Investigation of dual mode side and forward looking IVUS using a dual ring CMUT-on-CMOS array

Forward looking (FL) capability is desired in IVUS catheters to enable real time volumetric visualization of especially nearly or fully blocked arteries to guide interventions. The addition of side looking (SL) capability in the same catheter would be valuable to locate the device with respect to vessel walls and provide a conventional image to the clinicians. A single chip CMUT-on-CMOS array may provide both capabilities while enabling an extremely flexible catheter tip implementation. In this study, the combined side and forward viewing ability of the CMUT-on-CMOS IVUS array is investigated and initial experimental results are presented. To demonstrate SL imaging, we used a 20-MHz single chip dual-ring CMUT-on-CMOS array with 56 transmit and 48 receive elements fabricated on a 1.5-mm diameter 0.3-mm thick silicon donut. We placed four vertical wire targets close to the array plane and a front wire located above the same array. The frequency spectrums of the side and front targets have a center frequency of 12 MHz and 20 MHz, respectively. We also performed finite element method (FEM) simulations to obtain the frequency spectrums of the transient pressure signals at 0° and 90° which showed the same center frequencies. These results show promise for the viability of FLIVUS CMUT-on-CMOS device with dual mode side-forward looking imaging.