Spatially-Resolved Multiply-Excited Autofluorescence and Diffuse Reflectance Spectroscopy: SpectroLive Medical Device for Skin In Vivo Optical Biopsy

Walter Blondel,Alain Delconte,Amélie Gavoille,Marine Amouroux,Grégoire Khairallah,Frédéric Marchal

doi:10.3390/electronics10030243

Abstract

This contribution presents the development of an optical spectroscopy device, called SpectroLive, that allows spatially-resolved multiply-excited autofluorescence and diffuse reflectance measurements. Besides describing the device, this study aims at presenting the metrological and safety regulation validations performed towards its aimed application to skin carcinoma in vivo diagnosis. This device is made of six light sources and four spectrometers for detection of the back-scattered intensity spectra collected through an optical probe (made of several optical fibers) featuring four source-to-detector separations (from 400 to 1000 µm). In order to be allowed by the French authorities to be evaluated in clinics, the SpectroLive device was successfully checked for electromagnetic compatibility and electrical and photobiological safety. In order to process spectra, spectral correction and metrological calibration were implemented in the post-processing software. Finally, we characterized the device’s sensitivity to autofluorescence detection: excitation light irradiance at the optical probe tip in contact with skin surface ranges from 2 to 11 W/m², depending on the light source. Such irradiances combined to sensitive detectors allow the device to acquire a full spectroscopic sequence within 6 s which is a short enough duration to be compatible with optical-guided surgery. All these results about sensitivity and safety make the SpectroLive device mature enough to be evaluated through a clinical trial that aims at evaluating its diagnostic accuracy for skin carcinoma diagnosis.

Highlights

The gold standard method for skin cancer diagnosis is histo-pathology [1].This method requires the microscopic examination of a tumor sample, called a ‘biopsy’, taken from its original organ through a surgical procedure
In previous studies using an optical bench developed to the level 3 of the TRL scale (TRL stands for Technological Readiness Level; this scale is described in the ISO 16290:2013 standard) and performed on a preclinical mouse skin cancer model [23,33,34], allowed us to validate the proof of concept: we demonstrated that the combination of information from
Concerning the 365 nm excitation wavelength it does not match with the porphyrin absorption maximum, we found interesting to display the corresponding results because it is the shortest wavelength that the SpectroLive device is equipped with and shorter wavelengths are supposed to probe biological tissues more superficially than longer ones

Summary

Introduction

The gold standard method for skin cancer diagnosis is histo-pathology [1].This method requires the microscopic examination of a tumor sample, called a ‘biopsy’, taken from its original organ through a surgical procedure. Once the biological sample is surgically resected, it is fixed (for 12–24 h in formalin most often), dehydrated (several baths of increasing concentrations of ethanol), included into paraffin, cut into 5 μm-thick slices, colored (hematoxylin and eosin most often) and stuck on a glass slide for microscopic evaluation by a pathologist. This whole process has two drawbacks: it is invasive and time-consuming, i.e., two to five days are necessary from biopsy to diagnostic for regular procedures. Extemporaneous procedure induces partial loss of the biological materials that is no longer available for further staining

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