A Handheld Imaging Probe for Acoustic Angiography With an Ultrawideband Capacitive Micromachined Ultrasonic Transducer (CMUT) Array

This article presents an imaging probe with a 256-element ultrawideband (UWB) 1-D capacitive micromachined ultrasonic transducer (CMUT) array designed for acoustic angiography (AA). This array was fabricated on a borosilicate glass wafer with a reduced bottom electrode and an additional central plate mass to achieve the broad bandwidth. A custom 256-channel handheld probe was designed and implemented with integrated low-noise amplifiers and supporting power circuitry. This probe was used to characterize the UWB CMUT, which has a functional 3-dB frequency band from 3.5 to 23.5 MHz. A mechanical index (MI) of 0.33 was achieved at 3.5 MHz at a depth of 11 mm. These promising measurements are then combined to demonstrate AA. The use of alternate amplitude modulation (aAM) combined with a frequency analysis of the measured transmit signal demonstrates the suitability of the UWB CMUT for AA. This is achieved by measuring only a low level of unwanted high-frequency harmonics in both the transmit signal and the reconstructed image in the areas other than the contrast bubbles.