1Obstetrics and Gynecology, Showa University Northern Yokohama Hospital, 2Obstetrics and Gynecology, Showa University, School of Medicine
3D ultrasound can scan three-dimensionally with 3D probe, process acquired volume data on computer, construct various images and display them. Therefore, it is possible to acquire not only 3D image but also arbitrary cross sectional images and tomographic images by single scan. Volume data has been acquired so far by mechanically moving a tomographic probe of 3D probe, however, the scan by electronic control became possible by locating oscillators in a matrix form in the latest model of instrument and the acquisition time became dramatically shorter and the frame rate of 4D ultrasound was increased. In 3D ultrasound, the selection of various image construction methods and diagnostic mode methods became essential depending on the purpose that a user wants to know, and it is not too much to say that the selection is responsible for diagnostic accuracy. 3D display image: A change of display methods is possible according to applications, for example, an angle of drawing can be changed freely from same volume data and a direction of virtual light can be changed, and a drawing of perspective image is possible.A diagnosis of external malformation is sufficiently possible by 2D ultrasound image and it has been carried out by only 2D ultrasound. However, by using 3D ultrasound, because explanation to patient becomes easier and in addition, understanding of disease by patient deepens, 3D display image is very useful for a diagnosis of external malformation such as a fetus cleft lip. Arbitrary cross sectional and multitomographic images: Display of tomographic image cutting volume data by arbitrary plane is possible. Because a point called referential dot is displayed in the same position spatially on orthogonal three cross sections, the grasp of object position is easy spatially according to the point. These display methods are especially useful for the evaluation of central nerves. STIC: Even for rapid movement such as a fetus heart with more than one hundred of heart rate per second, scan of 150 frames per second in B mode is possible because of the small interest region. For the data acquired by one scan, firstly a fetus heart rate and the cardiac cycle are automatically detected, and secondly the cross sections are shifted per each 0.5 second because one cardiac cycle is 0.5 second if heart rate is 120，and thirdly the images are combined together by computer processing and 3D moving image of the whole heart for one heart rate is constructed. By using this method, the arbitrary orthogonal three cross sections of a fetus heart can be acquired. The 4D probe locating oscillators in a matrix form as described above also can be applied to STIC technique and the shortening of data acquisition time became possible and the reduction of artifact caused by fetal movement became possible. Various display methods became possible accompanying with the advance of instruments and it is also issue in future how we should use them effectively in medical practice.