Top-orthogonal-to-bottom-electrode (TOBE) CMUT arrays for 3-D ultrasound imaging

Abstract

Two-dimensional ultrasound arrays hold great promise for 3-D imaging; however, wiring of each channel becomes impractical for large arrays or for small-footprint catheter probes for which the number of wires must be limited. Capacitive micromachined ultrasound transducers offer a promising solution for such 2-D array applications, but channel routing is still non-trivial. A top-orthogonal-to-bottom-electrode (TOBE) 2-D CMUT array architecture is presented along with row-column addressing schemes for low-channel-count 3-D ultrasound imaging. An N × N TOBE array is capable of obtaining 3-D images using only 2N channels. An interfacing scheme is presented in which transmit-receive signals are routed along rows while bias voltages are applied along columns, effectively allowing for single-element transmit/receive control. Simulations demonstrated potentially finer resolution and improved side lobe suppression over a previously published row-column-based imaging method. Laser vibrometer testing was done to measure membrane displacement in air and confirmed that single-element air-coupled actuation in transmit mode could be achieved using our proposed interfacing scheme. Acoustic testing was also performed in both transmit and receive modes to characterize the ability of the proposed interfacing scheme to achieve dominant-element transmission and reception in immersion operation. It was seen that membrane displacement in both modes was indeed largely confined to the active area.

Volumetric ultrasound imaging with row-column addressed 2-D arrays using Spatial Matched Filter beamforming

“…2-D row-column addressed arrays have recently received some attention [3]- [5]. In a row-column addressed array, the elements are accessed by their row or column index.…”

3-D imaging using row–column-addressed arrays with integrated apodization— part ii: transducer fabrication and experimental results

“…More recently, chen et al [19] and yen et al [20] have introduced arrays manufactured with a dual-layer structure to simplify the fabrication process. Zemp et al [21] and sampaleanu et al [22] have performed feasibility studies and recently photoacoustic imaging [23] using capacitive micromachined ultrasonic transducers (cMUTs). additionally, the yeow's group has demonstrated both characterization [24] and imaging using 16 + 16-element [25] and 32 + 32-element [26], [27] row-column-addressed cMUT arrays.…”

Top orthogonal to bottom electrode (TOBE) 2-D CMUT arrays for 3-D photoacoustic imaging

“…Top orthogonal to bottom electrode (ToBE) cMUTs are a new transducer architecture that has recently been proposed to facilitate simple addressing of a 2-d cMUT array [5]. In this architecture, the top and bottom electrodes are routed in N orthogonal rows and columns, creating an N × N array.…”

“…dominant element transmit and receive sensitivity is possible because biased elements exhibit smaller gaps and sensitivity scales as the reciprocal of the gap squared. during dominant single-element reception, parasitic capacitance from unused elements can reduce overall sensitivity; however, ∼100 mPa/ Hz sensitivity was still achievable [5]. ToBE cMUTs have numerous applications for fast 3-d medical imaging, but experimental 3-d images have yet to be obtained.…”

“…We chose to mechanically scan a small ToBE array with a biased signal column to simply demonstrate that high-resolution images can be obtained with ToBE cMUTs. The full functionality of ToBE cMUTs has been verified in [5]. We use a hair phantom in oil immersion as a target.…”