Miniature ultrasound probes for real-time 3D imaging and monitoring of cardiac interventions

Publications

Integrated Transceivers for Emerging Medical Ultrasound Imaging Devices: A Review
C. Chen; M. Pertijs;
IEEE Open Journal of the Solid-State Circuits Society,
Volume 1, pp. 104-114, September 2021. DOI: 10.1109/OJSSCS.2021.3115398
Impact of Bit Errors in Digitized RF Data on Ultrasound Image Quality
Z. Chen; M. Soozande; H. Vos; J. Bosch; M. Verweij; N. de Jong; M. Pertijs;
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control,
Volume 67, Issue 1, pp. 13-24, January 2020. DOI: 10.1109/TUFFC.2019.2937462

Abstract: ...
This paper quantitatively analyzes the impact of bit errors in digitized RF data on ultrasound image quality. The quality of B-mode images in both linear and phased array imaging is evaluated by means of three objective image quality metrics: peak signal-to-noise ratio, structural similarity index and contrast-to-noise ratio, when bit errors are introduced to the RF data with different bit-error rates (BERs). The effectiveness of coding schemes for forward error detection and correction to improve the image quality is also studied. The results show that ultrasound imaging is inherently resilient to high BER. The image quality suffers unnoticeable degradation for BER lower than 1E-6. Simple 1-bit parity coding with 9% added redundancy helps to retain similar image quality for BER up to 1E-4, and Hamming coding with 33.3% added redundancy allows the BER to increase to 1E-3. These results can serve as a guideline in the datalink design for ultrasound probes with in-probe receive digitization. With much more relaxed BER requirements than in typical datalinks, the design can be optimized by allowing fewer cables with higher data rate per cable or lower power consumption with the same cable count.
A 1.54mW/Element 150μm-Pitch-Matched Receiver ASIC with Element-Level SAR/Shared-Single-Slope Hybrid ADCs for Miniature 3D Ultrasound Probes
J. Li; Z. Chen; M. Tan; D. van Willigen; C. Chen; Z. Y. Chang; E. Noothout; N. de Jong; M. D. Verweij; M. A. P. Pertijs;
In Dig. Techn. Paper IEEE Symposium on VLSI Circuits (VLSI),
IEEE, pp. 1-2, June 2019.
Multiline 3D beamforming using micro-beamformed datasets for pediatric transesophageal echocardiography
D. Bera; S. B. Raghunathan; C. Chen; Z. Chen; M. A. P. Pertijs; M. D. Verweij; V. Daeichin; H. J. Vos; A. F. W. van der Steen; N. de Jong; J. G. Bosch;
Physics in Medicine \& Biology,
Volume 63, Issue 7, pp. 1-16, March 2018. DOI: 10.1088/1361-6560/aab45e

Abstract: ...
Until now, no matrix transducer has been realized for 3D transesophageal echocardiography (TEE) in pediatric patients. In 3D TEE with a matrix transducer, the biggest challenges are to connect a large number of elements to a standard ultrasound system, and to achieve a high volume rate (>200 Hz). To address these issues, we have recently developed a prototype miniaturized matrix transducer for pediatric patients with micro-beamforming and a small central transmitter. In this paper we propose two multiline parallel 3D beamforming techniques (µBF25 and µBF169) using the micro-beamformed datasets from 25 and 169 transmit events to achieve volume rates of 300 Hz and 44 Hz, respectively. Both the realizations use angle-weighted combination of the neighboring overlapping sub-volumes to avoid artifacts due to sharp intensity changes introduced by parallel beamforming. In simulation, the image quality in terms of the width of the point spread function (PSF), lateral shift invariance and mean clutter level for volumes produced by µBF25 and µBF169 are similar to the idealized beamforming using a conventional single-line acquisition with a fully-sampled matrix transducer (FS4k, 4225 transmit events). For completeness, we also investigated a 9 transmit-scheme (3 × 3) that allows even higher frame rates but found worse B-mode image quality with our probe. The simulations were experimentally verified by acquiring the µBF datasets from the prototype using a Verasonics V1 research ultrasound system. For both µBF169 and µBF25, the experimental PSFs were similar to the simulated PSFs, but in the experimental PSFs, the clutter level was ~10 dB higher. Results indicate that the proposed multiline 3D beamforming techniques with the prototype matrix transducer are promising candidates for real-time pediatric 3D TEE.
Fast volumetric imaging using a matrix TEE probe with partitioned transmit-receive array
D. Bera; F. van den Adel; N. Radeljic-Jakic; B. Lippe; M. Soozande; M. A. P. Pertijs; M. D. Verweij; P. Kruizinga; V. Daeichin; H. J. Vos; A. F. W. van der Steen; J. G. Bosch; N. de Jong;
Ultrasound in Medicine \& Biology,
Volume 44, Issue 9, pp. 2025-2042, July 2018. DOI: 10.1016/j.ultrasmedbio.2018.05.017

Abstract: ...
We describe a 3-D multiline parallel beamforming scheme for real-time volumetric ultrasound imaging using a prototype matrix transesophageal echocardiography probe with diagonally diced elements and separated transmit and receive arrays. The elements in the smaller rectangular transmit array are directly wired to the ultrasound system. The elements of the larger square receive aperture are grouped in 4 × 4-element sub-arrays by micro-beamforming in an application-specific integrated circuit. We propose a beamforming sequence with 85 transmit–receive events that exhibits good performance for a volume sector of 60° × 60°. The beamforming is validated using Field II simulations, phantom measurements and in vivo imaging. The proposed parallel beamforming achieves volume rates up to 59 Hz and produces good-quality images by angle-weighted combination of overlapping sub-volumes. Point spread function, contrast ratio and contrast-to-noise ratio in the phantom experiment closely match those of the simulation. In vivo 3-D imaging at 22-Hz volume rate in a healthy adult pig clearly visualized the cardiac structures, including valve motion.
Acoustic characterization of a miniature matrix transducer for pediatric 3D transesophageal echocardiography
V. Daeichin; D. Bera; S. Raghunathan; M. ShabaniMotlagh; Z. Chen; C. Chen; E. Noothout; H. J. Vos; M. Pertijs; J. Bosch; N. de Jong; M. Verweij;
Ultrasound in Medicine \& Biology,
Volume 44, Issue 10, pp. 2143-2154, October 2018. DOI: 10.1016/j.ultrasmedbio.2018.06.009

Abstract: ...
This paper presents the design, fabrication and characterization of a miniature PZT-on-CMOS matrix transducer for real-time pediatric 3-dimensional (3D) transesophageal echocardiography (TEE). This 3D TEE probe consists of a 32 × 32 array of PZT elements integrated on top of an Application Specific Integrated Circuit (ASIC). We propose a partitioned transmit/receive array architecture wherein the 8 × 8 transmitter elements, located at the centre of the array, are directly wired out and the remaining receive elements are grouped into 96 sub-arrays of 3 × 3 elements. The echoes received by these sub-groups are locally processed by micro-beamformer circuits in the ASIC that allow pre-steering up to ±37°. The PZT-on-CMOS matrix transducer has been characterized acoustically and has a centre frequency of 5.8 MHz, -6 dB bandwidth of 67%, a transmit efficiency of 6 kPa/V at 30 mm, and a receive dynamic range of 85 dB with minimum and maximum detectable pressures of 5 Pa and 84 kPa respectively. The properties are very suitable for a miniature pediatric real-time 3D TEE probe.
An Element-Matched Electro-Mechanical ΔΣ ADC for Ultrasound Imaging
M. D'Urbino; C. Chen; Z. Chen; Z. Y. Chang; J. Ponte; B. Lippe; M. Pertijs;
IEEE Journal of Solid-State Circuits,
Volume 53, Issue 10, pp. 2795-2805, October 2018. DOI: 10.1109/JSSC.2018.2859961

Abstract: ...
This paper presents a power- and area-efficient approach to digitizing the echo signals received by piezoelectric transducer elements, commonly used for ultrasound imaging. This technique utilizes such elements not only as sensors but also as the loop filter of an element-level Δ Σ analog to digital converter (ADC). The receiver chain is thus greatly simplified, yielding savings in area and power. Every ADC becomes small enough to fit underneath a 150 μ m x 150 μ m transducer element, enabling simultaneous acquisition and digitization from all the elements in a 2-D array. This is especially valuable for miniature 3-D probes. Experimental results are reported for a prototype receiver chip with an array of 5 x 4 element-matched ADCs and a transducer array fabricated on top of the chip. Each ADC consumes 800 μ W from a 1.8 V supply and achieves a SNR of 47 dB in a 75% bandwidth around a center frequency of 5 MHz.
A Pitch-Matched Front-End ASIC with Integrated Subarray Beamforming ADC for Miniature 3-D Ultrasound Probes
C. Chen; Z. Chen; D. Bera; E. Noothout; Z. Y. Chang; M. Tan; H. Vos; J. Bosch; M. Verweij; N. de Jong; M. Pertijs;
IEEE Journal of Solid-State Circuits,
Volume 53, Issue 11, pp. 3050-3064, November 2018. DOI: 10.1109/JSSC.2018.2864295

Abstract: ...
This paper presents a front-end application-specified integrated circuit (ASIC) integrated with a 2-D PZT matrix transducer that enables in-probe digitization with acceptable power dissipation for the next-generation endoscopic and catheter-based 3-D ultrasound imaging systems. To achieve power-efficient massively parallel analog-to-digital conversion (ADC) in a 2-D array, a 10-bit 30 MS/s beamforming ADC that merges the subarray beamforming and digitization functions in the charge domain is proposed. It eliminates the need for costly intermediate buffers, thus significantly reducing both power consumption and silicon area. Self-calibrated charge references are implemented in each subarray to further optimize the system-level power efficiency. High-speed datalinks are employed in combination with the subarray beamforming scheme to realize a 36-fold channel-count reduction and an aggregate output data rate of 6 Gb/s for a prototype receive array of 24 x 6 elements. The ASIC achieves a record power efficiency of 0.91 mW/element during receive. Its functionality has been demonstrated in both electrical and acoustic imaging experiments.
A 0.91mW/Element Pitch-Matched Front-End ASIC with Integrated Subarray Beamforming ADC for Miniature 3D Ultrasound Probes
C. Chen; Z. Chen; D. Bera; E. Noothout; Z. Y. Chang; M. Tan; H. J. Vos; J. G. Bosch; M. D. Verweij; N. de Jong; M. A. P. Pertijs;
In Dig. Techn. Papers IEEE International Solid-State Circuits Conference (ISSCC),
pp. 186-187, February 2018. DOI: 10.1109/ISSCC.2018.8310246
A Power-Efficient Transmit Beamformer ASIC for 3-D Catheter-Based/ Endoscopic Probes
Z. Chen; E. Kang; Z. Y. Chang; E. Noothout; J. G. Bosch; M. Verweij; N. de Jong; M. Pertijs;
In Proc. IEEE International Ultrasonics Symposium (IUS),
IEEE, October 2018. (abstract).

Abstract: ...
To reduce cable count in 3D catheter-based or endoscopic probes, generation of the (HV) transmit (TX) signals using an in-probe ASIC is a promising solution. However, such ASICs are subject to stringent power-consumption constraints to limit self-heating. The power consumed by conventional HV pulsers is at least fCV^2, due to the periodic charging/discharging of the transducer element capacitance C. HV switches can be used to connect elements to a pulser in the imaging system, thus only dissipating a fraction of fCV^2 in the probe, but full TX beamforming (BF) cannot be realized using switches. In this work, we propose a power-efficient HV TX circuit capable of providing full TX BF using only 3 HV connections to the system. Implemented in a 0.18um BCD process, the ASIC was fully evaluated by means of post-layout simulations.
A quantitative study on the impact of bit errors on image quality in ultrasound probes with in-probe digitization
Z. Chen; M. Soozande; H. J. Vos; J. G. Bosch; M. Verweij; N. de Jong; M. Pertijs;
In Proc. IEEE International Ultrasonics Symposium (IUS),
IEEE, October 2018. (abstract).

Abstract: ...
Integrating ultrasound transducers with ASICs which digitize and multiplex the received echo signals effectively mitigates the burden of signal transmission for 3-D catheter-based or endoscopic probes. Multiplexing the echo signals from multiple elements onto a cable reduces the cable count, but requires a higher data rate per cable, which typically involves a trade-off between power consumption and bit-error rate (BER). Understanding the impact of finite BER on the resulting image quality is a necessity to optimize the cable count and power consumption. In this work, this impact is quantitatively assessed using Matlab simulations. The effectiveness of error correction is also investigated.
Front-End ASICs for 3-D Ultrasound: From Beamforming to Digitization
Chao Chen;
PhD thesis, Delft University of Technology, April 2018.
A Front-end ASIC with Receive Sub-Array Beamforming Integrated with a 32 × 32 PZT Matrix Transducer for 3-D Transesophageal Echocardiography
C. Chen; Z. Chen; D. Bera; S. B. Raghunathan; M. Shabanimotlagh; E. Noothout; Z. Y. Chang; J. Ponte; C. Prins; H. J. Vos; J. G. Bosch; M. D. Verweij; N. de Jong; M. A. P. Pertijs;
IEEE Journal of Solid-State Circuits,
Volume 52, Issue 4, pp. 994‒1006, April 2017. DOI: 10.1109/JSSC.2016.2638433

Abstract: ...
This paper presents a power- and area-efficient front-end application-specific integrated circuit (ASIC) that is directly integrated with an array of 32 × 32 piezoelectric transducer elements to enable next-generation miniature ultrasound probes for real-time 3-D transesophageal echocardiography. The 6.1 × 6.1 mm2 ASIC, implemented in a low-voltage 0.18-μm CMOS process, effectively reduces the number of receive (RX) cables required in the probe's narrow shaft by ninefold with the aid of 96 delay-and-sum beamformers, each of which locally combines the signals received by a sub-array of 3 × 3 elements. These beamformers are based on pipeline-operated analog sample-and-hold stages and employ a mismatch-scrambling technique to prevent the ripple signal associated with the mismatch between these stages from limiting the dynamic range. In addition, an ultralow-power low-noise amplifier architecture is proposed to increase the power efficiency of the RX circuitry. The ASIC has a compact element matched layout and consumes only 0.27 mW/channel while receiving, which is lower than the state-of-the-art circuit. Its functionality has been successfully demonstrated in 3-D imaging experiments.
Acoustic Characterization of a 32 × 32 Element PZT-on-ASIC Matrix Transducer for 3D Transesophageal Echocardiography
M. Shabanimotlagh; S. Raghunathan; D. Bera; Z. Chen; C. Chen; V. Daeichin; M. Pertijs; J. G. Bosch; N. de Jong; M. Verweij;
In Dutch Bio-Medical Engineering Conference,
The Netherlands, 2017.
A Front-End ASIC for Miniature 3-D Ultrasound Probes with In-Probe Receive Digitization
C. Chen; Z. Chen; D. Bera; E. Noothout; Z. Y. Chang; H. Vos; J. Bosch; M. Verweij; N. de Jong; M. Pertijs;
In Proc. IEEE International Ultrasonics Symposium (IUS),
IEEE, pp. 1-4, September 2017. Winner Best Student Paper Competition. DOI: 10.1109/ULTSYM.2017.8091913

Abstract: ...
This paper presents a front-end application-specific integrated circuit (ASIC) that demonstrates the feasibility of inprobe digitization for next-generation miniature 3-D ultrasound probes with acceptable power- and area-efficiency. The proposed design employs a low-power charge-domain ADC that is directly merged with the sample-and-hold delay lines in each subarray, and high-speed datalinks at the ASIC periphery to realize an additional channel-count reduction compared to prior work based on analog subarray beamforming. The 4.8 × 2 mm 2 ASIC, which has a compact layout element-matched to a 5-MHz 150-μm-pitch PZT matrix transducer, achieves an overall 36-fold channel-count reduction and a state-of-the-art power-efficiency with less than 1 mW/element power dissipation while receiving, which is acceptable even when scaled up to a 1000-element probe. The prototype ASIC has been fabricated in a 0.18 μm CMOS process. Its functionality has been successfully evaluated with both electrical and acoustical measurements.
Volumetric imaging using adult matrix TEE with separated transmit and receive array
D. Bera; F. van den Adel; N. Radeljic-Jakic; B. Lippe; M. Soozande; M. Pertijs; M. Verweij; P. Kruizinga; V. Daeichin; H. Vos; J. Bosch; N. de Jong;
In Proc. IEEE International Ultrasonics Symposium (IUS),
IEEE, pp. 1-1, September 2017. (abstract). DOI: 10.1109/ULTSYM.2017.8092906

Abstract: ...
The design of 3D TEE transducers poses severe technical challenges: channel count, electronics integration with high and low voltages, heat dissipation, etc. We present an adult matrix TEE probe with separate transmit (Tx) and receive (Rx) arrays allowing optimization in both Tx and Rx [1]. Tx elements are directly wired out, Rx employs integrated micro-beamformers in low-voltage (1.8/5.0V) chip technology. The prototype is fully integrated into a gastroscopic tube.
A Prototype PZT Matrix Transducer with Low-Power Integrated Receive ASIC for 3D Transesophageal Echocardiography.
C. Chen; S. Raghunathan; Z. Yu; M. Shabanimotlag; Z. Chen; Z. Y. Chang; S. Blaak; C. Prins; J. Ponte; E. Noothout; H. J. Vos; J. G. Bosch; M. D. Verweij; N. de Jong; M. A. P. Pertijs;
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control,
Volume 63, Issue 1, pp. 47‒59, January 2016. DOI: 10.1109/tuffc.2015.2496580

Abstract: ...
This paper presents the design, fabrication, and experimental evaluation of a prototype lead zirconium titanate (PZT) matrix transducer with an integrated receive ASIC, as a proof of concept for a miniature three-dimensional (3-D) transesophageal echocardiography (TEE) probe. It consists of an array of 9 × 12 piezoelectric elements mounted on the ASIC via an integration scheme that involves direct electrical connections between a bond-pad array on the ASIC and the transducer elements. The ASIC addresses the critical challenge of reducing cable count, and includes front-end amplifiers with adjustable gains and microbeamformer circuits that locally process and combine echo signals received by the elements of each 3 × 3 subarray. Thus, an order-of-magnitude reduction in the number of receive channels is achieved. Dedicated circuit techniques are employed to meet the strict space and power constraints of TEE probes. The ASIC has been fabricated in a standard 0.18-μm CMOS process and consumes only 0.44 mW/channel. The prototype has been acoustically characterized in a water tank. The ASIC allows the array to be presteered across ±37° while achieving an overall dynamic range of 77 dB. Both the measured characteristics of the individual transducer elements and the performance of the ASIC are in good agreement with expectations, demonstrating the effectiveness of the proposed techniques.
Acoustic Characterisation of a 32 × 32 Element PZT-on-CMOS Matrix Transducer for 3D TEE
S. Raghunathan; D. Bera; C. Chen; Z. Chen; M. Shabanimotlagh; E. Noothout; Z. Y. Chang; H. Vos; C. Prins; J. Ponte; J. Bosch; M. Pertijs; N. de Jong; M. Verweij;
In Proc. IEEE International Ultrasonics Symposium (IUS),
September 2016. (abstract).
A front-end ASIC with receive sub-array beamforming integrated with a 32 × 32 PZT matrix transducer for 3-D transesophageal echocardiography
C. Chen; Z. Chen; D. Bera; S. B. Raghunathan; M. Shabanimotlagh; E. Noothout; Z. Y. Chang; J. Ponte; C. Prins; H. J. Vos; J. G. Bosch; M. D. Verweij; N. de Jong; M. A. P. Pertijs;
In Dig. Techn. Paper IEEE Symposium on VLSI Circuits (VLSI),
IEEE, pp. 1‒2, September 2016. DOI: 10.1109/vlsic.2016.7573470
Three-dimensional beamforming combining micro-beamformed RF datasets
D. Bera; H. J. Vos; S. B. Raghunathan; C. Chen; Z. Chen; M. D. Verweij; M. A. P. Pertijs; N. de Jong; J. G. Bosch;
In Proc. IEEE International Ultrasonics Symposium (IUS),
IEEE, pp. 1‒4, September 2016. DOI: 10.1109/ultsym.2016.7728449

Abstract: ...
A general challenge in 3D volumetric imaging is the large channel count. One solution uses integrated microbeamformers. The reconstruction of the entire volume from these micro-beamformed datasets can be performed in many ways. In this paper we propose two 3D multiline beamforming techniques, suitable for producing volumes at high frame rate and compare the image qualities to a fully-sampled matrix. The performance of the proposed beamforming techniques was evaluated with simulations in FieldII. Results show that the proposed simple volume reconstruction technique (using 25 transmissions) produces volumes at very high frame rate, but with sharp intensity changes within the volume. The proposed advanced technique (using 169 transmissions) produces volumes very similar to a fully-sampled matrix transducer despite the micro-beamforming.
Acoustic Characterisation of a PZT Matrix With Integrated Electronics for a 3D-TEE Probe
S. Raghunathan; C. Chen; M. Shabanimotlagh; Z. Chen; S. Blaak; Z. Yu; C. Prins; M. Pertijs; J. Bosch; N. de Jong; M. Verweij;
In Proc. IEEE International Ultrasonics Symposium (IUS),
October 2015. (abstract).
Low Power Receive Electronics for a Miniature Real-Time 3D Ultrasound Probe
Z. Chen; C. Chen; S. B. Raghunathan; D. Bera; Z. Chang; S. Blaak; C. Prins; J. Ponte; J. G. Bosch; N. de Jong; M. D. Verweij; M. A. P. Pertijs;
In Proc. Conference for ICT-Research in the Netherlands (ICT.OPEN),
The Netherlands, March 2015.
A compact 0.135-mW/channel LNA array for piezoelectric ultrasound transducers
C. Chen; Z. Chen; Z. Y. Chang; M. A. P. Pertijs;
In Proc. European Solid-State Circuits Conference (ESSCIRC),
IEEE, pp. 404‒407, September 2015. DOI: 10.1109/esscirc.2015.7313913
Low-power receive electronics for a miniature real-time 3D ultrasound probe
M. Pertijs; C. Chen; S. Raghunathan; Z. Yu; M. ShabaniMotlagh; Z. Chen; Z. Y. Chang; E. Noothout; S. Blaak; J. Ponte; C. Prins; H. Bosch; M. Verweij; N. de Jong;
In Proc. IEEE International Workshop on Advances in Sensors and Interfaces (IWASI),
IEEE, pp. 235‒238, June 2015. invited paper. DOI: 10.1109/iwasi.2015.7184963
A mixed-signal multiplexing system for cable-count reduction in ultrasound probes
Q. Liu; C. Chen; Z. Y. Chang; C. Prins; M. A. P. Pertijs;
In Proc. IEEE International Ultrasonics Symposium (IUS),
IEEE, pp. 1‒4, October 2015. DOI: 10.1109/ultsym.2015.0141

Abstract: ...
This paper presents an approach to time-multiplexing multiple receive signals in a miniature ultrasound probe onto a single micro-coaxial cable. The resulting reduction in the number of receive cables alleviates the design of high-element-count endoscope- or catheter-based ultrasound probes. A prototype multiplexing system is presented that employs a custom multiplexing chip that uses current-mode drivers to combine four receive channels, sampled at 25 MHz each, on a single 3-m micro-coaxial cable. On the system-side of the cable, a transimpedance amplifier turns the multiplexed signal back into a voltage, after which it is digitized and equalized to correct for channel-to-channel crosstalk due to non-idealities of the cable. The chip has been implemented in a 0.18 μm CMOS process and consumes less than 1 mW per input channel. Experimental results show that the system can successfully convey 6 MHz Gaussian-shaped pulses applied to the four input channels of the multiplexing chip to the system with a channel-to-channel crosstalk below -31 dB.
Design of a Miniature Ultrasound Probe for 3D Transesophageal Echocardiography
D. Bera; S. B. Raghunathan; C. Chen; S. Blaak; C. Prins; M. A. P. Pertijs; M. D. Verweij; J. G. Bosch; N. de Jong;
In Annual Sensor Technology Workshop Sense of Contact,
The Netherlands, April 2014.
Design of a miniature ultrasound probe for 3D transesophageal echocardiography
S. B. Raghunathan; D. Bera; C. Chen; S. Blaak; C. Prins; M. A. P. Pertijs; J. G. Bosch; N. de Jong; M. D. Verweij;
In Proc. IEEE International Ultrasonics Symposium (IUS),
IEEE, pp. 2091‒2094, September 2014. DOI: 10.1109/ultsym.2014.0521

Abstract: ...
The relatively large size of most of the current 3D Transesophageal Echocardiography probes (TEE) enables their usage in adults for short procedures only. In this paper, we propose a new miniature 3D TEE probe with a head volume of 1 cm3, that would be suitable for use in neonates or for prolonged transnasal use in adults. We focus on partitioned designs, in which a minority of transmit elements is directly wired out and the majority of receive elements connect to a limited number of receive cables via an ASIC that performs a nine-fold data reduction in receive mode. The designs are motivated based on the pressure and beam width of the transmitted field, and the resolution, grating lobes and side lobes in the received field.
Front-end receiver electronics for a matrix transducer for 3-D transesophageal echocardiography
Z. Yu; S. Blaak; Z. Y. Chang; J. Yao; J. G. Bosch; C. Prins; C. T. Lancee; N. de Jong; M. A. P. Pertijs; G. C. M. Meijer;
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control,
Volume 59, Issue 7, pp. 1500‒1512, July 2012. DOI: 10.1109/tuffc.2012.2350

Abstract: ...
There is a clear clinical need for creating 3-D images of the heart. One promising technique is the use of transesophageal echocardiography (TEE). To enable 3-D TEE, we are developing a miniature ultrasound probe containing a matrix piezoelectric transducer with more than 2000 elements. Because a gastroscopic tube cannot accommodate the cables needed to connect all transducer elements directly to an imaging system, a major challenge is to locally reduce the number of channels, while maintaining a sufficient signal-to-noise ratio. This can be achieved by using front-end receiver electronics bonded to the transducers to provide appropriate signal conditioning in the tip of the probe. This paper presents the design of such electronics, realizing time-gain compensation (TGC) and micro-beamforming using simple, low-power circuits. Prototypes of TGC amplifiers and micro-beamforming cells have been fabricated in 0.35-μm CMOS technology. These prototype chips have been combined on a printed circuit board (PCB) to form an ultrasound-receiver system capable of reading and combining the signals of three transducer elements. Experimental results show that this design is a suitable candidate for 3-D TEE.
A 9-channel low-power receiver ASIC for 3D transesophageal echocardiography
Z. Yu; S. Blaak; C. Prins; Z. Y. Chang; C. T. Lancée; J. G. Bosch; N. de Jong; G. C. M. Meijer; M. A. P. Pertijs;
In Proc. IEEE International Ultrasonics Symposium (IUS),
IEEE, pp. 2063‒2066, October 2012. DOI: 10.1109/ultsym.2012.0516

Abstract: ...
This paper presents a 9-channel low-power receiver ASIC dedicated to a matrix piezoelectric ultrasound transducer for 3D Trans-Esophageal Echocardiography (TEE). It consists of 9 low-noise amplifiers (LNAs), 9 time-gain-compensation (TGC) amplifiers and a 9:1 micro-beamformer. A prototype ASIC has been implemented in 0.35 μm CMOS technology, with a core area of 0.98 mm × 1.7 mm. It is operated at a 3.3 V supply and consumes only 0.5 mW per channel. The measured channel-to-channel mismatch is within ±1 dB. Acoustic measurements proved the micro-beamforming function of the ASIC when processing real ultrasound signals from a 3 × 3 transducer array. These promising results show that this design, after layout optimization, is suitable to be scaled up to accommodate a full matrix transducer.
Low-Power Receive-Electronics for a Miniature 3D Ultrasound Probe
Zili Yu;
PhD thesis, Delft University of Technology, April 2012.
document
Ultrasound beamformer using pipeline-operated S/H delay stages and charge-mode summation
Z. Yu; M. A. P. Pertijs; G. C. M. Meijer;
Electronics Letters,
Volume 47, Issue 18, pp. 1011‒1012, September 2011. DOI: 10.1049/el.2011.1786

Abstract: ...
The proposed ultrasound beamformer is based on the delay-and-sum beamforming principle. The circuit consists of several programmable delay lines. Each delay line is constructed by pipeline-operated sample-and-hold (S/H) stages with digitally-assisted delay control, which ensure delay-independent gain and good timing accuracy. The summation is realised in the charge domain using the charge-averaging method, which consumes virtually no extra die area or power. A prototype beamformer has been fabricated in a 0.35 m CMOS process to interface nine transducer elements. Measurement results show that this circuit consumes much less power and chip area than the prior art, while maintaining good accuracy and flexibility.
Design of a Beamformer for an Ultrasonic Matrix Transducer for 3D Transesophageal Echocardiography
Z. Yu; S. Blaak; G. C. M. Meijer; M. A. P. Pertijs; C. T. Lancée; J. G. Bosch; C. Prins; N. de Jong;
In Annual Sensor Technology Workshop Sense of Contact,
The Netherlands, April 2010. (Best Poster Award).
Design of a low power time-gain-compensation amplifier for a 2D piezoelectric ultrasound transducer
J. Yao; Z. Yu; M. A. P. Pertijs; G. C. M. Meijer; C. T. Lancee; J. G. Bosch; N. de Jong;
In Proc. IEEE International Ultrasonics Symposium (IUS),
IEEE, pp. 841‒844, October 2010. DOI: 10.1109/ultsym.2010.5935775

Abstract: ...
In this paper, a programmable time-gain compensation amplifier dedicated to a 2D piezoelectric ultrasound transducer is presented. It uses an open-loop amplifier structure consisting of a voltage-to-current converter and a current-to-voltage converter. The circuit has been designed in a standard 0.35-μm CMOS process. Simulation and measurement results show that gains of 0dB, 12dB, 26dB and 40dB can be achieved for input signals centered at 6MHz with 80dB dynamic range (100μV to 1V). The measured gain errors at 6MHz are below 1dB for all gain settings. The amplifier consumes only 130μW when driving a 250fF load.

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