Just as peoples health can be observed from their complexion, that is, the amount of blood in the body, its possible to measure active biological functions by investigating changes in blood volume. The Okada Laboratory shines near-infrared, which has a longer wavelength than visible light, inside the body, and uses substances that are absorbed by the blood to measure biological functioning in the form of blood volume in the brain, which changes rapidly with time.
Q. "Because infrared can penetrate the body so we can see inside it, we can see, for example, through the skull into the head, and through the brain to the other side of the body. If we do this, we can find out where theres lots of blood, and where theres none, by measuring the amount of infrared absorbed. In parts of the brain that are active, blood increases, and we can obtain the information that blood has collected there. The aim of our research is, by doing this, to see which parts of the brain are currently active, and measure their functioning. "
When brain functioning is measured using light, the light passing through tissues such as bones and skin is scattered before being detected. So the resulting images arent sharp; instead, they resemble views through frosted glass.
The time taken for the light to reach the detector is determined by using time-resolved measurement. This has the amazingly high resolution of one-trillionth of a second, making it possible to track how the light is changing.
In addition, this research requires computer modeling of how light is transmitted through the body, to obtain more precise images.
Q. "For example, weve gotten the information that light has traveled 20 cm in the head, but the question is, where and how? For example, we dont know if it passed through the brain, the skull, or the skin. So we create a model of those parts in a computer, and analyze how light passes through the model by simulation. In this way, we obtain data that doesnt contradict experiments, so we can estimate where the light actually traveled."
Brain functions can also be measured using functional MRI, which is widely used in hospitals. But MRI has limitations: The equipment is very large, and the subject has to keep still for a long time. Measurement using light has the potential to solve those problems.
Q. "Light enables measurement just by placing an optical fiber on the head. So the equipment can be taken to a patients bedside, for example. In that sense, light measurement is very convenient compared to the bulkiness of MRI. It can be used in the sort of way youd measure brainwaves. So wed like to utilize the features of both methods to investigate brain functioning."
By using light, its possible to understand brain mechanisms that couldnt be seen before. The Okada Laboratory will continue to open up new areas of research by studying physical phenomena involving light.
Q. "We have students with very diverse interests here. For example, some focus on biology, some on light as a physical phenomenon, and some on creating computer models. If students are truly interested in the brain and in biology, its natural that theyll want to do simulations and lots of other things with computers. Meanwhile, some students are more interested in light. I think this field enables all kinds of students to do research that utilizes their knowledge in various areas. "
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岡田研究室：光を用いた生体機能の測定by keiouniversity1,190 views
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