Miniature masterpiece

For many expectant parents, deciphering the shape of their child on an ultrasound screen is like taking a Rorschach inkblot test. The grainy black and white images of the foetus often have mothers and their partners wondering whether they are looking at arm or foot.

With an eye on improving this situation, GE Healthcare has designed ultrasound technology capable of producing 3D pictures moving in real time. The images, which are enhanced with Speckle Reduction Imaging (SRI), can provide parents with an almost realistic picture of their child.

Called the Voluson I, the device is one of a family of imaging ultrasound systems introduced by the group over the past two years. The machines have been gaining recognition in the medical community for not only their high performance, but also their relatively miniature size.

Voluson I packs the same functionality and performance of full-featured, large-scale ultrasound systems into a portable, wireless design that weighs just a little more than a newborn baby. The system looks much like a laptop, and like a laptop, it can run on a rechargeable battery, which provides up to one hour of full-scan operation.

Because of their convenience, the machines are promising to change the way we receive medical care. This was demonstrated last year when GE donated some of their Vivid I cardiovascular imaging ultrasound systems to volunteer cardiologists on mission to rural areas of Jamaica and southern Egypt where hospitals and medical resources are scarce. The company’s compact systems could also be used as a space-saving feature in better-equipped medical facilities.

Miniaturisation has become an exciting concept for design engineers in a wide range of technologies. Francois Lenfant, the leader of the design team behind the Vivid I and Voluson I, said medical equipment miniaturisation was first discussed at GE about 10 years ago.

But the design team did not officially get started on any projects until five years later. The process began by stripping traditional ultrasound equipment of all its mechanical components. This forced engineers to design a device that was more reliant on electronics.

Lenfant admitted that much of the technology needed to do this was already available. ‘Then, as now, we wanted to innovate, but we also wanted to make sure that what we did was something that worked and was proven,’ he said. ‘There was a lot of experience in the field of compact and portable PC and laptops that we wanted to re-use.’

For example, when engineers were configuring a way to shrink the size of the system’s keyboard, they took inspiration from other compact devices such as mobile phones.

‘It’s the same kind of technology,’ said Lenfant, crediting advances in micro switch technologies. ‘I am not saying that we have a mobile phone-style keyboard, but those technologies can help us create the impression of tactile sensation that is very close to traditional equipment with very limited space.’

One of the more innovative ideas to come from GE’s design team was the ultrasound device’s magnesium cover. ‘This is the first time we have used magnesium,’ said Lenfant. ‘Because it is very thin it is more resistant than aluminium or any other material, allowing us to create a compact architecture with a high level of resistance.’

He added that the importance of the magnesium goes beyond the Voluson I’s compactness and the strength. ‘The material is also very good for electromagnetic compatibility, which is very important in a hospital environment’ he said. Electromagnetic compatibility is a safety and regulation directive requiring the risk of electromagnetic disturbance to be eliminated from all equipment that contains electrical parts. Metallic covers made of materials like magnesium are used to ward off the possibility of unintentional generation, propagation and reception of electromagnetic energy.

One of the biggest challenges for the design team was shrinking the size of the ultrasound’s transducers. Lenfant said it was a delicate process because they are the most important part of the machine. The transducer probe makes the soundwaves and receives the echoes. It generates and receives soundwaves using a principle called the piezoelectric effect. In the probe, there are one or more quartz piezoelectric crystals, and when an electric current is applied to them, they change shape rapidly. These quick shape changes, or vibrations, produce soundwaves that travel outward.

Conversely, when sound or pressure waves hit the crystals, they bounce back electrical currents. The probe also has a sound-absorbing mechanism to cancel out back-reflections from the probe itself, and an acoustic lens to help focus the emitted soundwaves.

Transducer probes come in many shapes and sizes. While the shape of the probe determines its field of view, the frequency of emitted soundwaves determines how deep they penetrate and the resolution of the image. The design team was able to reduce the size of transducer probe and cords to something around the size of a computer mouse and cord.

Lenfant said this miniaturisation work is still in progress, and engineers would like to one day eliminate the cord entirely so that probes work much like a wireless mouse or keyboard.

While the reduction in the size of the transducer probe and cords does make the system more compact, there is some sacrifice in terms of convenience. In traditional systems, multiple probes can be plugged into the ultrasound device at the same time. But the miniature devices are only able to handle one probe at a time. ‘It doesn’t mean you can’t change your probe,’ said Lenfant, ‘but it’s an additional flexibility that we cannot have on this system.’

One area that GE’s engineers thought they could improve on with the portable device was its ergonomics. According to recent research carried out in Australia, around 80 per cent of the world’s sonographers suffer from musculoskeletal injuries caused by their profession. Lenfant said engineers took this into account when they designed the device’s trackboard with a slight recess that gives a user’s wrist a bit more comfort.

‘It’s a small detail, but makes a very big difference at the end,’ he said.

While convenience is the obvious advantage for those who use smaller ultrasound devices, Lenfant said GE’s machines offer many other benefits to users. For instance, he said, the devices could help reduce healthcare costs and save medical resources, as hospitals will no longer need to dedicate entire rooms to ultrasound systems. ‘When you think of the cost of medical care, the fact that you don’t need to have a dedicated room in a hospital or clinic is a big win for everybody,’ he said.

Lenfant pointed to GE’s Logiqe as an example of a miniature ultrasound device that has been used to streamline operations and workflow in hospitals. The device, which was introduced last summer, is designed to diagnose a diverse array of patient conditions, and is intended to help emergency department physicians and surgeons make quick decisions.

In total, GE Healthcare has introduced five compact ultrasound systems since the Vivid I was first introduced in 2004. Since then, the overall trend of hand-held and portable devices appears to be slowly catching on. According to one magazine report late last year, the market for ultra-compact systems is about £150m. Although this is less than 10 per cent of the nearly £2bn ultrasound market worldwide, it is expected to grow by about 55 per cent this year.

The report also claimed that ultrasound companies specialising in compact systems are seeing large sales increases. SonoSite, the first to introduce hand-held sonographic systems in 1999, posted total worldwide results of £20.3m in the second quarter of 2006 compared with £17.3m for the same quarter of 2005 — up 18 per cent.

Lenfant said GE engineers would like to apply the concept of miniaturisation to other medical equipment such as X-ray machines or CT scanners, but the complexities of those technologies makes designing a microsystem difficult. But that does not mean engineers are not going to try.

‘It’s always a work in progress because miniaturisation is not something we decide for one product,’ said Lenfant. ‘It is just the way to go.’