Ultrasonic tomography using arc focusing beam

A novel tomographic reconstruction method for a phased array based on pulsed-echo imaging is proposed. A conventional sector scanning system uses a phased array to form a focusing beam for improvement of lateral resolution. However, the spatial resolution along normal direction to an image plane is not as good as the lateral resolution, since an acoustic lens which is used for the improvement of the resolution has a fixed focal length. The proposed method is based on a narrow phased array which forms an arc focusing beam instead of the point focusing beam. Since the echoes are expressed as an integration of the wavelets from the scatterers on the arc, the amplitude of echoes is a Radon transform of the distribution of the backscattering coefficient on a hemispherical surface. One of the methods to realize the arc focus beam is that a slit is attached in front of the array. Some experimental results on phantoms, using commercially available ultrasonic diagnosis equipment, are shown