Fig. 3.

A melanoma cell. (A) Optical brightfield image (inset shows optical image of the cell overlaid with a fluorescent image of the stained nucleus), and (B–E) photoacoustic images of a single fixed B16-F1 melanoma cell. Three transducers were used to measure the photoacoustic signal from the same cell: (B) 200, (C) 375, and (D) 1200 MHz. As the transducer frequency increases, the ability to resolve the small micron-sized particles increases. (E) A B-scan image around the nucleus as indicated by the arrow on (D). Scale bar A–D is 30 μm, scale bar on E is 15 μm.