Kinetics of Transient Tissue Transparency via Refractive Index Engineering (T3RIE) for <i>In Vivo</i> Optical Imaging

High-resolution, non-invasive dynamic imaging of internal anatomical structures is a central goal in biomedical imaging, ranging from applications in fundamental biological research to clinical care. Optical imaging modalities, despite their high resolution, are inherently limited by shallow penetration depth in tissue. Transient Tissue Transparency via Refractive Index Engineering (T3RIE) has emerged as a promising strategy to enable non-invasive optical imaging in living organisms. However, in vivo control over the kinetics and effectiveness of tissue transparency remains poorly understood. To address this gap, we developed an approach using an implanted self-illuminating light source to quantitatively assess changes in tissue transparency by directly measuring light transmittance. Furthermore, we introduced a complementary method employing a broad reflective indicator light to monitor local reflectance dynamics. Together, these strategies establish a foundation for real-time, non-invasive monitoring of tissue transparency in live animals, paving the way for advanced imaging applications and potential clinical translation.