A new contrast parameter to qualify 1D and 2D arrays

A Figure-of-Merit for the performance of any medical array is defined, which is new in the field of medical imaging: the object contrast parameter. This contrast parameter quantifies the contrast between an on-axis object and its surroundings and as such is closely related to the visibility of an object. Its behaviour as a function of depth depends on the physical array properties and the electronic settings (e.g. delay settings). With the aid of a simulation tool the significance of the contrast parameters is evaluated. It was shown that the contrast parameter is a useful parameter in addition to the conventional Figures-of-Merit used to assess the array performance, such as beam diameter and grating lobe level. In particular the contrast parameter facilitates the making of compromises between beamdiameter and grating lobe levels, which impose conflicting demands on the design of the array. It is concluded that the object-contrast parameter can be very helpful for finding the optimal design of the array and the optimal settings for electronic focusing.