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arXiv 2610.20217cs.CVcs.LG

用于任务对齐的前列腺MRI ViT编码器的持续预训练

Continual pretraining Prostate MRI ViT Encoder for task alignment

University College London(伦敦大学学院)

Bilal A. Sidiqi, Yipei Wang, Shaheer U. Saeed, Shiqi Huang, Daniel C. Alexander, Yipeng Hu

AI总结:

本研究针对MRI基础模型预训练与下游任务对齐不足的问题,采用LoRA对前列腺分割任务的ViT编码器持续预训练,结合CKA分析,使3/6下游任务性能提升。

摘要:

构建MRI基础模型已成为推进医学图像分析、提升特定任务模型可及性的有前景方向。现有方法主要聚焦于有效的预训练策略及其在各类下游任务中的性能评估,虽表现出性能提升,但对预训练与下游目标间的任务对齐研究关注有限。与语言模型中两阶段自然对齐不同,视觉应用中此类对齐并不明显。受此空白驱动,本研究探索持续预训练:具体而言,采用低秩适配(LoRA)在前列腺分割任务上对预训练ViT编码器进行持续预训练,以增强任务对齐性与下游性能;进一步使用中心化核对齐(CKA)开展分层表示分析,评估表示变化及其与任务结果的相关性。实验显示,6项下游任务中有3项性能提升,其余任务结果相当。特征分析表明,对于分割任务,经持续预训练的编码器特征相比原始预训练编码器,与微调编码器特征的相似性更高,这与观测到的性能提升相关。

英文摘要:

Building foundation models for MRI has emerged as a promising direction for advancing medical image analysis and improving accessibility of task specific models. Existing approaches primarily focus on effective pretraining strategies and evaluating their performance across diverse downstream tasks. While these methods show performance gains, limited attention has been given to understanding task alignment between pretraining and downstream objectives. Unlike language models, where the two stages are naturally aligned, such alignment is less evident in vision based applications. Motivated by this gap, we explore continual pretraining. Specifically, continually pretraining a pretrained ViT encoder using Low-Rank Adaptation (LoRA) on a prostate segmentation task to enhance task alignment and downstream performance. We further perform layer-wise representational analysis using Centered Kernel Alignment (CKA) to assess representational shifts and their correlation with task outcomes. Our experiments show improved performance in 3 of 6 downstream tasks and comparable results in the others. Our Feature analysis reveals that, for segmentation tasks, continually pretrained encoder features exhibit greater similarity to those of the finetuned encoder than the original pretrained encoder, correlating with observed performance gains.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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