Researchers have developed a new technique for three-dimensional (3D) refractive index reconstruction of biological samples, termed volumetric quantitative transmission optical coherence tomography (VQ-TOC). This method enables high-resolution imaging of internal structures without the need for labels or stains, which is crucial for studying living tissues. VQ-TOC overcomes the limitations of existing techniques by combining the sensitivity of optical coherence tomography (OCT) with the ability to measure the refractive index, a fundamental property that reveals the composition and density of biological materials.

The key advance of VQ-TOC lies in its ability to perform volumetric refractive index measurements with unprecedented precision. Unlike other techniques that only provide two-dimensional information or require multiple sample rotations, this method allows for a complete 3D reconstruction from a single scan. This is achieved by using a "coherence gate" that filters scattered light, improving signal quality and enabling deep tissue penetration. The technique is particularly useful for studying complex cells and tissues, where refractive index heterogeneity is an indicator of biological and pathological processes.

The implications of this technology are significant for biomedical research and clinical diagnosis. The ability to visualize the 3D refractive index of living tissues with high resolution opens new avenues for studying diseases such as cancer, where changes in cell density and tissue composition are important markers. Furthermore, as a non-invasive and label-free technique, VQ-TOC can facilitate real-time monitoring of biological processes, such as embryonic development or response to drug treatments. Future research is expected to explore the application of this technique in a wider range of biological samples and clinical settings.