Experimental verification of the correlation behavior of analytic ultrasound radiofrequency signals received from moving structures

Conventional pulsed ultrasound systems are only able to detect motion along the ultrasound beam (i.e., axial motion), If the angle between the actual motion direction and the ultrasound beam is known, then the magnitude of th e actual motion can be derived. This technique can be applied for laminar b lood-flow measurements in straight vessels, but for tissue motion it is ina dequate because the local tissue motion direction is unknown and may be pos ition-dependent. Assessment of both the axial motion and the lateral motion (i.e., in the direction perpendicular to the ultrasound beam) makes angle- independent assessment of the magnitude of the actual motion feasible. Info rmation about the axial and lateral motion is available in a set of radiofr equency (RF) signals obtained along the same line of observation (M-mode), The experiments described in the present paper show that axial and lateral motion can be estimated from the shape of the envelope of the 2-D (spatial and temporal) correlation function of analytic M-mode RF signals, Furthermo re, it is demonstrated that the shape is also affected by the Band width of the received RF signals, signal-to-noise ratio, and local amplitude and ph ase characteristics of the ultrasound beam. (C) 1998 World Federation for U ltrasound in Medicine & Biology.