Comparison of normal and harmonic ultrasonic imaging with a multirow array

Harmonic ultrasonic imaging is often qualitatively better in the clinical setting than normal ultrasonic imaging in the same frequency range. One possible factor in the differential image quality is the degree of aberration present in the imaged tissue. This work presents initial results of a quantitative comparison of normal and harmonic imaging in phantoms with aberration. We acquired single element RF data using an 8×128 array in normal (transmit frequency 6.7 MHz) and harmonic (transmit frequency 3.8 MHz) imaging modes. The multirow array allows a finer sampling of the aberrator as compared to a linear array. Estimates of apparent aberrator strength, apparent sound speed, and beam shape are compared for normal and harmonic data. Results demonstrate that the apparent aberration is generally greater for the normal mode than for the harmonic mode.