tailieunhanh - Design of curvilinear array apertures for 3D ultrasonic imaging

The development of ultrasonic volumetric imaging is closely linked to the development of systems that are able to operate bidimensional array transducers. These arrays are useful for ultrasonic volumetric imaging, because they produce steered and focused beams throughout a volume of interest. | 2 Design of Curvilinear Array Apertures for 3D Ultrasonic Imaging Oscar Martmez-Graullera1 Luis Gomez-Ullate2 David Romero3 Carlos J. Martín4 and Gregorio Godoy5 1 2 3 4Centro de Acústica Aplicada y Evaluation No Destructiva. UPM-CSIC. Ctra. Campo Real KM 0 200 28500 Arganda del Rey Madrid 5Dpto. Ing Electrónica. Universidad de Jaen Spain 1. Introduction The development of ultrasonic volumetric imaging is closely linked to the development of systems that are able to operate bidimensional array transducers. These arrays are useful for ultrasonic volumetric imaging because they produce steered and focused beams throughout a volume of interest. Typical 2-D arrays are based on a Squared Matrix SM configuration where the array elements are the matrix cells. Their performance is determined by their width in terms of wavelenght. Resolution and the dynamic range are determined by wavelenght aperture diameter ratio and number of elements and the wavelenght interelement distance ratio respectively Smith et al. 1991 . In SM apertures since element distribution is uniform the composition of the secondary lobes is determined by interelement distance. All elements contribute to its formation. These lobes are known as grating lobes and produce image artifacts that can reduce the signal-to-noise ratio. Nowadays avoiding image artifacts is key to array design. For matrix and linear arrays the composition of these lobes can only be avoided by limiting the interelement distance to A 2. In practice it means that for 1o of lateral resolution a 60A diameter aperture with 14400 elements is needed. Then several problems can be identified Thousands of electronic channels are needed which increases the cost and complexity of the imaging system. Thousands of elements are needed which increases the complexity of the transducer manufacture. The small size of the elements is associated to low signal-to-noise ratios. Considerable difficulties in making the electrical connections. These problems