Integrated photoacoustic microscopy and optical coherence tomography for in vivo imaging of choroidal neovascularization

Abstract

Purpose : Wet age-related macular degeneration (AMD) is the leading cause of irreversible blindness in the developed world. Early detection of choroidal neovascularization (CNV) may help treatment outcomes of AMD. We are aiming to develop a cutting-edge multimodal retinal imaging system for early detection and diagnosis of CNV.

Methods : The multimodal imaging system (Figs. 1A and 1B) integrates three modalities: photoacoustic microscopy (PAM), optical coherence tomography (OCT), and fluorescence microscopy. The PAM system employs a wavelength-tunable pulsed laser (Ekspla NT-242, Lithuania), a galvanometer, a scan lens, an ocular lens, and an ultrasonic transducer (center frequency: 35 MHz). The OCT system was acquired from Thorlabs (Ganymede-II-HR) and coaxially aligned with the PAM. The fluorescence microscopy shares the same source as PAM and consists of a filter, a lens, and a photodiode. High-speed imaging was achieved by taking advantage of the high pulse repetition rate (1 kHz) of the laser and fast scanning rate (36 kHz) of the galvanometer. CNV model was induced in three rabbits using a photocoagulator laser (Vitra, Quantel Medical), and its onset and propagation were serially monitored immediately after and at three-day intervals using the platform.

Results : A chrome grating was imaged at the focal plane of the scan lens for lateral resolution calibration, which is quantified as 2.6 μm (Figs. 1C and 1D). Grape tissue was imaged to verify the performance of the OCT (Fig. 1E). In vivo PAM image of a rabbit shows that the system can distinguish single blood vessels (Fig. 1G), which is validated through the fundus photograph in Fig. 1F. In vivo OCT image demonstrates that the system can visualize induced CNV (Fig. 1H).

Conclusions : A high-speed, high-resolution, multimodal retinal imaging system has been developed. Preliminary results show that the system can resolve single choroidal blood vessels and visualize laser-induced CNV. By incorporating cutting-edge technologies, the work will shed new light on early detection and diagnosis of CNV.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

Fig. 1 Multimodal imaging of CNV. A and B: Schematic diagram and physical setup. C: PAM image of a chrome grating. D: Fitted line spread function (LSF) of the edge in the red box in C. E: OCT image of grape tissue. F: Fundus photograph of a rabbit eye. G: PAM image revealing single blood vessels. H: OCT image visualizing laser-induced CNV.