MSc Y. Hopf

1. A Pitch-Matched High-Frame-Rate Ultrasound Imaging ASIC for Catheter-Based 3D Probes
   Yannick M. Hopf; Djalma Simoes dos Santos; Boudewine W. Ossenkoppele; Mehdi Soozande; Emile Noothout; Zu-Yao Chang; Chao Chen; Hendrik J. Vos; Johan G. Bosch; Martin D. Verweij; Nico de Jong; Michiel A. P. Pertijs;
   IEEE Journal of Solid-State Circuits,
   pp. 1--16, 2023. Early Access. DOI: 10.1109/JSSC.2023.3299749
   
   Abstract: ...

   This article presents an application-specific integrated circuit (ASIC) for catheter-based 3-D ultrasound imaging probes. The pitch-matched design implements a comprehensive architecture with high-voltage (HV) transmitters, analog front ends, hybrid beamforming analog-to-digital converters (ADCs), and data transmission to the imaging system. To reduce the number of cables in the catheter while maintaining a small footprint per element, transmission (TX) beamforming is realized on the chip with a combination of a shift register (SR) and a row/column (R/C) approach. To explore an additional cable-count reduction in the receiver part of the design, a channel with a combination of time-division multiplexing (TDM), subarray beamforming, and multi-level pulse amplitude modulation (PAM) data transmission is also included. This achieves an 18-fold cable-count reduction and minimizes the power consumption in the catheter by a load modulation (LM) cable driver. It is further explored how common-mode interference can limit beamforming gain and a strategy to reduce its impact with local regulators is discussed. The chip was fabricated in TSMC 0.18-μm HV BCD technology and a 2-D PZT transducer matrix of 16 × 18 elements with a pitch of 160 μm and a center frequency of 6 MHz was manufactured on the chip. The system can generate all required TX patterns at up to 30 V, provides quick settling after the TX phase, and has an reception (RX) power consumption of only 1.12 mW/element. The functionality and operation of up to 1000 volumes/s have been demonstrated in electrical and acoustic imaging experiments.

2. An ultrasound matrix transducer for high-frame-rate 3D intracardiac echocardiography
   Djalma Simoes dos Santos; Boudewine Ossenkoppele; Yannick M. Hopf; Mehdi Soozande; Emile Noothout; Hendrik J. Vos; Johan G. Bosch; Michiel A. P. Pertijs; Martin D. Verweij; Nico de Jong;
   Ultrasound in Medicine \& Biology,
   2023. accepted.
   
   Abstract: ...

   Objective: This paper presents the development of an ultrasound matrix transducer prototype for high frame rate three-dimensional (3D) intracardiac echocardiography (ICE). Methods: The matrix array consists of 16 ×18 lead zirconate titanate (PZT) elements with a pitch of 160 µm × 160 µm built on top of an application-specific integrated circuit (ASIC) 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 electro-mechanical wave tracking in the heart.

3. Effect of SAR-ADC Non-Idealities on Medical Ultrasound B-Mode Imaging
   N. Radeljic-Jakic; A. Flikweert; Y. Hopf; N. Rozsa; M. Pertijs;
   In Proc. IEEE International Ultrasonics Symposium (IUS),
   2023. abstract, accepted.

4. A prototype matrix transducer for high frame rate 3D intracardiac echography
   D. Santos; Y. Hopf; B. Ossenkoppele; J. Bosch; R. Vos; M. Pertijs; N. de Jong; M. Verweij;
   In Proc. IEEE International Ultrasonics Symposium (IUS),
   2023. abstract, accepted.

5. Pitch-Matched Integrated Circuits for Ultrasound Transducer Arrays
   Y. Hopf; P. Guo; M. Pertijs;
   In Proc. Workshop on Advances in Analog Circuit Design (AACD),
   April 2023. invited presentation.

6. A Compact Integrated High-Voltage Pulser Insensitive to Supply Transients for 3D Miniature Ultrasound Probes
   Yannick M. Hopf; Boudewine Ossenkoppele; Mehdi Soozande; Emile Noothout; Zu-Yao Chang; Hendrik J. Vos; Johan G. Bosch; Martin D. Verweij; Nico de Jong; Michiel A. P. Pertijs;
   IEEE Solid-State Circuits Letters,
   Volume 5, pp. 166--169, 2022. DOI: 10.1109/lssc.2022.3180071
   
   Abstract: ...

   In this paper, a compact high-voltage (HV) transmit circuit for dense 2D transducer arrays used in 3D ultrasonic imaging systems is presented. Stringent area requirements are addressed by a unipolar pulser with embedded transmit/receive switch. Combined with a capacitive HV level shifter, it forms the ultrasonic HV transmit circuit with the lowest reported HV transistor count and area without any static power consumption. The balanced latched-based level shifter implementation makes the design insensitive to transients on the HV supply caused by pulsing, facilitating application in probes with limited local supply decoupling, such as imaging catheters. Favorable scaling through resource sharing benefits massively arrayed architectures while preserving full individual functionality. A prototype of 8 x 9 elements was fabricated in TSMC 0.18 μm HV BCD technology and a 160 μm x 160 μm PZT transducer matrix is manufactured on the chip. The system is designed to drive 65 V peak-to-peak pulses on 2 pF transducer capacitance and hardware sharing of 6 elements allows for an area of only 0.008 mm2 per element. Electrical characterization as well as acoustic results obtained with the 6 MHz central frequency transducer are demonstrated.

7. Imaging Scheme for 3-D High Frame Rate Intracardiac Echography: a Simulation Study
   M. Soozande; B. Ossenkoppele; Y. Hopf; M. Pertijs; M. Verweij; N. de Jong; H. Vos; J. Bosch;
   IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control,
   Volume 69, Issue 10, pp. 2862--2874, October 2022. DOI: 10.1109/TUFFC.2022.3186487
   
   Abstract: ...

   Atrial fibrillation is the most common cardiac arrhythmia, and normally treated by RF ablation. Intracardiac echography (ICE) is widely employed during RF ablation procedures to guide the electrophysiologist in navigating the ablation catheter, although only 2-D probes are currently clinically used. A 3-D ICE catheter would not only improve visualization of the atrium and ablation catheter, it might also provide 3-D mapping of the electromechanical wave propagation pattern, which represents the mechanical response of cardiac tissue to electrical activity. The detection of this electromechanical wave needs 3-D high frame rate imaging, which is generally only realizable in trade-off with channel count and image quality. In this simulation-based study, we propose a high volume rate imaging scheme for a 3-D ICE probe design that employs 1-D micro-beamforming in elevation direction. Such probe can achieve a high frame rate while reducing the channel count sufficiently for realization in a 10-Fr catheter. To suppress the grating-lobe artifacts associated with micro-beamforming in elevation direction, a limited number of fan-shaped beams with a wide azimuthal and narrow elevational opening angle are sequentially steered to insonify slices of the region of interest. An angular weighted averaging of reconstructed sub-volumes further reduces the grating lobe artifacts. We optimize the transmit beam divergence and central frequency based on the required image quality for electromechanical wave imaging (EWI). Numerical simulation results show that a set of 7 fan-shaped transmission beams can provide a frame rate of 1000 Hz and a sufficient spatial resolution to visualize the electromechanical wave propagation on a large 3-D surface.

8. A Pitch-Matched Transceiver ASIC with Shared Hybrid Beamforming ADC for High-Frame-Rate 3D Intracardiac Echocardiography
   Yannick M. Hopf; Boudewine W. Ossenkoppele; Mehdi Soozande; Emile Noothout; Zu-Yao Chang; Chao Chen; Hendrik J. Vos; Johan G. Bosch; Martin D. Verweij; Nico de Jong; Michiel A. P. Pertijs;
   IEEE Journal of Solid-State Circuits,
   Volume 57, Issue 11, pp. 3228--3242, November 2022. DOI: 10.1109/jssc.2022.3201758
   
   Abstract: ...

   In this article, an application-specific integrated circuit (ASIC) for 3-D, high-frame-rate ultrasound imaging probes is presented. The design is the first to combine element-level, high-voltage (HV) transmitters and analog front-ends, subarray beamforming, and in-probe digitization in a scalable fashion for catheter-based probes. The integration challenge is met by a hybrid analog-to-digital converter (ADC), combining an efficient charge-sharing successive approximation register (SAR) first stage and a compact single-slope (SS) second stage. Application in large ultrasound imaging arrays is facilitated by directly interfacing the ADC with a charge-domain subarray beamformer, locally calibrating interstage gain errors and generating the SAR reference using a power-efficient local reference generator. Additional hardware-sharing between neighboring channels ultimately leads to the lowest reported area and power consumption across miniature ultrasound probe ADCs. A pitch-matched design is further enabled by an efficient split between the core circuitry and a periphery block, the latter including a datalink performing clock data recovery (CDR) and time-division multiplexing (TDM), which leads to a 12-fold total channel count reduction. A prototype of 8×9 elements was fabricated in a TSMC 0.18- μm HV BCD technology and a 2-D PZT transducer matrix with a pitch of 160μm , and a center frequency of 6 MHz was manufactured on the chip. The imaging device operates at up to 1000 volumes/s, generates 65-V transmit pulses, and has a receive power consumption of only 1.23 mW/element. The functionality has been demonstrated electrically as well as in acoustic and imaging experiments.

9. A Pitch-Matched ASIC with Integrated 65V TX and Shared Hybrid Beamforming ADC for Catheter-Based High-Frame-Rate 3D Ultrasound Probes
   Y. Hopf; B. Ossenkoppele; M. Soozande; E. Noothout; Z. Y. Chang; C. Chen; 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),
   February 2022. DOI: 10.1109/ISSCC42614.2022.9731597
   
   Abstract: ...

   With applications moving to 3D imaging, catheter-based ultrasound probes need to reach a new level of integration. This paper presents the first chip to combine high-voltage transmitters, analog front-ends, micro-beamforming, digitization and transducers, enabling high-frame-rate 3D imaging. Its pitch-matched architecture, made possible by a shared SAR/slope ADC that is 4x smaller and consumes 1.5x less power than the prior art, makes it a scalable solution for future digital imaging catheters.

10. Transceiver ASIC Design for High-Frame-Rate 3D Intracardiac Echocardiography
    Yannick M. Hopf; Boudewine Ossenkoppele; Mehdi Soozande; Emile Noothout; Zu-Yao Chang; Chao Chen; Hendrik J. Vos; Johan G. Bosch; Martin D. Verweij; Nico de Jong; Michiel A. P. Pertijs;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    2022.

11. A Pitch-Matched ASIC with Integrated 65V TX and Shared Hybrid Beamforming ADC for Catheter-Based High-Frame-Rate 3D Ultrasound Probes
    Yannick Hopf; Michiel Pertijs;
    In Annual Workshop on Circuits, Systems and Signal Processing (ProRISC),
    July 2022. Best presentation award.

12. A Compact Integrated High -Voltage Pulserfor 3D Miniature Ultrasound Probes
    Yannick Hopf; Mehdi Soozande; Boudewine Ossenkoppele; Hendrik J. Vos; Martin D. Verweij; Johan G. Bosch; Nico de Jong; Michiel A. P. Pertijs;
    In Annual Workshop on Circuits, Systems and Signal Processing (ProRISC),
    July 2021. poster.

13. Feasibility of High Frame Rate 3-D Intracardiac Echography using Fan-Beam Transmissions
    M. Soozande; B. Ossenkoppele; Y. Hopf; M. A. P. Pertijs; M. D. Verweij; H. J. Vos; J. G. Bosch; N. de Jong;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    IEEE, pp. 1-4, October 2019.

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