Three-Dimensional Optical-Resolution Photoacoustic Microscopy - Biomedical Optical Imaging Technologies: Design and Applications - page 75

generally involve water in acoustic coupling. This configuration leads to system
complexity and experimental inconvenience. Moreover, the detection sensitivity
of the transducer falls off with its element size. Higher detection frequency
is achieved at the expense of SNR. To overcome these limitations, noncontact
optical methods for ultrasonic detection need to be explored.

￿ Integrating OR-PAM with AR-PAM for multiscale imaging. As shown in

Fig. 2.1 , OR-PAM and AR-PAM are highly complementary in terms of spatial
resolution and tissue penetration. Combining them together would enable users
to select an optimal trade-off between the spatial resolution and the penetration
depth for different applications.

￿ Integrating OR-PAM with multiphoton fluorescence microscopy for neurovas-

cular imaging. OR-PAM and multiphoton microscopy have similar penetration
depths in soft brain tissues [ 8 ]. Combining them would enable direct visualization
of the interaction between neuron activities and vascular dynamics.

Being one of the most actively studied optical microscopy technologies, OR-
PAM has experienced a dramatic development within the last few years. We are
looking forward to see OR-PAM in the mainstream.

Acknowledgements This work was sponsored by National Institutes of Health Grants R01
EB000712, EB000712A2S1, R01 EB00071207S2, R01 EB008085, R01 CA113453901, U54
CA136398, and 5P60 DK02057933. Professor Lihong V. Wang has a financial interest in
Microphotoacoustics, Inc. and Endra, Inc., which, however, did not support this work.

Animal Ethics

All experimental animal procedures were carried out in conformance with the
laboratory animal protocol approved by the School of Medicine Animal Studies
Committee of Washington University in St. Louis.

References

1. S. Hu, L.V. Wang, Photoacoustic imaging and characterization of the microvasculature.
J. Biomed. Opt. 15 , 011101(2010)
2. L.V. Wang, H. Wu, Biomedical Optics: Principles and Imaging . (Wiley, Hoboken, 2007)
3. X. Wang, Y. Pang, G. Ku, X. Xie, G. Stoica, L.V. Wang, Noninvasive laser-induced photoa-
coustic tomography for structural and functional in vivo imaging of the brain. Nat. Biotechnol.
21 , 803-806 (2003)
4. K. Maslov, G. Stoica, L.V. Wang, In vivo dark-field reflection-mode photoacoustic microscopy.
Opt. Lett. 30 , 625-627 (2005)
5. H.F. Zhang, K. Maslov, G. Stoica, L.V. Wang, Functional photoacoustic microscopy for high-
resolution and noninvasive in vivo imaging. Nat. Biotechnol. 24 , 848-851 (2006)
6. K. Maslov, H.F. Zhang, S. Hu, L.V. Wang, Optical-resolution photoacoustic microscopy for in
vivo imaging of single capillaries. Opt. Lett. 33 , 929-931 (2008)