Development, validation, and pilot MRI safety study of a high-resolution, open source, whole body pediatric numerical simulation model

Abstract

Numerical body models of children are used for designing medical devices, including but not limited to optical imaging, ultrasound, CT, EEG/MEG, and MRI. These models are used in many clinical and neuroscience research applications, such as radiation safety dosimetric studies and source localization. Although several such adult models have been reported, there are few reports of full-body pediatric models, and those described have several limitations. Some, for example, are either morphed from older children or do not have detailed segmentations. Here, we introduce a 29-month-old male whole-body native numerical model, “MARTIN”, that includes 28 head and 86 body tissue compartments, segmented directly from the high spatial resolution MRI and CT images. An advanced auto-segmentation tool was used for the deep-brain structures, whereas 3D Slicer was used to segment the non-brain structures and to refine the segmentation for all of the tissue compartments. Our MARTIN model was developed and validated using three separate approaches, through an iterative process, as follows. First, the calculated volumes, weights, and dimensions of selected structures were adjusted and confirmed to be within 6% of the literature values for the 2-3-year-old age-range. Second, all structural segmentations were adjusted and confirmed by two experienced, sub-specialty certified neuro-radiologists, also through an interactive process. Third, an additional validation was performed with a Bloch simulator to create synthetic MR image from our MARTIN model and compare the image contrast of the resulting synthetic image with that of the original MRI data; this resulted in a “structural resemblance” index of 0.97. Finally, we used our model to perform pilot MRI safety simulations of an Active Implantable Medical Device (AIMD) using a commercially available software platform (Sim4Life), incorporating the latest International Standards Organization guidelines. This model will be made available on the Athinoula A. Martinos Center for Biomedical Imaging website.

Aluminum Thin Film Nanostructure Traces in Pediatric EEG Net for MRI and CT Artifact Reduction

“…Our previous studies showed the MRI RF safety of the NeoNet using numerical simulation [19]. This study showed that the high-power MPRAGE heating was well below 2 • C. Our recent simulation study on EEG safety with an infant/toddler [55] also showed a similar finding based on the dielectric properties of the resistive traces in infants/toddlers for safe EEG-MRI [56], where thin film resistive traces reduced the RF heating at 3 T MRI within the safety guidelines by the FDA [57]. Thus, resistive traces may improve the safety of infant/toddler EEG-MRI, as shown by our SAR, and thermal safety [10,58], regardless of the sequence used.…”

“…Thus, resistive traces may improve the safety of infant/toddler EEG-MRI, as shown by our SAR, and thermal safety [10,58], regardless of the sequence used. In this study, our target trace resistance of 10-15 kΩ was based on our recent study [55] in which we studied the safety using resistors of 10 kΩ, and the 5-15 kΩ industry standard. A lower resistance below 10 kΩ may affect the amount of RF-induced currents in the NeoNet traces inside a 3 T MRI, which could lead to both heating and greater B 1 artifacts.…”

Modifying the trajectory of epicardial leads can substantially reduce MRI-induced RF heating in pediatric patients with a cardiac implantable electronic device

“…Electromagnetic simulations were implemented in ANSYS Electronics Desktop 2020 R2 (ANSYS Inc., Canonsburg, PA). A pediatric body model consisting of average tissue, skull, brain, ribcage, and heart was created from segmented MRI images of a 29-month-old child (23) and post-processed to form a tetrahedral mesh for finite element simulations (see Figure 2). A model of a 16-rung high-pass birdcage coil with dimensions mimicking a Siemens 1.5 T Aera body coil was created based on technical specifications provided by the vendor and tuned to 63.6 MHz (24).…”

The Position and Orientation of the Pulse Generator Affects MRI RF Heating of Epicardial Leads in Children

“…A human shaped head and torso phantom representing a pediatric patient was designed based on segmented MR images of a 29-months-old child [15] (Fig. 1).…”