Demonstrate the magnitudes of typical time delays between pulse emissions from different transducer elements when focusing and steering the ultrasound beam by performing the following calculation.

a) Consider a 300 element, linear transducer, which is 50 mm between the centre lines of the first and the three-hundredth elements. Determine the pitch of the elements, that is to say, the distance between the centre lines of successive elements.

b) At a given time, a single beam is generated by an active group of 19 elements. This beam is steered 11.5 degrees off-axis to the right as measured at the centre of the group showing elements 1 to 19 and the focal point

c) State the order in which elements 1, 10 and 19 have to fired. Then, calling the time at which the first element is fired, time zero, calculate the time at which the other two elements are subsequently fired. The two successive times will be given in ms, s or ns as appropriate. Calculate, finally, the time delay between the firing of successive elements of the array.

Current element group using elements 1 to 19 (not all elements shown) 18 19 "'5: Element 1 path to focal point Flour. 1 A single active group of transducer elements with the beam steered 11.5' off axis to the ri ht to the focal - - int shown