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Nonlinear imaging techniques have been used in diagnostic ultrasound in tissue harmonic imaging (THI) and in imaging of ultrasound contrast agents (UCAs). While in THI the nonlinearity comes from propagation, in UCAs the nonlinearity comes from the scattering process. Nonlinear pulsing schemes, transmitting a series of pulses and then combining the scattered signals in a way that all linear components cancel, have been proposed and implemented in diagnostic scanners. Various pulsing schemes for the detection of nonlinear echoes from tissues and contrast microbubbles were investigated experimentally in the present work. The pulsing schemes considered were pulse inversion (PI), power modulation (PM), and their combination (PMPI). Emphasis was placed on identifying the unique nonlinear components in the various pulsing schemes and their relative harmonic levels. Experiments of nonlinear propagation in water and nonlinear scattering from microbubbles were performed with both single elements transducers and a diagnostic ultrasound scanner. In general, PI has the most 2 nd harmonic without any 'nonlinear' fundamental, PM has mostly 'nonlinear fundamental, and PMPI has as much 'nonlinear' fundamental as PM and only slightly less 2 nd harmonic.

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