Reflection‐mode switchable subwavelength Bessel‐beam and Gaussian‐beam photoacoustic microscopy in vivo

Abstract

We have developed a reflection-mode switchable subwavelength Bessel-beam (BB) and Gaussian-beam (GB) photoacoustic microscopy (PAM) system. To achieve both reflection-mode and high resolution, we tightly attached a very small ultrasound transducer to an optical objective lens with numerical aperture of 1.0 and working distance of 2.5 mm. We used axicon and an achromatic doublet in our system to obtain the extended depth of field (DOF) of the BB. To compare the DOF performance achieved with our BB-PAM system against GB-PAM system, we designed our system so that the GB can be easily generated by simply removing the lenses. Using a 532 nm pulse laser, we achieved the lateral resolutions of 300 and 270 nm for BB-PAM and GB-PAM, respectively. The measured DOF of BB-PAM was approximately 229 μm, which was about 7× better than that of GB-PAM. We imaged the vasculature of a mouse ear using BB-PAM and GB-PAM and confirmed that the DOF of BB-PAM is much better than the DOF of GB-PAM. Thus, we believe that the high resolution achieved at the extended DOF by our system is very practical for wide range of biomedical research including red blood cell (RBC) migration in blood vessels at various depths and observation of cell migration or cell culture.

Review on practical photoacoustic microscopy

“…However, unlike the previous methods, this type has the disadvantage that it cannot be used for in vivo imaging because of the way the system is configured. The last method can be an alternative to solve the problem of the transmission mode [[45], [46], [47]]. This method uses a very high NA optical lens and a tiny transducer just below the optical lens.…”

“…Fig. 3(a) shows the schematic of the Bessel-beam PAM (BB-PAM) system developed by Park et al [47]. This BB-PAM system can be easily modified to a Gaussian-beam PAM (GB-PAM) system by replacing a set of the optical system (blue boxes in Fig.…”

“…In blind deconvolution, the sidelobes of BB-PAM are corrected by estimating the optimal PSF of the system. Jiang et al [60] and Park et al [47] both used a blind deconvolution technique to reduce sidelobes in BB-PAM. Jiang et al reported the BB-PAM’s DoF to be 483 μm, about 7.4 times longer than that of GB-PAM (65 μm), and the lateral resolution to be about 1.7 μm for both systems.…”

A photoacoustic finder fully integrated with a solid-state dye laser and transparent ultrasound transducer

“…Photoacoustic (PA) imaging [ [12] , [13] , [14] , [15] , [16] , [17] , [18] , [19] , [20] , [21] , [22] , [23] , [24] , [25] , [26] , [27] ]has also been explored as a non-ionizing and non-invasive method of identifying SLNs, using blue or green dyes [ 11 , [28] , [29] , [30] , [31] ]. Advantageously, PA imaging can delineate SLNs in deep tissue with high resolution and high contrast.…”

GPU-accelerated 3D volumetric X-ray-induced acoustic computed tomography

“…The principle of XA imaging is similar to that of laser based photoacoustic (PA) imaging. With carefully selected wavelengths of excitation light, PA imaging can provide anatomical, functional, and molecular information about biological tissues [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. However, since optical light is strongly scattered in biological tissues, the light penetration is significantly limited, and consequently the PA imaging depth is relatively shallow compared to that of conventional medical imaging modalities.…”