Point of Care Device Development
If you come to visit us at our Bromborough facility, you will see our display cabinet which contains, amongst other things, full point of care systems, instrument and cartridge-based systems, and other medical devices that we have worked on, both at Medtechtomarket and in previous roles, from our earliest example in the 1990s to the present day.
Usually, we talk about the diagnostic test or procedure used to detect, identify, or monitor a disease, infection, or medical condition, and the benefits for the end user or patient. But it is also interesting to have a more detailed look inside the instruments themselves, and the technology inside.
Embedded Controllers
Each of our medical devices contain a microprocessor. However, they are embedded controllers, and quite different from the more mainstream Intel-compatible processors that are inside most laptop and desktop PCs. Embedded controllers usually contain the processor, RAM, flash storage and peripherals (for example, an analogue-to-digital converter) all in one chip package. Here are some examples…
Lateral Flow Reader
The first example is a lateral flow test reader; it contains a photometer and is powered by a sixteen-bit processor (TI MSP430P325) with 512 bytes of working memory and 16KB of program storage, operating at 2.3MHz. It featured ultralow power consumption and a built in LCD controller. It was designed in the mid to late nineties and had a fixed, non-rechargeable battery. We have developed many lateral flow tests at Medtechtomarket, some read by eye, some with a commercial reader and some with a bespoke instrument like this.
Chromatography Test
This is a chromatography test with an optical reader. It works with a cartridge with several different chambers and reagents. It is purely manual. Once the test has started, the machine beeps to prompt the operator to rotate the cartridge to the next position and pour in the reagents. It also uses an MSP430. With the appropriate cable, it could connect to a PC’s RS232 serial port and download a text file containing the last few results.
Automated Chromatography Test
The evolution of the chromatography test continued with this medical device – the automated chromatography test. It has a very similar optical system but as the name suggests, contains motors and actuators to move the cartridge itself. This had the advantage of allowing the operator to add the cartridge and walk away, leaving the instrument to complete the test and display the result itself. Inside is a 16-bit Renesas (formerly Mitsubishi) processor, with 20KB of RAM. The M16 was more usually found in automotive applications. It was quite fast for the time, but its main strength was being able to handle lots of sensors and actuators with a predictable response time. This instrument has a ‘hidden’ secondary processor, an Intel 8052, which is a design originally introduced in 1980 but still in use today. It was part of the USB controller chip. When the instrument was turned on, the 8052 started first and did some set-up before handing over to the M16. It then settled into the background, running the USB connection.
Medical Pump
Although this example is not strictly a point-of-care medical device, and smply a medical device, this example is a medical device from the mid-2000s which uses probably the least powerful processor – an 8-bit Microchip PIC16F88, with 7KB of storage and 368 bytes of memory. It’s interesting because the device comprises a couple of sensors, an alarm and a manually operated electric motor, which could have been implemented using discrete components on the board and no processor at all. Using the PIC meant that, during development, the device behaviour could be altered purely with software and shows how low-end processors can replace conventional electronic circuitry in some cases.
A New Generation of Processors
Mechanical Test
This instrument was designed in 2014 around an ARM Cortex M processor. ARM is a great British success story. From its origins in home computers of the 1980s ARM chips can now be found in the most powerful servers but also in domestic appliances. The key to this was ARM’s development of a family of chip designs which were very efficient and very flexible, which they then licensed widely. In this case the processor is a 32-bit model with 1024KB of RAM. It runs a sensor based on detecting tiny movements, and over the course of a test, collects a huge amount of data which it can then process in real time. This would simply not be possible using the M16 processor from the previous generation.
Development Instruments
In our lab, we have several instruments which are controlled by Raspberry Pi single board computers (SBCs). These are also ARM processors but are effectively mini-desktop computers, running Linux. It’s possible to connect a keyboard, mouse and monitor, and browse the web or play games as you would on a laptop. This can make it very easy for us to experiment at the start of a new development project – we can use all the software development and debugging tools that we use on the desktop. In many cases the exact same code can run on both.
This is not to say that every medical instrument should be built with a Raspberry Pi inside. For many uses, such a processor is overkill and running a desktop operating system means unnecessary complexity and poor real-time performance. Another reason is that many of these SBC manufacturers launch new products frequently – aimed at hobbyists. A medical device can take years to reach the market, and it would be very unfortunate if it were designed around an obsolete part. Suppliers exist who do guarantee longevity of supply, often for ten years or more.
In summary we can see that the CPU power, storage and RAM has increased over time, but there is still a huge difference between the embedded processor (even in the most recent instrument) and the desktop-class chip in the development rig – for example it’s got over 15,000 times more RAM!
The Future of Medical Devices
In the future we can expect to see computing power continue to increase. Developing an instrument with a high-resolution camera and the capacity to run an AI classification model entirely on the device is now possible and will become more sophisticated with time. On the other hand, true embedded processors are becoming smaller and cheaper, finding their way into wearable and implanted devices. Below is the picture of a TI MSPM0C1104, which is less than 2mm in size, yet is about as powerful as the MSP430 we used in the 1990s.
Risc-V Processor Architecture
A new processor architecture, Risc-V, is becoming more widely available. It is easier to license than ARM, which means it may become used in more bespoke hardware. The programming language Rust, which offers memory-safe programming, is also finding a niche in embedded processors.
Medical Device Regulation
One further aspect is regulation, which is having to keep up with advancing technology. Having devices with AI on board, or communicating via wireless networks, introduces new risks which did not exist previously. Even so, at Medtechtomarket we think the fundamental principles still stand: Define precisely what the device must and must not do, identify and analyse the risks, wherever they come from, and validate thoroughly, not just in normal use but when unusual circumstances arise.
If you have a medical device or IVD to develop, please contact us and let’s discuss how we can work together.