Scienct article review:
A recent review from the University of Washington published a review article entitled "Photoacoustic Tomography: In Vivo Imaging from Organelles to Organs", introducing a rapidly evolving imaging technology in recent years: photoacoustic tomography. This related article was published in Science magazine.
The author of the article is Professor Lihong V. Wang, a well-known biomedical optical expert at the University of Washington. Professor Wang is currently the President of the International Biomedical Optics Association and a professor of Changjiang Scholars at Huazhong University of Science and Technology. Professor Wang has achieved many achievements in biomedical optical imaging technology. He has published two monographs and published hundreds of papers in Nature Biotechnology, Physical Review Letters, Physical Review, Optics Letters, and IEEE Transactions.
In the application of tumors, due to the different peripheral and internal structures of the tumor, these two different regions may have different behaviors for the absorption of contrast agents: peripheral perfusion of tumors is usually faster, because there are more angiogenesis, metabolism. Exuberant, the clearance rate is also fast, and the curve shows a rapid rise and fall mode; on the contrary, due to slow metabolism, the perfusion shows a slow rise and fall mode, and the overall signal peak is much lower than the tumor peripheral signal. This can be used for tumor state determination. If these two peaks are gradually close in time, it indicates that the tumor is inhibited and progresses toward a good prognosis, and vice versa.
Photoacoustic imaging technology is believed to replace traditional scanning methods such as magnetic resonance (MRI) and X-ray based tomography in the future. The advantages of photoacoustic tomography (PAT) include the fact that it is a non-ionized technology that does not require biomarkers, and has extremely high resolution, real-time scanning, etc., so it can display some of the fine structures missing from conventional scanning equipment. One of the major limitations of photoacoustic imaging is its imaging depth, but this limitation is being gradually overcome, and now its imaging penetration depth can reach 7 cm.
Principle of photoacoustic imaging
Although we have accepted the gray photos obtained by X-ray imaging, this is only a sparse alternative to the “photos†inside our body. However, since the photon can only penetrate about one millimeter of soft tissue, it will then scatter out, unable to resolve its path and obtain graphics, so we can only accept such pictures.
But the scattering does not destroy the photons, which can reach as deep as 7 cm (about 3 inches). The method of photoacoustic imaging is to convert the deep absorption light into sound waves, which are a thousand times lower than the light scattering. This can be achieved by irradiating the imaged tissue with a nanosecond pulsed laser of a certain wavelength of light.
In addition, light is different from X-rays, does not pose any health threats, and photoacoustic imaging is also more contrasting than X-ray imaging, and can also obtain color molecular images from "endogenous" contrast agents, including hemoglobin. - Change color with the acquisition and loss of oxygen, as well as melanin, and DNA - DNA in the nucleus is "dark" than DNA in the cytoplasm.
In general, photoacoustic imaging, a non-destructive biophotonic imaging method based on the difference in optical absorption between biological tissues and ultrasound-mediated, combines the advantages of high-contrast characteristics of pure optical imaging with high penetration depth characteristics of pure ultrasound imaging. The use of ultrasonic detectors to detect photoacoustic waves instead of photon detection in optical imaging avoids the effects of optical scattering in principle, and provides high-contrast and high-resolution tissue images for studying the structural morphology, physiological characteristics, and metabolism of biological tissues. Functional and pathological features provide important tools and have broad application prospects in biomedical clinical diagnosis as well as in the field of tissue structure and functional imaging.
Photoacoustic imaging instrument
The current photoacoustic imaging instruments on the market mainly include:
Endra's NEXUS small animal photoacoustic imaging system, iThera's MSOT multi-spectral tomography system.
Endra was founded by Enlight Biosciences, a group of seven pharmaceutical companies including Pfizer, Merck, Johnson & Johnson, Abbott, Lilly, Novartis and Astra. The history of Endra's development of photoacoustics dates back to 2001 and has been 11 years old. Endra has been conducting applied research in cancer biology and probe development for more than three years.
The inventor of the Endra Nexus 128 Small Animal Photoacoustic Imaging System is Professor Wang Lihong, who is also a member of the Endra Scientific Advisory team. It is a new, non-invasive, in vivo imaging model with high contrast properties for optical imaging and high penetration depth for ultrasound imaging, providing high resolution and high contrast tissue imaging. The Nexus 128 imaging system enables both endogenous structural imaging and higher contrast 3D images with the aid of contrast enhancers. It can be applied to various research fields such as cardiovascular, drug metabolism, early diagnosis of diseases, gene expression research, stem cells and immunity, tumor biology, and brain neurobiology.
The multispectral optoacoustic tomography (MSOT) of the MSOT spectrometer can identify the spectral characteristics of the in vivo signal, and the obtained signal image has a good contrast with the surrounding tissue. This powerful imaging technique combines the multifaceted properties of optical contrast with high-resolution ultrasound imaging to provide information at the cellular and molecular levels that provide physiological processes within the tissue.
Original address: http://personales.unican.es/vallep/TIO/PAT1.pdf
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