Contrast mechanisms in pump-probe microscopy of melanin

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 are 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 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.

Recent Advances in Characterization of Melanin Pigments in Biological Samples

“…Pump-probe imaging techniques can be used to distinguish between EM and PM at the dermo-epidermal junction to assess the metastatic potential of melanin lesions and to characterize the packing of melanin oligomers within aggregates [198][199][200][201][202][203][204][205][206][207]. Pumpprobe microscopy is a combination of laser scanning microscopy and pump-probe spec-troscopy [204].…”

Non-destructive three-dimensional imaging of artificially degraded CdS paints by pump-probe microscopy

“…Here, we demonstrate the use of pump-probe microscopy, a nonlinear optical technique, to nondestructively generate three-dimensional, high-resolution maps of paint structures and to track the degradation process on a microscopic scale. Traditionally used in biological imaging [18,19], this technique has recently been applied in cultural heritage to create virtual cross-sections of paintings [20], differentiate red organic dyes [21], and identify the vermilion degradation product in a 14th-century painting [22].…”

Towards high-accuracy noninvasive ocular melanoma imaging and prognostics

“…Being able to accurately discriminate what type of melanin and surrounding tissue is present in the eye has potential to better prognose disease outcome. The previous successful efforts in discriminating different types of melanin were performed using pump-and-probe spectroscopy 4,5 , which assumes a relatively thin sample taken from a patient through a biopsy. We are trying to overcome the necessity for a biopsy by performing in situ analysis of melanin structure.…”