Grant-in-Aid for Scientific Research (B)
|Allocation Type||Single-year Grants |
Biomedical engineering/Biological material science
|Research Institution||HOKKAIDO UNIVERSITY |
YAMAMOTO Katsuyuki Hokkaido Univ., Grad. School of Inf. Sci. & Tech., Prof., 情報科学研究科, 教授 (10088867)
KUDO Nobuki Hokkaido Univ., Grad. School of Inf. Sci. & Tech., Inst., 情報科学研究科, 助手 (30271638)
KAWAHATSU Kiyonori Hokkaido Univ., Center for Res. & Dev. in Higher Edu., Prof., 高等教育有機能開発総合センター, 教授 (80026822)
KAWAHARA Kouichi Hokkaido Univ., Grad. School of Inf. Sci. & Tech., Prof., 情報科学研究科, 教授 (20125397)
TAKAHASHI Eiji Yamagata Univ., Medical Fac., Assoc. Prof., 医学部, 助教授 (30206792)
|Project Period (FY)
2004 – 2006
Completed (Fiscal Year 2006)
|Budget Amount *help
¥14,200,000 (Direct Cost: ¥14,200,000)
Fiscal Year 2006: ¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 2005: ¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 2004: ¥8,400,000 (Direct Cost: ¥8,400,000)
|Keywords||near-infrared light / skeletal muscle / muscle oxygenation / oxygen consumption rate / temporal and spatial analyses / exercise tests / microspectrophotometry / 組織酵素濃度|
In this study, a small and lightweight instrument based on spatially resolved near-infrared spectroscopy (SR-NIRS) was developed for real-time imaging of muscle oxygenation. From the results of temporal and spatial analyses of muscle oxygenation during exercise tests, we elucidated the relationship between changes in muscle oxygenation and metabolism and established the basics of NIRS as a standard technique for functional imaging of muscle. The following results were obtained.
1. Development of an imaging instrument for muscle oxygenation based on spatially resolved NIRS
Compact multi-channel optical probes with sufficient S/N were constructed. The measurement reliability of the probes was validated using a liquid tissue-mimic phantom experiment (blood and Intralipid). In addition, instrumentation control, data acquisition and user-interface programs were coded. The data acquisition time when 32 probes (3 channel X 32 probes = 96 channels) were used, including time for calculation of ox
ygenation, was about 500 ms. Therefore, real-time imaging of instantaneous changes in muscle oxygenation during exercise is possible.
2. Temporal and spatial analyses during exercise tests using human subjects
The developed instrument was used to analyze temporal and spatial changes in tissue oxygen saturation (TOS) in response to different exercises. Spatial and temporal differences in TOS of the quadriceps muscle during exercise tests with small modifications in exercise protocol (e.g., knee extension exercise without or with leg press action) were detected. In addition, the influence of oxygen debt on oxygen consumption rate ( Vo2) of the tibialis anterior muscle during repeated exercise (two similar protocols) was investigated, with comparison of Vo2 during the former and latter exercises. Due to oxygen debt, the VO2 values of the latter exercise are a direct summation of those of the former exercise if TOS did not decrease significantly during exercise.
3. Measurement of oxygen saturation of muscle using micro-spectroscopy
A micro-spectroscopy system that uses (i) light in the wavelength range of 400 to 850 nm to measure optical density (light attenuation) and (ii) multiple regression analysis to eliminate the scattering component was constructed. Using this system, imaging of oxygen saturation of the cremaster muscle of a rat was performed. Oxygen saturation of blood vessels with radii of about 10 μm can be sufficiently imaged using wavelengths around 500 nm. However, shorter wavelengths (400 to 500 nm range) are needed in order to image oxygen saturation of blood vessels with smaller radii.
4. Other techniques for utilizing SR-NIRS in practical applications
A highly-sensitive CCD camera was used in place of the multi-channel optical probes described above to validate the appropriateness of the solution of diffusion approximation for a highly scattered medium, in which SR-NIRS is based on. In addition, solid plastic phantoms which are easy to handle and stable over a long period, with optical properties matched to those of human tissue over a range of near-infrared wavelengths, were constructed. It is expected that these phantoms will be used in the future to calibrate imaging instruments designed for practical applications in sports and rehabilitation medicine. Less