Fig. 1. Handheld multispectral photoacoustic imaging probe and system for lipid imaging

Fig. 2. Photoacoustic imaging and spectral analysis results of the oil sample in the tube and ex vivo adipose tissue. (a) Photograph of the PVC pipe filled with vegetable oil; (b) photoacoustic images of the oil sample inside the tube under 930 nm and 1210 nm excitation wavelengths, with H₂O and D₂O used as coupling media in the probe, respectively; (c) optical absorption spectra of H₂O, D₂O, and lipid in the near-infrared region; (d) photoacoustic spectral curves of the oil sample in the tube under different combinations of coupling media and excitation wavelengths [corresponding to the imaging conditions in (b)]; (e) photograph of ex vivo white adipose tissue from mouse; (f) photoacoustic spectra of ex vivo adipose tissue under D₂O coupling at different wavelengths; statistical comparison of photoacoustic signal intensities between the oil sample in the tube (g) and ex vivo adipose tissue (h) under 930 nm and 1210 nm excitations

Fig. 3. Photoacoustic imaging results of the pork belly phantom. (a) Photograph of pork belly phantom; (b) phantom photoacoustic images under 930 nm and 1210 nm excitations; (c) lipid images obtained via spectral unmixing at different wavelengths

Fig. 4. In vivo imaging result of abdominal adipose tissue in mouse