Simultaneous Detection of Blood Flow Information in Deeper-Layer Blood Vessels and Capillaries Using Automatic Image Processing Technology for Visual Extraction

A densely-arranged network formed by blood vessels tens to hundreds of micrometers in diameter and extremely fine capillaries with a diameter of less than 10 micrometers is present in skin. Blood flowing through these vessels supplies heat, nutrients, water, and oxygen, and also collects waste products. Kao has been advancing research by investigation of the various functions of this blood vessel network from the perspective of maintaining beautiful and healthy skin.

It is known that blood vessels in the deeper layer and capillaries in the surface layer of skin differ in regard to their major roles and action characteristics. These differences are considered to be closely linked with skin condition. However, it is difficult to obtain details regarding blood flow for different vessels at an identical site simultaneously, as several different instruments are needed for acquiring information present in layers that vary in depth and have constant blood flow changes. In the present study, Kao researchers attempted simultaneous detection of blood flow information using a single image.

In the present study, it was noted that all blood flow information in the skin was visible by use of videomicroscopy to view the hemoglobin component image. Thus, it was considered that by integration of the brightness values in the image, blood flow could be estimated. As the capillaries accounted for a small percentage in the visualized portion, the hemoglobin component was considered to mainly demonstrate blood flow in the deeper layer and used for estimation.
With this technique, it is now possible to simultaneously obtain capillary blood flow information as well as that in the entire skin area by examining a single image.

Skin vessels are generally considered to have two major roles. One is in regard to heat transportation for regulating body temperature, which mainly involves blood flow in vessels in the deeper layer, while the other is related to material exchange, such as the supply of nutrients and oxygen, and removal of carbon dioxide, in which capillaries in the surface layer are primarily involved. To evaluate the proposed image analysis technology, heat and carbon dioxide (carbonic acid), which have different action mechanisms, were used to quantify and compare blood flow changes in vessels at different depths.

Skin of the inner part of the upper arm in 6 Japanese male and female subjects was sequentially treated with heat and carbonic acid.^*4 Images of the skin areas after each treatment were obtained and subjected to the above-mentioned image processing method for analyzing the amount of the hemoglobin component and capillary blood flow (Figure 2).
The results showed that when exposed to heat, the hemoglobin component level increased and blood flow throughout the skin was also increased, whereas nearly no changes were seen in the capillaries. Meanwhile, following exposure to carbonic acid, both the hemoglobin component throughout the skin and capillary blood flow volume were increased (Figure 3, 4). These results support previous findings indicating that heat and carbonic treatment have different characteristic actions on blood vessels.

These findings indicate that this image analysis technology can provide simultaneous evaluation of blood flow information from different blood vessels using a single image.

Development of this non-invasive and simple technique of image analysis provides an ability to simultaneously obtain blood flow information for both capillaries and vessels in the deeper layer of an identical site. This makes it possible to extensively investigate the relationship of blood flow at various depths with skin condition, as well as the effects of various approaches to promote blood circulation.

In the future, Kao plans to further study blood flow changes brought about by aging and environmental factors, and the effects of blood flow status on various skin conditions.

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