Zhang Yiming, Li Huakun, Cao Tongtong, Chen Ruixiang, Qiu Haixia, Gu Ying, Li Peng
State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, International research center for advanced photonics, Zhejiang University, Hangzhou, China.
Department of Laser Medicine, First Medical Center of PLA General Hospital, Beijing, China.
Quant Imaging Med Surg. 2021 Mar;11(3):895-906. doi: 10.21037/qims-20-868.
Vascular quantitative metrics have been widely used in the preclinical studies and clinical applications (e.g., the diagnosis and treatment of port wine stain, PWS), which require accurate vessel segmentation. An automatic 3D adaptive vessel segmentation is in need for a reproducible and objective quantification of the optical coherence tomography angiography (OCTA) image.
Human skin imaging was performed with a lab-built optical coherence tomography (OCT) system. Rather than separately applying the conventional 2-step (intensity and binarization) thresholding in the decorrelation-contrast OCTA, we proposed a 3D adaptive threshold using the linear relationship between the local intensity and complex-decorrelation which was termed as inverse SNR-decorrelation (ID) threshold. Furthermore, the ID threshold was automatically determined by defining a binary image similarity (BISIM) index as the feedback and searching the ID threshold with the minimal BISIM value. The proposed ID-BISIM threshold was applied to the acquired OCTA skin images for further vessel quantification.
The proposed ID-BISIM threshold enabled a 3D adaptive binarization and presented superior sensitivity and specificity in vessel segmentation over conventional 2-step thresholding method in the decorrelation-contrast OCTA and a 37-65% improvement of the Youden's index in human skin experiments. The 3D binarization enabled a depth-resolved vessel skeleton and enhanced the differentiation of the overlapping vessels in the depth direction. Using ID-BISIM, the quantitative OCTA image presented a significant increase of vessel diameter index (P=0.0015) and vessel area density (VAD) (P=0.0485) as well as a significant decrease of vessel complexity index (VCI) (P=0.0094) in PWS lesion skin compared with normal skin.
The proposed ID-BISIM method enables an automatic 3D adaptive vessel segmentation with enhanced performance in quantitative OCTA. The vascular quantitative metrics would be a useful tool for improving the diagnosis and the treatment of PWS.
血管定量指标已广泛应用于临床前研究和临床应用（如葡萄酒色斑的诊断和治疗），这需要精确的血管分割。为了对光学相干断层扫描血管造影（OCTA）图像进行可重复且客观的量化，需要一种自动的三维自适应血管分割方法。
使用实验室构建的光学相干断层扫描（OCT）系统对人体皮肤进行成像。在去相关对比度OCTA中，我们没有分别应用传统的两步（强度和二值化）阈值法，而是利用局部强度与复去相关之间的线性关系提出了一种三维自适应阈值，即反信噪比去相关（ID）阈值。此外，通过定义二元图像相似度（BISIM）指数作为反馈并搜索具有最小BISIM值的ID阈值来自动确定ID阈值。将所提出的ID-BISIM阈值应用于获取的OCTA皮肤图像，以进行进一步的血管量化。
所提出的ID-BISIM阈值实现了三维自适应二值化，在去相关对比度OCTA中，与传统的两步阈值法相比，在血管分割方面具有更高的灵敏度和特异性，在人体皮肤实验中约登指数提高了37%-65%。三维二值化实现了深度分辨的血管骨架，并增强了深度方向上重叠血管的区分度。使用ID-BISIM，与正常皮肤相比，定量OCTA图像显示葡萄酒色斑病变皮肤的血管直径指数（P=0.0015）和血管面积密度（VAD）（P=0.0485）显著增加，以及血管复杂性指数（VCI）（P=0.0094）显著降低。
所提出的ID-BISIM方法能够实现自动的三维自适应血管分割，在定量OCTA中具有增强的性能。血管定量指标将成为改善葡萄酒色斑诊断和治疗的有用工具。
