通过显式层次结构提升牙层分割精度,更符合临床解剖逻辑。
Restrictive Hierarchical Semantic Segmentation for Stratified Tooth Layer Detection
- 采用分层递归预测与上下文特征调制,显式建模牙层层级关系。
- 在TL-pano数据集上,细粒度牙层分割的IoU和召回率显著提升。
- 适合低数据量牙科影像分析,结果更具临床可解释性。
准确理解解剖结构对可靠分期某些牙科疾病至关重要。现有层次感知分割方法主要通过损失函数间接编码解剖结构,监督较弱。本文提出一种通用框架,通过结合递归分层预测、限制性输出头和自顶向下特征调制,将显式解剖层次嵌入语义分割。在每一层级,主干网络在原始图像与前一层概率图拼接后重新运行;子类特征通过父类概率进行特征调制,以细化检测能力。概率组合规则确保父类与子类的一致性。层次损失包含逐层加权Dice和交叉熵损失,以及一致性项损失,强制父类预测等于其子类之和。在自建数据集TL-pano(含194张全景牙片,标注牙层与牙槽骨的密集实例与语义分割)上验证,使用UNet和HRNet作为基础模型,5折交叉验证下,层次变体在细粒度结构上持续提升IoU、Dice和召回率,生成更符合解剖学的分割掩码。但层次模型也出现召回率高于精确率,表明假阳性增加。结果表明,显式层次结构能提升性能与临床合理性,尤其适用于数据有限的牙科影像场景。
原文摘要 · Abstract (English)
Accurate understanding of anatomical structures is essential for reliably staging certain dental diseases. A way of introducing this within semantic segmentation models is by utilising hierarchy-aware methodologies. However, existing hierarchy-aware segmentation methods largely encode anatomical structure through the loss functions, providing weak and indirect supervision. We introduce a general framework that embeds an explicit anatomical hierarchy into semantic segmentation by coupling a recurrent, level-wise prediction scheme with restrictive output heads and top-down feature conditioning. At each depth of the class tree, the backbone is re-run on the original image concatenated with logits from the previous level. Child class features are conditioned using Feature-wise Linear Modulation of their parent class probabilities, to modulate child feature spaces for fine grained detection. A probabilistic composition rule enforces consistency between parent and descendant classes. Hierarchical loss combines per-level class weighted Dice and cross entropy loss and a consistency term loss, ensuring parent predictions are the sum of their children. We validate our approach on our proposed dataset, TL-pano, containing 194 panoramic radiographs with dense instance and semantic segmentation annotations, of tooth layers and alveolar bone. Utilising UNet and HRNet as donor models across a 5-fold cross validation scheme, the hierarchical variants consistently increase IoU, Dice, and recall, particularly for fine-grained anatomies, and produce more anatomically coherent masks. However, hierarchical variants also demonstrated increased recall over precision, implying increased false positives. The results demonstrate that explicit hierarchical structuring improves both performance and clinical plausibility, especially in low data dental imaging regimes.
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