143,032 research outputs found
Local feature selection for multiple instance learning with applications.
Feature selection is a data processing approach that has been successfully and effectively used in developing machine learning algorithms for various applications. It has been proven to effectively reduce the dimensionality of the data and increase the accuracy and interpretability of machine learning algorithms. Conventional feature selection algorithms assume that there is an optimal global subset of features for the whole sample space. Thus, only one global subset of relevant features is learned. An alternative approach is based on the concept of Local Feature Selection (LFS), where each training sample can have its own subset of relevant features. Multiple Instance Learning (MIL) is a variation of traditional supervised learning, also known as single instance learning. In MIL, each object is represented by a set of instances, or a bag. While bags are labeled, the labels of their instances are unknown. The ambiguity of the instance labels makes the feature selection for MIL challenging. Although feature selection in traditional supervised learning has been researched extensively, there are only a few methods for the MIL framework. Moreover, localized feature selection for MIL has not been researched. This dissertation focuses on developing a local feature selection method for the MIL framework. Our algorithm, called Multiple Instance Local Salient Feature Selection (MI-LSFS), searches the feature space to find the relevant features within each bag. We also propose a new multiple instance classification algorithm, called MILES-LFS, that integrates information learned by MI-LSFS during the feature selection process to identify a reduced subset of representative bags and instances. We show that using a more focused subset of prototypes can improve the performance while significantly reducing the computational complexity. Other applications of the proposed MI-LSFS include a new method that uses our MI-LSFS algorithm to explore and investigate the features learned by a Convolutional Neural Network (CNN) model; a visualization method for CNN models, called Gradient-weighted Sample Activation Map (Grad-SAM), that uses the locally learned features of each sample to highlight their relevant and salient parts, and a novel explanation method, called Classifier Explanation by Local Feature Selection (CE-LFS), to explain the decisions of trained models. The proposed MI-LSFS and its applications are validated using several synthetic and real data sets. We report and compare quantitative measures such as Rand Index, Area Under Curve (AUC), and accuracy. We also provide qualitative measures by visualizing and interpreting the selected features and their effects
Cross-attention-based saliency inference for predicting cancer metastasis on whole slide images
Although multiple instance learning (MIL) methods are widely used for
automatic tumor detection on whole slide images (WSI), they suffer from the
extreme class imbalance within the small tumor WSIs. This occurs when the tumor
comprises only a few isolated cells. For early detection, it is of utmost
importance that MIL algorithms can identify small tumors, even when they are
less than 1% of the size of the WSI. Existing studies have attempted to address
this issue using attention-based architectures and instance selection-based
methodologies, but have not yielded significant improvements. This paper
proposes cross-attention-based salient instance inference MIL (CASiiMIL), which
involves a novel saliency-informed attention mechanism, to identify breast
cancer lymph node micro-metastasis on WSIs without the need for any
annotations. Apart from this new attention mechanism, we introduce a negative
representation learning algorithm to facilitate the learning of
saliency-informed attention weights for improved sensitivity on tumor WSIs. The
proposed model outperforms the state-of-the-art MIL methods on two popular
tumor metastasis detection datasets, and demonstrates great cross-center
generalizability. In addition, it exhibits excellent accuracy in classifying
WSIs with small tumor lesions. Moreover, we show that the proposed model has
excellent interpretability attributed to the saliency-informed attention
weights. We strongly believe that the proposed method will pave the way for
training algorithms for early tumor detection on large datasets where acquiring
fine-grained annotations is practically impossible
Automatic annotation for weakly supervised learning of detectors
PhDObject detection in images and action detection in videos are among the most widely studied
computer vision problems, with applications in consumer photography, surveillance, and automatic
media tagging. Typically, these standard detectors are fully supervised, that is they require
a large body of training data where the locations of the objects/actions in images/videos have
been manually annotated. With the emergence of digital media, and the rise of high-speed internet,
raw images and video are available for little to no cost. However, the manual annotation
of object and action locations remains tedious, slow, and expensive. As a result there has been
a great interest in training detectors with weak supervision where only the presence or absence
of object/action in image/video is needed, not the location. This thesis presents approaches for
weakly supervised learning of object/action detectors with a focus on automatically annotating
object and action locations in images/videos using only binary weak labels indicating the presence
or absence of object/action in images/videos.
First, a framework for weakly supervised learning of object detectors in images is presented.
In the proposed approach, a variation of multiple instance learning (MIL) technique for automatically
annotating object locations in weakly labelled data is presented which, unlike existing
approaches, uses inter-class and intra-class cue fusion to obtain the initial annotation. The initial
annotation is then used to start an iterative process in which standard object detectors are used to
refine the location annotation. Finally, to ensure that the iterative training of detectors do not drift
from the object of interest, a scheme for detecting model drift is also presented. Furthermore,
unlike most other methods, our weakly supervised approach is evaluated on data without manual
pose (object orientation) annotation.
Second, an analysis of the initial annotation of objects, using inter-class and intra-class cues,
is carried out. From the analysis, a new method based on negative mining (NegMine) is presented
for the initial annotation of both object and action data. The NegMine based approach is a
much simpler formulation using only inter-class measure and requires no complex combinatorial
optimisation but can still meet or outperform existing approaches including the previously pre3
sented inter-intra class cue fusion approach. Furthermore, NegMine can be fused with existing
approaches to boost their performance.
Finally, the thesis will take a step back and look at the use of generic object detectors as prior
knowledge in weakly supervised learning of object detectors. These generic object detectors are
typically based on sampling saliency maps that indicate if a pixel belongs to the background
or foreground. A new approach to generating saliency maps is presented that, unlike existing
approaches, looks beyond the current image of interest and into images similar to the current
image. We show that our generic object proposal method can be used by itself to annotate the
weakly labelled object data with surprisingly high accuracy
Salient Objects in Clutter: Bringing Salient Object Detection to the Foreground
We provide a comprehensive evaluation of salient object detection (SOD)
models. Our analysis identifies a serious design bias of existing SOD datasets
which assumes that each image contains at least one clearly outstanding salient
object in low clutter. The design bias has led to a saturated high performance
for state-of-the-art SOD models when evaluated on existing datasets. The
models, however, still perform far from being satisfactory when applied to
real-world daily scenes. Based on our analyses, we first identify 7 crucial
aspects that a comprehensive and balanced dataset should fulfill. Then, we
propose a new high quality dataset and update the previous saliency benchmark.
Specifically, our SOC (Salient Objects in Clutter) dataset, includes images
with salient and non-salient objects from daily object categories. Beyond
object category annotations, each salient image is accompanied by attributes
that reflect common challenges in real-world scenes. Finally, we report
attribute-based performance assessment on our dataset.Comment: ECCV 201
Multiple Instance Curriculum Learning for Weakly Supervised Object Detection
When supervising an object detector with weakly labeled data, most existing
approaches are prone to trapping in the discriminative object parts, e.g.,
finding the face of a cat instead of the full body, due to lacking the
supervision on the extent of full objects. To address this challenge, we
incorporate object segmentation into the detector training, which guides the
model to correctly localize the full objects. We propose the multiple instance
curriculum learning (MICL) method, which injects curriculum learning (CL) into
the multiple instance learning (MIL) framework. The MICL method starts by
automatically picking the easy training examples, where the extent of the
segmentation masks agree with detection bounding boxes. The training set is
gradually expanded to include harder examples to train strong detectors that
handle complex images. The proposed MICL method with segmentation in the loop
outperforms the state-of-the-art weakly supervised object detectors by a
substantial margin on the PASCAL VOC datasets.Comment: Published in BMVC 201
Active Classification: Theory and Application to Underwater Inspection
We discuss the problem in which an autonomous vehicle must classify an object
based on multiple views. We focus on the active classification setting, where
the vehicle controls which views to select to best perform the classification.
The problem is formulated as an extension to Bayesian active learning, and we
show connections to recent theoretical guarantees in this area. We formally
analyze the benefit of acting adaptively as new information becomes available.
The analysis leads to a probabilistic algorithm for determining the best views
to observe based on information theoretic costs. We validate our approach in
two ways, both related to underwater inspection: 3D polyhedra recognition in
synthetic depth maps and ship hull inspection with imaging sonar. These tasks
encompass both the planning and recognition aspects of the active
classification problem. The results demonstrate that actively planning for
informative views can reduce the number of necessary views by up to 80% when
compared to passive methods.Comment: 16 page
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