Spatial frequency domain imaging


Spatial frequency domain imaging (SFDI) is the heart of our technology platform and the next generation in optical imaging. Invented by Modulim’s founder and CTO David Cuccia, Ph.D., and his colleagues at UC Irvine’s Beckman Laser Institute, SFDI provides accurate quantitative measurement of tissue oxygen availability, extraction, and saturation in tissue by incorporating the following patented proprietary processes:


  • Multispectral imaging: Multiple wavelengths of visible and near-infrared light. This broad spectrum of light provides clinically relevant surface (0-1mm deep) and subsurface (1-3mm deep) tissue contrast over large areas.
  • Structured illumination: A proprietary technique based on years of research that allows us to calculate tissue scattering and ensures accurate, repeatable measurements of hemoglobin across different tissue types.
  • Predictive algorithms: Ongoing development to translate SFDI outputs for clinical decision support.


By using all three in concert, we can better guide clinicians in doing what they need to do for their patients.

Light and tissue


In our circulatory system, hemoglobin delivers oxygen to the tissue. Because of the differences in absorption between oxyhemoglobin and deoxyhemoglobin, it is an excellent measure of tissue oxygenation. These values can then be used to calculate the arterial oxygenation (SaO2), which is one of the factors that reveals how the heart and lungs are functioning.


But there is more to the story.


Oxygen is also delivered and exchanged through the capillaries. At this level, the color and intensity of light output is no longer a simple function of hemoglobin absorption, but instead a complex combination of reflection, absorption, and light scattering (turbidity) from collagen and other tissue structures.


We see a similar scattering phenomenon every day when particles and clouds in the atmosphere scatter sunlight, making the sky appear different colors.


SFDI is a technique for clarifying turbidity non-invasively — like x-rays. However, unlike x-rays which use ionizing radiation, we use visible and near-infrared light, which are more benign and safer for patients and caregivers alike.