title: Label-free imaging of melanoma with nonlinear photothermal microscopy.
abstract: Nonlinear photothermal microscopy, in which the intensity of the pump heating beam is modulated at f and the photothermal signal is extracted from the probe beam with a lock-in amplifier referred to 2f, is applied to the imaging of mouse melanoma without any staining. The pump and probe pulses, with central wavelengths of 488 and 632 nm, and a pulse duration of ∼100  ps, are filtered from a compact commercial supercontinuum fiber laser source. An auto-balanced detector is applied to accumulate the signal and remove the laser noise of the probe. The spatial resolution of the nonlinear photothermal imaging is enhanced by ∼18% in both theoretical calculations and experiments, compared with a linear photothermal mechanism, and the resolution enhancement is theoretically ∼42% compared with conventional optical microscopy. This imaging technique shows possibilities for the clinical evaluation of melanoma with a high contrast and spatial resolution.
authors.forename: Jinping
authors.initials: J
authors.lastname: He
authors.forename: Jun
authors.initials: J
authors.lastname: Miyazaki
authors.forename: Nan
authors.initials: N
authors.lastname: Wang
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Tsurui
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Kobayashi
mesh_terms: D000818:Animals; D006358:Hot Temperature; D008545:Melanoma / Q000473:pathology*; D051379:Mice; D008853:Microscopy / Q000379:methods*; D057054:Molecular Imaging / Q000379:methods*