VS-FPM: large-format, label-free virtual histopathology microscopy

<b>Abstract</b>By generating realistic histologically stained images from label-free image data, virtual staining (VS) methods have the potential to streamline clinical workflows, improve image consistency and enable new ways of visualizing and analysing tissues. This article describes a new VS approach based on the application of conditional generative adversarial networks to translate high-resolution phase images of unstained tissues, recovered using Fourier ptychographic microscopy (FPM), into brightfield H&amp;E images. Compared to other label-free imaging methods, FPM offers unique advantages for VS as it allows simultaneous capture of sample amplitude and phase information, simplifying the pixelwise registration required for supervised training. FPM combines high spatial resolution with a large field of view and a large depth of field making it well suited to large format imaging of histological tissues. The method is readily implemented by modifying a conventional brightfield microscope using simple, low-cost optoelectronic hardware. Using colonic polyps as a test case, we compare FPM and VS-FPM images to brightfield whole slide images (WSIs) captured using a pathology slide scanner. Our results show that FPM images captured at 4x magnification have a spatial resolution equivalent to WSIs captured at 20x magnification and virtual H&amp;E images of unstained tissues generated using VS-FPM closely match brightfield images of the same tissue sections captured after chemical staining, enabling pathological assessment and diagnosis.<b>Dataset:</b>This dataset contains pathology images of intestinal polyps from 3 patients. For each polyp section, there is are 4 registered images, 3 of which are chemically stained with H&amp;E: WSI (captured with a NanoZoomer S360MD), FPM reconstructed amplitude and raw 4x brightfield. The 4th image is virtually stained from FPM phase images of unstained tissue.<br>

<b>摘要</b>通过从无标记图像数据生成逼真的组织学染色图像，虚拟染色（virtual staining, VS）方法有望优化临床工作流程、提升图像一致性，并为组织的可视化与分析开辟全新途径。本文提出一种基于条件生成对抗网络的新型虚拟染色方法，可将利用傅里叶叠层显微术（Fourier ptychographic microscopy, FPM）采集的未染色组织高分辨率相位图像转换为明场苏木精-伊红（H&E）染色图像。相较于其他无标记成像方法，傅里叶叠层显微术在虚拟染色应用中具备独特优势：它可同时采集样本的振幅与相位信息，简化了监督训练所需的逐像素配准步骤。傅里叶叠层显微术兼具高空间分辨率、大视场与大景深特性，非常适合组织学样本的大视场成像。该方法仅需借助简单低成本的光电硬件对传统明场显微镜进行改造即可实现。本研究以结肠息肉为测试对象，将傅里叶叠层显微术图像与虚拟染色傅里叶叠层显微术（VS-FPM）图像同病理切片扫描仪采集的明场全视野数字切片（whole slide images, WSI）进行对比。研究结果表明，4倍放大倍率下采集的傅里叶叠层显微术图像空间分辨率等同于20倍放大倍率下的全视野数字切片；利用虚拟染色傅里叶叠层显微术生成的未染色组织虚拟H&E染色图像，与经化学染色后同一组织切片的明场图像高度吻合，可支持病理评估与诊断工作。
<b>数据集：</b>本数据集包含3名患者的肠息肉病理图像。针对每一例息肉切片，均配有4张配准后的图像，其中3张为经H&E化学染色的图像：分别为采用NanoZoomer S360MD采集的全视野数字切片（WSI）、傅里叶叠层显微术重建振幅图像以及原始4倍明场图像。第4张图像则是利用未染色组织的傅里叶叠层显微术相位图像生成的虚拟染色图像。