山口 匡

This study aimed to investigate the possibility of using ultrasound images as a tool of quantitative analysis for muscle activity. One expected advantage of ultrasound imaging is that it could provide a non-invasive way to investigate the activities of both outer and inner muscles. In the literature, there have been fewer studies exploring the ultrasound image analysis for quantitative analysis of muscle activity, i.e., the estimation of spatiotemporal aspect of muscle contraction, such as, the power, the latency. This is why this study attempted to investigate different features extracted from the ultrasound images, to represent the muscle activity. For this purpose we measured the ultrasound images, as well as Electromyogram, and joint angle simultaneously, during the voluntary contraction, and muscle activity activated by the Achilles tendon reflex, in which temporal aspect of muscle activity should be precisely investigated. We were able to quantify the inner and outer muscle activity by measuring the muscle thickness, pennation angle and long-axis displacement.

Early detection of hepatitis is critical for proper patient management and improving disease prognosis. Ultrasound imaging is ideally suited for early-stage assessments, but conventional ultrasound images based on backscatter do not display quantitative tissue information because conventional ultrasound lacks essential modeling of the complex interaction between ultrasound and liver tissue in normal and diseased states. Therefore, speed-of-sound (SOS) measurements were obtained from three types of rat livers (normal, fatty, and fibrosis). Livers were harvested, fixed, and embedded in paraffin a single 10-μm thin section was obtained using a microtome and placed on a microscope slide. A scanning acoustic microscope incorporating transducers operating at 80-MHz and 250-MHz center frequencies was used to scan the 10-μm section. An adjacent 4-μm thin section was stained with H&amp E (normal and fatty livers) or Azan (fibrosis livers). The SOS measured with both transducers displayed the same trend: SOS in fatty liver was lower than in normal liver and SOS in fibrosis liver was higher than in normal liver. SOS differences were greater at 250 MHz because of the improved spatial resolution, which allowed choosing regionof-interests containing only fat or fibrosis tissue. These initial results also were used to correlate the pathologic state with the SOS. © 2013 Acoustical Society of America.

Quantitative diagnosis method of liver fibrosis using ultrasound echo signal is highly required. The distribution of echo envelope from a homogeneous medium with high scatterer density, such as normal liver, can be approximated by Rayleigh distribution. As the fibrotic liver disease progresses, the distribution begins to deviate from Rayleigh distribution. In our study, we proposed a quantitative method for liver fibrosis staging based on new echo envelope model. We examined a multi-Rayleigh model with three Rayleigh distributions. This model is expressed by the combination of three Rayleigh distributions, corresponding to the echo signal from hypoechoic, normal, and fibrous tissue respectively. Clinical data classified into F0 (normal liver), F1 (early-hepatitis), F2 (moderate hepatitis), and F3 (late-hepatitis) in accordance with the new-Inuyama classification based on the result of biopsy were analyzed by the proposed model. We showed that the multi-Rayleigh model can approximate amplitude distribution of the fibrotic liver accurately using KL divergence, that is an index of the difference between two probability distributions. Additionally, it was found that fibrosis indices of the multi-Rayleigh model obviously increase as the liver fibrosis progresses. These results suggest that the multi-Rayleigh model with three Rayleigh distributions can evaluate the degree of progression of liver fibrosis. © 2013 IEEE.

肝RFA治療は,超音波によりリアルタイムに臓器内部状態を観察しながら,体表からの穿刺により病変組織の焼灼を行う低侵襲な手技である.この時使用される超音波像は主に二次元画像であり,描出される断層以外の組織構造情報は得られない.そのため,描出されていない領域において血管等を損傷してしまう危険性がある.そこで本研究では,超音波診断装置で取得した肝臓のボリュームデータから血管部を抽出し,点群表示により三次元空間へと配置するとともに,穿刺針の先端を基準とした視点をシミュレートして術者へと提示する方法を開発した.これにより,穿刺領域における周辺情報を容易に認識することが可能となり,より安全な穿刺治療を行うことが可能となる.

我々はこれまで,肝線維症の定量評価を目的としたエコー信号の解析手法について検討してきた.本手法では,病変肝からのエコー信号を正常組織と線維組織からの反射信号の二成分と考え,エコー信号の振幅分布を2つのレイリー分布のたし合わせによって表現したモデルを提案している.このモデルを用いることで生体組織の質と量に相当するパラメータをエコー信号振幅の統計量から逆問題を解き定量的に求めることができる.本報告では,本手法を用いてヒトリンパ節の散乱体密度を推定することを目的とし,癌転移の有無によりパラメータへ与える影響について検討した.その結果,癌転移の有無によってパラメータの変化傾向が異なることを確認した.

Laparoscopic surgery is one of the most challenging surgical operations, because inside information about the target organ cannot be fully understood from the laparoscopic image. Therefore, a fusion technique of laparoscopic and ultrasonic images is proposed for guidance during laparoscopic surgery. The proposed technique can display the internal organ structure by overlaying a three-dimensional (3D) ultrasonic image over a 3D laparoscopic image, which is acquired using a stereo laparoscope. The registration of the 3D images is performed by registering the surface of the target organ, which is found in the two 3D images without requiring the use of an external position detecting device. The proposed technique was evaluated experimentally using a tissue-mimicking phantom. Results obtained led to registration accuracy better than 2 cm. The total computation time was 3.1 min on a personal computer (Xeon processor, 3 GHz CPU). The structural information permits the visualization of target organs during laparoscopic surgery. (C) 2012 The Japan Society of Applied Physics

Laparoscopic surgery is one of the most challenging surgical operations, because inside information about the target organ cannot be fully understood from the laparoscopic image. Therefore, a fusion technique of laparoscopic and ultrasonic images is proposed for guidance during laparoscopic surgery. The proposed technique can display the internal organ structure by overlaying a three-dimensional (3D) ultrasonic image over a 3D laparoscopic image, which is acquired using a stereo laparoscope. The registration of the 3D images is performed by registering the surface of the target organ, which is found in the two 3D images without requiring the use of an external position detecting device. The proposed technique was evaluated experimentally using a tissue-mimicking phantom. Results obtained led to registration accuracy better than 2 cm. The total computation time was 3.1 min on a personal computer (Xeon processor, 3 GHz CPU). The structural information permits the visualization of target organs during laparoscopic surgery. (C) 2012 The Japan Society of Applied Physics

<B>目的</B>：超音波凝固切開装置は腹腔鏡手術下などで広く利用されているが，処置部分とは異なる離れた位置の組織に損傷を与えることがあるのではないかと懸念され，その原因としてキャビテーションが指摘されている．そこで，実際の装置を用いてブレードからのキャビテーションの発生状況について検討する．<B>対象と方法</B>：超音波凝固切開装置ブレードの振動分布を，レーザードプラ振動計を用いて計測すると共に，水中観測においてキャビテーションの発生状況を確認し，ハイドロホンにより水中での音圧分布を測定し，超音波振動源から離れた位置にまで作用が波及する可能性について検討した．<B>結果と考察</B>：レーザードプラ振動計によって測定したブレードの振動分布と観察したキャビテーション気泡の発生位置の関係から，振動振幅の大きな領域から気泡が発生していることがわかった．さらに，水中でのブレード周囲の音圧測定，周波数解析から，キャビテーションが発生する可能性のある領域について，検討を行った．気泡の観察結果と音圧測定結果は整合性があり，キャビテーションが発生し，生体作用を及ぼす範囲は，最大でもブレードから数mm以内であると推定された．<B>結論</B>：キャビテーションはブレードのごく近傍から局所的に発生し，音響流によって移動する可能性はあるものの，キャビテーションによる直接的作用はブレード近傍に限定されると推測された．

医用超音波の分野において,断層画像に含まれるスペックルノイズを除去し,病変組織の量や分布の様子を詳細に捉えたいという要求が強い.本論文では,肝エコー信号に含まれるスペックルノイズと生体組織構造を反映したエコー信号との独立性を指標とし,独立成分分析(ICA)による肝臓病変の組織構造抽出法を提案する.一枚のエコー画像から組織構造とは独立した信号成分であるスペックルノイズを除去するため,同様のノイズを付加情報として用いることでICAを適用した.計算機シミュレーションによる基礎検討では,正負の値をもつ出力の負部に組織構造を反映した情報が抽出され,実際のエコーデータにおいても同様に線維構造が抽出されることを確認した.また,付加情報として与えるノイズの性質は照射超音波の音場特性で決定されるため,音場の違いが解析結果に与える影響について検討を行ったところ,エコー信号の分解能や減衰率に依存した出力が得られ,独立性を指標とした新たな組織構造抽出法の可能性が示された.

腹腔鏡手術は開腹手術に比べ切開創が小さいことなどから低侵襲な手技であるが,腹腔鏡の映像を頼りに行うために手技の難易度が高い.腹腔鏡手術の新しい試みとして,近年では腹腔内を液体で満たした状態で手技を行う研究が進められている.腹腔内を液体で満たすことにより水温と水圧が臓器に与える影響については今後の検討課題となっているが,現状で考えられるメリットとしては術中に体表から超音波診断装置によって腹腔内を観察することができることが挙げられている.そこで本研究では,組織内部情報をリアルタイムで表示可能な超音波診断装置を使用し,術中の腹腔鏡による臓器表面光学情報と超音波診断装置による内部超音波情報との重畳表示を行う手術支援システムを提案する.提案システムでは,光学系と超音波系において臓器表面情報を取得し,表面形状をもとに両モダリティ間の位置合せを行い,重畳表示を行う.生体を模して作成したファントムを用いて手法の検証を行った結果,光学像と超音波像の臓器表面形状の位置合せ結果は2.10mm±1.74mmの誤差を有し,最終的な重畳表示までに要する処理時間は4分程度であった.

我々は,肝炎線維化の定量評価を目的とし,病変肝からのエコー信号を正常組織と線維組織からの反射信号の組合せにより表現したモデルを提案している.本論文では,KL情報量を分布の近似精度の指標として用い,提案モデルが,正常肝から肝硬変までのエコー信号の性質を良好に近似していることを示した.

In the clinical diagnosis of liver fibrosis using ultrasound B-mode images, there are some differences between individual doctors' diagnosis results. Hence, the realization of a quantitative diagnosis method using ultrasonic echo signals is strongly required. The probability density function (PDF) of the echo signal envelope is an important factor for ultrasound tissue characterization (TC). To realize the quantitative diagnosis of the stage of liver fibrosis, we proposed an amplitude distribution model using two Rayleigh distributions. We have been studying the possibility of the quantitative estimation of liver fibrosis by using this model. In this paper, we present the evaluation results of liver fibrosis for clinical data using the amplitude distribution model. Then, we present the stability of the quantitative estimation method of liver fibrosis using the amplitude distribution model by a simulation, and compare the results using the simulation and clinical data. Stability evaluation has enabled the estimation of the progress of liver fibrosis considering statistical dispersion. (C) 2011 The Japan Society of Applied Physics

A reliable means of detecting metastases in lymph nodes is essential for accurate staging of cancer and effective planning of therapy. The standard means of detecting metastases in nodes is histopathologic evaluation of surgically dissected nodes; however, because examinations tend to be limited to thin sections derived from the center of the node, this time‐consuming procedure appears to have high false‐negative rates for metastases that are 2 mm or smaller. We have been investigating high‐frequency (HF) quantitative ultrasound (QUS) methods as a more‐effective means of providing a rapid and reliable detection of metastases in dissected nodes based on their ultrasound‐scattering properties. We acquired HF ultrasound and histological data from dissected lymph nodes of patients with colorectal, gastric, breast, and other cancers. Freshly dissected nodes were scanned in a saline bath using a raster pattern to acquire 3D RF echo‐signal data. Scans utilized a broadband, F‐2, 25.6‐MHz, single‐element transducer with scan vectors separated by 25 μm in X and Y directions. Scanned nodes were color inked to provide references for subsequent orientation, then fixed and serially‐sectioned in their entire volume at 50‐μm intervals. The presence of metastatic foci was determined histologically in every section; evaluation of node status in the center section provided a basis for comparison with conventional methods. To date, we have analyzed the echo signals of more than 240 nodes including abdominal nodes of colorectal and gastric cancer patients and axillary nodes of breast‐cancer patients. 3D images generated from RF data were segmented semi‐automatically to select nodal tissue for analysis. Echo signals from nodal tissue were processed to yield QUS estimates, which included spectral parameters, scatterer‐property estimates, and B‐mode envelope‐signal statistical features. Different histological node architectures were observed and different QUS results were obtained for abdominal compared to axillary nodes. Linear discriminant analysis and ROC‐curve methods were applied to assess the ability of QUS estimates to distinguish cancerous from non‐cancerous nodes. Classification performance was assessed for individual estimates and various linear combinations of estimates. ROC results for axillary as well as abdominal nodes showed excellent classification. For abdominal nodes, the best area under the ROC curve exceeded 0.95. For axillary nodes, the best area approached 0.90. Images based on QUS parameters showed an excellent ability to depict metastatic foci. Results to date strongly suggest that HF QUS methods may provide a clinically valuable means of detecting small metastatic cancers in dissected lymph nodes and significantly improving the sensitivity for metastases that might not be detected using current, standard histopathology procedures. The ability of HF QUS to reveal otherwise missed metastases will enable pathologists to more‐ efficiently focus histological effort on regions of nodes that have a high suspicion of containing cancer and minimizing wasted time evaluating actually cancer‐free nodes. Future studies will investigate the applicability of these methods to detection of nodal metastases in situ. © 2011, American Association of Physicists in Medicine. All rights reserved.