High Resolution Multimodal Photoacoustic Microscopy and Optical Coherence Tomography Visualization of Choroidal Vascular Occlusion

Abstract

Photoacoustic microscopy is a novel, non-ionizing, non-invasive imaging technology that evaluates tissue absorption of short-pulsed light through the sound waves emitted by the tissue and has numerous biomedical applications. In this study, a custom-built multimodal imaging system, including photoacoustic microscopy (PAM) and optical coherence tomography (OCT), has been developed to evaluate choroidal vascular occlusion (CVO). CVO was performed on three living rabbits using laser photocoagulation. Longitudinal imaging of CVO was obtained using multiple imaging tools such as color fundus photography, fluorescein angiography, indocyanine green angiography (ICGA), OCT, and PAM. PAM images were acquired at different wavelengths, ranging from 532 to 700 nm. The results demonstrate that the CVO was clearly observed on PAM in both two dimensions (2D) and 3D with high resolution longitudinally over 28 days. In addition, the location and margin of the CVO were distinguished from the surrounding choroidal vasculature after the injection of ICG contrast agent. PAM imaging was achieved using a laser energy of approximately 80 nJ, which is about half of the American National Standards Institute safety limit. The proposed imaging technique may provide a potential tool for the evaluation of different chorioretinal vascular disease pathogeneses and other biological studies.

Gold Nanorod Enhanced Photoacoustic Microscopy and Optical Coherence Tomography of Choroidal Neovascularization

“…For applications in ophthalmology, PAM has been integrated with OCT, SLO, and fluorescence microscopy to combine the benefits of each imaging modality. These multimodality imaging systems have been extensively explored for identification of retinal vessels (RVs), choroidal vessels (CVs), retinal pigment epithelium (RPE) cells, − melanin, corneal neovascularization, retinal neovascularization (RNV), , laser-induced injury, retinal vein occlusion, − and choroidal neovascularization (CNV) in rodents ( e.g. , mice and rats) and large animal eyes ( e.g.…”

The Development and Clinical Application of Innovative Optical Ophthalmic Imaging Techniques

“…Combining PAM with OCT imaging establishes complementary structural and vascular contrast, which has been used to capture neovascularization associated with DR and wet AMD in animal models (483)(484)(485)(486)(487). Nguyen et al further demonstrated that the multimodal combination of PAM with OCT has utility in monitoring vascular and structural changes associated with vascular occlusion (488,489). PAM has additionally been combined with Doppler OCT to measure retinal oxygen metabolism with the potential to aid in an earlier diagnosis of DR, AMD, and glaucoma (478,490).…”

Advances in multimodal imaging in ophthalmology

“…[255][256][257][258][259] Combined PAM and OCT has also shown advantages for visualizing vascular and structural changes associated with retinal vein occlusion (Figure 7) and choroidal vascular occlusion over FA. 260,261 Finally, PAM and OCT can be used to quantify Source: Reprinted with permission from Carrasco-Zevallos and colleagues 243 and Ehlers and colleagues. 249 4D, 4-dimensional; iOCT, intraoperative optical coherence tomography.…”