Integrated Circuits for Medical Ultrasound Applications: Imaging and Beyond

Medical ultrasound has become a crucial part of modern society and continues to play a vital role in the diagnosis and treatment of illnesses. Over the past decades, the develop- ment of medical ultrasound has seen extraordinary progress as a result of the tremendous research advances in microelectronics, transducer technology and signal processing algorithms. How- ever, medical ultrasound still faces many challenges including power-efficient driving of transducers, low-noise recording of ultrasound echoes, effective beamforming in a non-linear, high- attenuation medium (human tissues) and reduced overall form factor. This paper provides a comprehensive review of the design of integrated circuits for medical ultrasound applications. The most important and ubiquitous modules in a medical ultrasound system are addressed, i) transducer driving circuit, ii) low- noise amplifier, iii) beamforming circuit and iv) analog-digital converter. Within each ultrasound module, some representative research highlights are described followed by a comparison of the state-of-the-art. This paper concludes with a discussion and recommendations for future research directions

A Balanced Slew-Rate High-Voltage Integrated Bipolar Pulse Generator for Medical Ultrasonic Imaging Applications

This chapter describes the use of silicon-on-insulator (SOI) technology to develop balanced slew-rate pulse generators for medical ultrasound scanners, especially for multi-channel portable systems. Since ultrasonic transducers are usually composed of piezoelectric materials, most of which are capacitive, and the resonant frequency is usually in the order of tens of MHz, it is preferred to convert the high-frequency excited signals into high-voltage pulses to efficiently drive the transducers. In addition, the second harmonic leakage of the high-voltage pulse signal output by the pulse generator needs to be controlled such that the pulse generator can be applied to tissue harmonic imaging. Based on these considerations, the pulse generator architecture with balanced rising and falling edges proposed in this chapter is designed by synthesizing low-power, high-speed level shifters and a high-voltage H-bridge output stage to output high-voltage pulse signals with low harmonic distortion. The entire circuit integrates an 8-channel pulse generator, producing pulse signals >100 Vpp. The rise and fall times of the pulses are within 18.6 and 18.5 ns, respectively. The overall quiescent current is 2 A and the second harmonic distortion is as low as −40 dBc, indicating that the integrated pulse generator can be used in advanced, portable ultrasonic harmonic imaging systems

Development of Ultrasonic Devices for Non-destructive Testing: Ultrasonic Vibro-tactile Sensor and FPGA-Based Research Platform

This thesis is focused on the development of ultrasonic devices for industrial non-destructive testing (NDT). Ultrasound is generated from mechanical vibrations and then propagates through the medium. Ultrasonic devices can make use of the ultrasound in both aspects, vibrations and propagations, to perform inspections of the objects. To this end, two devices were developed in this research, each pertaining to NDT of the objects. The first device is the vibro-tactile sensor which aims to estimate the elastic modules of soft materials with minimally invasive technique. Inspired by load sensitivity studies in the high-power ultrasonic applications, vibration characteristics in resonance were utilized to perform the inspection. Only a minimal force to ensure contact with the object surface needs to be applied for a vibro-tactile sensor to perform inspection of the object; hence, it can be used for in-vivo measurement of the soft materials’ elastic moduli without causing severe surface deformation. The design and analysis of the device were carried out using the electro-mechanical analogy to address the electro-mechanical nature of piezoelectric devices. The designed vibro-tactile sensor resonates at ~40 kHz and can be applied to differentiate the elastic modulus of isotropic soft samples with a range from 10 kPa to 70 kPa. The second device developed is a field-programmable development platform for ultrasonic pulse-echo testing. Ultrasonic testing, utilizing sound wave propagation, is a widely used technique in the industry. The commercially available equipment for industrial NDT is highly dependent on the competence of the inspector and rarely provides the access to raw data. For successful transition from traditional labor-intensive manufacturing to the next generation “smart factory” where intelligent machines replace human labor, inspection equipment with automated in-line data collection and processing capability is highly needed. To this end, a flexible platform which provides the access to raw data for algorithm development and implementation should be established. Therefore, an affordable, versatile, and researcher-friendly development platform based on field-programmable gate array (FPGA) was developed in the research. Both hardware and software development tools and procedures were discussed. In the lab experiment, the developed prototype exhibited its competence in NDT applications and successfully carried out hardware-based auto-detection algorithm for mm-level defects on steel and aluminum specimens. Comparisons with commercial systems were provided to guide future development

Ultrasound Imaging

In this book, we present a dozen state of the art developments for ultrasound imaging, for example, hardware implementation, transducer, beamforming, signal processing, measurement of elasticity and diagnosis. The editors would like to thank all the chapter authors, who focused on the publication of this book

Development of electronics for microultrasound capsule endoscopy

Development of intracorporeal devices has surged in the last decade due to advancements in the semiconductor industry, energy storage and low-power sensing systems. This work aims to present a thorough systematic overview and exploration of the microultrasound (µUS) capsule endoscopy (CE) field as the development of electronic components will be key to a successful applicable µUSCE device. The research focused on investigating and designing high-voltage (HV, < 36 V) generating and driving circuits as well as a low-noise amplifier (LNA) for battery-powered and volume-limited systems. In implantable applications, HV generation with maximum efficiency is required to improve the operational lifetime whilst reducing the cost of the device. A fully integrated hybrid (H) charge pump (CP) comprising a serial-parallel (SP) stage was designed and manufactured for > 20 V and 0 - 100 µA output capabilities. The results were compared to a Dickson (DKCP) occupying the same chip area; further improvements in the SPCP topology were explored and a new switching scheme for SPCPs was introduced. A second regulated CP version was excogitated and manufactured to use with an integrated µUS pulse generator. The CP was manufactured and tested at different output currents and capacitive loads; its operation with an US pulser was evaluated and a novel self-oscillating CP mechanism to eliminate the need of an auxiliary clock generator with a minimum area overhead was devised. A single-output universal US pulser was designed, manufactured and tested with 1.5 MHz, 3 MHz, and 28 MHz arrays to achieve a means of fully-integrated, low-power transducer driving. The circuit was evaluated for power consumption and pulse generation capabilities with different loads. Pulse-echo measurements were carried out and compared with those from a commercial US research system to characterise and understand the quality of the generated pulse. A second pulser version for a 28 MHz array was derived to allow control of individual elements. The work involved its optimisation methodology and design of a novel HV feedback-based level-shifter. A low-noise amplifier (LNA) was designed for a wide bandwidth µUS array with a centre frequency of 28 MHz. The LNA was based on an energy-efficient inverter architecture. The circuit encompassed a full power-down functionality and was investigated for a self-biased operation to achieve lower chip area. The explored concepts enable realisation of low power and high performance LNAs for µUS frequencies