Faster Photoacoustic Microscopy

Photoacoustic images of microvessels in the ears of mice captured by the newly developed photoacoustic microscopy. (Source: C. Kim, Postech)

Up to now, the best tool that provides anatomical, functional, and molecular infor­mation of human and animal is the photo­acoustic microscopy. Now, super-resolution localization photo­acoustic micro­scopy which is 500 times faster than the conven­tional photo­acoustic micro­scopy system is developed by the research team from Postech in Korea. Chulhong Kim of Creative IT Engineering with Jinyoung Kim, a research professor and Jongbeom Kim, a PhD student developed a fast photoacoustic micro­scopy system with custom-made scanning mirror. This micro­scopy uses a stable and commercial galvano­meter scanner with a custom-made scanning mirror and can find blocked or burst blood vessels by monitoring the flow of red blood cells without using a contrast absorber.

The photo­acoustic microscopy images cells, blood vessels, and tissues by inducing vibrations when the optic energy is converted to heat after an object absorbs light from the laser beam fired. The conven­tional photo­acoustic micro­scopy systems using a galvano­meter scanner have a narrow field of view because they do not scan photo­acoustic waves but only the optical beam. The conventional photo­acoustic micro­scopy systems using a linear motorized stage also have temporal limitation in making images.

The research team developed a new photo­acoustic micro­scopy system with improved performances. It can scan both photo­acoustic waves and optical beams simul­taneously as they implemented the custom-made scanning mirror in the existing photo­acoustic micro­scopy system. Also, it can monitor very small vessels using intrinsic red blood cells without a contrast absorber which helps the system to image blood vessels well. Furthermore, the new system is 500 times faster than that of the con­ventional ones. With this improvement, it can demonstrate super-reso­lution image by localizing photo­acoustic signals and the spatial resolution is enhanced by 2.5 times.

Their research accomplish­ment is meaningful in many ways. Especially, this system is expected to be very promising in diagnosis and treatment of stroke and cardio­vascular disease. Because it can monitor and image the blood vessels with the flow of blood cells in real time, it can also be used in vascular disease which needs urgent diagnosis and treatment. Moreover, it allows direct monitoring of hemo­dynamics in the micro­vessels. It is anticipated to be applied in various fields including hemo­dynamic response, contrast agent dynamics in blood vessels and transient micro­circulatory abnormalities.

Chulhong Kim said, “We success­fully imaged micro­vessels in the ears, eyes, and brains of mice and a human fingertip with this new photo­acoustic micro­scopy system. What we have developed can be a compli­mentary tool to the conventional brain imaging system and it can also be a promising tool for future pre­clinical and clinical studies.” (Source: Postech)

Reference: J. Kim et al.: Super-resolution localization photoacoustic microscopy using intrinsic red blood cells as contrast absorbers, Light: Sci. & App. 8, 103 (2019); DOI: 10.1038/s41377-019-0220-4

Link: Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea

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