The STORM and PALM techniques developed in the past decade in optics allow resolving sub-wavelength structures based on localization. Here, we demonstrate that localization can be used to go beyond the diffraction limit in acoustic resolution photoacoustic imaging. To this end, a proof-of-concept photoacoustic localization experiment was conducted. A silicone sample containing five parallel microchannels (channel’s width is 40μm; center-to center distance equals 180μm), fed with a water suspension of 10μm red coated microbeads at a constant flow rate, was exposed to 5ns laser pulses (wavelength=532nm, fluence=3.0 mJ/cm2). At each laser pulse the microbeads produced a photoacoustic response that was then detected by a linear US array (128 elements, L22-8v, Verasonics, USA) connected to an acquisition device (High Frequency Vantage 256, Verasonics, USA). The design of the microfluidic circuit and the concentration of microbeads ensured sparse but random distribution of microbeads at any moment. The photoacoustic data was processed by a delay-and-sum algorithm, whose output was correlated with the system’s PSF function to obtain the position of microbeads at each laser shot. These positions were accumulated onto the localization grid providing a super-resolved image of the micro-fluidic circuit. Although being indistinguishable in a conventional US image, the microchannels dimensions and position were accurately reconstructed on the localization grid with 34.8±1.3μm for the channel’s width and 179±2.5μm for the center-to-center distance. As the first demonstration of super-localization in photoacoustics, these results constitute the first step towards imaging of red blood cells at depth beyond the acoustic diffraction limit.
Conference Presentations are recordings of oral presentations given at SPIE conferences and published as part of the conference proceedings. They include the speaker's narration along with a video recording of the presentation slides and animations. Many conference presentations also include full-text papers. Search and browse our growing collection of more than 12,000 conference presentations, including many plenary and keynote presentations.