COMPUTATION OF ELECTRIC FIELD IN TORSO OF CHILD

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Placement of Implantable Cardiac Defibrillators (ICDs) in children is a unique and challenging problem due to the variety of shapes and sizes, ranging from neonate to adolescent, the need for anticipating growth, the cost of device replacement due to battery drainage, and the psychological intolerance of the device by this population. ICD placement in adults, while more routine, is also clearly suboptimal, producing wasted energy, increased pain levels, and reduced battery life. The result in children is an ad hoc array of device placement strategies, based on sparse experience and ignorant of biophysical principles. Although in many cases this approach is ultimately successful in as much as the result is clinically acceptable fibrillation protection, the lack of cohesive strategy leads to inefficient overall management. Moreover, when, in adults and children, a device implant fails, there are no robust guidelines to suggest alternatives and no tools to evaluate such alternatives. Finite element modeling has been shown in adult torso models to correlate well with clinical results but has not enjoyed use in the pediatric population. Nor has there emerged a generally validated software tool that clinicians can use to evaluate device placement options, neither before nor after implantation. Thus, the goal of this collaboration is to model defibrillation in child torso models to develop optimization strategies and software that could help physicians gain insight into this important problem. Dr. John Triedman at the Department of Cardiology, Children's Hospital Boston is the collaborative investigator of this project, assisted in the project by Dr. Matthew Jolley, now an anesthesiology resident at Stanford University Medical Center. The project also has local collaborative support through Drs. Elizabeth Saarel, Tom Pilcher, and Michael Puchalski, all from the Department of Cardiology at Primary Childrens' Hospital in Salt Lake City. The main clinical goal is thus to Determine strategies for optimal, patient specific lead and device placements of ICDs. From this clinical goal come three specific engineering aims of this project: (1) Create subject specific 3D models of children based on CT and MRI data sets for modeling internal and external defibrillation in the SCIRun environment; (2) Explore different metrics of successful defibrillation that can be derived from simulations of ICD placement; (3) Validate simulation results from clinical measurements. Technical progress in this project addresses the larger question of creating subject specific models that are based on medical imaging data and that include different tissue regions. The project will also drive the development of new algorithms, modules, and user interface elements in the SCIRun environment that will find application in other cases of image based modeling and simulation of electric fields (see description of the project on orthopedic bone implant stimulation for an example of how software created for cardiac defibrillation was directly useful for a dramatically different application). The project also represents part of an expanding collaboration between SCI (http://www.sci.utah.edu/) and SPL (http://splweb.bwh.harvard.edu:8000/), the goal of which is to create compatibility integrated open source tools for the creation, visualization, and computational simulation from image based, patient specific models.