Photoacoustic Imaging the Relative Size of Optical Absorbing Aggregates

Traditional photoacoustic (PA) images are formed from the amplitudes of the envelope-detected PA data. This approach largely ignores encoded spectral information that may provide more insight about tissue function and pathology. Here we introduce a new PA graphic equalization (PAGE) algorithm that divides the PA signal into a collection of frequency bands that are related to different-sized optical absorbers. Radiofrequency (RF) PA data were obtained using a Vevo 3100 with LAZR-X system (Fujifilm VisualSonics Inc). Experiments were performed using phantom materials and narrow translucent silicone tubes with clotting blood (inner diameter of 0.30, 0.51, or 0.64 mm). Phantoms were created by embedding an agar solution with fluorescent microspheres having diameters of 10 to 45 µm or 106 to 125 µm. Overall, preliminary in vitro results demonstrate that PAGE processing can distinguish micrometer-sized optical absorbers of varying size.