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Hoifung Poon

21 accepted papers

2026

Learning Sparse Visual Representations via Spatial-Semantic Factorization

ICML 2026poster

Self-supervised learning (SSL) faces a fundamental conflict between semantic understanding and image reconstruction. High-level semantic SSL (e.g., DINO) relies on global tokens that are forced to be location-invariant for augmentation alignment, a process that inherently discards the spatial coordi…

Cited by 0SourceScholar
2026

Masked-Diffusion Autoencoders for 3D Medical Vision Representation Learning

CVPR 2026

Effective medical image analysis requires representations that capture both global anatomical structure and fine-grained tissue texture. Current self-supervised approaches exhibit limited capacity to address both requirements simultaneously. Invariance-based methods learn through augmentation consis

Cited by 0SourceScholar
2026

OctoMed: Data Recipes for State-of-the-Art Multimodal Medical Reasoning

CVPR 2026

High-quality and carefully curated data is a cornerstone of training medical large language models, as it directly impacts both generalization and robustness to unseen clinical tasks. We investigate strategies for training and data curation to develop a robust multimodal reasoning model in the medic

Cited by 0SourceScholar
2025

Boltzmann Attention Sampling for Image Analysis with Small Objects

CVPR 2025poster

Detecting and segmenting small objects, such as lung nodules and tumor lesions, remains a critical challenge in image analysis. These objects often occupy less than 0.1% of an image, making traditional transformer architectures inefficient and prone to performance degradation due to redundant attent…

Cited by 0SourcePDFScholar
2025

From Introspection to Best Practices: Principled Analysis of Demonstrations in Multimodal In-Context Learning

NAACL 2025long

Motivated by in-context learning (ICL) capabilities of Large Language Models (LLMs), multimodal LLMs with additional visual modality are also exhibited with similar ICL abilities when multiple image-text pairs are provided as demonstrations. However, relatively less work has been done to investigate…

2025

MuirBench: A Comprehensive Benchmark for Robust Multi-image Understanding

ICLR 2025poster

We introduce MuirBench, a comprehensive benchmark that focuses on robust multi-image understanding capabilities of multimodal LLMs. MuirBench consists of 12 diverse multi-image tasks (e.g., scene understanding, ordering) that involve 10 categories of multi-image relations (e.g., multiview, temporal…

2024

DocLens: Multi-aspect Fine-grained Medical Text Evaluation

ACL 2024long

Medical text generation aims to assist with administrative work and highlight salient information to support decision-making.To reflect the specific requirements of medical text, in this paper, we propose a set of metrics to evaluate the completeness, conciseness, and attribution of the generated te…

2024

UniversalNER: Targeted Distillation from Large Language Models for Open Named Entity Recognition

ICLR 2024poster

Large language models (LLMs) have demonstrated remarkable generalizability, such as understanding arbitrary entities and relations. Instruction tuning has proven effective for distilling LLMs into more cost-efficient models such as Alpaca and Vicuna. Yet such student models still trail the original…

Cited by 133SourcePDFScholar
2024

mDPO: Conditional Preference Optimization for Multimodal Large Language Models

EMNLP 2024main

Direct preference optimization (DPO) has shown to be an effective method for large language model (LLM) alignment. Recent works have attempted to apply DPO to multimodal scenarios but have found it challenging to achieve consistent improvement. Through a comparative experiment, we identify the uncon…

2023

Continual Contrastive Finetuning Improves Low-Resource Relation Extraction

ACL 2023long

Relation extraction (RE), which has relied on structurally annotated corpora for model training, has been particularly challenging in low-resource scenarios and domains. Recent literature has tackled low-resource RE by self-supervised learning, where the solution involves pretraining the entity pair…

Cited by 7SourcePDFScholar
2023

Exploring the Boundaries of GPT-4 in Radiology

EMNLP 2023long main

The recent success of general-domain large language models (LLMs) has significantly changed the natural language processing paradigm towards a unified foundation model across domains and applications. In this paper, we focus on assessing the performance of GPT-4, the most capable LLM so far, on the…

Cited by 0SourceScholar
2023

LLaVA-Med: Training a Large Language-and-Vision Assistant for Biomedicine in One Day

NeurIPS 2023spotlight

Conversational generative AI has demonstrated remarkable promise for empowering biomedical practitioners, but current investigations focus on unimodal text. Multimodal conversational AI has seen rapid progress by leveraging billions of image-text pairs from the public web, but such general-domain vi…

Cited by 828SourcePDFScholar
2023

Optimizing Bi-Encoder for Named Entity Recognition via Contrastive Learning

ICLR 2023poster

We present a bi-encoder framework for named entity recognition (NER), which applies contrastive learning to map candidate text spans and entity types into the same vector representation space. Prior work predominantly approaches NER as sequence labeling or span classification. We instead frame NER a…

2022

Knowledge-Rich Self-Supervision for Biomedical Entity Linking

EMNLP 2022finding

Entity linking faces significant challenges such as prolific variations and prevalent ambiguities, especially in high-value domains with myriad entities. Standard classification approaches suffer from the annotation bottleneck and cannot effectively handle unseen entities. Zero-shot entity linking h…

Cited by 45SourcePDFScholar
2022

Making the Most of Text Semantics to Improve Biomedical Vision-Language Processing

ECCV 2022poster

"Multi-modal data abounds in biomedicine, such as radiology images and reports. Interpreting this data at scale is essential for improving clinical care and accelerating clinical research. Biomedical text with its complex semantics poses additional challenges in vision-language modelling compared to…

2021

Modular Self-Supervision for Document-Level Relation Extraction

EMNLP 2021main

Extracting relations across large text spans has been relatively underexplored in NLP, but it is particularly important for high-value domains such as biomedicine, where obtaining high recall of the latest findings is crucial for practical applications. Compared to conventional information extractio…

Cited by 10SourcePDFScholar
2021

Self-Supervised Self-Supervision by Combining Deep Learning and Probabilistic Logic

AAAI 2021technical

Labeling training examples at scale is a perennial challenge in machine learning. Self-supervision methods compensate for the lack of direct supervision by leveraging prior knowledge to automatically generate noisy labeled examples. Deep probabilistic logic (DPL) is a unifying framework for self-sup…

Cited by 17SourcePDFScholar
2021

Targeted Adversarial Training for Natural Language Understanding

NAACL 2021long

We present a simple yet effective Targeted Adversarial Training (TAT) algorithm to improve adversarial training for natural language understanding. The key idea is to introspect current mistakes and prioritize adversarial training steps to where the model errs the most. Experiments show that TAT can…

2017

Estimating Accuracy from Unlabeled Data: A Probabilistic Logic Approach

NeurIPS 2017poster

We propose an efficient method to estimate the accuracy of classifiers using only unlabeled data. We consider a setting with multiple classification problems where the target classes may be tied together through logical constraints. For example, a set of classes may be mutually exclusive, meaning th…

Cited by 75SourcePDFScholar