The Clinical Benefits of Adding a Third Dimension to Assess the Left Ventricle with Echocardiography
Figure 3
(a) Schematic drawing of a full matrix array transducer where about 3000 acoustically independent piezoelectric elements are arranged in row and columns and used to steer the beam electronically. This matrix arrangement of piezoelectric elements allows their phasic firing to produce an ultrasound beam that can be steered in vertical (axial), lateral (azimuthal), and anteroposterior (elevation) directions in order to acquire a volumetric (pyramidal) data set. (b) Beamforming with 3D matrix array transducers. To save power and electronic circuitry needs (costs) and reduce the connection cable size the beamforming and steering processes have been split into two: the transducer and the ultrasound machine levels. The transducer contains the piezoelectric elements arranged in a matrix array, interconnection technology and integrated analog circuits (DELAY) to control transmit and receive signals using different subsections of the matrix (patches) to control analog prebeamforming and fine steering. Signals from each patch are summed in order to reduce the number of digital lines in the coaxial cable that connects the transducer to the ultrasound system from 3000 to the conventional size of 128–256 channels. At the ultrasound machine level, analog-to-digital (A/D) convertors amplify, filter, and digitize the elements signals. The resulting digital signals are focused (coarse steering) using digital delay (DELAY) circuitry and summed together () to form the received signal from a desired object.
