Applications of real-time ultrasound in obstetrics: the linear and dynamically focused phased arrays.

Real-time ultrasound is a dynamic imaging technique that allows in utero orientation to the fetus. It permits rapid and efficient examination of fetal anatomy and provides a dynamic assessment of fetal well-being. The energy dissipation can be comparable to that in conventional ultrasonic B-mode scanning. We have used both linear and dynamically focused phased arrays for fetal examinations in conjunction with conventional gray scale B-mode scanners. The sophisticated phased-array real-time systems have demonstrated higher resolution and an improved gray scale as compared with the linear arrays. Applications of real-time ultrasound in obstetrics are discussed, and appropriate clinical examples are cited that illustrate the value of the technique for study of both normal and abnormal fetal development. We believe that this technique is the most sensitive method of detecting intrauterine fetal demise. The relative advantages and disadvantages of linear and dynamically focused phased arrays in obstetric evaluation are considered.