44-MHz LiNbO3 transducers for UBM-guided Doppler ultrasound.

In the post genome-sequencing era, physiological phenotyping of genetically engineered mice is critical to further our understanding of the functional consequences of specific genetic defects. We have developed a 40-50 MHz ultrasound biomicroscopy-(UBM) guided, pulsed Doppler system for the sensitive detection of in vivo blood velocity waveforms in the mouse embryonic cardiovascular system. Our approach uses separate transducers for simultaneous imaging and Doppler blood flow measurements. To this end, unfocused, air-backed lithium niobate (LiNbO3) transducers provide sensitive Doppler detection and the flexibility of adjusting the axial position of the pulsed Doppler sample volume over many millimeters depth range of the collimated ultrasound beam. In this paper we describe the fabrication and characterization of the electromechanical and ultrasonic beam properties of 44-MHz LiNbO3 Doppler transducers. We further demonstrate the utility of these Doppler transducers for interrogating blood vessels such as the dorsal aorta over a range of mouse embryonic stages and axial range-gate depths.