Optical resolution photoacoustic microscopy based on multimode fibers.

Malini Olivo,Jin Young Kim,Chulhong Kim,Renzhe Bi,Seungwan Jeon,Mohesh Moothanchery

doi:10.1364/boe.9.001190

Abstract

Photoacoustic microscopy (PAM) is a multiscale imaging technique. In optical-resolution photoacoustic microscopy (OR-PAM), a single mode (SM) fiber is normally used as the source of optical excitation to be focused into a diffraction-limited spot. Recent advances in OR-PAM have improved its imaging speed using microelectromechanical systems (MEMS). Here we report for the first time the use of a multimode (MM) fiber as the optical excitation source for high resolution OR-PAM in vivo imaging. A high-speed MEMS scanner based OR-PAM system combined with the mechanical movement to provide wide area imaging was used. The use of multimode fiber for achieving tight optical focus would make the optical alignment easier and high repetition rate light delivery possible for high-speed OR-PAM imaging. A lateral resolution of 3.5 µm and axial resolution of 27 µm with ~1.5 mm imaging depth was successfully demonstrated using the system. The efficacy of multimode fibers for achieving tight focus is beneficial for developing high-resolution photoacoustic endoscopy systems and can be combined with other optical endoscopic imaging modalities as well.

Highlights

Photoacoustic microscopy (PAM) is an emerging innovative hybrid in vivo imaging modality, which combines optical absorption contrast and ultrasonic resolution [1,2,3,4,5,6,7,8,9]
In opticalresolution photoacoustic microscopy (OR-PAM), a single mode (SM) fiber is normally used as the source of optical excitation to be focused into a diffraction-limited spot
We report for the first time the use of a multimode (MM) fiber as the optical excitation source for high resolution OR-PAM in vivo imaging

Summary

Introduction

Photoacoustic microscopy (PAM) is an emerging innovative hybrid in vivo imaging modality, which combines optical absorption contrast and ultrasonic resolution [1,2,3,4,5,6,7,8,9]. Focusing light beam through a multimode fiber for high resolution photoacoustic endoscopic applications was previously reported using optical phase conjugation technique [22] which have a limited microscopic field of view. The use of multimode fibers for pure optical endoscopic imaging modalities was demonstrated which further reduced the footprint of the endoscopic devices as well as improved the imaging resolution and collection efficiency of the detected signals [25, 26]. An integrated micro-endoscopy system based on an image-guided fiber bundle for simultaneous optical resolution photoacoustic and fluorescence imaging was reported previously [28]. We propose the use of multimode fibers for achieving diffraction limited optical focusing for OR-PAM high speed imaging applications. The use of MM fibers can make the way for developing high-resolution PAE system and is advantageous for combining PAE with other optical endoscopic imaging modalities as well

System description

Results and discussion

Conclusions