arXivDaily arXiv每日学术速递 周一至周五更新
arXiv周末暂无论文更新,休息一下吧,周末愉快~~
arXiv 1807.05972cs.CV
收藏

胸部CT成像中肺结节的单时相单阶段检测

Towards Single-phase Single-stage Detection of Pulmonary Nodules in Chest CT Imaging

Imperial College London(帝国理工学院)

Zhongliu Xie

摘要:

胸部CT影像中肺结节的检出对肺癌的早期诊断起着至关重要的作用。人工检测耗时长且容易出错,需要计算机辅助检测,既提高效率又减少误诊。多年来,已经提出了一系列系统,主要遵循两阶段范式:1)候选检测,2)误报减少。最近,深度学习已经成为算法开发的主导力量。至于候选检测,现有技术主要基于两阶段的Faster R-CNN框架,该框架从初始子网开始生成一组类别不可知的区域建议,然后是第二子网来执行分类和边界框回归。相比之下,我们完全放弃了传统的两阶段范例和两阶段框架,并提出训练单个网络用于端到端结节检测,而无需迁移学习或进一步的后处理。我们的特征学习模型是对ResNet和特征金字塔网络的修改,由RReLU激活提供支持。主要的挑战是极端的类间和类内样本不平衡的情况,其中阳性被大量的阴性池淹没,其中主要由简单和少量的硬阴性组成。直接对所有样本进行训练可能会严重破坏训练效果。我们提出了一个基于补丁的采样策略,在一组定期更新的锚,缩小采样范围,所有的积极和只有硬负,有效地解决了这个问题。因此,我们的方法在准确性和速度方面都大大优于现有技术。最后,在每次扫描的[1/8,1/4,1/2,1,2,4,8]假阳性上的普遍FROC评估在实际临床环境中远非理想。我们建议FROC超过[1,2,4]假阳性作为更好的度量。

英文摘要:

Detection of pulmonary nodules in chest CT imaging plays a crucial role in early diagnosis of lung cancer. Manual examination is highly time-consuming and error prone, calling for computer-aided detection, both to improve efficiency and reduce misdiagnosis. Over the years, a range of systems have been proposed, mostly following a two-phase paradigm with: 1) candidate detection, 2) false positive reduction. Recently, deep learning has become a dominant force in algorithm development. As for candidate detection, prior art was mainly based on the two-stage Faster R-CNN framework, which starts with an initial sub-net to generate a set of class-agnostic region proposals, followed by a second sub-net to perform classification and bounding-box regression. In contrast, we abandon the conventional two-phase paradigm and two-stage framework altogether and propose to train a single network for end-to-end nodule detection instead, without transfer learning or further post-processing. Our feature learning model is a modification of the ResNet and feature pyramid network combined, powered by RReLU activation. The major challenge is the condition of extreme inter-class and intra-class sample imbalance, where the positives are overwhelmed by a large negative pool, which is mostly composed of easy and a handful of hard negatives. Direct training on all samples can seriously undermine training efficacy. We propose a patch-based sampling strategy over a set of regularly updating anchors, which narrows sampling scope to all positives and only hard negatives, effectively addressing this issue. As a result, our approach substantially outperforms prior art in terms of both accuracy and speed. Finally, the prevailing FROC evaluation over [1/8, 1/4, 1/2, 1, 2, 4, 8] false positives per scan, is far from ideal in real clinical environments. We suggest FROC over [1, 2, 4] false positives as a better metric.

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。

↑