Piezoelectric micromachined ultrasound transducers (pMUTs) are potentialcandidates for catheter-based ultrasound phased arrays. pMUTs consist of leadzirconate titanate (PZT) thin film membranes formed on silicon substrates andare operated in flexure mode by driving the PZT film above its coercive field toinduce flextensional motion. The fundamental operation of pMUT devices has beendemonstrated; however, pulse-echo imaging has been limited to date. Theobjective of this work was to optimize transducer design for improved pulse-echoimaging performance. Flexure mode operation was optimized by (1) increasingtransmit voltage above the PZT coercive field to induce ferroelectric domainswitching, and (2) using partial cycle transmit pulses to increase thepolarization in the PZT thin film and increase receive signal. As a result,pulse-echo images of tissue were obtained. 1-D arrays operating at 5 MHz werecapable of resolving targets in a commercial tissue phantom as well as humananatomy. Real-time 3-D imaging was also demonstrated using 2-D arrays at 5 and12.5 MHz. These results suggest that pMUTs have sufficient performance forapplication in ultrasound imaging with frequency range suitable forcatheter-based phased-array transducers. © 2010 IEEE.