横山 智大¹, 森 翔平², 荒川 元孝^{1, 2}, 大西 詠子³, 山内 正憲³, 金井 浩^{1, 2}

Tomohiro YOKOYAMA¹, Shohei MORI², Mototaka ARAKAWA^{1, 2}, Eiko ONISHI³, Masanori YAMAUCHI³, Hiroshi KANAI^{1, 2}

¹東北大学大学院医工学研究科, ²東北大学大学院工学研究科, ³東北大学大学院医学系研究科麻酔科学・周術期医学分野

¹Graduate School of Biomedical Engineering, Tohoku University, ²Graduate School of Engineering, Tohoku University, ³Department of Anesthesiology and Perioperative Medicine, Tohoku University School of Medicine

キーワード : ultrasound imaging, epidural anesthesia, bone, muscle, scattering, reflection

目的：医用超音波は，硬膜外麻酔時の穿刺位置の特定に用いられている．しかし，胸椎の構造は複雑であり，胸椎と筋組織の描出の区別は難しい．本研究では，超音波の反射・散乱特性の差異に基づき，骨と筋組織の描出を区別することを目的とする．方法：骨と筋組織からの受信信号の差を実験的に調べた．骨を強調するための新しいパラメータとして，理想的な遅延線上のみの受信信号の振幅と，その周囲の広い範囲における受信信号の平均振幅との比を提案した．結果：はじめに，基礎実験により，骨と筋組織からの受信信号の差を確認した．また，トリもも肉を用いたin vitro実験，ヒトにおけるin vivo実験により，その差を確認した．両実験において，提案法は，通常のBモード像と比較して，骨の描出を強調し，筋組織の描出を抑制することに成功した．結論：骨からの反射特性と筋組織からの散乱特性の差を用いて，提案法により，骨と筋組織を区別することができた．

Purpose: Medical ultrasound is often used to specify the puncture position during epidural anesthesia. However, visualization of the thoracic spine is difficult because of the complex structure, i.e., it is difficult to determine whether the thoracic spine or muscle is depicted. Therefore, this study aims to distinguish bone from muscle tissue using the differences in reflection and scattering characteristics of ultrasound. Methods: We experimentally investigated the difference in signals received from bone and muscle. We proposed a new parameter utilizing the ratio of the amplitude of the received signals averaged in a wide range around the ideal delay line and that only along the ideal delay line, to emphasize the bone. Results: First, we confirmed the difference in signals received from bone and muscle tissue by basic experiments. We also investigated the difference by in vitro experiments using chicken thigh and in vivo experiments in humans. In both experiments, the proposed method succeeded to clearly depict bone, suppressing the depiction of muscle, compared with conventional B-mode imaging. Conclusion: Using the difference in the characteristics of reflection from bone and scattering from muscle tissue, we could distinguish bone from muscle tissue with the proposed method.