The feasibility to individually localize and manipulate individual particles flowing in blood can lead to important advances in super-resolution imaging, targeted drug delivery, and other fields. State-of-the-art optoacoustic (OA) tomographic imaging systems provide a unique high frame rate imaging capability in three dimensions, which can be exploited for this purpose if particles are sufficiently absorbing. In this work, we introduce silica-core microparticles with a polypyrrole-gold composite shell deposited with a layer-by-layer approach. Microparticles as small as 2 microns could be individually detected. Laser-induced motion of the particles was also observed, which provides a new means for motion control.
Comprehensive evaluation of microvascular function under normal and pathological conditions requires high-resolution three-dimensional microangiography capable of providing both morphological and functional information. Herein, we propose the stereovision Diffuse Optical Localization imaging (sDOLI) approach to attain transcranial volumetric brain microangiography through triangulation and stereo-matching of images collected with two short-wave infrared cameras. The spatio-temporal sparsity of flowing microparticles allows their precise localization while minimizing structural overlaps occurring in the dual-view projections. sDOLI is shown to preserve high spatial resolution which enables transcranial mapping of murine cortical microcirculation at capillary resolution while retrieving quantitative functional information across the entire mouse cortex.
High-intensity focused ultrasound (HIFU) capitalizes on both heating and cavitation effects for the treatment of several conditions. Optoacoustic (OA) imaging has previously been shown to provide high sensitivity to temperature changes and coagulation in HIFU-ablated tissues. In this work, we demonstrate the feasibility of real-time monitoring of heating and cavitation with a hybrid optoacoustic-ultrasound (OPUS) imaging system based on a multi-segment transducer array. The OPUS results in experiments with liver tissues ex-vivo and a mouse post-mortem were validated with thermal camera measurements and with cryo-sections of the mouse. The suggested approach thus holds promise to be clinically translated.
KEYWORDS: Animals, Optoacoustics, Head, Spherical lenses, Tomography, Light sources and illumination, Imaging systems, Data acquisition, Whole body imaging, In vivo imaging
Small animal preclinical research is indispensable to study human disease progression and to monitor potential treatment therapies. Optoacoustic tomography has been recognized as a powerful imaging modality for preclinical whole-body imaging of rodents. In particular, spiral volumetric optoacoustic tomography (SVOT) capitalizes on the large angular coverage of a spherical transducer array to provide otherwise-unattainable optoacoustic images of mice. However, only thoracic and/or abdominal regions of the animal could be imaged with this approach. Efficient whole-body coverage indeed demands continuous acoustic coupling between the animal and the detector surface. In this work, we implement panoramic (3600) head-to-tail imaging of mice with SVOT combined with multi-beam illumination. For this, a dedicated animal holder enables uninterrupted acoustic coupling for whole-body scans. Proper coverage of cranial regions in addition to thoracic and abdominal regions is then feasible in a single set up. Self-gated motion rejection and dual speed-of-sound correction algorithms were employed to optimize the image fidelity. The developed system is highly suitable for label-free imaging of hemodynamics across individual organs, total body accumulation and clearance dynamics of molecular agents and drugs, as well as for monitoring responses to stimuli with unparalleled contrast and spatio-temporal
resolution.
Accurate visualization of biological events at scales in the order of seconds requires high frame rate acquisition of image data from living tissues. Yet, fast imaging performance commonly comes at the cost of limited field-of-view (FOV) and reduced image quality. Here we present single-sweep volumetric optoacoustic tomography (sSVOT) for whole-body imaging of mice from head to tail within 1.8 s. sSVOT capitalizes on a custom-made spherical matrix array transducer together with a multi-beam illumination approach, the latter playing a critical role in maximizing the effective FOV. We compare the performance metrics to the previously reported whole-body mouse imaging implementations.
Laser ablation (LA) is gaining acceptance for the treatment of tumors as a viable alternative to surgical resection. In parallel, optoacoustic tomography (OAT) has enabled defining new regimes for diagnosis and characterization of malignant neoplastic lesions with high sensitivity and specificity. Even though pulsed nanosecond lasers are commonly used for both imaging and therapeutic purposes, real-time thermal treatment monitoring with a single laser source has not been previously attempted. Herein, we demonstrate the feasibility of combined OAT and LA by percutaneous irradiation of subcutaneous tumors with a 100 mJ short-pulsed (~5 ns) laser operating at 1064 nm and 100 Hz pulse repetition frequency. The OAT images rendered with a spherical ultrasound transducer array enabled real-time monitoring of the LA lesion progression, which is essential for determining the optimal treatment end-point. Local changes in the optoacoustic signal intensity associated with the induced temperature changes as well as structural alterations in the tumor vasculature could clearly be observed. The optoacoustic volumetric projections further correlated with crosssections extracted from the excised tumors. This newly enabled capability anticipates new theranostic approaches in cancer research and treatment with potential applicability in a clinical setting.
Laser ablation (LA) represents a minimally invasive intervention that is gaining acceptance for the treatment of different types of cancer, leading to important advantages such as less pain and shorter recovery time. Accurate monitoring of ablation progression is crucial to prevent damage of non-cancerous tissues and optimize the outcome of the intervention. To this end, imaging techniques such as ultrasound, computed tomography or magnetic resonance imaging have been used for monitoring LA. However, these techniques feature important drawbacks such as the need of contrast agents, poor spatio-temporal resolution or high cost. Optoacoustics (OA, photoacoustic) has recently been shown to provide unique properties to monitor thermal treatments. Herein, we demonstrate the feasibility of optoacoustic laser-ablation (OLA) monitoring in a murine breast tumor model using a single short-pulsed 1064 nm laser source. The effect of irradiation was volumetrically tracked with the OA images acquired with a 256-element spherical array. Structural damage of the tissue was clearly seen during the LA procedure.
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