1b) that correspond to the particle’s OA signals. Then, the OA images are superimposed after filtering each image to obtain local maximum pixels (bright dots in Fig. In LOT, multiple OA images are obtained at the same location using a portable volumetric OAT system that is equipped with a spherical array probe (Fig. applied the localization imaging approach to OAT to enhance the visualization of flowing particles that are embedded in an optical scattering medium in 3D and referred to this approach as localization optoacoustic tomography (LOT). applied a wavefront-shaping technology to squeeze the spatial resolution of OAT to smaller than the acoustic diffraction limit 7.Ĭompared to the previous results, Luís et al. demonstrated superresolution OAT beyond the acoustic diffraction limit by either probing the fluctuations of OA signals with dynamic optical speckle excitation or detecting the fluctuating OA signals from flowing optical absorbers 5, 6. In the optical diffusive domain, Thomas et al. developed superresolution photoactivated atomic force microscopy and improved the resolution to ~8 nm 4. In the optical ballistic domain, Lihong’s group explored subdiffraction OAM using either nonlinear optical saturation or photobleaching effects 2, 3. Recently, several attempts were made by multiple researchers to exceed these diffraction limits to achieve superresolution imaging. The resolutions of OAT in both regimes are limited by either the optical or acoustic diffraction limit. In the optical diffusive regime, the resolution is determined by the acoustic focus and/or ultrasound parameters, and this technology is referred to as acoustic-resolution OAT. In the optical ballistic regime, the lateral resolution of OA imaging is determined by the tight optical focus, and the technology is referred to as optical-resolution OA microscopy (OAM). OAT is mainly implemented in two domains: the optical ballistic regime (~1 mm in biological tissues). More importantly, the applications of OAT have been extended to include many clinical trials, such as early diagnosis and treatment monitoring of cancers, imaging of the bowel for diseases, human neuroimaging for diagnosing neurological defects, imaging of peripheral arteries and veins for detecting vascular disease, and intravascular imaging for characterizing plaque. Thanks to these hybrid technologies, the use of preclinical OAT to study cancer physiopathology, neural physiology, drug delivery, vascular diseases, etc., has spread globally to many laboratories. Through advances in ultrasound imaging technologies, OAT provides rich optical contrast while achieving high spatial resolution deep inside living subjects (up to several centimeters). OAT breaks the long-standing shallow imaging depth limitation of conventional optical imaging by forming an image using the optoacoustic (OA) effect. Optoacoustic (also referred to as photoacoustic) tomography (OAT) has been gaining popularity for preclinical and clinical imaging during the past couple of decades 1.
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