A Simplified Ultrasound Phased Array Sector Scanner

The phased array principle was introduced into medical ultrasound by Somer (1) and is now mainly used in two-dimensional echocardiography. In a phased array the ultrasound beam is rotated around the transducer and a sector scan is performed. The transducer typically has a width of 1–2 cm and consists of many elements, usually about 30. The rotation of the ultrasound beam is achieved by emitting the ultrasound pulses from the different elements at different instants and subjecting the received echo signals to delays, which are different for each element of the array. The principles of the ultrasound phased array are well known by now (see e.g. (1). (2)). The difference in delay τk between adjacent elements is given by $$\tau_{\rm k}=\rm x_k \cdot (sin\ \alpha)/c$$ where xk is the distance between elements, α is the deflection angle and c is the sound velocity.