Real-time whole slide mosaicing for non-automated microscopes in histopathology analysis

Context: Mosaics of whole slides (WS) are a valuable resource for pathologists in order to have the whole sample available at high resolution. The WS mosaic provides pathologists with an overview of the whole sample at a glance, helping them to make a reliable diagnosis. Despite recent solutions exist for creating WS mosaics based, for instance, on automated microscopes with motorized stages or WS scanner, most of the histopathology analysis are still performed in laboratories endowed with standard manual stage microscopes. Nowadays there are lots of dedicated devices and hardware to achieve Whole Slides (WS) automatically and in batch, but only few of them are conceived to work tightly connected with a microscope and none of them is capable of working in real time with common light microscopes. However, there is a need of having low-cost yet effective mosaicing applications even in small laboratories in order to improve routine histopathological analyses or to perform remote diagnoses. Aims: The purpose of this work is to study and develop a real time mosaicing algorithm working even using non-automated microscopes, to enable pathologists to achieve WS while moving the holder manually, without exploiting any dedicated device. This choice enables pathologists to build WS in real time, while browsing the sample as they are accustomed to, helping them to identify, locate and digitally annotate lesions fast. Methods and Material: Our method exploits fast feature tracker and frame to frame registration that we implemented on common GPU cards. The system work with common light microscopes endowed with a digital camera and connected to a commodity PC. The system has been tested on several histological samples to test the effectiveness of the algorithm to work with mosaicing having different appearances as far as brightness, contrast, texture and detail levels are concerned.