Photoacoustic imaging is attracting worldwide attention as a bioimaging device that does not use radiation and harm the body. Recently, researches for observing deep tissues have been actively conducted to apply photoacoustic imaging to clinical practice.

POSTECH(Pohang University of Science and Technology) researchers, including prof. Cheol-hong Kim, Byul-lee Park, prof. Hyung-woo Kim, and Kyung-min Lee, suggested deep tissue photoacoustic imaging. It uses nano-sized nickel-based contrast agent and 1064nm lasers. The result came out to be 3.4cm, and this is the deepest of the preclinical studies so far in vivo.

▲ Photoacoustic Imaging Before and After Implantation of Contrast Agents in the Rat Gastrointestinal Tract (Image by POSTECH)

The photoacoustic imaging detects and images a sound wave (photoacoustic) signal generated by instantaneous thermal expansion of the tissue that absorbs the light when irradiated with human tissue. While conventional imaging techniques can only observe very shallow depths (~ 1mm), photoacoustic imaging has the advantage of acquiring images based on optical contrast up to several cms in human tissue.

On the other hand, studies about photoacoustic contrast agents are actively progressed to observe various organs located in deep tissues deeply, but it is difficult to deliver short-wavelength light (650 to 900nm) deep into the human body. Because of this, there was a limit that it is not suitable to observe deep tissue.

Therefore, the research team introduced deep tissue photoacoustic imaging using nickel-based nanoparticle contrast agents with strong absorption of long-wavelength light (1064nm). The biocompatibility of all nickel-based nanoparticles was verified, and photoacoustic images were acquired at depths of up to 3.4 cm by injecting nanoparticles into the lymph nodes, gastrointestinal tract and bladder of rats.

The new photoacoustic imaging, unlike CT, which requires radioactive materials, can help diagnose diseases in deep tissues that are not invasive without the risk of exposure. In addition, the 1064nm wavelength laser is expected to be clinically available soon as it is relatively inexpensive and can be used with general commercial ultrasound equipment.

This research was supported by the ICT Talent Cultivation Project of the Ministry of Science and ICT, the Health and Medical Technology R & D Project of the Ministry of Health and Welfare, and the Pioneer Project of the Korea Research Foundation. (Theranostics) 'cover paper.

The finding was published in a cover paper in Theranostics, an international journal of molecular imaging and therapy.