Scanning for solutions - Medical electronics

4 min read

OS portability enhances leading edge medical technology.

International medical technology group Elekta is basing new generations of equipment on LynxOS-SE to get to market quickly with systems that deliver high levels of functionality, fault tolerance and safety. While Elekta's platforms run one operating system on one processor, there are signs that medical systems of the future will require multiple operating systems running on single or multicore processors. Elekta specialises in systems and solutions for radiotherapy and radiosurgery, for the treatment of cancer and brain disorders. The company markets a number of treatment systems, including Leksell Gamma Knife and image guided radiation therapy systems. The Elekta Synergy image guided radiation therapy system uses high resolution imaging taken in 3d and at the time of treatment. By streamlining the process of assessing patients and beginning treatment, surgeons can start treatment directly. This means surgeons can work with up to date image data and can be sure to target a higher proportion of the affected area, while minimising damage to surrounding healthy tissue. The company's current product development activities include a new digital treatment control system named Integrity, used to drive the digital linear accelerator range of products. "A key factor of our development strategy is to accelerate completion of new products," said Adrian Smith, Elekta's product system engineer for linear accelerators. "Hence it is important that we can quickly port proven software applications to a variety of products to enhance reliability and reduce time to market." To meet these objectives, the OS' properties are a fundamental consideration. Although quality standards covering the design of medical systems are well developed, there are fewer stipulations concerning the technical requirements and safety provisions for operating systems. A number of OSs currently on the market have been used successfully in medical systems. However, for its new treatment system, and subsequent generations of products, Elekta sought a higher performing solution, with hard partitioning that could allow other applications to run concurrently without interfering with each other. "In addition, we wanted to find a solution that would allow us to use proven applications across a number of systems, for example using POSIX technology," Smith added. Development of the rtos image, using LynxOS-SE, was carried out at Elekta's UK design centre in Crawley. A small team of engineers who are experienced in realtime development, completed the design, including porting and writing of drivers, within project timescales. The portability and open-standards aspects of LynxOS-SE were fundamental to achieving this short time to availability of the first prototype image. Looking ahead, another key objective for the Elekta team is to create a generic base on which products of the future can be built. These will include additional radiotherapy systems and a number of other products that will make complex procedures faster and more effective. As an example of measures to aid code portability between systems, the Portable Operating System Interface (POSIX) is an open operating interface standard that places certain requirements on aspects of the OS such as signals, calls and management of processes and threads. Since LynxOS-SE and other LynxOS derivatives are POSIX conformant –supporting the POSIX.1 standard in its entirety – this provides Elekta engineers with the basis to port software quickly between platforms in future projects. This flexibility and portability has allowed Elekta to consider LynxOS SE version 6.0, which includes features to support emerging 64bit multiprocessing architectures. "This is important to us as we plan our future product strategy," said Smith. "Medical control systems can be highly processing intensive and have, historically, required several processor boards. Multiprocessing will offer significant design flexibility. Building our software development strategy on the LynxOS family will allow us to take full advantage of multiprocessing in future products, both to reduce the number of boards and to increase the performance of our systems." The LynxOS-SE is available both as a standalone OS as used by Elekta, or as a paravirtualised guest operating system running on top of the LynxSecure virtualisation platform. The LynxOS-SE user interface and any applications running on top of LynxOS-SE remain unchanged between the standalone and virtualised versions, allowing for seamless migration to a virtualised medical platform. Elekta's platform is typical of today's medical device systems and uses a single operating system, typically an rtos. However, as systems grow in complexity and feature set, developers may find advantages in using a general purpose operating system such as Linux or Windows for their user interface and connectivity to medical networks. In this case, the ideal scenario would be to use a general purpose operating system for communications with the outside world and the rtos for real time functions, such as patient monitoring. Let's look at a practical application of this technology. When monitoring vital signs such as EKG and blood oxygenation during a patient's hospital stay, numerous sensors must be attached to the body. To help untether patients, the wires could be eliminated by using Bluetooth wireless biometric sensors communicating to a single workstation. Within that workstation would be a virtualised environment running one or multiple virtual machines (VM) dedicated to the real time monitoring and analysis of the patient. The heart rate sensor would report its data in one VM, while the blood oxygenation sensor would connect to another VM, and so on. Each VM would run either an rtos or a general purpose OS like Linux, with real time scheduling and determinism guaranteed by the underlying separation kernel. Information from all patient sensors could then be displayed graphically in a familiar Windows environment running in another VM, all running on the same workstation. This could be done using virtualisation to run multiple OSs on the same physical platform. Virtualization abstracts the underlying processing cores, memory and devices by running VMs on top of an embedded hypervisor; each VM runs its own OS and related applications. A hypervisor is a software layer that either resides directly on the hardware (type 1) or is hosted on top of a conventional OS running on the hardware platform (type 2). A secure virtualisation platform combines a type 1 hypervisor with a small separation kernel to provide secure isolation of the VMs and offer real time performance and determinism when required. LynuxWorks and Portwell have teamed up to create a proof of concept wireless sensor platform for hospitals. Based on Intel technology, the platform uses Portwell's WADE-8067, an Intel Core 2 Duo based Mini-ITX board. LynxSecure provides software virtualisation technology that makes it possible to securely run both a Linux OS and an unmodified Windows operating system in parallel on the platform. "LynuxWorks provided us with a stable, fast POSIX compliant rtos with a multicore roadmap and quality developer tools. This has allowed us to further enhance our strategy to deliver solutions that are always the safest and best performing on the market, and to introduce new products quickly at competitive prices," Smith concluded. Looking forward to the next generation of multicore, multiple OS medical platforms, the proof of concept demonstrates a way for medical equipment manufacturers to port legacy wired sensor applications to a new wireless multicore platform. Author profiles: George Brooks is director of business development, medical segment. Robert Day, is vice president, marketing. Both are with LynuxWorks.