As a part of a research team, scientists from the National Research Nuclear University "MEPhI" (Moscow, Russia), have developed a method for imaging of blood vessels using laser radiation. The authors of the development argue that their system allows high-contrast imaging of blood vessels in any selected area of the human body.
In their opinion, the system will be useful in diagnosing vascular conditions, for venipuncture procedures and in vascular surgery, for example, in the treatment of phlebeurysm (varicose veins). The results of the research are published in the journal Infrared Physics & Technology.
“Our work is devoted to the imaging of human blood vessels in the near-infrared range by the method of backscattered laser radiation. We have determined the optimal wavelength range for imaging blood vessels. This is 760–800 nanometers,” said Kanamat Efendiev, one of the authors behind the newly developed system, who is currently a postgraduate student at the Engineering Physics Institute of Biomedicine of NRNU MEPhI.
The researchers maintain that imaging of blood vessels and analysis of their condition remain a vital task for modern medicine. In particular, high-contrast IR-imaging of blood vessels makes it possible to diagnose vascular pathologies (including expansion or narrowing of the blood vessels lumen, conditions that are usually accompanied by impaired blood circulation), in the arms, legs, abdominal cavity or in other areas.
What’s more, it is useful when carrying out one the most common medical procedures – venipuncture, which is a percutaneous puncture of the venous vessel’s wall followed by the introduction of an injection needle.
In modern medicine, to obtain images of the circulatory system medical experts often resort to X-ray scans, ultrasound scans and infrared (IR) images.
Radiography calls for an introduction of a contrast agent, while ultrasound scanning requires the application of a gel to the skin surface, which could make these procedures more complicated.
In this case, the main advantage of IR-imaging is its safety and non-invasiveness. It does not require the introduction of any contrasting agents or foreign objects (needles, etc.) into the human body, while low-intensity laser radiation in the near-infrared range does not harm the patient’s tissues.
The Russia-based system includes a laser radiation source, 20 polymer optical fibers with a diameter of 500 mcm (micrometers), a varifocal lens with a focal length of 3.6-10 mm and a digital IR camera with CMOS sensor.
The system allows the optical fibers to be evenly distributed around the imaging area. While irradiation occurs in contact with the skin, this makes it possible to increase the sounding depth while maintaining a uniform distribution of radiation in the imaging area.
Laser radiation is applied to the tissues of the human body through optical fibers that remain in direct contact with the skin. Its power on each optical fiber is 2–3 mW. The laser radiation is then scattered and absorbed inside the tissue. Meanwhile, blood vessels absorb radiation better than the surrounding tissues.
An IR-camera registers the backscattered laser radiation, while displaying a shadow image of the blood vessels on the monitor screen. This makes it possible to evaluate the distribution of the intensity of backscattered radiation along the selected profile and to determine the actual boundaries of the blood vessels.
The authors of the work note that it is also possible to increase the power of the laser source to obtain high-contrast images and increase the depth of imaging, however, this will increase the amount of heat transferred from the laser to the patient, which can be damaging to the tissue.
Therefore, it is important to identify the optimal range of radiation wavelengths, at which the greatest imaging depth is achieved at the lowest radiation intensity.
According to Russian researchers, during their experimental studies, the optimal wavelength range for obtaining IR images of blood vessels was registered at 760–800 nanometers, while the greatest contrast was observed at a wavelength of 760 nm.
“Thus, we have presented an effective approach to IR imaging of human bloodstream for diagnosing the state of vessels and also identified the optimal wavelength range,” said Efendiev.
The study included researchers from NRNU MEPhI and Prokhorov General Physics Institute of the Russian Academy of Sciences