Vascular imaging is an essential tool for understanding tissue health in the diagnosis and treatment of disease, especially for applications in cancer and ophthalmology. This work explores the application of Photon Absorption Remote Sensing (PARS) microscopy to several established in vivo vasculature models including chicken embryo and mouse ear. Significant system improvements are presented which have enabled the repeatable acquisition of images that are larger, require less scan time, and capture detailed absorption contrast of both radiative and non-radiative relaxation. The presented work demonstrates PARS as a promising platform for future clinical evaluation of disease pathology and treatment efficacy.
Detailed vasculature imaging is a critical tool for understanding tissue health especially for applications in cancer and ophthalmic diagnostics. Photoacoustic remote sensing (PARS), a novel imaging technology, has previously been successfully applied for both structural and functional imaging of vasculature including in dermatologic and ophthalmic imaging while remaining non-contact and label-free. To provide better molecular specificity, this work demonstrates a total-absorption PARS imaging system which incorporates sensitivity to both non-radiative and radiative contrast. This additional contrast enables more advanced molecular unmixing (e.g. between melanin, hemoglobin, and oxyhemoglobin) which will prove essential for all PARS vasculature imaging systems.
In this work, a synchronized dual-modal imaging system is used for in-vivo, non-contact ophthalmic imaging. The apparatus is comprised of both Photoacoustic Remote Sensing (PARS) and Swept-Source Optical Coherence Tomography (SS-OCT) subsystems. The PARS utilizes a multi-wavelength excitation source to target hemoglobin absorption and an 830 nm interrogation source to detect photoacoustic signals. PARS provides the measurements for computing blood oxygen saturation (sO2) mapping in the mouse and rat eyes. Meanwhile, a 1060 nm SS-OCT is employed to obtain volumetric tissue structure. To our knowledge, this is the first report of non-contact functional photoacoustic imaging in ophthalmic applications.
A non-contact, dual-modal imaging apparatus is introduced which will be used to obtain the Metabolic Rate of Oxygen (mRO2) in the live murine eye, based on the blood flow rate and blood Oxygen Saturation (sO2) measurements. The apparatus is comprised of both Photoacoustic Remote Sensing (PARS) and Swept-Source Optical Coherence Tomography (SS-OCT) systems, operating synchronously. A phantom model will be imaged using the proposed system to validate the accuracy of the blood flow and sO2 measurements. To the best of our knowledge, this work would report for the first time, non-contact, in-vivo measurement of the mRO2 in the ophthalmic tissues.
A dual-modal optical imaging system combining photoacoustic remote sensing (PARS) and swept-source optical coherence tomography (SS-OCT) is presented. The PARS subsystem utilized a pulsed excitation beam at 532 nm confocal with a low-coherence interrogation beam centered at 830 nm to detect photoacoustic signals. The OCT subsystem employs a 1060 nm VCSEL swept source with a 60 kHz A-scan rate and 8 μm axial resolution in tissue. Volumetric images were acquired from carbon fibers and in-vivo biological tissues. To our knowledge, this is the first study demonstrating a combination of SS-OCT with optical-resolution photoacoustic microscopy for in-vivo, non-contact imaging of tissues.
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