Virtual Microscopy
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Virtual Slide
Virtual Slide
The traditional pathology workflow which is based on the combination of the glass slide and a microscope is struggling to match the requirements of modern health care. The constraints are mainly due to the obsolete way of acquiring and processing of information lying in the tissue or smear samples.
A very simple yet effective parallel can be drawn with photography. If we compare the state of the still camera market of 2006 and, for example 5 years ago, one thing is obvious: digital photography has swept across the board. The digital camera not only offers identical or even better image quality than a film camera but it is also faster, more convenient and gives the user the opportunity to edit, print and share the photos very easily.
The same process is happening in microscopy today. We are very proud that 3DHISTECH Ltd is one of the initiators of the change to virtual microscopy.
Virtual microscopy is based on the concept of virtual slide. A virtual slide is the digital image of the sample on a glass slide. Of course it is necessary that the digital image offers the resolution of a sample we can get when looking into the ocular of a microscope. How can this be achieved?
The solution is as follows: instead of taking one, big picture of the sample (it could not be big enough, i.e. of enough resolution) we take thousands of pictures provided by the objective of the microscope at its maximum magnification.
Here are the steps:
- Focusing: the slide is moved in Z-direction until the scanning program decides the picture provided by the objective is as sharp as possible
- Taking the picture: the digital image sensor takes the picture and stores it on the computer
- Moving the slide to the next position: the slide is moved in X or Y-direction so that the next picture will be adjacent to the previous one.
This sounds really simple and the concept is simple indeed. Realizing it was not easy at all, though.
- Accuracy in micrometers is to be achieved when moving the slide in all the three dimensions.
- Advanced image processing algorithms are needed for seamless stitching of thousands of pictures.
- Speed issues: optimal coordination of several factors is necessary in order to be able to scan an average sample in 3-4 minutes. Also, viewing a virtual slide should be as fast as for example viewing web pages in a browser.
- Optical matters: perfect optical parameters are a must to avoid aberration and to get constant high image quality.
- Storage space: high speed image compression algorithms are to be used in order to save space while maintaining the image quality.
When this concept was formulated (1998-1999) it seemed like a good idea but also like an idea that is almost impossible to realize. This was mainly because the computers back that time had not enough computing power and storage was expensive. Computing power and available storage space grew rapidly since that. Now, several years later the concept of virtual slides is flourishing and everyone is starting to realize the advantages that can be achieved with them.
