Fig. 3: Single- and dual-wavelength FDOM imaging of a mouse ear in vivo.

a FDOM imaging at 488  nm. Cyan color represents the reconstructed image, namely, \({\mathrm{Recon}}_{FSR}\left( {x,y,\mathop {\sum}\nolimits_{i = 1}^n f } \right)\), from nine equally spaced frequencies in the range of 10 to 50 MHz. Scale bar, 150 μm. b–d Individual images obtained at modulation frequencies of 10, 30, and 50 MHz, which depict the structures in the dashed box in panel a. Scale bar, 50 μm. e SNR as a function of n frequencies that were used for FSR reconstruction. An asymptotic improvement is observed for n > 8 discrete frequencies. f A profile view of the dashed box in panel a, which is delineated by a white dashed arrow. It demonstrates the relationship between modulation frequency and imaging resolution. Yellow crosses highlight the imaging resolution as a function of the modulation frequency: faster modulation (50 MHz) can clearly resolve small structures, even down to 4 µm, while slower modulation (10 MHz) cannot. g–l Hybrid FDOM/multiphoton imaging of a mouse ear following the injection of melanoma cells. g An overlay image that was obtained using four label-free microscopy modalities: FDOM at 488 nm and 808 nm, SHG at 522 nm, and THG at 348 nm. h A bright-field image validating the results that were obtained via hybrid microscopy; MC, melanoma cells. i FDOM imaging at 488 nm showing vasculature and melanoma cells. j An FDOM image at 808 nm that shows B16F10 melanoma cells injected in the mouse ear. k An SHG image showing the collagen distribution in the epidermis. l A THG image that shows the tissue morphology; predominantly keratinocytes and hair follicles