What is a digital pathology slide scanner?

Digital pathology slide scanner is an analytical instrument used in basic medicine, clinical medicine and biology. Compared with traditional microscope, it can acquire digital slide images with higher resolution via automated scanning. It realized high-precision and multi-view seamless digital image stitching and K-SCP special color processing to restore the original image to the greatest extent.

The image data is stored and compressed into an electronic image file. It’s quite convenient for medical, scientific research personnel, and engineers to scale, read, measure and annotate via slide reading software. It provides technical support and data foundation for remote consultation and AI pathology.

What are the advantages of digital pathology slide scanners over traditional microscopes?

1. Faster speed

Traditional microscopes can only be operated manually, the slide reading speed depends on the experience and energy of the pathologist. And only one slide can be viewed one time.

The digital pathology slide scanner can scan high-throughput slides automatically. KFBIO digital pathology slide scanner has a maximum speed of 25s/slide, and can scan up to 400 slides one time.

2. More stable and quiet experience

The scanning accuracy of traditional microscopes depends on many factors such as microscope quality, user experience, etc. For the same slide, different microscopes, different environments, and different observers will result in different diagnosis results, resulting in poor scanning stability.

Digital pathology scanners transforms digital slides into high-resolution images automatically for pathologists to diagnose more efficiently. The KFBIO digital pathology scanner adopts the magnetic motor control to avoid mechanical wear and backlash. The scanning process is more stable and quiet. And the success rate of slide scanning can reach 99.85%.

3. Automatic scanning, intelligent analysis

Traditional microscope must be manually operated by professionals. Operators are required to analyze slides based on technology and experience to generate results, which is easily affected by subjective factors.

The digital pathology scanner can scan large-throughput slides automatically with one-click. It allows pathologists to step out. Besides, based on the deep learning of annotated slide database, KFBIO AI products help analyze digital images intelligently.

4. High resolution and fidelity

Traditional microscopes can achieve higher resolution, but it’s not easy to view the whole slide.

The highest resolution of a digital pathology scanner can achieve about 0.125um/pixel. It can restore the original image to the greatest extent through the high-precision seamless image stitching technology. It compares the image gradient ratio of the two images with the preset value to judge whether two images is stitched perfectly. It helps judge the image quality objectively and realize the optimal image stitch.

KFBIO digital pathology scanner uses K-SCP special color processing technology to systematically improve the restoration of color saturation, color temperature, color contrast and other indicators. The color compensation of different monitors after imaging is also considered to ensure the high fidelity of image.

Parameters to focus on when choosing a digital pathology scanner

1. Scanning speed

Faster scanning speed, higher efficiency. The maximum number of scanning slides per day can be calculated by the scanning speed, which helps the arrangement of workload.

2. Scanning Mode

The scanning mode determines whether the scanning is stable, whether the working process is quiet, and whether the output file is qualified. The scanning modes of digital slide scanners mainly include flat whole-slide scanning, Z-Stack scanning and extended focus scanning.

(1) Flat whole-slide scanning:

Combine a large number of square image frames to form a mosaic pattern. Due to the saccade movement of the slide table, there is typically a 2%–5% overlap in a given tile. Then the tiles are automatically stitched to form a single, huge seamless whole-slide image.

The disadvantage of this type of scanning is that it is only suitable for single-layer imaging of a flat slide. It will be difficult to scan uneven and thick slides.

(2) Z-Stack scanning:

The scanner is capable of digitizing slides in various z-axes (vertical focal plane). A servo motor moves along a single acquisition axis in a jitter-free linear way. After it moves at different locations on the slide, a set of images are produced in the form of long, consecutive lines. Then the images are stacked to produce composite multiplanar images. It could simulate the fine focus control of conventional microscopes.

This approach greatly simplifies the image stitch process as the number of lines/tiles required are significantly reduced. Multi-layer information can be obtained, and a clearer single-layer image can be obtained through the deconvolution algorithm. It solves the problems of blurred background and uneven slides.

(3)Extended focus scanning:

This method combines multiple smaller images (each in a best focus plane) into a composite image. Compared to multi-planar virtual images, image acquisition of this method is faster and the file size is smaller.

Mainstream product comparison

Brand	KFBIO	LEICA	3DHISTECH	MOTIC
Scan mode	Multilayer scanning (Z-stack)	Multilayer scanning (Z-stack)	Multilayer (Z-stack) and extended focus scanning	Multilayer scanning (Z-stack)

Considering the scanning effect, stability and cost factors, the current mainstream scanning mode is Z-Stack. KFBIO scanners adopt this scanning mode to ensure higher scanning stability and accuracy.

3.Objective lens

The objective lens is the core component of a digital slide scanner. Its quality and various indicators determine the quality and accuracy of the output image. The well-known objective lenses brands are Olympus, Zeiss, Nikon, Leica, etc.

KFBIO digital slide scanner adopts Olympus top dual objective lens and top filter system. The narrow-band single-pass filter ensures the unicity of spectral frequency and effectively prevent cross-color. The transmittance reaches 99%. The cut-off frequency reaches OD6. High contrast, high brightness, no cross color, zero drift.

What are the indicators of the objective lens?

(1) Resolution:
Resolution refers to the ability to distinguish the minimum distance between two adjacent object points. It’s called the resolution distance. The smaller the distance, the higher the resolution.

Generally speaking, the minimum distance between two adjacent object points of the human eye is 100µm. And the minimum distance of an optical microscope is 0.2µm. The minimum distance of KFBIO digital slide scanners is 0.25µm.

(2) Numerical aperture:
The relationship between Numerical Aperture (N.A.) and Resolution is:
δ=0.61λ/NA （λ≈0.555μm）
δ is the minimum distance between resolvable points.
λ is the wavelength of light, emission wavelength, in the case of fluorescence. The average wavelength of white light is 0.55μm.
N.A. is the numerical aperture.
So the resolution is inversely proportional to the numerical aperture (N.A.), which means that the larger the N.A. is, the more the resolvable details are and the stronger the resolving power is.

The numerical apertures of different objectives and condensers are different. The NA of the dry objective objective is 0.05-0.95, and the NA of the oil immersion objective is 0.85-1.4.

The higher the resolution, the larger the numerical aperture. If the NA of the objective lens reaches 0.95, it is already very high. At present, the KFBIO objective lens can reach this level.

(3) Magnification:
The ratio of the the final image size to the original object size is called the magnification. The total magnification for a microscope is equal to the magnification of the objective multiplied by the magnification of the eyepiece. The magnification is also limited by the resolution limit. Generally speaking, the maximum magnification of a light microscope can only be one thousand times the numerical aperture of the lens. When air is used as the medium, the maximum magnification is about 1000 times.

Digital slide scanners are generally used to observe cells. Too high magnification is not necessary. The mainstream magnifications are 20x, 40x, and 80x.

Mainstream product comparison

Brand	KFBIO	LEICA	MOTIC
Objective lens	OLYMPUS apochromat objective lens	Aperio GT，Custom-made by Leica Microsystems	Plan APOCHROMAT
Numerical Aperture	20X, NA 0.8 40X, NA 0.95	20x, NA 0.75	20X,NA 0.75
Resolution	≤0.5 µm/pixel(20X) ≤0.25 µm/pixel(40X)	0.26 µm/pixel(40X)	0.52µm/pixel(20X) 0.26µm/pixel(40X)
Magnification	20X/40X/80Xx	1.25X/5X/10X/20X/40X/63X	20X/40X

4. illumination

It determines the applicable scenes of the digital slice scanner. Generally, there are two modes: bright-field and fluorescence.

Bright-field is to allow the light passes through the specimen directly into the objective lens, and the field of view is bright.

Fluorescence is to observe the fluorescence signal under a fluorescence microscope or fluorescence scanner. It allows pathologists to observe the morphology and distribution of cells that are stained after hybridization with specific probes, or DNA regions or RNA molecules bound to fluorescent probes located in chromosomes or in other organelles.

Mainstream product comparison

Brand	KFBIO	LEICA	3DHISTECH
Illumination	Bright-field & Fluorescence	Bright-field & Fluorescence	Bright-field & Fluorescence

It will be more convenient if the digital pathology scanner supports both bright-field and fluorescence modes. At present, the KFBIO digital slide scanner supports both modes. Two modes can be switched freely. And the independent optical path design is adopted to make the scanning process more stable and efficient.

KFBIO digital slide scanners: The bright-field mode adopts a professional 3CCD linear camera, and the fluorescence mode adopts a scientific-grade SCMOS fluorescence camera. Three primary colors have independent color processing channels to ensure more natural and accurate color reproduction and clarity.

5. Capacity

Capacity indicates the number of slides that the digital slide scanner can scan at one time. Large capacity can improve scanning efficiency, but the price is relatively expensive. Users can purchase scanners with different capacity according to different needs.

Mainstream product comparison

Brand	KFBIO	LEICA	3DHISTECH
Capacity	2/5/20/40/120/400	120/400/450	1/11/12/150/250/1000

KFBIO has a number of digital scanning equipment suitable for multiple scenarios and purposes: low-throughput scanning equipment for remote pathology, high-throughput scanner for full digitization and intelligent pathology department construction, and bright-field and fluorescence scanner for scientific research.