Contrast mechanisms in pump-probe microscopy of melanin

TL;DR

This paper develops a polarization-controlled pump-probe microscopy method to decompose melanin signals in tumors, enabling better diagnosis of melanoma by highlighting disaggregation-related molecular mechanisms.

Contribution

It introduces a systematic approach to interpret complex melanin signals by decomposing nonlinear processes, aiding melanoma diagnosis and applicable to various samples.

Findings

False-colored images correlate with clinical concern in melanoma tumors

Polarization control helps identify molecular mechanisms of melanin disaggregation

Method can be applied broadly to different biological samples

Abstract

Pump-probe microscopy of melanin in tumors has been proposed to improve diagnosis of malignant melanoma, based on the hypothesis that aggressive cancers disaggregate melanin structure. However, measured signals of melanin are complex superpositions of multiple nonlinear processes, which makes interpretation challenging. Polarization control during measurement and data fitting is used to decompose signals of melanin into their underlying molecular mechanisms. We then identify the molecular mechanisms that are most susceptible to melanin disaggregation and derive false-coloring schemes to highlight these processes in biological tissue. We exemplary demonstrate that false-colored images of a small set of melanoma tumors correlate with clinical concern. More generally, our systematic approach of decomposing pump-probe signals can be applied to a multitude of different samples.