A Study on Color Standardization in Whole

Slide Imaging

Pinky A. Bautista and Yukako Yagi

MASSACHUSETTSGENERAL HOSPITAL

PATHOLOGY

HARVARDMEDICAL SCHOOL

Color standardization -- Important aspect in the implementation of digital

pathology

Variations in digital

slide colors

Whole slide scanners and Color Imaging

Whole slide

scanner 1 (WSI 1)

Whole slide

scanner 2 (WSI 2)

What is the cause of the

color variations??

H&E stained images

The same tissue slide scanned by different scanners .

How to improve the color accuracy of digital images?

MASSACHUSETTSGENERAL HOSPITAL

PATHOLOGY

HARVARDMEDICAL SCHOOL

By Color calibration???

Color chart-- Physical arrangement of standardized color samples

Used for color comparison measurements

Used for Checking color reproduction of an imaging system.

Used to calibrate and to profile graphic devices

The theoretical RGB values are stored and compared to measured values….

Color chart in medical applications

1. Sven Van Poucke et al,” Automatic colorimetric calibration of human wounds”, BMC Medical imaging, 2010,10:7

The color chart is utilized to calibrate images of wound

captured at different lighting condition

1

2. C. Grana et al , “ Color calibration for a Dermatological Video Camera System”, proc. Intl. Conference on Pattern Recognition (ICPR) 2004.

2

lesion Images captured with two different imaging system Corrected

color

Objective

MASSACHUSETTSGENERAL HOSPITAL

PATHOLOGY

HARVARDMEDICAL SCHOOL

To perform an initial investigation o

color standardization in whole slide imaging using a

color chart..

Calibration slide for use in microscope

Set of Color filters

Yagi Adaptation Color Calibration Slide(Overview of telepathology, virtual microscopy, and whole

slide imaging: prospects for the future, Ronald Weinstein et al. In Human Pathology, 2009)

9 color filters were selected for Histology Stained Slides The filters were identified in previous study The filters works well with H&E stained slides

HARVARDMEDICAL SCHOOL

The color calibration slide for whole slide scanner

This is Manually made

MethodUncorrected

ImagePolynomial transformation

Gamma correction

Corrected Image

Polynomial function:

Polynomial transformation

HARVARD

MEDICAL

SCHOOLReference color of the color patches

Color of the patches as produced by a particular scanner

Each scanner will have its own Color transformation matrix

Color transformation matrix will be stored for used in color standardization

Color patches

Original Reference

Standardize using the original and reference color patches

Original Reference

Original - Produced by a whole slide scanner

Colors are not accurate enough

Reference - Produced by using spectral information of the patches

MASSACHUSETTSGENERAL HOSPITAL

PATHOLOGY

HARVARDMEDICAL SCHOOL

Results on H&E stained images…

Original Image Result of the color standardization

The color improves…Gamma =1

Original Image Result of the color standardization

Contrast between nuclei and other eosin stained tissue structures becomes better; color of red blood cells has been enhanced.

Red blood cells

Red blood cells

Nucleus Nucleus

Original Image Result of the color standardization

Texture pattern is clearer…

Original Image Result of the color standardization

The color attributes of the tissue components improves

Original Image Result of the color standardization

The nuclei are clearly delineated…

Regardless of the image composition, i.e. what type of tissue structures are present, the current color standardization equally results to improved color attributes of the image.

We can observed more details in the standardized image.

MASSACHUSETTSGENERAL HOSPITAL

PATHOLOGY

HARVARDMEDICAL SCHOOL

HARVARDMEDICAL SCHOOL

This is Manually made

Using these two slides would further improve the current results…

Calibration slides… Color calibration slides – color chart

H&E stained slide ( mouse embryo)

H&E stained slide of a mouse embryoOptimally stained

Conclusions

MASSACHUSETTSGENERAL HOSPITAL

PATHOLOGY

HARVARDMEDICAL SCHOOL

Utilization of a calibration slide is practical and easy to implement to standardized the color of digital slides

Color standardization of digital slides is possible using the color calibration slide

Future works Include a grey-level balancing in the method and add neutral colors to the color calibration slide to further improve the results Use the optimally stained embryo slide together with the color calibration slide Extend the method to special stains.

MASSACHUSETTSGENERAL HOSPITAL

PATHOLOGY

HARVARDMEDICAL SCHOOL

Thank you……