Degree of optical polarization as a tool for detecting melanoma: proof of principle.

Daniel C Louie,Tim K Lee,Harvey Lui,Jamie Phillips,Lioudmila Tchvialeva,Sunil Kalia,Wei Wang

doi:10.1117/1.jbo.23.12.125004

Abstract

Determining the optical polarization properties of a skin lesion is a proposed method to differentiate melanoma from other skin lesions. We developed an in vivo Stokes polarimetry probe that fires a laser of known polarization at the skin and measures the Stokes parameters of the backscattered light in one shot. From these measured Stokes parameters, we can calculate the degree of polarization (DOP). Through testing on rough skin phantoms, a correlation between backscattered DOP and skin roughness was identified for both linear and circular input polarization, the latter of which was found to be more useful. In a pilot clinical trial of 69 skin lesions in vivo, it was found that the mean DOP for melanoma (linear input on melanoma: 0.46 ± 0.09) was greater than that of other lesions (linear input on all other lesions: 0.28 ± 0.01). This separation is greater for circular polarized input light, and it is likely that circular polarized light's greater sensitivity to surface roughness contributes to this result. In addition, all skin lesions demonstrated a stronger depolarizing effect on circular polarized light than linear polarized light. We have identified DOP as a potentially useful measurement to identify melanoma among other types of skin lesions.

Highlights

Skin cancer is the most common form of cancer in North America, Australia, and other predominantly fair-skinned populations worldwide, and the incidence of skin cancer has been rapidly increasing over the past several decades.[1]
A oneshot Stokes polarimetry probe was used to analyze the polarimetric properties of skin lesions in vivo by measuring the Stokes parameters of backscattered laser light in both linear and circular initial polarization
Through trials on rough skin phantoms, it was demonstrated that there is a correlation between backscattered degree of polarization (DOP) and skin roughness

Summary

Introduction

Skin cancer is the most common form of cancer in North America, Australia, and other predominantly fair-skinned populations worldwide, and the incidence of skin cancer has been rapidly increasing over the past several decades.[1]. Polarization has been applied to reduce glare in clinical photography,[4] increase sensitivity to collagen in confocal microscopy,[5] and measure birefringence in optical coherence tomography.[6] Of particular interest is direct polarimetry for cancer screening and diagnosis. This has been typically approached with a Mueller matrix model, in which the diagnostic parameters of tissue are determined by the degree to which input polarized light is altered.

Methods

Results

Conclusion