Use of Computational Simulation of Medical Technology – Part 1

Introduction

Medical devices continue to provide a crucial component in the diagnosis, prevention, monitoring, and treatment for diseases. Unlike drugs or biologics, a medical device can vary from the simple, which poses little or no risk to the user such as a tongue depressor or toothbrush, to the life-sustaining such as a pacemaker or medical imaging equipment. Traditionally, assessment of the safety, reliability and effectiveness of medical devices has relied on laboratory based in vitro testing of physical prototypes and subsequent in vivo testing in animals and/or humans. While physical testing can provide valuable information, it is slow, expensive and can only examine a limited number of variables. In vivo testing presents further difficulties in measuring any device performance: the inability to look at variations quickly and systematically, and ethical considerations associated with conducting extensive in vivo tests.

Here we will present a series of Blogs that will describe the application of Physics-based Computer Modeling and Simulation to a range of activities associated with the development of medical devices and technology.

1. Background

Physics-based Computer Modeling and Simulation (PCM&S) can provide an alternative approach to examine the limitations of initial design concepts and explore the use of novel technology without the need for physical prototype development and testing. While PCM&S has typically been used in the early design and development of devices, it is also being increasingly applied to study performance under envisaged operating conditions. In parallel, the U.S. Food and Drug Administration (FDA) is actively encouraging the use of PCM&S to support patient safety and technology innovation in medical devices.

Developers of medical technology are consistently under pressure to develop and extend the use of life-saving therapies, while simultaneously meeting safety standards, obtaining regulatory approval and reducing the time and cost for increasingly complex technology to reach the patient. Computational simulation is becoming increasingly important in overcoming these obstacles and expediting the development and implementation of life-saving medical technology. Current uses for simulation range from physical medical devices, pharmaceutical development, manufacturing technology and replacement of human trials to name but a few.

Developers can build predictive simulation models of devices to calculate the behavior of a device under a wide range of conditions. Adjustments can be made quickly to assess the response of different designs and operating conditions, allowing a large number of scenarios to be investigated in a relatively short period of time. These in silico tests will not replace traditional in vitro and in vivo tests but are designed to complement them by reducing the reliance on bench, animal and human testing. In this way, it is expected that the use of PCM&S for development of medical devices will reduce the time and cost of the development process, and enhance confidence in future application.

With the increasing complexity of new medical devices, the technology and design can rely on any combination of mechanical, electronic, software or chemical/biochemical action to achieve their purpose.  For many years, PCM&S studies have been used to support device design/development and reported in submissions for authorization of medical device use. Traditionally these studies have covered the simulation of fluid dynamics to evaluate flow phenomena in ventricular assist devices; solid mechanics to assess stresses in hip implants; electromagnetics for radiofrequency safety; optics for spectroscopy devices; ultrasound propagation in body tissue; and heat transfer from devices into body tissue. With the increasing sophistication and capability of computational simulation, and in particular simulation of multiple physical phenomena, the utility of computational simulation for advancing medical technology is crucial. Some examples of medical technologies that have used simulation in their development are shown in Figure 1.1.

Figure 1.1: Examples of medical technology developed using computational simulation.

Developers of innovative medical technology face a number of pressures among which are:

• The complexity in the response of the human body, coupled with the inherent variability encountered across the billions of potential human subjects, makes it impossible to investigate performance using experimental approaches.
• Increased levels of miniaturization and functional integration allow medical devices to be developed to address an increasing number of potential applications across the broad field of biotechnology. The complexity of the new device operation can no longer be represented by traditional build and test approaches.
• Gaining support for new device development increasingly requires early demonstration of performance to meet targeted therapeutic needs. The pressure to demonstrate feasibility as early as possible helps minimize the need for continued redesign and additional prototype development and testing.
• With the increased complexity of device functionality, device design needs to be optimized as soon as possible in the development cycle to minimize delays in getting functioning prototypes to the market. This can only be done by having a more detailed understanding of the device operation and what may be limiting achievement of defined performance criteria.
• In a competitive market, alternative devices will be available such that the window for successful development, demonstration and implementation of new therapies may vanish quickly.
• In vitro testing and in vivo trials can be both expensive and time consuming. While they cannot be eliminated, in silico simulations can be used to identify critical cases for physical testing and support demonstrations of efficacy of new treatments thereby potentially reducing obstacles for regulatory approval.

In the past decade, major changes have taken place that have played a significant role in stimulating the use of computational simulation in the development of novel medical technology, namely:

1. Successful application of medical devices typically requires the integration of multiple physics within any operation. Computational simulation software is now available that can provide integrated simulation of multiple physical phenomena. The algorithms that represent the mathematical description of the physical phenomena of interest have greatly expanded over recent years and the improved accuracy and efficiency of solving the equations has allowed solutions to previously intractable problems to be achieved.
2. Regulatory bodies have become increasingly aware of how and when simulation can provide value and benefit. They are now accepting, and in some cases, actively promoting the inclusion of simulation in device submissions.
3. Improvements in computer hardware and its availability at relatively low cost has allowed widespread use across the scientific and engineering community, providing support and competition to conventional build and test development approaches.

In the remainder of this article, we will look at some examples where computational simulation has been successfully used in the development of a medical technology from the initial proof of concept to application in the design of patient therapies. We will conclude the article with a look at some emerging trends in computational simulation that may be important for expanded use in the medical industry.