An Adjustable Dark-Field Acoustic-Resolution Photoacoustic Imaging System with Fiber Bundle-Based Illumination.

Yuhling Wang,De-Fu Jhang,Li-Tzong Chen,Tzong-Rong Ger,Tsung-Sheng Chu,Lun-De Liao,Wun-Shaing Wayne Chang,Chiung-Cheng Chuang,Chia-Hua Tsai,Chia-Hui Tsao

doi:10.3390/bios11080262

Abstract

Photoacoustic (PA) imaging has become one of the major imaging methods because of its ability to record structural information and its high spatial resolution in biological tissues. Current commercialized PA imaging instruments are limited to varying degrees by their bulky size (i.e., the laser or scanning stage) or their use of complex optical components for light delivery. Here, we present a robust acoustic-resolution PA imaging system that consists of four adjustable optical fibers placed 90° apart around a 50 MHz high-frequency ultrasound (US) transducer. In the compact design concept of the PA probe, the relative illumination parameters (i.e., angles and fiber size) can be adjusted to fit different imaging applications in a single setting. Moreover, this design concept involves a user interface built in MATLAB. We first assessed the performance of our imaging system using in vitro phantom experiments. We further demonstrated the in vivo performance of the developed system in imaging (1) rat ear vasculature, (2) real-time cortical hemodynamic changes in the superior sagittal sinus (SSS) during left-forepaw electrical stimulation, and (3) real-time cerebral indocyanine green (ICG) dynamics in rats. Collectively, this alignment-free design concept of a compact PA probe without bulky optical lens systems is intended to satisfy the diverse needs in preclinical PA imaging studies.

Highlights

Introduction iationsIn medical research, the use of optical imaging techniques is of particular interest because the intrinsic optical contrast found in in vivo systems can be used instead of having to inject contrast agents [1]
These results demonstrate that at 750 nm excitation, the signal-to-noise ratios (SNRs) is best at 100% laser power (95 mJ) with undiluted blue ink and is acceptable down to 50% laser power (46 mJ) and with blue ink diluted to 6.25%
We developed a dual-modality, compact AR-PA microscopy (PAM) imaging system consisting of a light-adjustable fiber-bundle-based illumination system integrated with a US platform and a high-frequency transducer

Summary

Introduction

The use of optical imaging techniques is of particular interest because the intrinsic optical contrast found in in vivo systems can be used instead of having to inject contrast agents [1]. The nonionizing radiation used in optical imaging techniques is safer for use in humans [2]. The strong light scattering in pure optical imaging modalities results in poor spatial resolution and shallow penetration depth [3,4,5]. An example is diffuse optical tomography (DOT), in which the scattering behavior of photons in tissue is modeled to reconstruct images [6]. As the spatial resolution is approximately 1/5th the imaging depth, the DOT technique suffers from poor spatial resolution [3,6]

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Results

Conclusion