通过早期稳定操作快速搜索自适应模块,显著降低医疗图像分割的计算成本。
Efficient Search of Implantable Adaptive Cells for Medical Image Segmentation

- 基于熵稳定性准则,在搜索早期淘汰低重要性操作,加速模块发现。
- 在4个公开数据集上实现与全周期搜索相当的分割性能,速度提升3.7至16倍。
- 适用于多种网络结构和训练设置,适合资源受限的实际医学影像应用。
自适应跳接模块可提升医学图像分割性能,但搜索过程计算开销大。植入式自适应单元(IAC)是插入U-Net跳接路径的紧凑神经架构搜索模块,相比全网搜索缩小了搜索空间。然而,原始IAC框架仍需针对每种主干网络和数据集进行200轮可微分搜索。本文分析了在公共医学图像分割基准上的可微搜索中,操作与边的时序行为,发现最终离散单元中采用的操作通常在训练初期即为强候选,并在接近末期前即趋于稳定。基于此,提出一种基于詹森-香农散度的稳定性判据,追踪每条边的操作重要性分布并逐步剪枝低重要性操作,构建出加速框架IAC-LTH。在四个公开基准(ACDC、BraTS、KiTS、AMOS)、多个2-D U-Net主干及2-D nnU-Net流程上,IAC-LTH所发现的IAC单元在患者级分割性能上与原全周期搜索相当甚至略优,同时将实际搜索耗时减少3.7至16倍。该结果在不同架构、基准及增强/非增强训练设置下均保持一致,且保留了配备IAC的U-Net相对于强注意力与密集跳接基线的性能优势。结论表明:仅依赖早期稳定的操作即可识别具有竞争力的IAC架构,使自适应跳接模块设计在现实计算约束下更具可行性。
原文摘要 · Abstract (English)
Purpose: Adaptive skip modules can improve medical image segmentation, but searching for them is computationally costly. Implantable Adaptive Cells (IACs) are compact NAS modules inserted into U-Net skip connections, reducing the search space compared with full-network NAS. However, the original IAC framework still requires a 200-epoch differentiable search for each backbone and dataset. Methods: We analyzed the temporal behavior of operations and edges within IAC cells during differentiable search on public medical image segmentation benchmarks. We found that operations selected in the final discrete cell typically emerge among the strongest candidates early in training, and their architecture parameters stabilize well before the final epoch. Based on this, we propose a Jensen--Shannon-divergence-based stability criterion that tracks per-edge operation-importance distributions and progressively prunes low-importance operations during search. The accelerated framework is called IAC-LTH. Results: Across four public benchmarks (ACDC, BraTS, KiTS, AMOS), several 2-D U-Net backbones, and a 2-D nnU-Net pipeline, IAC-LTH discovers IAC cells whose patient-level segmentation performance matches and sometimes slightly exceeds that of cells found by the original full-length search, while reducing wall-clock NAS cost by 3.7x to 16x across datasets and backbones. These results are consistent across architectures, benchmarks, and both non-augmented and augmented training settings, while preserving the gains of IAC-equipped U-Nets over strong attention-based and dense-skip baselines. Conclusion: Competitive IAC architectures can be identified from early-stabilizing operations without running the full search, making adaptive skip-module design more practical for medical image segmentation under realistic computational constraints.
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