Intelligent Medical Systems

28 February 2006 (Last Updated February 28th, 2006 18:30)

Dr Diana Hodgins is coordinator of the Healthy Aims project. She looks at the work being done to extend the existing state of the art in microsystems, biomaterials, wireless communications, power sources and medical practices.

Early adopters of new technologies require both innovative product partners and clinical teams. With this in mind, a group of forward-thinking researchers, clinical experts and innovative product partners have formed the Healthy Aims consortium. The
consortium has chosen a range of implants and diagnostic equipment to demonstrate how key microsystem technology components and processes can be developed and integrated into new products.

To quickly demonstrate technology integration, some products have been chosen which can be designed, fabricated and prepared for clinical trials within four years. Core technologies are being developed for the integration of these products and for
subsequent clinical trials. These products include a functional electrical stimulation (FES) implant, an implant intracranial pressure sensor system, retina and cochlear implants, and glaucoma, sphincter and inertial sensors. Collectively, these utilise
a full range of microsystem technologies:

CORE TECHNOLOGIES

The consortium's effort has been put into developing core technologies that will enable more advanced implants and diagnostic equipment to be developed in the future. For example, the biofuel cell will enable low-power-consuming devices, such as drug
delivery systems and pain management systems, to be powered continuously, without external recharging, over their lifetime. Encapsulation and biomaterial coatings to suit complex forms will be used on implants where space is critical. High-density
electrodes and interconnects will be adopted in applications such as a retina implants, where the nerves are densely packed and current density is a key design factor.

"Device manufacturers will be able to design new products using these core technologies."

These technologies take many years to develop to approval standard before they can be considered for use in medical products: the gestation period from initial research through to integration into a final product is typically six to eight years.
Considerable commitment is required from the product partners who provide the product specification around which these technologies can be developed. At the end of the project, device manufacturers will be able to design new products using these core
technologies. The technology partners will also be able to exploit their knowledge in developing other innovative products outside the consortium.

ON TARGET

At the end of two years, the project is on target to achieve its goals. Product developments have all progressed to the point where the design is complete and key technologies have been proven. Within the next few months, there will be a design freeze
on all the planned products to allow animal or clinical trials. These products include:

  • A retina implant
  • A two-channel FES implant for the upper limb
  • A glaucoma sensor
  • An intracranial pressure sensor
  • A sphincter sensor
  • A motion sensing system for specific activity monitoring

The final ethics approval process and prototype manufacture will take up much of the third year of the project. These tasks must be completed by the end of year three so that clinical trials can take place in year four. The following is a brief
description of the current status of the product designs:

Retina implant. The implant design incorporates 231 electrodes in the array. Glasses are worn on the patient, from which power is applied to the implant through inductive coupling, and the image information is transmitted through an IR link.
Data processing will be done in a pocket PC, which will be linked to the glasses. In year four, this design will be tested in human trials on up to 70 patients.

FES implant for upper limb. The two-channel implant will be used to help stroke patients with wrist extension and hand opening. The implant will be triggered using a simple inertial measuring unit and algorithms currently under development.
Already, a two-channel surface stimulator has been designed, manufactured and used in clinical trials to test the efficacy of the system prior to producing the implant.

Glaucoma sensor. This design utilises a novel flexible strain gauge which is formed into a contact lens to monitor intraocular pressure. Preliminary clinical trials have been successfully completed and system integration is underway, focusing
on the integration of the sensor read electronics and the inductive coupling system for power.

Intracranial pressure sensor. The design prototype uses a stable pressure sensor chip to monitor the pressure. The primary application is for patients with hydrocephalus, hence the system needs to be stable over many years. Lab trials indicate
that the system developed will meet the stability requirements. This design will now be fabricated using biocompatible materials and processes so that full lab and animal trials can begin in year three and clinical efficacy can be determined.

Sphincter sensor. The sphincter sensor is designed to be applied to a number of different sphincters in the body. The first design effort focused on the sensor, which needs to be small, flexible and inexpensive to manufacture. The strain gauge
design has been proven, under lab conditions, to be suitable for monitoring the pressures that are likely to occur to the required accuracy. Clinical trials on the first system are planned for the end of 2006, and in 2007 systems will be available that
can monitor remotely over 24 hours.

Motion sensing system. A number of technologies are required for monitoring human motion. In years one and two, the core inertial sensors, a three-axis accelerometer and a three-axis gyro, together with systems for integrating these core
components, were developed. At the end of year two, a wireless three-axis accelerometer system and a breadboard three-axis gyro were both successful in lab trials. In years three and four, these units will be developed further to produce a wireless 6DOF
unit. In addition, algorithms will be developed to enable the sensor module to provide a suitable trigger for the FES. Other applications will be developed relating to activity.

These products will continue to incorporate core technology developments still underway. By the end of year four, the goal is to have a further design freeze on the following products:

  • A six-channel fully implantable FES for the upper limb
  • A three-channel FES for other applications
  • A FES for urinary incontinence
  • A sphincter sensor for ambulatory measurement
  • A cochlear implant incorporating novel electrode designs and an implantable battery

THE WIRELESS CONNECTION

"These products will continue to incorporate core technology developments."

All of the products described will ultimately have a wireless link from inside or on the body to a base station, which can be up to 3m away. The development of the MICS chip, running at 403MHz provides the wireless link from FES implants to the base
station. With the other implants, the local link varies: some use inductive coupling for data transmission and the retina uses IR. This brings the signals to 'on the body'. The protocol for data communications from on the body to the base station is
currently being developed and will become the Healthy Aims project data protocol for the body area network.

FORGING AHEAD

At the end of year two of the project, the consortium is confident that the clinical efficacy of medical implants and diagnostic equipment utilising microsystem technology and other related technologies will be proven, extending the current state of
the art in medical products.

The consortium is aware that it is only by regular communication between the technologists, product partners and clinical teams that they have been able to achieve this. The team has extended its scope for the next two years, introducing new implants
ready for clinical trials.