Nonlinear difference-frequency ultrasound via dual-annular capacitive micromachined ultrasonic transducer array

Difference-frequency-based ultrasound imaging has emerged as a promising new modality in medical imaging, allowing for high-contrast elastographic imaging to diagnose conditions such as osteoporosis and tumors. Previous reported approaches to difference-frequency ultrasound (dfUS), however, are hampered by the bulk caused by needing multiple discrete transducers, limiting their practicality and integration into more compact and user-friendly devices. Our research presents a breakthrough by successfully integrating dfUS signal generation capabilities into a compact device utilizing a custom-designed dual-annular capacitive micromachined ultrasonic transducer (CMUT) array. We successfully fabricated and evaluated a broadbandwidth (178%) device based on this design. In addition, we used our device to obtain a dfUS image with a high contrast of 61.15 dB, a marked improvement from the low 8.463 dB contrast of the linear ultrasound image. This innovative approach significantly advances the dfUS generation process by reducing the system’s size and complexity while enhancing portability.