Tissue harmonic imaging with CMUT probe by amplitude modulation

Tissue harmonic imaging (THI) based on amplitude modulation by controlling the number of driving elements (AM-CNDE) with a prototype CMUT probe is demonstrated. AM-CNDE requires multiple transmission pulses and the amplitude of each pulse is controlled by changing the number of driving channels in a probe. The harmonic signals are extracted clearly even if the CMUTs have large nonlinearity. The beam patterns of these transmissions and extracted harmonic components are investigated using two approaches: nonlinear propagation simulation and measurement using a manufactured CMUT probe that is able to transmit sufficient pressure (over 1.5 MPa) to generate tissue harmonic components. Results show that the extracted harmonic beam is narrower than that of the fundamental component. Moreover, practical image quality can be obtained by AM-CNDE with the manufactured CMUT probe and a commercially available ultrasound scanner.