Designing & testing Sonopill: the future of capsule ultrasound
01 November 2019
To accelerate design & test of Sonopill, a revolutionary ultrasound endoscopy capsule, researchers at University of Glasgow, Heriot-Watt University, University of Dundee & University of Leeds required a single, unified instrumentation platform to take them from component & system integration testing, through lab-based in vitro testing, to in vivo pre-clinical trials.
This case study was originally featured in the November 2019 issue of EPDT magazine [read the digital issue]. Sign up to receive your own copy each month.
Sonopill encompasses microelectronic sensors, including ultrasonic technology, to perform advanced health diagnostics as it travels through a patient’s gastrointestinal tract. Combining LabVIEW software with a broad range of NI measurement hardware, including PXIe, CompactRIO, myRIO and Diagnostic Sonar’s FlexRIO-based FIToolbox, the team, led by Dr Holly Lay, Dr Gerard Cummins, David Lines, Professor Marc Desmulliez & Professor Sandy Cochran, implemented a full-featured system taking the Sonopill prototypes from initial characterisation through encapsulation to final deployment for preclinical validation.
Sonopill is a 5-year, $10M programme, established to develop a multimodal capsule endoscopy device, including ultrasound and other capabilities. It involves four university partners in the UK, Glasgow, Dundee, Heriot-Watt and Leeds, and features a multidisciplinary team of researchers ranging from electrical and mechanical engineers to life scientists and clinical fellows – all of whom have used NI measurement hardware and software.
In 2010, there were almost 50 million visits to doctors in the US for gut-related disorders. In the UK, 20-40% of the population report gastric conditions. Clearly, there is an urgent need for practical and accurate diagnosis and treatment options.
Current clinical endoscopy uses conventional devices, which are inserted into a natural orifice and manually controlled via external manipulation, with limited reach. These devices rely mainly on high definition optical sensors, with some also supporting low to mid-frequency ultrasound sensors. The last three decades have also seen the development of capsule endoscopy devices capable of passing through the entire gastrointestinal system. However, these systems are limited to lower definition optical imaging and do not exploit ultrasound imaging at all.
To integrate ultrasound imaging into a capsule-sized device requires highly miniaturised sensors and electronics, capable of operating in a power-limited, hermetically-sealed enclosure, measuring just 20-30 mm in length and 10 mm in diameter. There are currently no commercial components that can meet these demanding system specifications – so, sub-components of the Sonopill capsule had be developed from scratch and tested on the bench.
Once developed, these sub-components must then be functionally tested in isolation, then retested during system integration into the final capsule. Tests include measuring basic device parameters, such as signal integrity and power usage, as well as replication of imaging modalities for benchmarking image quality and sensing capabilities.
Finally, all capsules must be tested preclinically in vivo to establish safe operating conditions. These tests are done in a specialised facility with a variety of prototype devices, requiring a robust instrumentation solution, with a wide range of data logging and control options.
One of the team’s primary goals was to identify a single-vendor instrumentation solution, which allowed replication of tests and results across all sites without significant equipment transport.
After evaluating possible test equipment vendors, National Instruments (NI) emerged as providing the best combination of equipment capability, flexibility, customisation and support. LabVIEW provides an intuitive means of building complex systems, and allows the seamless integration of NI hardware along with specialised equipment, such as ultrasonic pulser/receivers and high-resolution motor controllers, using third-party LabVIEW drivers.
Implementation of the test systems
To maximise usability of the systems during and after development, NI provided instructor-led training for Sonopill team members, as well as on-going support through its Field Engineers, who helped with developing the specifications of the required equipment for all phases. Online support, from both NI staff and the wider LabVIEW community, was also pivotal in the development and debugging of our various test software applications.
The NI platform provided a unifying system development experience, allowing the team to transfer code assets seamlessly between sections of the project and efficiently handover entire systems when engineers moved on to other tasks.
When establishing the testing requirements, several discrete phases in the device development were identified, with corresponding instrumentation solutions, as detailed below.
Ultrasound capsules use the natural motion of the human gastrointestinal tract to allow linear scanning of the full length of tissue. As this motion was not present during preliminary tests, a motorised scanning and integrated ultrasound generation and data capture system was developed. The team used a FlexRIO PXIe-1071 chassis, housing PXIe-8360, NI-5772, PXIe-7966 and PXIe-5451 modules, and connected it to a pair of MotionLink linear motors and an Imaginant DPR 500 ultrasonic pulser/receiver.
The team used a PXIe-7966 FlexRIO module, coupled with an NI-5772 digitiser adapter module, to acquire data sets at very high repetition rates and to synchronise the Imaginant pulser/receiver.
To ensure intuitive control of the motors, the team wrote custom LabVIEW-based GUIs suitable for use by research students and clinical users. Data was captured with high-speed FIFO buffers on the PXIe-7966’s integrated FPGA, before being streaming to the desktop application using a 100MB/s MXI link (established through a PXIe-8360). Using the PXIe-5451 with a custom amplifier allowed testing of alternative transmit signals with the same data acquisition architecture.
For array devices, the team used FIToolbox from Diagnostic Sonar to supply electronic focusing and steering of the ultrasonic beams. Its FlexRIO-based integrated solution allowed full control of the formation of the ultrasound beam during transmission and reception, along with full data capture – a critical requirement for device performance analysis and benchmarking.
Non-acoustic sensor verification & validation
For testing sensors for pressure and pH, the team used a multi-functional test platform comprising a CompactRIO (9035), with a wide range of IO modules (including NI 9220, NI 9485, NI 9237, NI 9505, NI 9403, NI 9264 and NI 9214).
For example, it built a pressure test chamber with pressure valves that were activated by the NI 9485 solid-state relays module, while the NI 9403 was used for digital monitoring of off-the-shelf pressure sensors used for calibration and validation of the custom sensors.
Functional test of integrated circuits
The team designed an ASIC (application specific integrated circuit) in-house, with both analogue and digital functions, to allow full integration of all sensor technologies in a single, miniature package.
It used a PXIe-1082 chassis, with a PXIe-6545 digital waveform instrument, to validate the functionality of the digital components of the ASIC. This was particularly useful with the first prototype ASIC, as the ability to fine-tune control signals allowed it to analyse a malfunctioning processor and correct the design errors in the second iteration of the ASIC.
In Vivo device instrumentation
Once the team developed and verified devices through the appropriate test path, it manufactured biologically compatible prototypes to establish functionality in a realistic operating environment.
As it was working on-site at the University of Edinburgh’s Dryden Farm facility, the team required an equipment controller/data logger solution that would adapt well to various test conditions and sensors, while remaining compact and highly portable. The myRIO-1900 was identified as the best solution for its variety of IO ports, small footprint and intuitive programming experience. This last point was key to ensuring research students could use myRIO to quickly develop sensor testing systems, without undue impact on their thesis progress.
The team has used the myRIO in the testing of prototype devices featuring wireless data antennas (RFCap), temperature and power measurement circuits (ThermoCap), and high-frequency ultrasound sensors (SonoCap).
• In RFCap, it used myRIO to monitor surface and internal temperature and supply power, while transmitting RF signals to the prototype device for wireless reception at a third-party base-station. It then used LabVIEW to run a sequence of pre-programmed test sequences at varying power levels.
• In ThermoCap and SonoCap, it used a single myRIO to supply power to both capsules, while simultaneously monitoring the output from 14 temperature sensors placed along the surface of the capsule during cycling of an on-board power resistor. myRIO also communicated via SPI with an on-board temperature/humidity sensor to obtain internal readings. The team used LabVIEW applications to log data from myRIO for ThermoCap and from a Tektronix oscilloscope for SonoCap, and to store them in date-stamped text files for later analysis.
Impact & results
By choosing NI, the team secured a critical mass of instrumentation and test equipment, taking it from concept through to translational trials, faster and more efficiently than would otherwise have been possible.
The design, development and implementation of this solution was also excellent training for numerous students, ranging from undergraduate through to PhD level. NI support has allowed the students and affiliated Research Associates to become proficient in the implementation of LabVIEW and NI measurement hardware for large-scale, multi-year projects, providing key skills for future career development.
The development of this instrumentation also allowed the collection of data critical for four PhD theses, the contents of 4 book chapters and 22 peer reviewed journal papers (including IEEE). As well as being covered by national media, including The Times and the BBC, the Sonopill research has also generated lively discussion among politicians, clinicians, industrialists and academics in the Scottish Parliament.
The future: Sonopill to Multipill
Early results from the Sonopill prototypes, developed using the team’s NI based test-bed, have directly led to the submission of a follow-up grant proposal (NI-supported), worth a total of $10M (MultiPill, 444 man-months). If funded, it will take the research from preclinical measurements to the first-in-human testing.
This is a critical and necessary step to bring the technology into clinical use – where it has the potential to fundamentally impact health outcomes for many millions of people suffering from gastrointestinal diseases.
The MultiPill grant will focus on the challenges of integration necessary for first-in-human trials and multimodal functionality. The level of inter-site coordination and communication that will be required to achieve this will demand standardisation of the existing solutions across all relevant work sites, with a particular focus on developing portable instrumentation, based on the current myRIO-based in vivo test rig, which can be deployed on short notice to any site in the UK.
The Sonopill programme also launched investigation of the use of robotic manipulation for positioning and localisation of capsules during passage through the human body. MultiPill will place a much stronger emphasis on this aspect of the work and it is expected that future instrumentation developments, that will include NI instrumentation, will feature direct feedback between the ultrasonic, diverse electronic sensors and robotic control systems.
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