Role of Modeling and Virtualization In
Medical Device Development
•
White Paper
Abstract
The medical devices and diagnostics industry is increasingly adapting advances in information technologies and systems for better diagnosis, delivery of treatment, product lifecycle management, new functionalities and features, enhanced usability and product innovations to reduce time-to-market. Software is playing a major role in new features and functionalities of devices, introducing an additional dimension to the product development process. With an increasing focus on regulatory compliance in light of adverse incidents, these challenges can be more effectively tackled by leveraging information technologies. Modeling and simulation is one such
Advances in technology have enabled the integration of mathematical models and virtualization on a single platform. This platform can be seen as a key enabler to reduce time and cost while prototyping medical devices and systems. Mathematical models that mimic the functional behavior of a system have found applications in various domains such as process control and automotive, where these models have been successfully deployed for design, operational control and optimization and diagnostic solutions. Recently, the medical device industry has begun exploring the use of models for new product introductions, improving performance or reliability of existing designs
and overall re-engineering. Virtualization allows the simulation of hardware components with concurrent operating systems before actually building the hardware prototype. Mathematical models in conjunction with the simulated hardware and applications forms the complete system simulation.
This paper provides an overview of systems modeling and its relevance to virtualized, platform-based solution development. Such a virtual platform allows device manufacturers to use a range of simulation technologies with which to test products for feasibility, design sensitivity, performance, reliability, endurance, safety and any other issues. A typical infusion pump provides a good example to illustrate the modeling paradigm and its applicability.
Overview
solutions overview
2
into devices. Such “electronic” medical devices are becoming intricate due to multiple boards, processors, operating systems and complex decision making processes.
The typical product life cycle for a medical device is shown in Figure 1.
The design phase covers stages such as ideation and research, product design or prototyping,
1 2. The design phase, especially prototyping,
goes through various iterations, adding to both cost and time. Functionality changes or design alternatives means re-testing and validation, hardware iterations. The absence of an interacting environment limits the ability to achieve the required functionality, which can be validated during clinical trials only after the prototype is developed. Compliance with regulatory and effort, since the product and development process itself is subject to scrutiny. Thus, to perform hardware prototype testing for every new product development cycle -- or to conduct systematic analysis during re-engineering -- is both costly and time consuming.
Modeling and Virtualization Paradigm
in addressing the needs of faster development can be incorporated within model and software simulations. Simulations comprise both the functional behavior of the device or system and the hardware components. The virtualplatform-based approach has three main elements.
Modeling that mimics the behavioral
functionality of the device and the interacting systems.
Embedded hardware device simulation that mimics the behavior of the target board (CPU, memory, battery, etc.), enabling quick
The ability for models running on the Windows platform to coexist and interact with embedded target hardware simulators and the functionality of the device running on an embedded operating system on a single PC.
The role of a virtualized platform in medical device development is depicted in Figure 2.
Modeling involves the use of a mathematical representation to describe a system. This can be in the form of equations, data-driven models or representations developed from domain experts’ knowledge. Various techniques can be used, such as CFD, parametric techniques, black-box methods such as neural networks and other
A virtualized platform consists of a mix of virtualized systems development (VSD) and virtualization. VSD is product development without the use of, or need of, the target hardware platform on which the software will eventually run. With VSD, the target hardware is simulated and runs on each developer’s development workstation. For the target software, the virtualized target hardware Medical Devices Product Lifecycle Ideation & Research Product Design Sustenance PMA & 510 (k) Support Testing &
Medical Device Product Life Cycle
Figure 1 Figure 2 SW – HMI, Hardware Model Test Plan, Environment Environment Model Program Quick design savings Virtual
thus fewer trials,
Environment Model Monitor Hardware Model Design Develop Run Prototype Device Clinical Trials Hardware industry-standard techniques Develop the systems with the applicable IDE
Manufacture prototypes Find only usability issues as previous phase Prepare for Study
Environment
behaves exactly the same as the physical target hardware. The schematic representation of VSD is shown in Figure 3.
Schematic VSD
Virtualization is a technology that allows the concurrent running of two or more operating systems on a single PC or embedded system, and is being rapidly adopted in the engineering world. It is enabled by a hypervisor, which is a software layer that abstracts the hardware from the operating system, permitting multiple operating systems to run. A candidate representation of virtualization is shown in Figure 4.
Representation of Virtualization
A virtualized platform allows for configurability of design, enabling designers to iterate designs quickly and develop a robust solution architecture after considering all the possible alternatives in a virtual manner. The simulations on a virtualized
platform help designers conduct what-if analysis on various design aspects instead of
experimenting on developed hardware that could be limited, underachieving and expensive. Modeling medical devices or equipment can be done mainly for new product development, re-engineering or re-design. Such models can learn from expert information or from an experimental database. Models can be developed, with appropriate fidelity, using tools such as Matlab, Scilab, Mathematica, etc. The VSD allows developers to define, develop, deploy and
integrate target-specific firmware, operating system kernel and device drivers, and application and communication stacks, even while the hardware design and production progresses in parallel, while virtualization allows them to save costs, reduce footprint and consolidate systems. The following section illustrates the use of
mathematical model and virtualization technology for the design of a typical infusion pump. The infusion pump is designed to provide a measured flow of infusion fluid, medication or nutrients to the patient. It has three major components: the fluid reservoir, a mechanism such as a tube for transferring the fluid to the patient and a mechatronic system to generate and regulate flow.
The regulation of the drug concentration in the body to achieve and maintain the desired result is highly critical. An under-dosage may not provide sufficient treatment, while an overdose can produce dangerous side effects. The industry is currently experiencing an increase in the number and severity of infusion pump product recalls1. Figure 3
Virtualized Target System with
Application
Application program and interfaces Target operating system Target hardware drivers and boot code
PC
Processors Memory Devices Network I/O
Figure 4
App1
Embedded OS
Hypervisor/Virtual Machine Monitor Shared hardware Another OS (Windows) App1 App1 App1 Advantages of VSD
• What-if analysis of various architectures and design • Identify problems early
• Quicker detection and resolution of bugs • Highest quality assurance, early validation and
automated testing
• Optimize hardware and software co-development to produce higher quality systems in less time • Improve on time to market and overall saving in
development and deployment costs
On a broad level, Modeling serves as
• Enabler for new product development, • Platform for re-engineering and re-design. • Catalyst in choosing right-fit technologyalternative,
• Tool to perform sensitivity analysis on various
design
Benefits of Virtualization
• Save Hardware cost and footprint • Make use of multi-core processors • Test beta systems and maintain legacyap-plications
This underlines the necessity of a platform to experiment with and accelerate development.
Use of Modeling and Virtualization for
Designing Infusion Pumps
The infusion pump is designed to provide measured flow of infusion fluid, medication or nutrients to the patient. It has three major components, fluid reservoir, mechanism such as tube for transferring the fluid to the patient and mechatronic system to generate and regulate flow. The regulation of the drug concentration in the body to achieve and maintain a desired result is highly critical. Underdose may not provide sufficient treatment, while overdose can produce side effects. Infusion pump in current scenario is going through a phase where there is rise in number and severity of product recalls [1]. This underlines the necessity of a platform; to experiment and accelerate the development. The infusion pump is an intricate system
comprising mechanical, electrical and software systems. A high-level schematic of a typical pump is shown in Figure 5. The pump motor drives the mechanism, including the gearbox and cam, to achieve the required reciprocating action, such as valves and/or shuttle mechanisms, that results in the squeezing and unsqueezing of the tube. This operation provides a positive displacement
of fluid, thus delivering the requisite fluid flow to the patient. The accuracy of the output flow is a critical performance parameter, and typically there is no feedback available for it. The motor controller is a hardware platform to which all the sensors are interfaced, and it generates a control signal for the motor operation. The power and battery module manages the power supply for the set-up.
High-Level Schematic of an Infusion Pump
The motor, and the associated drive mechanismalong with the tube, can be modeled using tools such as Matlab. This detailed, high-fidelity mathematical model helps in understanding the interaction of the various subsystems, as well as with optimizing overall system performance. The motor controller and power and battery target hardware are simulated on the virtualized platform. The strategy and functionality code for both is developed using a standard integrated
development environment and is integrated into the virtual platform. The user interface is developed on a platform for configuring hardware and functionality parameters. Various design alternatives can be tested by varying these parameters. The mathematical model developed in the Matlab environment runs on the Windows OS and interfaces with the simulated motor controller and power module through the virtualized platform.
Virtualized Infusion Pump
Figure 6 shows the virtualized platform for designing the infusion pump.
This virtualized platform offers the following advantages.
The opportunity to test different components of the power module and motor controller.
Mathematical models that enable design
sensitivity analysis, in the form of technology change, material changes, etc.
Testing of the end-to-end functionality of the power module and motor controller.
Minimal performance degradation from the simulated hardware to the actual hardware.
Ability to host various operating systems that could be crucial from a functionality perspective. For example, models can
solutions overview 4 Patient Motor Controller Power and Battery Module Sensors (Temp, Pressure, Position etc.)
Drive Mechanism
Comprises gearbox, cam, valves, shuttle etc.
Tube Administered flow
Motor
be executed on the Windows OS, as the numerical methods or solvers are best suited for such an operating system, whereas hardware functionality needs a real-time operating system.
Ability to perform data exchange between disparate operating system applications.
Facilitation of experimentation, such as
Ability to more easily develop performance analysis and test automation tools.
The Road Ahead
A number of things need to be addressed when using a development platform for design at this time.
Supporting various types of hardware devices from different manufacturers.
time performance.
tested in real time.
Handling complexity issues due to
hierarchical scheduling as part of virtualization.
Developing life cycle development tools for analyzing performance, timing, memory, code coverage and enabling test automation for the virtual platform.
Conclusion
Modeling and virtualization together provide a systematic integrated platform to accelerate the can be expected across the ideation and research, prototyping and sustenance stages, where models can be exploited for system representations, enhancements and re-engineering, while the iterations in system prototyping can be reduced through virtualization principles.
References
1. Total Product Life Cycle. FDA. www.fda.gov
2. National Instruments. www.ni.com
3. AJ5800 Volumetric Infusion Pump
operation manual. 4.
Baxter.
5. Wind River Systems Inc. www.windriver.com
6. Virtutech. www.virtutech.com
7. Eureka Infusion Pump operator’s manual by Universal Medical Technologies.
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