Adaptive Mechanical Models for Realistic Radiation Sterilization Simulations

Project Summary Medical Device development has an underlying paradigm to reduce risk early in the development cycle. Developers are using computational tools such as finite element analysis to mitigate risks from thermal loads, mechanical stresses etc. There is one exception to this paradigm: sterilization validation. Sterilization validation is addressed late in the development cycle as an actual physical device is needed to perform these activities. Sterilization configurations (e.g., packaging design, radiation beam direction, etc.) are iteratively modified until the regulatory requirements are met. This “trial-and-error” approach is prevalent throughout all aspects of sterilization. As another example, when choosing between sterilization modalities, medical device companies often rely on rules-of-thumb which may lead to a suboptimal choice for their device. However, use of simulations to model the radiation sterilization process is an emerging field that has the promise to address sterilization validation early in the development process and thereby allow for a Design for Sterilization approach. That means as soon as a Computer Aided Design (CAD) model of the device exists, simulation can be performed to analyze whether the device will pass sterilization validation or mitigations will be needed. While simulations are a key ingredient to address sterilization early in the design process, we find that a single representation of the device might not be sufficient to tell the whole story. Sterile packaging is another important factor that needs to be considered. The package determines how the device is presented to the radiation beam, but within the package the device can move to a certain degree with separate parts of the device also can move against each other. Thus, there is a range of possible orientations and positions of the device that will influence the overall radiation dose that the device will receive. In this project we propose to develop a software tool that can generate a family of CAD models that spans the realistic range of device orientations and positions expected from packaging constraints and device configuration. The tool will account for gravity and other forces to realistically describe the range of possible configurations. We also will develop a custom phantom that can be used in simulations and in measurements to explore the range of dose received. The comparative study of measured and simulated dose will be used to overall validate our approach. The new tool developed under this project will improve the utility of radiation sterilization simulations and pave the path for Design for Sterilization.