Design and characterization of a novel multimodal fiber-optic probe and spectroscopy system for skin cancer applications

Abstract

The design and characterization of an instrument combining Raman, fluorescence, and reflectance spectroscopic modalities is presented. Instrument development has targeted skin cancer applications as a novel fiber-optic probe has been specially designed to interrogate cutaneous lesions. The instrument is modular and both its software and hardware components are described in depth. Characterization of the fiber-optic probe is also presented, which details the probe's ability to measure diagnostically important parameters such as intrinsic fluorescence and absorption and reduced scattering coefficients along with critical performance metrics such as high Raman signal-to-noise ratios at clinically practical exposure times. Validation results using liquid phantoms show that the probe and system can extract absorption and scattering coefficients with less than 10% error. As the goal is to use the instrument for the clinical early detection of skin cancer, preliminary clinical data are also presented, which indicates our system's ability to measure physiological quantities such as relative collagen and nicotinamide adenine dinucleotide concentration, oxygen saturation, blood volume fraction, and mean vessel diameter.

FIG. 1.

Schematics of the MMS probe. The left panel, (a), shows the probe distal end front view. The right panel, (b), shows the assembly exploded view with optical elements such as the filters and front lens identified along with the collection and delivery fibers for all three modalities.

FIG. 2.

Photo of the MMS clinical system (left) and the MMS probe (right).

FIG. 3.

Comparison between fitted (LUT) and expected (experimental) for the reduced scattering coefficient (left) and absorption coefficient (right).

FIG. 4.

Sample in vivo Raman spectra obtained using the MMS probe for various body locations. Exposure time is 4 s.

FIG. 5.

MMS clinical data of a basal cell carcinoma for Raman (left), diffuse reflectance (right), and intrinsic fluorescence (right) modalities. Physiological quantities obtained from DRS spectral fitting were ${\mu }_s^{\prime }\left({\lambda }_0\right)=1.7{\mathrm{mm}}^{-1}$, υ = 2.87, α = 0.46, and D_vessel = 0.48 μm and χ_nadh = 0.55 and χ_collagen = 0.45 from the intrinsic fluorescence spectral fitting.