196 research outputs found
Optimization frameworks and sensitivity analysis of Stackelberg mean-field games
This paper proposes and studies a class of discrete-time finite-time-horizon
Stackelberg mean-field games, with one leader and an infinite number of
identical and indistinguishable followers. In this game, the objective of the
leader is to maximize her reward considering the worst-case cost over all
possible -Nash equilibria among followers. A new analytical paradigm
is established by showing the equivalence between this Stackelberg mean-field
game and a minimax optimization problem. This optimization framework
facilitates studying both analytically and numerically the set of Nash
equilibria for the game; and leads to the sensitivity and the robustness
analysis of the game value. In particular, when there is model uncertainty, the
game value for the leader suffers non-vanishing sub-optimality as the perturbed
model converges to the true model. In order to obtain a near-optimal solution,
the leader needs to be more pessimistic with anticipation of model errors and
adopts a relaxed version of the original Stackelberg game
Assessing Test-time Variability for Interactive 3D Medical Image Segmentation with Diverse Point Prompts
Interactive segmentation model leverages prompts from users to produce robust
segmentation. This advancement is facilitated by prompt engineering, where
interactive prompts serve as strong priors during test-time. However, this is
an inherently subjective and hard-to-reproduce process. The variability in user
expertise and inherently ambiguous boundaries in medical images can lead to
inconsistent prompt selections, potentially affecting segmentation accuracy.
This issue has not yet been extensively explored for medical imaging. In this
paper, we assess the test-time variability for interactive medical image
segmentation with diverse point prompts. For a given target region, the point
is classified into three sub-regions: boundary, margin, and center. Our goal is
to identify a straightforward and efficient approach for optimal prompt
selection during test-time based on three considerations: (1) benefits of
additional prompts, (2) effects of prompt placement, and (3) strategies for
optimal prompt selection. We conduct extensive experiments on the public
Medical Segmentation Decathlon dataset for challenging colon tumor segmentation
task. We suggest an optimal strategy for prompt selection during test-time,
supported by comprehensive results. The code is publicly available at
https://github.com/MedICL-VU/variabilit
Promise:Prompt-driven 3D Medical Image Segmentation Using Pretrained Image Foundation Models
To address prevalent issues in medical imaging, such as data acquisition
challenges and label availability, transfer learning from natural to medical
image domains serves as a viable strategy to produce reliable segmentation
results. However, several existing barriers between domains need to be broken
down, including addressing contrast discrepancies, managing anatomical
variability, and adapting 2D pretrained models for 3D segmentation tasks. In
this paper, we propose ProMISe,a prompt-driven 3D medical image segmentation
model using only a single point prompt to leverage knowledge from a pretrained
2D image foundation model. In particular, we use the pretrained vision
transformer from the Segment Anything Model (SAM) and integrate lightweight
adapters to extract depth-related (3D) spatial context without updating the
pretrained weights. For robust results, a hybrid network with complementary
encoders is designed, and a boundary-aware loss is proposed to achieve precise
boundaries. We evaluate our model on two public datasets for colon and pancreas
tumor segmentations, respectively. Compared to the state-of-the-art
segmentation methods with and without prompt engineering, our proposed method
achieves superior performance. The code is publicly available at
https://github.com/MedICL-VU/ProMISe.Comment: updated acknowledgments and fixed typo
Pixel-wise Smoothing for Certified Robustness against Camera Motion Perturbations
In recent years, computer vision has made remarkable advancements in
autonomous driving and robotics. However, it has been observed that deep
learning-based visual perception models lack robustness when faced with camera
motion perturbations. The current certification process for assessing
robustness is costly and time-consuming due to the extensive number of image
projections required for Monte Carlo sampling in the 3D camera motion space. To
address these challenges, we present a novel, efficient, and practical
framework for certifying the robustness of 3D-2D projective transformations
against camera motion perturbations. Our approach leverages a smoothing
distribution over the 2D pixel space instead of in the 3D physical space,
eliminating the need for costly camera motion sampling and significantly
enhancing the efficiency of robustness certifications. With the pixel-wise
smoothed classifier, we are able to fully upper bound the projection errors
using a technique of uniform partitioning in camera motion space. Additionally,
we extend our certification framework to a more general scenario where only a
single-frame point cloud is required in the projection oracle. This is achieved
by deriving Lipschitz-based approximated partition intervals. Through extensive
experimentation, we validate the trade-off between effectiveness and efficiency
enabled by our proposed method. Remarkably, our approach achieves approximately
80% certified accuracy while utilizing only 30% of the projected image frames.Comment: 32 pages, 5 figures, 13 table
Learning-Based Biharmonic Augmentation for Point Cloud Classification
Point cloud datasets often suffer from inadequate sample sizes in comparison
to image datasets, making data augmentation challenging. While traditional
methods, like rigid transformations and scaling, have limited potential in
increasing dataset diversity due to their constraints on altering individual
sample shapes, we introduce the Biharmonic Augmentation (BA) method. BA is a
novel and efficient data augmentation technique that diversifies point cloud
data by imposing smooth non-rigid deformations on existing 3D structures. This
approach calculates biharmonic coordinates for the deformation function and
learns diverse deformation prototypes. Utilizing a CoefNet, our method predicts
coefficients to amalgamate these prototypes, ensuring comprehensive
deformation. Moreover, we present AdvTune, an advanced online augmentation
system that integrates adversarial training. This system synergistically
refines the CoefNet and the classification network, facilitating the automated
creation of adaptive shape deformations contingent on the learner status.
Comprehensive experimental analysis validates the superiority of Biharmonic
Augmentation, showcasing notable performance improvements over prevailing point
cloud augmentation techniques across varied network designs
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