CVPR 2024 Papers

Single-pixel imaging (SPI) is a potential computational imaging technique which produces image by solving an ill-posed reconstruction problem from few measurements captured by a single-pixel detector. Deep learning has achieved impressive success on SPI reconstruction. However previous poor reconstruction performance and impractical imaging model limit its real-world applications. In this paper we propose a deep unfolding network with hybrid-attention Transformer on Kronecker SPI model dubbed HATNet to improve the imaging quality of real SPI cameras. Specifically we unfold the computation graph of the iterative shrinkage-thresholding algorithm (ISTA) into two alternative modules: efficient tensor gradient descent and hybrid-attention multi-scale denoising. By virtue of Kronecker SPI the gradient descent module can avoid high computational overheads rooted in previous gradient descent modules based on vectorized SPI. The denoising module is an encoder-decoder architecture powered by dual-scale spatial attention for high- and low-frequency aggregation and channel attention for global information recalibration. Moreover we build a SPI prototype to verify the effectiveness of the proposed method. Extensive experiments on synthetic and real data demonstrate that our method achieves the state-of-the-art performance. The source code and pre-trained models are available at https://github.com/Gang-Qu/HATNet-SPI.

Recently deep unfolding methods have achieved remarkable success in the realm of Snapshot Compressive Imaging (SCI) reconstruction. However the existing methods all follow the iterative framework of a single image prior which limits the efficiency of the unfolding methods and makes it a problem to use other priors simply and effectively. To break out of the box we derive an effective Dual Prior Unfolding (DPU) which achieves the joint utilization of multiple deep priors and greatly improves iteration efficiency. Our unfolding method is implemented through two parts i.e. Dual Prior Framework (DPF) and Focused Attention (FA). In brief in addition to the normal image prior DPF introduces a residual into the iteration formula and constructs a degraded prior for the residual by considering various degradations to establish the unfolding framework. To improve the effectiveness of the image prior based on self-attention FA adopts a novel mechanism inspired by PCA denoising to scale and filter attention which lets the attention focus more on effective features with little computation cost. Besides an asymmetric backbone is proposed to further improve the efficiency of hierarchical self-attention. Remarkably our 5-stage DPU achieves state-of-the-art (SOTA) performance with the least FLOPs and parameters compared to previous methods while our 9-stage DPU significantly outperforms other unfolding methods with less computational requirement.

Annotation ambiguity due to inherent data uncertainties such as blurred boundaries in medical scans and different observer expertise and preferences has become a major obstacle for training deep-learning based medical image segmentation models. To address it the common practice is to gather multiple annotations from different experts leading to the setting of multi-rater medical image segmentation. Existing works aim to either merge different annotations into the "groundtruth" that is often unattainable in numerous medical contexts or generate diverse results or produce personalized results corresponding to individual expert raters. Here we bring up a more ambitious goal for multi-rater medical image segmentation i.e. obtaining both diversified and personalized results. Specifically we propose a two-stage framework named D-Persona (first Diversification and then Personalization). In Stage I we exploit multiple given annotations to train a Probabilistic U-Net model with a bound-constrained loss to improve the prediction diversity. In this way a common latent space is constructed in Stage I where different latent codes denote diversified expert opinions. Then in Stage II we design multiple attention-based projection heads to adaptively query the corresponding expert prompts from the shared latent space and then perform the personalized medical image segmentation. We evaluated the proposed model on our in-house Nasopharyngeal Carcinoma dataset and the public lung nodule dataset (i.e. LIDC-IDRI). Extensive experiments demonstrated our D-Persona can provide diversified and personalized results at the same time achieving new SOTA performance for multi-rater medical image segmentation. Our code will be released at https://github.com/ycwu1997/D-Persona.

Hyperspectral 3D imaging aims to acquire both depth and spectral information of a scene. However existing methods are either prohibitively expensive and bulky or compromise on spectral and depth accuracy. In this paper we present Dispersed Structured Light (DSL) a cost-effective and compact method for accurate hyperspectral 3D imaging. DSL modifies a traditional projector-camera system by placing a sub-millimeter thick diffraction grating film front of the projector. This configuration enables dispersing structured light based on light wavelength. To utilize the dispersed structured light we devise a model for dispersive projection image formation and a per-pixel hyperspectral 3D reconstruction method. We validate DSL by instantiating a compact experimental prototype. DSL achieves spectral accuracy of 18.8nm full-width half-maximum (FWHM) and depth error of 1mm outperforming prior work on practical hyperspectral 3D imaging. DSL promises accurate and practical hyperspectral 3D imaging for diverse application domains including computer vision and graphics cultural heritage geology and biology.

This paper endeavors to advance the precision of snapshot compressive imaging (SCI) reconstruction for multispectral image (MSI). To achieve this we integrate the advantageous attributes of established SCI techniques and an image generative model propose a novel structured zero-shot diffusion model dubbed DiffSCI. DiffSCI leverages the structural insights from the deep prior and optimization-based methodologies complemented by the generative capabilities offered by the contemporary denoising diffusion model. Specifically firstly we employ a pre-trained diffusion model which has been trained on a substantial corpus of RGB images as the generative denoiser within the Plug-and-Play framework for the first time. This integration allows for the successful completion of SCI reconstruction especially in the case that current methods struggle to address effectively. Secondly we systematically account for spectral band correlations and introduce a robust methodology to mitigate wavelength mismatch thus enabling seamless adaptation of the RGB diffusion model to MSIs.Thirdly an accelerated algorithm is implemented to expedite the resolution of the data subproblem. This augmentation not only accelerates the convergence rate but also elevates the quality of the reconstruction process.We present extensive testing to show that DiffSCI exhibits discernible performance enhancements over prevailing self-supervised and zero-shot approaches surpassing even supervised transformer counterparts across both simulated and real datasets. Code is at https://github.com/PAN083/DiffSCI.

4D medical images which represent 3D images with temporal information are crucial in clinical practice for capturing dynamic changes and monitoring long-term disease progression. However acquiring 4D medical images poses challenges due to factors such as radiation exposure and imaging duration necessitating a balance between achieving high temporal resolution and minimizing adverse effects. Given these circumstances not only is data acquisition challenging but increasing the frame rate for each dataset also proves difficult. To address this challenge this paper proposes a simple yet effective Unsupervised Volumetric Interpolation framework UVI-Net. This framework facilitates temporal interpolation without the need for any intermediate frames distinguishing it from the majority of other existing unsupervised methods. Experiments on benchmark datasets demonstrate significant improvements across diverse evaluation metrics compared to unsupervised and supervised baselines. Remarkably our approach achieves this superior performance even when trained with a dataset as small as one highlighting its exceptional robustness and efficiency in scenarios with sparse supervision. This positions UVI-Net as a compelling alternative for 4D medical imaging particularly in settings where data availability is limited. The source code is available at https://github.com/jungeun122333/UVI-Net.

In the realm of medical 3D data such as CT and MRI images prevalent anisotropic resolution is characterized by high intra-slice but diminished inter-slice resolution. The lowered resolution between adjacent slices poses challenges hindering optimal viewing experiences and impeding the development of robust downstream analysis algorithms. Various volumetric super-resolution algorithms aim to surmount these challenges enhancing inter-slice resolution and overall 3D medical imaging quality. However existing approaches confront inherent challenges: 1) often tailored to specific upsampling factors lacking flexibility for diverse clinical scenarios; 2) newly generated slices frequently suffer from over-smoothing degrading fine details and leading to inter-slice inconsistency. In response this study presents CycleINR a novel enhanced Implicit Neural Representation model for 3D medical data volumetric super-resolution. Leveraging the continuity of the learned implicit function the CycleINR model can achieve results with arbitrary up-sampling rates eliminating the need for separate training. Additionally we enhance the grid sampling in CycleINR with a local attention mechanism and mitigate over-smoothing by integrating cycle-consistent loss. We introduce a new metric Slice-wise Noise Level Inconsistency (SNLI) to quantitatively assess inter-slice noise level inconsistency. The effectiveness of our approach is demonstrated through image quality evaluations on an in-house dataset and a downstream task analysis on the Medical Segmentation Decathlon liver tumor dataset.

Self-supervised learning (SSL) is an efficient pre-training method for medical image analysis. However current research is mostly confined to certain modalities consuming considerable time and resources without achieving universality across different modalities. A straightforward solution is combining all modality data for joint SSL which poses practical challenges. Firstly our experiments reveal conflicts in representation learning as the number of modalities increases. Secondly multi-modal data collected in advance cannot cover all real-world scenarios. In this paper we reconsider versatile SSL from the perspective of continual learning and propose MedCoSS a continuous SSL approach for multi-modal medical data. Different from joint representation learning MedCoSS assigns varying data modalities to separate training stages creating a multi-stage pre-training process. We propose a rehearsal-based continual learning approach to manage modal conflicts and prevent catastrophic forgetting. Specifically we use the k-means sampling to retain and rehearse previous modality data during new modality learning. Moreover we apply feature distillation and intra-modal mixup on buffer data for knowledge retention bypassing pretext tasks. We conduct experiments on a large-scale multi-modal unlabeled dataset including clinical reports X-rays CT MRI and pathological images. Experimental results demonstrate MedCoSS's exceptional generalization ability across 9 downstream datasets and its significant scalability in integrating new modality data. The code and pre-trained model are available at https://github.com/yeerwen/MedCoSS.

Both limited annotation and domain shift are prevalent challenges in medical image segmentation. Traditional semi-supervised segmentation and unsupervised domain adaptation methods address one of these issues separately. However the coexistence of limited annotation and domain shift is quite common which motivates us to introduce a novel and challenging scenario: Mixed Domain Semi-supervised medical image Segmentation (MiDSS). In this scenario we handle data from multiple medical centers with limited annotations available for a single domain and a large amount of unlabeled data from multiple domains. We found that the key to solving the problem lies in how to generate reliable pseudo labels for the unlabeled data in the presence of domain shift with labeled data. To tackle this issue we employ Unified Copy-Paste (UCP) between images to construct intermediate domains facilitating the knowledge transfer from the domain of labeled data to the domains of unlabeled data. To fully utilize the information within the intermediate domain we propose a symmetric Guidance training strategy (SymGD) which additionally offers direct guidance to unlabeled data by merging pseudo labels from intermediate samples. Subsequently we introduce a Training Process aware Random Amplitude MixUp (TP-RAM) to progressively incorporate style-transition components into intermediate samples. Compared with existing state-of-the-art approaches our method achieves a notable 13.57% improvement in Dice score on Prostate dataset as demonstrated on three public datasets. Our code is available at https://github.com/MQinghe/MiDSS

Recent advancements in large-scale visual-language pre-trained models have led to significant progress in zero-/few-shot anomaly detection within natural image domains. However the substantial domain divergence between natural and medical images limits the effectiveness of these methodologies in medical anomaly detection. This paper introduces a novel lightweight multi-level adaptation and comparison framework to repurpose the CLIP model for medical anomaly detection. Our approach integrates multiple residual adapters into the pre-trained visual encoder enabling a stepwise enhancement of visual features across different levels. This multi-level adaptation is guided by multi-level pixel-wise visual-language feature alignment loss functions which recalibrate the model's focus from object semantics in natural imagery to anomaly identification in medical images. The adapted features exhibit improved generalization across various medical data types even in zero-shot scenarios where the model encounters unseen medical modalities and anatomical regions during training. Our experiments on medical anomaly detection benchmarks demonstrate that our method significantly surpasses current state-of-the-art models with an average AUC improvement of 6.24% and 7.33% for anomaly classification 2.03% and 2.37% for anomaly segmentation under the zero-shot and few-shot settings respectively. Source code is available at: https://github.com/MediaBrain-SJTU/MVFA-AD