尾長谷 喜久子¹, 大倉 宏之²

Kikuko OBASE¹, Hiroyuki OKURA²

¹シカゴ大学循環器内科学循環器画像研究室, ²川崎医科大学循環器内科学

¹Cardiac Imaging Research, Section of Cardiology, Department of Medicine, University of Chicago, ²Department of Cardiology, Kawasaki Medical School

キーワード : mitral valve complex, three-dimensional echocardiography, surgeon's view, multiplanar reconstruction

経食道心エコーで左房側から描出されるsurgeon’s viewは，リアルタイムで描出が可能で僧帽弁の解剖を容易に理解できることから，3次元心エコー図法のなかで最も臨床に応用される手法である．また，取り込まれた3次元画像から2次元画像を切り出すmultiplaner reconstruction（MPR）法は，2次元心エコーでは描出の難しい断面を描出することができ，僧帽弁病変の詳細な観察が可能である．僧帽弁逆流ではカラードプラ法を用いてvena contracta areaを切り出して計測することにより重症度の指標となる．3次元心エコーの弱点にスティッチアーチファクトがあるが，僧帽弁狭窄例の弁口面積の計測では心房細動例であっても関心領域をできるだけ小さく設定すると，1心拍で弁口の3次元データを取り込むことが可能で，これから正確な弁口を切り出し，面積を計測することができる．弁下構造を捉えるためには，経食道心エコーの経胃アプローチが有用であり，通常の中部食道アプローチと合わせて観察することで僧帽弁複合体全体を把握できる．弁輪のサドル型形状の評価や弁尖のtenting volumeといった3次元計測は臨床応用には至っていない．経食道心エコーと比較し非侵襲的な経胸壁心エコーの解像度がさらに改善され，3次元指標の自動解析が正確にできるようになれば臨床応用も進むであろう．

The surgeon's view by three-dimensional (3D) transesophageal echocardiography is widely accepted as a useful way of imaging in clinical settings. It allows us to easily understand the anatomy of the mitral valve in real time. Another useful way of imaging in 3D echocardiography is the multiplanar reconstruction (MPR) method, which enables us to crop the acquired 3D data and have optimal images that are difficult to visualize in two-dimensional echocardiography. Vena contracta area can be measured using MPR from the color Doppler 3D volume dataset to evaluate the severity of mitral regurgitation. Stich artifact is one of the limitations of 3D echocardiography, but minimizing the area of interest allows one-beat acquisition of high-quality volume data even in patients with atrial fibrillation. Transthoracic one-beat acquisition of the mitral orifice allows precise measurement of the orifice area with cropping of the true orifice by MPR. To visualize the submitral apparatus, including the papillary muscle and chordae tendineae, the transgastric approach in transesophageal echocardiography should be performed as an adjunct to the conventional mid-esophageal approach. 3D quantification, such as tenting volume or leaflet surface area, is one of the big advantages of 3D echocardiography. However, it does not easily lend itself to clinical settings, because it is labor-intensive and time-consuming. An automated approach for quantification that minimizes inter-operator variability needs to be developed not only for transesophageal but also for transthoracic images.