Refractive index of some mammalian tissues using a fiber optic cladding method

Area of Science:

• Biomedical Optics
• Materials Science

Background:

• The refractive index (n) of mammalian tissues is a critical optical property, yet existing values are often imprecise and lack experimental validation.
• Previous estimations relied on water's refractive index or theoretical calculations based on elemental composition, leading to inaccuracies.

Purpose of the Study:

• To develop a simple, rapid, and reliable method for the experimental determination of the refractive index of mammalian tissues.
• To establish precise refractive index values for various mammalian tissues at a specific wavelength.

Main Methods:

• Utilized a quartz optical fiber, replacing its standard cladding with the target tissue.
• Applied the principle of internal reflection, measuring the angle of the emergent light cone.
• Calculated the tissue's refractive index using known indices of air and quartz.

Main Results:

• Determined refractive indices for bovine, porcine, canine, and human tissues at 632.8 nm.
• Found that, with few exceptions, tissue refractive indices consistently fall within the 1.38-1.41 range.
• Observed that species type did not significantly impact the refractive index; bovine muscle exhibited normal dispersion.

Conclusions:

• The developed optical fiber method provides accurate and reliable refractive index measurements for mammalian tissues.
• The established refractive index range of 1.38-1.41 is broadly applicable across mammalian species.
• Tissue denaturation was found to significantly alter the refractive index, highlighting its sensitivity to structural changes.