藤本 研治^{1, 2, 3, 4}, 東 哲明¹, 山田 幸則⁴, 山本 佳司³, 加藤 道夫^{2, 3}

Kenji FUJIMOTO^{1, 2, 3, 4}, Tetsuaki HIGASHI¹, Yukinori YAMADA⁴, Keiji YAMAMOTO³, Michio KATO^{2, 3}

¹特定医療法人三和会永山病院内科, ²独立行政法人国立病院機構南和歌山医療センター臨床研究部, ³独立行政法人国立病院機構南和歌山医療センター内科, ⁴市立貝塚病院消化器内科

¹Department of Internal Medicine, Nagayama Hospital, ²Division of Clinical Research, ONH Minamiwakayama Medical Center, ³Department of Internal Medicine, ONH Minamiwakayama Medical Center, ⁴Department of Gastroenterology and Hepatology, Kaizuka City Hospital

キーワード : chronic liver disease, strain elastography, liver fibrosis index, elastic ratio, real-time tissue elastography

びまん性肝疾患の長期予後において，肝発癌リスクの評価として肝線維化の診断や治療による肝線維化の改善の評価，予測をすることは非常に重要である．肝線維化の評価は肝生検組織診断がゴールドスタンダードとされるが，侵襲的であるため繰り返し評価が困難であることや，サンプリングエラーなどの理由により，肝生検に代わる非侵襲的かつ正確な肝線維化評価法が望まれている．これまでに血小板数や肝線維化マーカーの測定，血液検査を基にした肝線維化計算式などが試みられてきた．また，超音波を用いた肝線維化評価法も開発され，その有用性が報告されつつある．Real-time tissue elastography（RTE）は日本で開発，市販の診断装置に搭載された技術で，生体内の組織ひずみを高速演算する手法であるcombined autocorrelation method（CAM）を用いて，リアルタイムで組織の相対的な硬さ情報をカラー表示するものである．肝線維化の評価においてRTEは非侵襲的かつ簡便に計測可能である．RTE画像から得られた特徴量や様々な肝線維化stage評価法と肝線維化との関係が報告されたが，RTEは炎症や胆汁うっ滞および脂肪沈着の影響を受けることなく線維化を良好に反映した．また，治療による肝線維化の改善を経時的に評価可能であった．

The long-term prognosis for patients with diffuse liver disease depends on an accurate diagnosis of hepatic fibrosis and assessment and prediction of improvements in this fibrosis with treatment. These assessments are vital for determining the hepatic cancer risk. A histological diagnosis of liver biopsy specimens is regarded as the gold standard for the assessment of hepatic fibrosis; however, noninvasive and accurate assessment methods for hepatic fibrosis are desired because of difficultly with repeated assessments due to the invasiveness and sampling errors encountered with biopsy. Based on platelet count and hepatic fibrosis marker measurements as well as relevant blood tests, formulas for calculating hepatic fibrosis have been tested. A method of assessing hepatic fibrosis using ultrasound was also developed, and its usefulness has been reported. Real-time tissue elastography (RTE) is a technology developed in Japan that can be loaded into commercially available diagnostic equipment. It provides a color display of information on tissue hardness in real time using a fast computation method, Combined Autocorrelation Method (CAM), for relative hardness based on tissue deformation in vivo. RTE enables measurements to be performed simply and noninvasively for the assessment of hepatic fibrosis. Relationships between the degrees or severity of features on RTE images and various stage assessment methods for hepatic fibrosis have been reported, but RTE most favorably reflects fibrosis without the effects of inflammation, cholestasis, or fatty deposition. It also enables serial assessments of improvements in hepatic fibrosis in response to treatment to be performed.