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Real-World Applications
Sonopill: The Future of Capsule Ultrasound
Company: University of Glasgow, Heriot-Watt University, University of Dundee, University of Leeds
Author(s):
Holly Lay, Gerard Cummins, David Lines, Marc Desmulliez, Sandy Cochran
NI Product(s) Used: PXIe-1071, PXIe-8360, NI-5772, PXIe-7966, PXIe-5451, FI Toolbox, CRIO-9035, NI 9220, NI 9485, NI 9237, NI 9505, NI 9403, NI 9264, NI 9214, PXIe-1082, PXIe-6545 and myRIO-1900
Industry: Research
Introduction
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 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.
Demanding Test Requirements
To integrate ultrasound imaging into a capsule-sized device requires the highly miniaturised sensors and electronics, capable of operating in a power-limited, hermetically-sealed enclosure measuring 20-30 mm (length) and 10 mm (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.
Figure 1: The Design of Sonopill
Once developed, these sub-components must then be functionally tested in isolation, then retested during system integration into the final capsule. These tests include measuring of basic device parameters, such as signal integrity and power usage, as well as the 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 our primary goals was to identify a single-vendor instrumentation solution, which allowed replication of tests and results across all sites without significant equipment transport.
When we evaluated possible test equipment vendors, NI emerged as providing the best combination of equipment capability, flexibility, customisation and customer service. 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. These capabilities made NI products the winning solution.
The entire Sonopill team was involved in the development of this solution, and we want to acknowledge their massive contribution to the work.
Implementation of the Test Systems
To maximise the usability of the systems during and after development, NI provided instructor-led training for our team members, as well as on-going support through its Field Sales Engineers who helped with developing the specifications of the required equipment for all phases. The 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 us to transfer code assets seamlessly between sections of the project and efficiently handover entire systems when our engineers moved on to other tasks.
When establishing the testing requirements, we identified several discrete phases in the device development, with the corresponding instrumentation solutions detailed below.
Ultrasonics Testing
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. We acquired a FlexRIO PXIe-1071 chassis, housing a PXIe-8360, NI-5772, PXIe-7966 and PXIe-5451, and connected it to a pair of linear motors (MotionLink Ltd, Newbury, UK) and an ultrasonic pulser/receiver (DPR 500, Imaginant Inc, NY, USA).
Figure 2 Ultrasonic scanning rig featuring FlexRIOTM (red rectangle)
We used the PXIe-7966 FlexRIO module, coupled with a NI-5772 digitizer 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, we wrote custom LabVIEW-based GUIs that were suitable for use by research students and clinical users. We captured the data with high-speed FIFO buffers on the PXIe-7966’s integrated FPGA, before streaming the data to the desktop application using a 100MB/s MXI link (established through a PXIe-8360). We used the PXIe-5451 with a custom amplifier to allow testing of alternative transmit signals with the same data acquisition architecture.
For array devices, we used an FI Toolbox (Diagnostic Sonar Ltd, Livingston, Scotland) 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 and Validation
For testing sensors for pressure and pH, we acquired a multi-functional test platform comprising a CompactRIO (9035) with a wide range of IO modules (such as NI 9220, NI 9485, NI 9237, NI 9505, NI 9403, NI 9264 and NI 9214).
For example, we 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
We designed an application specific integrated circuit (ASIC) in-house, with both analogue and digital functions to allow full integration of all sensor technologies in a single, miniature package.
We obtained 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 us to analyse a malfunctioning processor and correct the design errors in the second iteration of the ASIC.
In Vivo Device Instrumentation
Once we developed and verified devices through the appropriate test path, we manufactured biologically compatible prototypes to establish functionality in a realistic operating environment.
As we were working on-site at the University of Edinburgh’s Dryden Farm facility, we required an equipment controller/data logger solution that would adapt well to various test conditions and sensors while remaining compact and highly portable. We identified the myRIO-1900 as the best solution for its variety of IO ports, small footprint, and intuitive programming experience. This last point was key to ensuring our students could use myRIO to quickly develop their sensor testing systems, without undue impact on their thesis progress.
To date, we’ve 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, we 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. We then used LabVIEW to run a sequence of pre-programmed test sequences at varying power levels.
- In ThermoCap and SonoCap, we used a single myRIO to supply power to both capsules, whilst 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. We 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.
Figure 3 Instrumentation cart for ThermoCap and SonoCap, featuring myRIOTM (red rectangle) and LabVIEWTM-based GUI
Figure 4 ThermoCap and SonoCap power and control system data flow
Impact/Results
By choosing NI, we have secured a critical mass of instrumentation and test equipment, which has taken us from concept through to translational trials, faster and more efficiently that would’ve been otherwise possible.
Figure 5 Devices developed in association with the test system
The design, development and implementation of this solution has also been an excellent training project for numerous students ranging from undergraduate through to PhD level. The NI support has allowed the students and affiliated Research Associates to become proficient in the implementation of LabVIEW and NI hardware for large-scale, multiyear projects, and providing key skills for their future career development.
The development of this instrumentation has 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).
The sonopill research has also been covered in the mass media, including The Times and BBC, and has generated lively discussion amongst politicians, clinicians, industrialists and academics in the Scottish Parliament.
Figure 6. [left] Our sponsor, Kezia Dugdale, opens the discussion in parliament
[middle] Prof. Kev Dhaliwal introduced a clinician's perspective
[right] Dr Gerard Cummins introduces Sonopill
