須藤 理¹, 鶴岡 信治¹, 木村 文隆¹, 三宅 康二¹, 本康 宗信², 関岡 清次², 中野 赳²

Osamu SUDO¹, Sinji TSURUOKA¹, Fumitaka KlMURA¹, Yasuji MlYAKE¹, Munenobu MOTOYASU², Kiyotsugu SEKIOKA², Takeshi NAKANO²

¹三重大学工学部, ²三重大学第1内科

¹Faculty of Engineering Mie University, ²First Department of Internal Medicine Mie University School of Medicine

キーワード : Acceleration image　, Strain image　, Ultrasonic Doppler image

Color Doppler flow imaging without the low-cut filter that normally suppresses clutter signals has recently been used to assess ventricular wall function. This modality provides an objective measure of velocity of wall motion. Some attention is required to interpret the images obtained with this system, however, because the displayed velocity varies with direction of the ultrasonic scan beam. Further, wall velocity represents not only regional contraction and dilatation but translational or rotational motion of the whole heart as well. We therefore evaluated two functional images: the acceleration image, to detect asynchronous wall motion, and the regional strain image, to detect pure regional wall function while minimizing the effect of translational and rotational motion. Color Doppler images and B-mode images measuring 640×512 pixels and having 6-bit resolution were transferred to a work station. Identification of the ventricular wall was based on B-mode brightness. Acceleration images were obtained from the velocity difference between two consecutive frames and frame rate. Strain images were obtained as the velocity difference between two appropriately spaced (5 to 7 mm) points along the scan-beam line. These points were acceptable when both were judged to lie in the ventricular wall. We evaluated the present method in subjects with normal hearts and in those with WPW syndrome, myocardial infarction, and similar disorders. In the normal heart, acceleration image the ventricular wall was encoded in approximately homogeneous color. Variation in color accurately represented end-ejection and early diastolic filling phase. In type-B WPW syndrome, a part of the anterior wall was encoded in red (acceleration) in the end-ejection phase, while other regions were encoded in blue (deceleration); these colors were reversed in the early diastolic phase. Strain image also showed abnormal wall motion in cases of myocardial infarction. Consequentially, strain image is susceptible to speckle noise and requires higher resolution of velocity in order to produce a useful image. It is much easier to interpret the two images presented here, because computer processing has removed the effect of location of the ventricular wall, whereas both the short-axis anterior and posterior walls are displayed in opposite colors in conventional Doppler color images, reflecting direction of motion against the scan-beam line.