Poster R18 - Simultaneous color and birefringence imaging using multispectral polarized light

Introduction: Polarized light imaging (PLI) has been an effective method for obtaining organizational information about collagen and other birefringent materials at both micro and macroscopic levels. However, typical PLI images lack information about the non-birefringent part of the tissue, which is essential for providing important contextual information. Recent advances in PLI have allowed simultaneous capture of color and birefringent information in thin sections using transmission mode. In this study, we demonstrate a high-speed polarized light imaging technique that can be used to obtain both color and birefringent information in both transmission and reflection imaging modes. We term this technique ColorPOL.

Materials and

Methods: Illumination: We adopted a digital light processing (DLP) projector as the illumination source. The light engine of the projector consists of red, green, and blue LEDs. The projector, however, does not natively support rapidly changing the illumination colors during the operation. To circumvent this limitation, we developed a separate light engine control system based on a Raspberry Pi and dedicated LED drivers. With the LED driver, the brightness of each LED can be adjusted and the LED can be individually triggered.

Image acquisition: A polarization-sensitive camera was used for acquiring images. The camera was synchronized with the illumination to achieve high-speed image acquisition at 75 frames/second.

A custom Python script was developed to generate trigger signals for LEDs and the camera acquisition. LEDs were triggered sequentially. A camera trigger was sent after the LED trigger to acquire an image under the current illumination.

We imaged a pre-prepared histology slide of human skin with a microscope configuration and a chicken thigh with a widefield configuration to demonstrate its capabilities.

Results, Conclusions, and Discussions: Both the true color and birefringent information of the tissue can be accurately visualized and quantified. Additionally, in reflection mode, tissue deformation and movement can be faithfully recorded, facilitating applications such as image-guided surgery and mechanical testing. In summary, ColorPOL is capable of providing rich tissue information and is versatile and valuable in both basic science and translational research.

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