A high-sensitive time-domain method to identify fluorescence targets in thick biological tissue

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K04421
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 21030:Measurement engineering-related
• Research Institution: Hokkaido University
• Principal Investigator: Nishimura Goro 北海道大学, 電子科学研究所, 助教 (30218193)
• Co-Investigator(Kenkyū-buntansha): 藤井 宏之 北海道大学, 工学研究院, 助教 (00632580)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 多重散乱 / 蛍光 / 逆問題 / 散乱係数 / 時間応答関数 / ICG

Outline of Final Research Achievements

We studied the basic properties of scattering and light transport to improve the identification of fluorophores embedded in biological tissue. We found that the excluded volume effect dominantly affects the scattering coefficient in dense scattering material. On the other hand, we also found that the angle-dependent temporal response function is well explained by considering the flow term derived by the photon diffusion equation. Further, we have discussed the identification of fluorophores with a simple shape for this distribution. First, we derived an analytic expression of the fluorescence temporal response function with a cuboid shape and demonstrated its identification. Then, we discussed a point target model of fluorophores for a mathematical analysis of the inverse problem. We derived the analytic expression of the peak time of the response function. We also proofed the minimum number of data to identify the target.

Free Research Field

医用生体光学

Academic Significance and Societal Importance of the Research Achievements

生体組織などに埋め込まれた蛍光体の高感度高精度な同定のためには、散乱体組織のなかの光伝搬を解析する必要があったが、本研究ではそのうち、散乱の度合いに当たる散乱係数が濃度に対する振る舞いや計測データの角度依存性に対して、解析的なアプローチから物理的な解釈を可能とした。また、蛍光体の位置の同定に関して、数学的に厳密な議論を行った。このような基礎的なアプローチからもたらされた物理的な理解はこれまでにあまりなく、今後の方向性への指針を与えるものと考えられる。