Virtual specimen

Virtual specimen, also digitized specimen or virtual slide, is a term denoting a completely digitized histological specimen. The virtual specimen is a basic tool of telepathology (digital pathology, computer pathology). The digitization process is referred to in the English literature as Whole Slide Imaging (WSI).

Benefits
A pathologist does not have to be physically present in the hospital, one pathologist can serve e.g. several hospitals in real time, in which there may be a requirement to read an intraoperative biopsy. A difficult case can be consulted practically in real time with an expert specialized in the given issue, even if it is located hundreds of kilometers away. Teaching through digitized specimens allows the teacher to conveniently draw students' attention to everything that they should notice and that is diagnostically significant. There is no risk of confusion. Practically the entire preparation can be an appendix to a scientific publication or a textbook. You can also work with multispectral images in a natural way (they are used in basic biological research, they are not of much use in pathological practice for the time being). In a natural way, image analysis methods can be used to support the diagnostic balance.

Cons
Due to the image quality requirements, it is not advisable to use lossy compression algorithms. Furthermore, as a prevention of the loss of a significant amount of information, e.g. when the specimen is folded during mounting, it is advisable to scan the slide in several planes of focus. This significantly increases the memory requirement, one high-quality virtual specimen can be in the order of hundreds of megabytes to units of gigabytes. The range of images requires new approaches in the field of computer graphics, from the level of simple imaging to the level of computer support for diagnostics. Due to the large volume of data, most sophisticated algorithms are excruciatingly slow. The digitized specimen cannot be used for further processing. If we have an image in basic staining, it is not possible to additionally perform immunochemical staining or molecular biological analysis. This limits the possibility of consultation to those specialists to whom, if necessary, a physical specimen can be sent without problems; even so, this can be a source of delay. The high acquisition costs of slide scanners and sufficiently powerful graphic workstations probably do not cover the benefits of digitization, especially in small workplaces. In connection with the introduction of virtual slides in teaching, in some countries there is talk of "weaning from the microscope".

The delay due to the actual scanning of the preparation refers to more "improvised" solutions (e.g. a classic microscope equipped with a regular camera and controlled stage movement), a modern scanner designed only for scanning histological preparations processes one preparation for approximately one minute.

The term virtual histology usually refers to a technique based on a more detailed analysis of scattered ultrasound waves during an ultrasound examination with a high frequency of the applied wave.

Related Articles

 * Digital image
 * Telemedicine
 * Teleradiology