全载玻片成像(WSI)系统是数字病理学中使用的数字彩色成像系统,具有替代常规光学显微镜的潜力。WSI系统通过使用扫描仪将光学图像转换为数字数据并且然后使用显示器将数字数据转换回光学图像来将载玻片数字化。在数字到光学或光到数字转换期间,需要一个颜色空间来定义数字域和光学域之间的映射,以便可以有意义地解释每个颜色像素的数值数据。不幸的是,目前许多WSI产品没有明确规定指定的颜色空间,这让用户使用通用默认的颜色空间,sRGB。sRGB是一个传统的色彩空间,具有有限的色域,已知无法再现组织学幻灯片中存在的所有颜色阴影。在这项工作中,进行了实验以定量研究WSI系统中使用的sRGB颜色空间的局限性。八个苏木精和伊红(H和E)染色的组织样本,包括人类膀胱,大脑,乳房,结肠,肾,肝脏,肺,还有子宫,用多光谱成像系统测量,以获得像素级的真彩色。将所测量的每个像素的颜色真值转换成标准CIELAB颜色空间,以测试其是否在sRGB颜色空间的色域内。实验结果表明,所有8幅图像都有一部分像素超出sRGB色域。在最坏的情况下,膀胱样本,约35%的图像超过了sRGB色域。结果表明,sRGB颜色空间不足以使WSI扫描仪对H和E染色的整个幻灯片图像进行编码,和sRGB显示器可能具有不足以显示H和E染色的组织学图像的色域。
A whole-slide imaging (WSI) system is a digital color imaging system used in digital pathology with the potential to substitute the conventional light microscope. A WSI system digitalizes a glass slide by converting the optical image to digital data with a scanner and then converting the digital data back to the optical image with a display. During the digital-to-optical or optical-to-digital conversion, a color space is required to define the mapping between the digital domain and the optical domain so that the numerical data of each color pixel can be interpreted meaningfully. Unfortunately, many current WSI products do not specify the designated color space clearly, which leaves the user using the universally default color space, sRGB. sRGB is a legacy color space that has a limited color gamut, which is known to be unable to reproduce all color shades present in histology slides. In this work, experiments were conducted to quantitatively investigate the limitation of the sRGB color space used in WSI systems. Eight hematoxylin and eosin (H and E)-stained tissue samples, including human bladder, brain, breast, colon, kidney, liver, lung, and uterus, were measured with a multispectral imaging system to obtain the true colors at the pixel level. The measured color truth of each pixel was converted into the standard CIELAB color space to test whether it was within the color gamut of the sRGB color space. Experiment results show that all the eight images have a portion of pixels outside the sRGB color gamut. In the worst-case scenario, the bladder sample, about 35% of the image exceeded the sRGB color gamut. The results suggest that the sRGB color space is inadequate for WSI scanners to encode H and E-stained whole-slide images, and an sRGB display may have insufficient color gamut for displaying H and E-stained histology images.