Performance of image analysis algorithms in digital pathology whole slide images (WSI) is usually hampered by the stain variations cross images. To overcome such difficulties, many stain normalization methods have been proposed where normalization is applied to all the stains in the image. However, for immunohistochemistry (IHC) images, there exist situations where not all the stains in the images are desired or feasible to be normalized, especially when the stain variations relate to certain biological indications. In contrast, the counter stain, usually hematoxylin (HTX), is always desired to be consistent cross images for robust nuclei detection. In this work, we present a framework to normalize the HTX stain in an IHC WSI through alignment to a template IHC WSI. For this purpose, we use the Hue-Saturation- Density (HSD) model and align the chromatic components distribution of the image to the template. Then we shift and scale density component to match the template. In order to retain the non-HTX stain, we differentiate the pixels which have pure HTX stain from those which are mixture of HTX and non-HTX stains, and different normalization strategy is applied accordingly. In the results, for a wide range of HTX stain variations, we show qualitatively the performance of the method. We also show algorithm performance dependence on the stain concentration can be much reduced by the proposed method.
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