Combined shortwave infrared fluorescence and Raman for real-time, high-resolution imaging through tissue

About This Grant

PROJECT SUMMARY Optical imaging is a widely used technique in medicine and research, allowing tissue examination in a non- invasive manner. A significant limitation of optical imaging methods is that tissues scatter, reflect, and absorb light, making it difficult to obtain clear images of deeper structures. As a result, most optical imaging methods struggle to visualize tissues more than a few millimeters beneath the surface, even when using special contrast agents. Our research focuses on improving deep-tissue imaging by using shortwave infrared (SWIR) technology. SWIR imaging allows various modalities in one image, including SWIR Raman, absorption, and fluorescence imaging. SWIR imaging has better tissue penetration due to reduced scattering and provides increased contrast than near-infrared imaging when combined with clinically available dyes such as indocyanine green (ICG). One of our key goals in this proposal is to develop wide-field SWIR Raman imaging (SWIRRI), which allows us to understand the chemical composition of tissue in a label-free manner. Our preliminary studies have shown the ability to detail subcutaneous tissue composition by looking at the scattering of their molecules. In Aim 1, we will optimize the SWIRRI system for imaging above 1500 nm and quantify the depth and resolution of SWIRRI. We then apply this method in two areas: first, to study wound healing and infections, helping us distinguish between normal inflammation and bacterial infection; and second, to examine cancerous tumors, focusing on how they change surrounding tissues and help identify cancer spread to nearby lymph nodes. In our second aim, we create new fluorescent dyes that work effectively in the longer wavelengths of the SWIR spectrum above 1500 nm. While existing dyes like indocyanine green (ICG) are useful in SWIR imaging, they are inadequate for visualizing deep structures. We plan to develop new probes that are more efficient, produce higher contrast images, and can be used with current SWIR imaging systems already used in clinical trials. We will also combine our SWIRRI with these dyes to achieve higher molecular specificity and allow visualization of arterial flow not seen on SWIRI and detection of cancer metastasis. By combining Raman imaging and improved fluorescence imaging, this non-invasive modality can revolutionize medical diagnostics, surgical guidance, and disease monitoring.