High-precision measurement of in vivo elasticity distribution by advanced mathematical analysis and ultrasonic

2020 Fiscal Year Final Research Report

• Project/Area Number: 17K01406
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Medical systems
• Research Institution: University of Toyama
• Principal Investigator: Sato Masahiro 富山大学, 学術研究部工学系, 教授 (90132563)
• Co-Investigator(Kenkyū-buntansha): 長谷川 英之 富山大学, 学術研究部工学系, 教授 (00344698)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Keywords: ずり弾性波 / 超音波診断 / 数値シミュレーション / FDTD法

Outline of Final Research Achievements

The beating of the heart causes shear waves to occur in the liver. The velocity is measured by an ultrasonic diagnostic device. If the elasticity distribution in the liver can be analyzed from the wave velocity, it is able to be used for the diagnosis of cirrhosis and liver tumors. In this way, it is necessary to examine the effect of the elastic nonuniformity in the liver on the wave propagation. Therefore, numerical analysis was carried out by finite difference time domain method (FDTD method). First, the reflection and refractive characteristics of the shear waves were analyzed by the FDTD method. As a result, the existence of pseudo boundary waves was confirmed. Next, we analyzed the wave propagation of fibrous tissue of cirrhosis. The change in the wave velocity due to the difference in frequency was within a few percent. On the other hand, the phase velocity value was about 1.1 to 1.2 times higher than the velocity average of normal part and fibrosis part.

Free Research Field

数値シミュレーション

Academic Significance and Societal Importance of the Research Achievements

高精度ずり波伝搬計測法（HSM）とは，心拍をずり波（SV）の励振源とし超音波診断装置でSVを観測，そこから解析によりずり波速度分布を得るものである．病変部はずり波速度が異なるので，肝硬変や肝腫瘍の診断に利用できる．心拍を使えば，簡便で安全な繰り返し診断が行える．もとより心臓の拍動により血管が収縮する．血管は全身に分布しており，他の部位においてもHSMを適用できる可能性がある．本研究では肝臓内の弾性的不均一性がずり波の伝搬にどう影響するかを確認した．実験は困難であり，数値解析を用いている．この成果は，HSMの実現に直接役立つ．また，これまでそのような解析例はなく学術的にも大変興味がある．