la pratique en raison non seulement
des efforts fastidieux nĂ©cessaires pour annoter manuellement chaque tranche dâun volume
dâIRM, mais aussi du dĂ©saccord et des biais introduits par diffĂ©rents annotateurs humains.
Toutefois, il existe de nombreuses méthodes semi-automatiques ou entiÚrement automatiques
pour annoter chaque voxel, mais la plupart dâentre elles sont composĂ©es dâapproches en
plusieurs Ă©tapes pouvant propager des erreurs dans le pipeline, sâappuient sur des dictionnaires
de donnĂ©es ou ne gĂ©nĂ©ralisent pas bien lorsquâil y a des changements anatomiques. Il est
bien connu que les techniques modernes basĂ©es sur lâapprentissage par la reprĂ©sentation et
lâapprentissage en profondeur ont obtenu dâexcellents rĂ©sultats dans un large Ă©ventail de
tĂąches allant de la vision par ordinateur Ă lâimagerie mĂ©dicale.
Le programme de recherche de ce projet consiste à améliorer les résultats les plus récents des
mĂ©thodes existantes au moyen de techniques modernes dâapprentissage en profondeur grĂące
Ă la conception, la mise en oeuvre et lâĂ©valuation de ces mĂ©thodes pour la segmentation de
la substance grise de la moelle épiniÚre. Dans ce projet, trois techniques principales ont été
développées: en open source, comme décrit ci-dessous.
La premiĂšre technique consistait Ă concevoir une architecture dâapprentissage en profondeur
pour segmenter la matiĂšre grise de la moelle Ă©piniĂšre et a permis dâobtenir de meilleures
résultats comparé à six autres méthodes développées précédemment pour la segmentation de
la matiĂšre grise. Cette technique a Ă©galement permis de segmenter un volume ex vivo avec
plus de 4000 tranches en fournissant au préalable et moins de 30 échantillons annotés du
mĂȘme volume.
La deuxiÚme technique a été développée pour tirer profitnon seulement des données anotées,
mais aussides donnĂ©es qui ne le sont pas (donnĂ©es non anotĂ©es) au moyen dâune mĂ©thode
dâapprentissage semi-supervisĂ©e Ă©tendue aux tĂąches de segmentation. Cette mĂ©thode a apportĂ©
des améliorations significatives dans un scénario réaliste sous un régime de données réduit en
ajoutant des données non annotées au cours du processus de formation du modÚle.
La troisiĂšme technique dĂ©veloppĂ©e est une mĂ©thode dâadaptation de domaine non supervisĂ©e
pour la segmentation. Dans ce travail, nous avons abordé le problÚme du décalage de
distribution présent sur les données IRM, qui est principalement causé par différents paramÚtres
dâacquisition. Dans ce travail, nous avons montrĂ© quâen adaptant le modĂšle Ă un domaine
cible prĂ©sentĂ© au modĂšle sous forme de donnĂ©es non annotĂ©es, il est possible dâamĂ©liorer de
maniĂšre significative la segmentation de la matiĂšre grise pour le domaine cible invisible.
Conformément aux principes de la science ouverte pour tous (open science), nous avons ouvert
toutes les méthodes sur des référentiels publics et en avons implémenté certaines sur la Spinal
Cord Toolbox (SCT) 1, une bibliothĂšque complĂšte et ouverte dâoutils dâanalyse pour lâIRM
de la moelle épiniÚre. Nous avons également utilisé uniquement des ensembles de données
accessibles au public pour toutes les Ă©valuations et la formation de modĂšles, ainsi que pour la
publication de tous les articles sur les revues en libre accÚs, avec une disponibilité gratuite sur
les serveurs dâarchives prĂ©-imprimĂ©es.
Dans ce travail, nous avons pu constater que les modĂšles dâapprentissage en profondeur
peuvent en effet fournir des progrÚs considérables par rapport aux méthodes précédemment
dĂ©veloppĂ©es. Les mĂ©thodes dâapprentissage en profondeur sont trĂšs flexibles et robustes. Elles
permettent dâapprendre de bout en bout lâensemble des pipelines de segmentation tout en
permettant de tirer profit de donnĂ©es non annotĂ©es pour amĂ©liorer les performances du mĂȘme
domaine dans un scĂ©nario dâapprentissage semi-supervisĂ© ou en tirant parti de donnĂ©es non
étiquetées pour améliorer les performances des modÚles dans des domaines cibles non vus.
Il est Ă©galement clair que lâapprentissage en profondeur nâest pas une panacĂ©e pour lâimagerie
médicale. De nombreux problÚmes demeurent en suspens, tels que le décalage de généralisation
toujours prĂ©sent lors de lâutilisation de ces modĂšles sur des domaines non vus. Un
futur axe de recherche inclut le développement en cours de techniques pour éclairer les modÚles
dâapprentissage automatique avec paramĂ©trisation dâacquisition IRM afin par exemple
dâamĂ©liorer la gĂ©nĂ©ralisation du modĂšle Ă diffĂ©rents contrastes, ainsi que dâamĂ©liorer la variabilitĂ©
inhérente de ces images due aux différentes machines et aux changements anatomiques.
Lâestimation de lâincertitude liĂ©e Ă la distillation des connaissances au cours des phases de
formation des approches décrites dans ce travail constitue un autre domaine de recherche
1disponible Ă https://github.com/neuropoly/spinalcordtoolbox.
potentiel. Cependant, les mesures dâincertitude font partie dâun domaine de recherche en
cours dâĂ©volution dans le Deep Learning. En effet la plupart des mĂ©thodes fournissant une
approximation mĂ©diocre ou une sous-estimation de lâincertitude Ă©pistĂ©mique prĂ©sente dans
ces modĂšles.
Lâimagerie mĂ©dicale reste un domaine trĂšs difficile pour les modĂšles dâapprentissage automatique
en raison des fortes hypothĂšses dâidentitĂ© distributionnelle formulĂ©es par les algorithmes
dâapprentissage statistique ainsi que de la difficultĂ© Ă incorporer de nouveaux biais inductifs
dans ces modĂšles pour tirer parti de la symĂ©trie, de lâinvariance de rotation, entre autres. NĂ©anmoins,
avec la quantité croissante de données disponibles, elles offrent de grandes promesses
et gagnent lentement en robustesse pour pouvoir entrer dans la pratique clinique.----------ABSTRACT
The human spinal cord, part of the Central Nervous System (CNS), is the main pathway
responsible for the connection of brain and peripheral nervous system. The gray matter
present in the spinal cord is known to be associated with many neurological disorders such as
multiple sclerosis and amyotrophic lateral sclerosis.
Magnetic Resonance Imaging (MRI) is often used to study diseases and monitor the disease
burden/progression during the course of the disease. To that goal, morphometrics extracted
from the spinal cord gray matter such as gray matter volume can be used to identify and
understand tissue changes that are associated with the aforementioned neurological disorders.
To extract morphometrics from the spinal cord gray matter, a voxel-wise annotation is required
for each slice of the MRI volume. Manual annotation becomes prohibitive in practice due to the
time-consuming efforts required to manually annotate each slice of an MRI volume voxel-wise,
not to mention the disagreement and bias introduced by different human annotators.
Many semi-automatic or fully-automatic methods exist but most of them are composed by
multi-stage approaches that can propagate errors in the pipeline, rely on data dictionaries,
or doesnât generalize well when there are anatomical changes. It is well-known that modern
techniques based on representation learning and Deep Learning achieved excellent results in a
wide range of tasks from computer vision and medical imaging as well.
The research agenda of this project is to advance the state-of-the-art results of previous
methods by means of modern Deep Learning techniques through the design, implementation,
and evaluation of these methods for the spinal cord gray matter segmentation. In this project,
three main techniques were developed an open-sourced, as described below.
The first technique is the design of a Deep Learning architecture to segment the spinal cord
gray matter that achieved state-of-the-art results when evaluated by a third-party system
and compared to other 6 independently developed methods for gray matter segmentation.
This technique also allowed to segment an ex vivo volume with more than 4000 slices by just
providing less than 30 annotated samples from the same volume.
The second technique was developed to take leverage not only of labeled data but also
from unlabeled data by means of a semi-supervised learning method that was extended to
segmentation tasks. This method achieved significant improvements in a realistic scenario
under a small data regime by adding unlabeled data during the model training process.
The third developed technique is an unsupervised domain adaptation method for segmentation. In this work, we addressed the problem of the distributional shift present on MRI data that
is mostly caused by different acquisition parametrization. In this work, we showed that by
adapting the model to a target domain, presented to the model as unlabeled data, it is possible
to achieve significant improvements on the gray matter segmentation for the unseen target
domain.
Following the open science principles, we open-sourced all the methods on public repositories
and implemented some of them on the Spinal Cord Toolbox (SCT) 2, a comprehensive and
open-source library of analysis tools for MRI of the spinal cord. We also used only public
available datasets for all evaluations and model training, and also published all articles on
open-access journals with free availability on pre-print archive servers as well.
In this work, we were able to see that Deep Learning models can indeed provide huge steps
forward when compared to the previously developed methods. Deep Learning methods are
very flexible and robust, allowing end-to-end learning of entire segmentation pipelines while
being able to take leverage of unlabeled data to improve the performance for the same domain
on a semi-supervised learning scenario, or by taking leverage of unlabeled data to improve
the performance of models in unseen target domains.
It is also clear that Deep Learning is not a panacea for medical imaging. Many problems
remain open, such as the generalization gap that is still present when using these models on
unseen domains. A future line of research includes the on-going development of techniques
to inform machine learning models with MRI acquisition parametrization to improve the
generalization of the model to different contrasts, to the inherent variability of these images
due to different machine vendors and anatomical changes, to name a few. Another potential
area of research is the uncertainty estimation for knowledge distillation during training phases
of the approaches described in this work. However, uncertainty measures are still an open
area of research in Deep Learning with most methods providing a poor approximation or
under-estimation of the epistemic uncertainty present in these models.
Medical imaging is still a very challenging field for machine learning models due to the strong
assumptions of distributional identity made by statistical learning algorithms as well as the
difficulty to incorporate new inductive biases into these models to take leverage of symmetry,
rotation invariance, among others. Nevertheless, with the amount of data availability growing,
they show great promises and are slowly gaining robustness enough to be able to enter in clinical practice
Deep semi-supervised segmentation with weight-averaged consistency targets
Recently proposed techniques for semi-supervised learning such as Temporal
Ensembling and Mean Teacher have achieved state-of-the-art results in many
important classification benchmarks. In this work, we expand the Mean Teacher
approach to segmentation tasks and show that it can bring important
improvements in a realistic small data regime using a publicly available
multi-center dataset from the Magnetic Resonance Imaging (MRI) domain. We also
devise a method to solve the problems that arise when using traditional data
augmentation strategies for segmentation tasks on our new training scheme.Comment: 8 pages, 1 figure, accepted for DLMIA/MICCA
Automatic Segmentation of Intramedullary Multiple Sclerosis Lesions
Contexte: La moelle Ă©piniĂšre est un composant essentiel du systĂšme nerveux central. Elle contient des neurones responsables dâimportantes fonctionnalitĂ©s et assure la transmission dâinformations motrices et sensorielles entre le cerveau et le systĂšme nerveux pĂ©riphĂ©rique. Un endommagement de la moelle Ă©piniĂšre, causĂ© par un choc ou une maladie neurodĂ©gĂ©nĂ©rative, peut mener Ă un sĂ©rieux handicap, pouvant entraĂźner des incapacitĂ©s fonctionnelles, de la paralysie et/ou de la douleur. Chez les patients atteints de sclĂ©rose en plaques (SEP), la moelle Ă©piniĂšre est frĂ©quemment affectĂ©e par de lâatrophie et/ou des lĂ©sions. Lâimagerie par rĂ©sonance magnĂ©tique (IRM) conventionnelle est largement utilisĂ©e par des chercheurs et des cliniciens pour Ă©valuer et caractĂ©riser, de façon non-invasive, des altĂ©rations micro-structurelles. Une Ă©valuation quantitative des atteintes structurelles portĂ©es Ă la moelle Ă©piniĂšre (e.g. sĂ©vĂ©ritĂ© de lâatrophie, extension des lĂ©sions) est essentielle pour le diagnostic, le pronostic et la supervision sur le long terme de maladies, telles que la SEP. De plus, le dĂ©veloppement de biomarqueurs impartiaux est indispensable pour Ă©valuer lâeffet de nouveaux traitements thĂ©rapeutiques. La segmentation de la moelle Ă©piniĂšre et des lĂ©sions intramĂ©dullaires de SEP sont, par consĂ©quent, pertinentes dâun point de vue clinique, aussi bien quâune Ă©tape nĂ©cessaire vers lâinterprĂ©tation dâimages RM multiparamĂ©triques. Cependant, la segmentation manuelle est une tĂąche extrĂȘmement chronophage, fastidieuse et sujette Ă des variations inter- et intra-expert. Il y a par consĂ©quent un besoin dâautomatiser les mĂ©thodes de segmentations, ce qui pourrait faciliter lâefficacitĂ© procĂ©dures dâanalyses. La segmentation automatique de lĂ©sions est compliquĂ© pour plusieurs raisons: (i) la variabilitĂ© des lĂ©sions en termes de forme, taille et position, (ii) les contours des lĂ©sions sont la plupart du temps difficilement discernables, (iii) lâintensitĂ© des lĂ©sions sur des images MR sont similaires Ă celles de structures visiblement saines. En plus de cela, rĂ©aliser une segmentation rigoureuse sur lâensemble dâune base de donnĂ©es multi-centrique dâIRM est rendue difficile par lâimportante variabilitĂ© des protocoles dâacquisition (e.g. rĂ©solution, orientation, champ de vue de lâimage). MalgrĂ© de considĂ©rables rĂ©cents dĂ©veloppements dans le traitement dâimages MR de moelle Ă©piniĂšre, il nây a toujours pas de mĂ©thode disponible pouvant fournir une segmentation rigoureuse et fiable de la moelle Ă©piniĂšre pour un large spectre de pathologies et de protocoles dâacquisition. Concernant les lĂ©sions intramĂ©dullaires, une recherche approfondie dans la littĂ©rature nâa pas pu fournir une mĂ©thode disponible de segmentation automatique.
Objectif: Développer un systÚme complÚtement automatique pour segmenter la moelle épiniÚre et les lésions intramédullaires sur des IRM conventionnelles humaines.
MĂ©thode: Lâapproche prĂ©sentĂ©e est basĂ©e de deux rĂ©seaux de neurones Ă convolution mis en cascade. La mĂ©thode a Ă©tĂ© pensĂ©e pour faire face aux principaux obstacles que prĂ©sentent les donnĂ©es IRM de moelle Ă©piniĂšre. Le procĂ©dĂ© de segmentation a Ă©tĂ© entrainĂ© et validĂ© sur une base de donnĂ©es privĂ©e composĂ©e de 1943 images, acquises dans 30 diffĂ©rents centres avec des protocoles hĂ©tĂ©rogĂšnes. Les sujets scannĂ©s comportent 459 sujets sains, 471 patients SEP et 112 avec dâautres pathologies affectant la moelle Ă©piniĂšre. Le module de segmentation de la moelle Ă©piniĂšre a Ă©tĂ© comparĂ© Ă une mĂ©thode existante reconnue par la communautĂ©, PropSeg.
RĂ©sultats: Lâapproche basĂ©e sur les rĂ©seaux de neurones Ă convolution a fourni de meilleurs rĂ©sultats que PropSeg, atteignant un Dice mĂ©dian (intervalle inter-quartiles) de 94.6 (4.6) vs. 87.9 (18.3) %. Pour les lĂ©sions, notre segmentation automatique a permis d'obtenir un Dice de 60.0 (21.4) % en le comparant Ă la segmentation manuelle, un ratio de vrai positifs de 83 (34) %, et une prĂ©cision de 77 (44) %.
Conclusion: Une mĂ©thode complĂštement automatique et innovante pour segmenter la moelle Ă©piniĂšre et les lĂ©sions SEP intramĂ©dullaires sur des donnĂ©es IRM a Ă©tĂ© conçue durant ce projet de maĂźtrise. La mĂ©thode a Ă©tĂ© abondamment validĂ©e sur une base de donnĂ©es clinique. La robustesse de la mĂ©thode de segmentation de moelle Ă©piniĂšre a Ă©tĂ© dĂ©montrĂ©e, mĂȘme sur des cas pathologiques. Concernant la segmentation des lĂ©sions, les rĂ©sultats sont encourageants, malgrĂ© un taux de faux positifs relativement Ă©levĂ©. Je crois en lâimpact que peut potentiellement avoir ces outils pour la communautĂ© de chercheurs. Dans cette optique, les mĂ©thodes ont Ă©tĂ© intĂ©grĂ©es et documentĂ©es dans un logiciel en accĂšs-ouvert, la âSpinal Cord Toolboxâ. Certains des outils dĂ©veloppĂ©s pendant ce projet de MaĂźtrise sont dĂ©jĂ utilisĂ©s par des analyses dâĂ©tudes cliniques, portant sur des patients SEP et sclĂ©rose latĂ©rale amyotrophique.----------ABSTRACT
Context: The spinal cord is a key component of the central nervous system, which contains neurons responsible for complex functions, and ensures the conduction of motor and sensory information between the brain and the peripheral nervous system. Damage to the spinal cord, through trauma or neurodegenerative diseases, can lead to severe impairment, including functional disabilities, paralysis and/or pain. In multiple sclerosis (MS) patients, the spinal cord is frequently affected by atrophy and/or lesions. Conventional magnetic resonance imaging (MRI) is widely used by researchers and clinicians to non-invasively assess and characterize spinal cord microstructural changes. Quantitative assessment of the structural damage to the spinal cord (e.g. atrophy severity, lesion extent) is essential for the diagnosis, prognosis and longitudinal monitoring of diseases, such as MS. Furthermore, the development of objective biomarkers is essential to evaluate the effect of new therapeutic treatments. Spinal cord and intramedullary MS lesions segmentation is consequently clinically relevant, as well as a necessary step towards the interpretation of multi-parametric MR images. However, manual segmentation is highly time-consuming, tedious and prone to intra- and inter-rater variability. There is therefore a need for automated segmentation methods to facilitate the efficiency of analysis pipelines. Automatic lesion segmentation is challenging for various reasons: (i) lesion variability in terms of shape, size and location, (ii) lesion boundaries are most of the time not well defined, (iii) lesion intensities on MR data are confounding with those of normal-appearing structures. Moreover, achieving robust segmentation across multi-center MRI data is challenging because of the broad variability of data features (e.g. resolution, orientation, field of view). Despite recent substantial developments in spinal cord MRI processing, there is still no method available that can yield robust and reliable spinal cord segmentation across the very diverse spinal pathologies and data features. Regarding the intramedullary lesions, a thorough search of the relevant literature did not yield available method of automatic segmentation.
Goal: To develop a fully-automatic framework for segmenting the spinal cord and intramedullary MS lesions from conventional human MRI data.
Method: The presented approach is based on a cascade of two Convolutional Neural Networks (CNN). The method has been designed to face the main challenges of âreal worldâ spinal cord MRI data. It was trained and validated on a private dataset made up of 1943 MR volumes, acquired in different 30 sites with heterogeneous acquisition protocols. Scanned subjects involve 459 healthy controls, 471 MS patients and 112 with other spinal pathologies. The proposed spinal cord segmentation method was compared to a state-of-the-art spinal cord segmentation method, PropSeg.
Results: The CNN-based approach achieved better results than PropSeg, yielding a median (interquartile range) Dice of 94.6 (4.6) vs. 87.9 (18.3) % when compared to the manual segmentation. For the lesion segmentation task, our method provided a median Dice-overlap with the manual segmentation of 60.0 (21.4) %, a lesion-based true positive rate of 83 (34) % and a lesion-based precision de 77 (44) %.
Conclusion: An original fully-automatic method to segment the spinal cord and intramedullary MS lesions on MRI data has been devised during this Masterâs project. The method was validated extensively against a clinical dataset. The robustness of the spinal cord segmentation has been demonstrated, even on challenging pathological cases. Regarding the lesion segmentation, the results are encouraging despite the fairly high false positive rate. I believe in the potential value of these developed tools for the research community. In this vein, the methods are integrated and documented into an open-source software, the Spinal Cord Toolbox. Some of the tools developed during this Masterâs project are already integrated into automated analysis pipelines of clinical studies, including MS and Amyotrophic Lateral Sclerosis patients
White Matter, Gray Matter and Cerebrospinal Fluid Segmentation from Brain Magnetic Resonance Imaging Using Adaptive U-Net and Local Convolutional Neural Network
According to the World Alzheimer Report 2015, 46 million people are living with dementia in the world. The diagnosis of diseases helps doctors treating patients better. One of the signs of diseases is related to white matter, grey matter and cerebrospinal fluid. Therefore, the automatic segmentation of three tissues in brain imaging especially from magnetic resonance imaging (MRI) plays an important role in medical analysis. In this research, we proposed an effective approach to segment automatically these tissues in three-dimensional (3D) brain MRI. First, a deep learning model is used to segment the sure and unsure regions. In the unsure region, another deep learning model is used to classify each pixel. In the experiments, an adaptive U-net model is used to segment the sure and unsure regions, and the Local Convolutional Neural Network (CNN) model with multiple inputs is used to classify each pixel only in the unsure region. Our method was evaluated with a real image database, Internet Brain Segmentation Repository database, with 18 persons (IBSR 18) (https://www.nitrc.org/projects/ibsr) and compared with state of art methods being the results very promising
SoftSeg: Advantages of soft versus binary training for image segmentation
Most image segmentation algorithms are trained on binary masks formulated as
a classification task per pixel. However, in applications such as medical
imaging, this "black-and-white" approach is too constraining because the
contrast between two tissues is often ill-defined, i.e., the voxels located on
objects' edges contain a mixture of tissues. Consequently, assigning a single
"hard" label can result in a detrimental approximation. Instead, a soft
prediction containing non-binary values would overcome that limitation. We
introduce SoftSeg, a deep learning training approach that takes advantage of
soft ground truth labels, and is not bound to binary predictions. SoftSeg aims
at solving a regression instead of a classification problem. This is achieved
by using (i) no binarization after preprocessing and data augmentation, (ii) a
normalized ReLU final activation layer (instead of sigmoid), and (iii) a
regression loss function (instead of the traditional Dice loss). We assess the
impact of these three features on three open-source MRI segmentation datasets
from the spinal cord gray matter, the multiple sclerosis brain lesion, and the
multimodal brain tumor segmentation challenges. Across multiple
cross-validation iterations, SoftSeg outperformed the conventional approach,
leading to an increase in Dice score of 2.0% on the gray matter dataset
(p=0.001), 3.3% for the MS lesions, and 6.5% for the brain tumors. SoftSeg
produces consistent soft predictions at tissues' interfaces and shows an
increased sensitivity for small objects. The richness of soft labels could
represent the inter-expert variability, the partial volume effect, and
complement the model uncertainty estimation. The developed training pipeline
can easily be incorporated into most of the existing deep learning
architectures. It is already implemented in the freely-available deep learning
toolbox ivadomed (https://ivadomed.org)
Deep Semantic Segmentation of Natural and Medical Images: A Review
The semantic image segmentation task consists of classifying each pixel of an
image into an instance, where each instance corresponds to a class. This task
is a part of the concept of scene understanding or better explaining the global
context of an image. In the medical image analysis domain, image segmentation
can be used for image-guided interventions, radiotherapy, or improved
radiological diagnostics. In this review, we categorize the leading deep
learning-based medical and non-medical image segmentation solutions into six
main groups of deep architectural, data synthesis-based, loss function-based,
sequenced models, weakly supervised, and multi-task methods and provide a
comprehensive review of the contributions in each of these groups. Further, for
each group, we analyze each variant of these groups and discuss the limitations
of the current approaches and present potential future research directions for
semantic image segmentation.Comment: 45 pages, 16 figures. Accepted for publication in Springer Artificial
Intelligence Revie
U-Net and its variants for medical image segmentation: theory and applications
U-net is an image segmentation technique developed primarily for medical
image analysis that can precisely segment images using a scarce amount of
training data. These traits provide U-net with a very high utility within the
medical imaging community and have resulted in extensive adoption of U-net as
the primary tool for segmentation tasks in medical imaging. The success of
U-net is evident in its widespread use in all major image modalities from CT
scans and MRI to X-rays and microscopy. Furthermore, while U-net is largely a
segmentation tool, there have been instances of the use of U-net in other
applications. As the potential of U-net is still increasing, in this review we
look at the various developments that have been made in the U-net architecture
and provide observations on recent trends. We examine the various innovations
that have been made in deep learning and discuss how these tools facilitate
U-net. Furthermore, we look at image modalities and application areas where
U-net has been applied.Comment: 42 pages, in IEEE Acces
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