Design, modeling and characterization of a 35MHz 1-D CMUT phased array

High frequency ultrasound arrays have applications ranging from imaging of small animals, skin and eye to intravascular ultrasound (IVUS). We describe an application where a guidewire IVUS system uses high frequency phased arrays with integrated electronics placed directly on the guidewire rather than a catheter for imaging. Multiple arrays provide the full transverse cross section of the artery during percutaneous interventions. We focus on a 1-D CMUT phased array to be used in the guidewire IVUS. CMUTs are particularly suitable for this application with their ease of fabrication and single chip electronics integration. The array frequency is chosen to be around 35-40MHz with 10MHz bandwidth so that the 1-D CMUT phased array with a 300um wide aperture can closely match the lateral resolution of a current 20MHz, 3.5F solid state IVUS array. Here we discuss the initial design, large signal modeling, fabrication and experimental characterization of a 12 element, 300×1000um CMUT array with 25um pitch. The electrical and acoustic characterization results for a CMUT array with 20um square membranes are presented. Modeling results for different size membranes indicating adequate performance for higher bandwidth applications are also discussed.