Harmonic Generation Optical Biopsy in the Oral Diagnostics

Objectives: Early disease diagnosis and intervention are critical for clinical success. Pathological diagnosis has been recognized as the final gold standard for definite diagnosis in many diseases. However, traditional biopsy process require taking away tissue physically and may subject to risks of seeding tumor cells, infectious pathogen, bleeding and bias from sampling area of interest. Methods: We developed stain-free in vivo optical biopsy to provide histology examine resolution and minimize energy deposition to the tissue through the use of harmonic generation modality. This harmonic generation microscopy (HGM) system used home-built Cr:forsterite laser operates at 1230 nm and below 100 mW average power as the light source. The NIR range enabled higher penetration depth and sub-micron resolution could be achieved without true energy deposition in the interacted tissues. Results: In this report, we present real-time live tomographic imaging of the hamster oral cancer angiogenic blood vessels and the dynamics of blood cells in the vessel. We also demonstrate the first in vivo optical virtual biopsy of human oral mucosa and a fibrous dysplasia lesion based on epi-HGM. We reveal the ability to image human epithelial cells and the subcellular organelles and collagen fibers in the lamina propria as well as osteoblast cells in the fibrosseous lesion. Besides, we discover that 4% edible acid applied on the oral mucosa could significantly enhance THG contrast of the nucleus, and the enhancement is found to be decayed due to the metabolic clearance of the contrast enhancer by the oral mucosa. Conclusions: With harmonic nonlinearity, the combined epi-THG and epi-SHG microscopy is a great imaging tool for in vivo optical virtual biopsy of head and neck lesions. The study reveals a promising future for its clinical application for noninvasive in vivo diseases diagnosis.