Handheld Three-Dimensional Cross-Polarized Microscope: In Vivo Imaging of Individual Pigmented Cells

Abstract

Dermatoscopy has been used to examine and diagnose pigmented lesions over the last fifty years. Dermatologists use dermatoscopes to identify patterns, structures, and colors for skin lesion diagnosis. However, there are still challenges in the specificity and selectivity of this lesion that is subjective to healthcare providers. One solution is visualizing individual pigmented cells to help monitor disease progression, diagnose lesions, and develop treatment plans. However, the current dermatoscope has a small NA and low magnification incapable of visualizing individual melanocytes. To combat this, we developed a cross-polarized microscope (CPM) with capabilities to visualize individual pigmented cells in 3D. This simple method used a high-NA, water-immersion objective lens, polarizing beam splitter, and tube lens to achieve in vivo imaging of individual pigmented cells. When light illuminates the skin, multiply scattered photons enter and exit without maintaining spatial information. However, melanin spectrally absorbs some of these photons, which provides colored shadows that can be observed with an imaging sensor. Additionally, we developed a modular objective lens holder to rapidly exchange objective lenses, altering the magnification. In this report, we evaluated the CPM capabilities of imaging skin lesions in vivo in a clinical setting. These preliminary results showed that CPM could allow us to reduce specular reflection, identify melanin distribution in the superficial layers of the skin, and visualize the cytoplasmic distribution of melanin.