In vivo photoacoustic imaging of chorioretinal oxygen gradients

Abstract

Chorioretinal imaging has a crucial role for the patients with chorioretinal vascular diseases, such as neovascular age-related macular degeneration. Imaging oxygen gradients in the eye could better diagnose and treat ocular diseases. Here, we describe the use of photoacoustic ocular imaging (PAOI) in measuring chorioretinal oxygen saturation (CR - sO2) gradients in New Zealand white rabbits (n = 5) with ocular ischemia. We observed good correlation (R2 = 0.98) between pulse oximetry and PAOI as a function of different oxygen percentages in inhaled air. We then used an established ocular ischemia model in which intraocular pressure is elevated to constrict ocular blood flow, and notice a positive correlation (R2 = 0.92) between the injected volume of phosphate buffered saline (PBS) and intraocular pressure (IOP) as well as a negative correlation (R2 = 0.98) between CR - sO2 and injected volume of PBS. The CR - sO2 was measured before (baseline), during (ischemia), and after the infusion (600-μL PBS). The ischemia-reperfusion model did not affect the measurement of the sO2 using a pulse oximeter on the animal's paw, but the chorioretinal PAOI signal showed a nearly sixfold decrease in CR - sO2 (n = 5, p = 0.00001). We also observe a sixfold decrease in CR - sO2 after significant elevation of IOP during ischemia, with an increase close to baseline during reperfusion. These data suggest that PAOI can detect changes in chorioretinal oxygenation and may be useful for application to imaging oxygen gradients in ocular disease.

Noninvasive staging of pressure ulcers using photoacoustic imaging

“…These initial data were collected with a laser‐based scanner; however, these systems are bulky, delicate, and expensive. More recently, LED‐based photoacoustic imaging system has offered important improvements in size, cost, and stability . Thus, we also evaluated these ulcers with LED‐based photoacoustics.…”

The double-stage delay-multiply-and-sum image reconstruction method improves imaging quality in a LED-based photoacoustic array scanner

“…Finally, we evaluated the utility of DS-DMAS with in vivo data. We and others [ 20 , 21 , 53 , 54 ] have previously imaged the retina with photoacoustic imaging, and use it as an example here. The reconstructed images obtained by the algorithms are shown in Fig.…”

“…Finally, an optical absorption distribution map (image) of the target/tissue can be obtained using mathematical processing of this data [ [10] , [11] , [12] , [13] , [14] , [15] ]. PAI has been used in tumor detection [ 16 , 17 ], cancer detection and staging [ 18 , 19 ], ocular imaging [ 20 , 21 ], monitoring oxygenation in blood vessels [ 22 , 23 ], molecular imaging [ 24 ], functional imaging [ 25 , 8 , 26 ], oncology [ 27 , 28 ], ophthalmology [ 29 ], cardiology [ 30 ], etc.…”

Concurrent photoacoustic and ultrasound microscopy with a coaxial dual-element ultrasonic transducer

“…We have also implemented an alternative design with commercial focused ultrasonic transducer, for readers without access to the customized DE-UST. While hemoglobin was used as the endogenous chromophore for PA imaging in this study [23], multiple wavelengths could be incorporated into the system in the future for measuring oxygen saturation of hemoglobin (sO 2 ) [29][30][31] and oxygen partial pressure (pO 2 ) [24,32,33], as well as for molecular imaging of exogenous probes [2,34,35]. Our PAUS system can also be used to image microbubbles to provide blood flow velocity [36][37][38] and nonlinear mechanical properties [39][40][41].…”