An Ultrasound Matrix Transducer for High-Frame-Rate 3-D Intra-cardiac Echocardiography

Objective: Described here is the development of an ultrasound matrix transducer prototype for high-frame-rate 3-D intra-cardiac echocardiography. Methods: The matrix array consists of 16 × 18 lead zirconate titanate elements with a pitch of 160 µm × 160 µm built on top of an application-specific integrated circuit that generates transmission signals and digitizes the received signals. To reduce the number of cables in the catheter to a feasible number, we implement subarray beamforming and digitization in receive and use a combination of time-division multiplexing and pulse amplitude modulation data transmission, achieving an 18-fold reduction. The proposed imaging scheme employs seven fan-shaped diverging transmit beams operating at a pulse repetition frequency of 7.7 kHz to obtain a high frame rate. The performance of the prototype is characterized, and its functionality is fully verified. Results: The transducer exhibits a transmit efficiency of 28 Pa/V at 5 cm per element and a bandwidth of 60% in transmission. In receive, a dynamic range of 80 dB is measured with a minimum detectable pressure of 10 Pa per element. The element yield of the prototype is 98%, indicating the efficacy of the manufacturing process. The transducer is capable of imaging at a frame rate of up to 1000 volumes/s and is intended to cover a volume of 70° × 70° × 10 cm. Conclusion: These advanced imaging capabilities have the potential to support complex interventional procedures and enable full-volumetric flow, tissue, and electromechanical wave tracking in the heart.</p

High-Frame-Rate Volumetric Porcine Renal Vasculature Imaging

Objective:The aim of this study was to assess the feasibility and imaging options of contrast-enhanced volumetric ultrasound kidney vasculature imaging in a porcine model using a prototype sparse spiral array. Methods: Transcutaneous freehand in vivo imaging of two healthy porcine kidneys was performed according to three protocols with different microbubble concentrations and transmission sequences. Combining high-frame-rate transmission sequences with our previously described spatial coherence beamformer, we determined the ability to produce detailed volumetric images of the vasculature. We also determined power, color and spectral Doppler, as well as super-resolved microvasculature in a volume. The results were compared against a clinical 2-D ultrasound machine. Results: Three-dimensional visualization of the kidney vasculature structure and blood flow was possible with our method. Good structural agreement was found between the visualized vasculature structure and the 2-D reference. Microvasculature patterns in the kidney cortex were visible with super-resolution processing. Blood flow velocity estimations were within a physiological range and pattern, also in agreement with the 2-D reference results. Conclusion:Volumetric imaging of the kidney vasculature was possible using a prototype sparse spiral array. Reliable structural and temporal information could be extracted from these imaging results.</p

A Pitch-Matched Low-Noise Analog Front-End With Accurate Continuous Time-Gain Compensation for High-Density Ultrasound Transducer Arrays

This article presents a compact analog front-end (AFE) circuit for ultrasound receivers with linear-in-dB continuous gain control for time-gain compensation (TGC). The AFE consists of two variable-gain stages, both of which employ a novel complementary current-steering network (CCSN) as the interpolator to realize continuously variable gain. The first stage is a trans-impedance amplifier (TIA) with a hardware-sharing inverter-based input stage to save power and area. The TIA's output couples capacitively to the second stage, which is a class-AB current amplifier (CA). The AFE is integrated into an application-specific integrated circuit (ASIC) in a 180-nm high-voltage BCD technology and assembled with a 100 mu m-pitch PZT transducer array of 8 x 8 elements. Both electrical and acoustic measurements show that the AFE achieves a linearin-dB gain error below +/- 0.4 dB within a 36-dB gain range, which is &gt;2x better than the prior art. Per channel, the AFE occupies 0.025 mm(2) area, consumes 0.8 mW power, and achieves an input-referred noise density of 131 pA/root Hz.</p

A Pitch-Matched Low-Noise Analog Front-End With Accurate Continuous Time-Gain Compensation for High-Density Ultrasound Transducer Arrays

This article presents a compact analog front-end (AFE) circuit for ultrasound receivers with linear-in-dB continuous gain control for time-gain compensation (TGC). The AFE consists of two variable-gain stages, both of which employ a novel complementary current-steering network (CCSN) as the interpolator to realize continuously variable gain. The first stage is a trans-impedance amplifier (TIA) with a hardware-sharing inverter-based input stage to save power and area. The TIA's output couples capacitively to the second stage, which is a class-AB current amplifier (CA). The AFE is integrated into an application-specific integrated circuit (ASIC) in a 180-nm high-voltage BCD technology and assembled with a 100 mu m-pitch PZT transducer array of 8 x 8 elements. Both electrical and acoustic measurements show that the AFE achieves a linearin-dB gain error below +/- 0.4 dB within a 36-dB gain range, which is >2x better than the prior art. Per channel, the AFE occupies 0.025 mm(2) area, consumes 0.8 mW power, and achieves an input-referred noise density of 131 pA/root Hz

A 1.2-mW/Channel Pitch-Matched Transceiver ASIC Employing a Boxcar-Integration-Based RX Micro-Beamformer for High-Resolution 3-D Ultrasound Imaging

This article presents a low-power and small-area transceiver application-specific integrated circuit (ASIC) for 3-D trans-fontanelle ultrasonography. A novel micro-beamforming receiver architecture that employs current-mode summation and boxcar integration is used to realize delay-and-sum on an N -element sub-array using N× fewer capacitive memory elements than conventional micro-beamforming implementations, thus reducing the hardware overhead associated with the memory elements. The boxcar integration also obviates the need for explicit anti-aliasing filtering in the analog front end, thus further reducing die area. These features facilitate the use of micro-beamforming in smaller pitch applications, as demonstrated by a prototype transceiver ASIC employing micro-beamforming on sub-arrays of N=4 elements, targeting a wearable ultrasound device that monitors brain perfusion in preterm infants via the fontanel. To meet its strict spatial resolution requirements, a 10-MHz 100- μ m-pitch piezoelectric transducer array is employed, leading to a per-element die area &gt; 2 × smaller than prior designs employing micro-beamforming.</p

A 1.2-mW/Channel Pitch-Matched Transceiver ASIC Employing a Boxcar-Integration-Based RX Micro-Beamformer for High-Resolution 3-D Ultrasound Imaging

This article presents a low-power and small-area transceiver application-specific integrated circuit (ASIC) for 3-D trans-fontanelle ultrasonography. A novel micro-beamforming receiver architecture that employs current-mode summation and boxcar integration is used to realize delay-and-sum on an N -element sub-array using N× fewer capacitive memory elements than conventional micro-beamforming implementations, thus reducing the hardware overhead associated with the memory elements. The boxcar integration also obviates the need for explicit anti-aliasing filtering in the analog front end, thus further reducing die area. These features facilitate the use of micro-beamforming in smaller pitch applications, as demonstrated by a prototype transceiver ASIC employing micro-beamforming on sub-arrays of N=4 elements, targeting a wearable ultrasound device that monitors brain perfusion in preterm infants via the fontanel. To meet its strict spatial resolution requirements, a 10-MHz 100- μ m-pitch piezoelectric transducer array is employed, leading to a per-element die area &gt; 2 × smaller than prior designs employing micro-beamforming.</p

A front-end ASIC with high-voltage transmit switching and receive digitization for forward-looking intravascular ultrasound

This paper presents a front-end ASIC for forward-looking intravascular ultrasound (IVUS) imaging. The ASIC is intended to be mounted at the tip of a catheter and can interface a total of 80 piezo-electric transducer elements with an imaging systems using only 4 cables, thus significantly reducing the system complexity compared to the prior art. It is capable of switching high-voltage transmit pulses to 16 transmit elements, and capturing the resulting echo signals using 64 multiplexed receive elements. The ASIC digitizes the received signals locally, providing more robust communication than prior analog approaches. Measurements show that the ASIC effectively switches transmit pulses up to 30 V, and digitizes echo signals with a bandwidth of 16 MHz, while consuming only 10 mW. Acoustic measurements in combination with a prototype transducer array demonstrate pulse transmission and reception. Finally, a B-mode image of a needle phantom demonstrates the imaging capability.</p

Experimental Investigation of the Effect of Subdicing on an Ultrasound Matrix Transducer

Over the past decades, real-time three-dimensional (3D) medical ultrasound has attracted much attention since it enables clinicians to diagnose more accurately. This calls for ultrasound matrix transducers with a large number of elements, which can be interfaced with an application-specific integrated circuit (ASIC) for data reduction. An important aspect of the design of such a transducer is the geometry of each element, since it affects the mode of vibration and, consequently, the efficiency of the transducer. In this paper, we experimentally investigate the effect of subdicing on a piezoelectric (PZT) transducer. We fabricate and acoustically characterize a prototype PZT matrix transducer built on top of ASICs. The prototype transducer contains subdiced and non-subdiced elements, whose performance can be directly compared under the same conditions. Measurement results show that subdiced elements have a better performance compared to non-subdiced ones. Subdicing increases the peak pressure by 25%, raises the bandwidth by 10% and reduces the ringing time by 25%. </p

Sparse volumetric PZT array with density tapering

© 2018 IEEE. Volumetric medical ultrasound imaging currently provides either high resolution or high frame rates. We propose a sparse array probe with only 256 elements that are density tapered. All elements are directly wired to an ultrasound engine, thus being flexible in transmission and reception. Here we present the design, realization, and characterization of a probe prototype for carotid 3D high frame rate scanning (5 MHz). The design is based on rapid prototyping with printed circuit board substrates to wire the elements to external connectors. The results show that 95% of the elements was acoustically active, producing a peak pressure of 400 kPa when focused at 24 mm with a 20 V amplitude, 3-cycle tone burst. The fractional one-way -6dB bandwidth (FBW) was 32 %, which is narrower than the designed one (50% FBW), due to an unexplained ringing effect. These results show that the probe is viable for volumetric imaging tests, albeit that it can be further optimized.status: publishe