Reflection-mode optical-resolution photoacoustic microscopy based on a reflective objective

Abstract

We developed a new reflection-mode optical-resolution photoacoustic microscopy (OR-PAM) based on the cooperation of a reflective objective and an ultrasonic transducer. The reflective objective is used to produce nearly diffraction-limited optical focusing, and the excited ultrasound waves are then directly detected by an ultrasonic transducer that was placed in the central cone of the objective. This new design avoids the coupling between optical focusing and ultrasound transmission in the reflection mode. Moreover, the proposed system is able to provide lateral resolution of 1.2 μm at 580 nm, penetration depth of 0.9 mm in biological tissues, and a work distance of 6.0 mm. We present in vivo imaging of the microvasculature in mouse ears and in vitro imaging of red blood cells (RBCs), which demonstrate the capability of the system to study microcirculation.

Reflection-mode in vivo photoacoustic microscopy with subwavelength lateral resolution

“…As a result, it allows the imaging of many more anatomic sites, including the brain and the eye. However, it is quite challenging for reflection-mode systems to realize fine subwavelength resolution due to the very limited working distance of optical objectives with high numerical aperture (NA) [3,13]. Until now, the reported highest resolution of reflection-mode OR-PAM is about 500 nm with an optical objective of 0.63 NA at 532-nm laser illumination [6].…”

In-Vivo functional optical-resolution photoacoustic microscopy with stimulated Raman scattering fiber-laser source

“…Acousticresolution PAM derives its lateral spatial resolution from acoustic focusing, while opticalresolution photoacoustic microscopy (OR-PAM) can achieve micron-scale resolution by using optical focusing to determine lateral resolution. By taking advantage of the high optical absorption of hemoglobin and micron-scale optical spot sizes, OR-PAM has proven invaluable for visualizing superficial capillary networks non-invasively and label-free, in vivo [6,7]. Furthermore, OR-PAM has proven useful for quantifying functional parameters down to capillary sizes [8].…”

Photoacoustic imaging of prostate cancer

“…PAI, also known as optoacoustic imaging, is an innovative, noninvasive hybrid imaging system that holds potential in various¯elds including, but not limited to, medical diagnosis, therapy monitoring, biological studies, and inorganic imaging. [37][38][39][40][41][42][43][44][45][46][47] The PAI system is based on the photoacoustic (PA) e®ect, discovered by Bell in 1880 when he observed sound waves produced by a solid sample exposed to sunlight. 48 The PA e®ect is the phenomenon that light induces the generation of US waves in the irradiated object.…”