Why Having Your Medical Device Tested By HPC FOR MRI SAFETY?
II. HPC's Unique Scientific Expertise
- HPC's Team published more than 1000 peer-reviewed publications related to PIMDs, AIMDs, PIPOs, MDAPs, and MRI safety in general.
- HPC's Team developed anatomically correct models of the human anatomy for MRI safety, i.e., the Virtual Family and the MIDA Model.
- HPC's Team members have given hundreds of lectures on MRI safety and currently lecture in MRI safety workshops and training.
- HPC's Team members have developed numerous methodologies and theories to improve the safety of medical devices in the MR environment.
IV. HPC's Unique Contributions to MRI Safety
HPC developed 8 Regulatory Science Tools which are heavily used by FDA and industry for testing medical devices in the MR environment. These Regulatory Science Tools are FDA 'approved' and listed in FDA's "Catalog of Regulatory Science Tools to Help Assess New Medical Devices".
- HPC developed an E-field generator to generate uniform and high-strength E-fields at multiple frequencies. The generator can be used to assess the radio frequency (RF) hazards of implantable medical devices (IMDs) in magnetic resonance imaging (MRI) environments.
Transfer Function Measurement Method for Implanted Leads - 'A'
Part 'A' of this HPC developed Regulatory Science Tool is novel technique to efficiently evaluate MRI-induced E-fields or induced voltages in the vicinity of implanted metallic leads. The technique is based on the reciprocity theorem in conjunction with the Huygens Principle. This approach allows to decouple the micro-scale lead simulation from the macro-scale human simulations within the MRI scanners.
Transfer Function Measurement Method for Implanted Leads - 'B'
Part 'B' of this HPC developed Regulatory Science Tool developed a transmission line model for RF-induced fields in AIMDs. The model analyzes the influences of the AIMD lead body, the lead tip, and the IPG. Together with the transfer function method, this method establishes a systematic approach for analyzing MRI RF safety problems.
- This HPC developed Regulatory Science Tools is a novel test instrument & methodology for AIMD model validation under MRI RF exposure. The tool consists of a compact and power efficient high E-field generator in combination with a set of transfer function validation pathways, based on the Hadamard matrix. These pathways provide low correlations among incident E-fields; yet generate high temperature rises. This method provides an efficient and effective alternative for all AIMD model validation.
This HPC developed Regulatory Science Tool provides a novel approach for validating computational simulation results by combining systematic, National Institute of Standards and Technology-guideline-based uncertainty assessment with the Gamma Dose Distribution (GDD) comparison method. It can be applied to complicated simulated and measured spatial pressure, EM, and thermal distributions. The combined approach of systematic uncertainty evaluation and the GDD method permits thorough validation with meaningful and reasonable tolerances. The tool provides a scalar agreement metric and a natural means of visualizing areas of disagreement. The generality of this tool makes it applicable to a wide range of computational models for MRI safety.
o2S2PARC is an online web-based simulation platform, recognized by FDA as a Regulatory Science Tool, enabling users to create, access, tune, and run predictive, multi-scale, multi-physics models of modulation sources acting on the peripheral nervous system as access points for modulation of organ functional response. o2S2PARC also has all tool for computational MRI safety integrated and is heavily used by industry and academia for MRI safety evaluations and research.
- The Virtual Family (VF) is a set of four highly detailed, anatomically correct whole-body models of an adult male, an adult female, and two children. The four VF models are based on high-resolution MRI data of healthy volunteers. Organs and tissues of the VF models are represented by three-dimensional, highly detailed CAD objects without self-intersections and gaps. The VF models are used for MRI safety testing of all medical devices in need of electromagnetic, thermal, acoustic, and computational fluid dynamics simulations. Examples of applications of electromagnetic and thermal simulations are the assessment of the safety of active and passive medical implants in an MRI environment and the evaluation of the safety and efficacy of ablation devices. Electromagnetic and thermal simulations have been performed on the entire set of VF models and additional models of children to calculate the whole-body averaged and local specific absorption rate (SAR) during exposure to 1.5 and 3T whole-body MRI coils. The VF was used in more than 1200 medical device submissions to FDA and was cited more than 380 times in peer-reviewed literature.
The MIDA model is a multimodal imaging-based detailed anatomical computer model of the human head and neck. The model offers detailed representation of brain surfaces, meninges, cerebrospinal fluid distribution, eyes, ears, and a number of deep brain structures, as well as several distinct muscles, bones and skull layers, blood vessels, cranial nerves, dental structures, and glands. Organs and tissues of the MIDA model are represented by three-dimensional, highly detailed computer-aided design (CAD) objects in standardized CAD data format. The MIDA model can be used in all software capable of importing and manipulating CAD data. The MIDA model includes segmentation of 153 different structures. Of particular interest are computational simulations to potentially investigate the safety and efficacy of medical devices in, on, or near the head.
