# Design and Validation of a Multimodal Diffuse Reflectance and Spatially Offset Raman Spectroscopy System for In Vivo Applications

## TL;DR

A new handheld system combines two light-based techniques to measure both surface and deeper layers of tissues, validated on chicken tissue and human skin.

## Contribution

A novel multimodal system integrating diffuse reflectance and spatially offset Raman spectroscopy for in vivo subsurface and surface measurements.

## Key findings

- The system successfully collected subsurface and surface measurements from chicken breast tissue.
- Distinct Raman peaks were observed in human skin measurements depending on the probe configuration.
- Melanin-related Raman peaks were prominent in surface measurements but not in subsurface ones.

## Abstract

We report on the development of a multimodal spectroscopy system, combining diffuse reflectance spectroscopy (DRS) and spatially offset Raman spectroscopy (SORS). A fiber optic probe was designed with spatially offset source–detector fibers to collect subsurface measurements for each modality, as well as ball lens‐coupled fibers for superficial measurements. The system acquires DRS, zero‐offset Raman spectroscopy (RS) and SORS with good signal‐to‐noise ratio. Measurements on chicken breast tissue demonstrate that both DRS and RS can acquire spectra from similar depths within tissue. Measurements acquired from the skin of a human volunteer demonstrate distinct Raman peaks at 937 and 1755 cm−1 that were unique to the zero‐offset ball lens configuration and 718 and 1089 cm−1 for the spatially offset setting. We also identified Raman peaks corresponding to melanin that were prominent in the superficial measurements obtained with the ball lens‐coupled fibers but not in the spatially offset fibers.

This work presents the combination of diffuse reflectance spectroscopy and spatially offset Raman spectroscopy into a multimodal system with a fiber optic handheld probe and optical switch. The probe was designed with a spatially offset source–detector configuration to collect subsurface measurements for each modality, as well as ball lens‐coupled fibers for surface measurements. The results of validation studies using the system with measurements on a chicken breast tissue phantom consisting of fat and muscle tissue, as well as measurements acquired from the skin of a human volunteer, are shown.