Low-cost high-resolution photoacoustic microscopy of blood oxygenation with two laser diodes

Abstract

Optical-resolution photoacoustic microscopy (OR-PAM) has been widely used for imaging blood vessel and oxygen saturation of hemoglobin (sO2), providing high-resolution functional images of living animals in vivo. However, most of them require one or multiple bulky and costly pulsed lasers, hindering their applicability in preclinical and clinical settings. In this paper, we demonstrate a reflection-mode low-cost high-resolution OR-PAM system by using two cost-effective and compact laser diodes (LDs), achieving microvasculature and sO2 imaging with a high lateral resolution of ∼6 µm. The cost of the excitation sources has dramatically reduced by ∼20–40 times compared to that of the pulsed lasers used in state-of-the-art OR-PAM systems. A blood phantom study was performed to show a determination coefficient R2 of 0.96 in linear regression analysis. Experimental results of in vivo mouse ear imaging show that the proposed dual-wavelength LD-based PAM system can provide high-resolution functional images at a low cost.

Design and simulation of high brightness green LD fiber coupling module

“…In addition, the selection of the focal length range of the focusing mirror should meet the following requirements: the divergence angle of the spot after focusing should be smaller than that corresponding to the numerical aperture of the optical fiber, and the diameter of the spot after focusing should be smaller than that of the core diameter of the optical fiber, so as to obtain the formula for calculating the focal length range of the focusing mirror: Under the premise of satisfying the fiber coupling conditions, this paper adopts an aspherical focusing lens for beam focusing and thus coupling into the fiber. The parameters of the spot after beam combining are brought into equations ( 6), and the range of values of the fast and slow axis focal lengths can be calculated: In the software Zemax simulation, the focused spot is coupled into the fiber, the output power of the fiber is 30.08W, the coupling efficiency of the fiber is 97.63%, and the output brightness after fiber coupling is 10.08MW/(cm 2 •Sr) according to equations (2). The final optical path of the fiber-coupled green diode laser is shown in Figure 9.…”

“…Green light semiconductor lasers (LDs) have many advantages such as long lifetime, small size, and easy modulation, and have important applications in the fields of communication, medicine, display, security, and military [1][2][3][4][5] . The application of non-lethal weapons using green light band in the tasks of advance warning, security defense, anti-terrorism and stability maintenance, and riot control is increasing, and the demand for high-brightness green light sources is also increasing [6] .…”

Photoacoustic imaging plus X: a review

“…(b) The system schematic of the dual-wavelength LD-based PAM. 55 (c) A schematic diagram of dual-compressed PA single-pixel imaging. 56 (d) Depth-resolved imaging of carbon fibers with a needle-shaped beam (OR-PAM with a needle-shaped beam).…”

“…Li et al. 55 demonstrated a compact dual-LD PAM with a cost reduction of nearly 20 to 40 times that of standard pulsed laser systems typically used for PA excitation [as shown in Fig. 4(b) ].…”

“…Therefore, lower system costs combined with the smaller size of laser sources facilitates the development of portable imaging systems that can be moved close to the patient bedside or surgical suite. Li et al 55 demonstrated a compact dual-LD PAM with a cost reduction of nearly 20 to 40 times that of standard pulsed laser systems typically used for PA excitation [as shown in Fig. 4(b)].…”