In the SNPRM on advanced air bags, the National Highway Traffic Safety Administration (NHTSA) proposed a comprehensive set of injury criteria for evaluating the potential for injury to the head, neck, chest and lower extremities for the various dummy sizes, ranging from the 1-year-old child to the 50th percentile male. The comments received and the agency's responses are summarized in this paper and the various performance limits implemented in the final rule are shown in Table SES-1.In the SNPRM on advanced air bags, the National Highway Traffic Safety Administration (NHTSA) proposed a comprehensive set of injury criteria for evaluating the potential for injury to the head, neck, chest and lower extremities for the various dummy sizes, ranging from the 1-year-old child to the 50th percentile male. The comments received and the agency's responses are summarized in this paper and the various performance limits implemented in the final rule are shown in Table SES-1.

Supplement: development of improved injury criteria for the assessment of advanced automotive restraint systems - ii

Objective Modern neuronavigation systems lack spatial accuracy during ongoing surgical procedures because of increasing brain deformation, known as brain shift. Intraoperative magnetic resonance imaging was used for quantitative analysis and visualization of this phenomenon. Methods For a total of 64 patients, we used a 0.2-T, open-configuration, magnetic resonance imaging scanner, located in an operating theater, for pre- and intraoperative imaging. The three-dimensional imaging data were aligned using rigid registration methods. The maximal displacements of the brain surface, deep tumor margin, and midline structures were measured. Brain shift was observed in two-dimensional image planes using split-screen or overlay techniques, and three-dimensional, color-coded, deformable surface-based data were computed. In selected cases, intraoperative images were transferred to the neuronavigation system to compensate for the effects of brain shift. Results The results demonstrated that there was great variability in brain shift, ranging up to 24 mm for cortical displacement and exceeding 3 mm for the deep tumor margin in 66% of all cases. Brain shift was influenced by tissue characteristics, intraoperative patient positioning, opening of the ventricular system, craniotomy size, and resected volume. Intraoperative neuronavigation updating (n = 14) compensated for brain shift, resulting in reliable navigation with high accuracy. Conclusion Without brain shift compensation, neuronavigation systems cannot be trusted at critical steps of the surgical procedure, e.g., identification of the deep tumor margin. Intraoperative imaging allows not only evaluation of and compensation for brain shift but also assessment of the quality of mathematical models that attempt to describe and compensate for brain shift.

Quantification of, visualization of, and compensation for brain shift using intraoperative magnetic resonance imaging.

This study was conducted to investigate differences in brain response due to frontal and lateral impacts based on a partially validated three-dimensional finite element model with all essential anatomical features of a human head. Identical impact and boundary conditions were used for both the frontal and lateral impact simulations. Intracranial pressure and localized shear stress distributions predicted from these impacts were analyzed. The model predicted higher positive pressures accompanied by a relatively large localized skull deformation at the impact site from a lateral impact when compared to a frontal impact. Lateral impact also induced higher localized shear stress in the core regions of the brain. Preliminary results of the simulation suggest that skull deformation and internal partitions may be responsible for the directional sensitivity of the head in terms of intracranial pressure and shear stress response. In previous experimental studies using subhuman primates, it was found that a lateral impact was more injurious than a frontal impact. In this study, shear stress in the brain predicted by the model was much higher in a lateral impact in comparison with a frontal impact of the same severity. If shear deformation is considered as an injury indicator for diffuse brain injuries, a higher shear stress due to a lateral impact indicate that the head would tend to have a decreased tolerance to shear deformation in lateral impact. More research is needed to further quantify the effect of the skull deformation and dural partitions on brain injury due to impacts from a variety of directions and at different locations.

Comparison of Brain Responses Between Frontal and Lateral Impacts by Finite Element Modeling

Three-dimensional finite element analysis for stress in the periodontal tissue by orthodontic forces.

Recent advances in the field of sterotactic neurosurgery have made it possible to coregister preoperative computed tomography (CT) and magnetic resonance (MR) images with instrument locations in the operating field. However, accounting for intraoperative movement of brain tissue remains a challenging problem. While intraoperative CT and MR scanners record concurrent tissue motion, there is motivation to develop methodologies which would be significantly lower in cost and more widely available. The approach the authors present is a computational model of brain tissue deformation that could be used in conjunction with a limited amount of concurrently obtained operative data to estimate subsurface tissue motion. Specifically, the authors report on the initial development of a finite element model of brain tissue adapted from consolidation theory. Validations of the computational mathematics in two and three dimensions are shown with errors of 1%-2% for the discretizations used. Experience with the computational strategy for estimating surgically induced brain tissue motion in vivo is also presented. While the predicted tissue displacements differ from measured values by about 15%, they suggest that exploiting a physics-based computational framework for updating preoperative imaging databases during the course of surgery has considerable merit. However, additional model and computational developments are needed before this approach can become a clinical reality.

A computational model for tracking subsurface tissue deformation during stereotactic neurosurgery

Parametric study of head response by finite element modeling

Crash test dummies serve as human surrogates in automotive crash simulations, and accelerations monitored in the heads of these dummies are used for assessment of human head injury hazard. For these acceleration measurements to be meaningful indicators of head injury, the impact response of the human head must be a part of dummy head design. This paper describes the conception, design and development of a crash test dummy head. Geometric, inertial, and performance requirements based on biomechanical information are presented and discussed. The head design concept is compatible with current head injury assessment procedures, and the configuration is based on the GM Research skull and head geometry models. The manufacture and development are described, and the test procedures and results are presented and discussed with reference to the biomechanical and functional requirements. The resulting dummy head is shown to comply with these requirements.

Robert P. Hubbard

Papers

Parametric study of head response by finite element modeling

Definition and development of a crash dummy head

The Highway Safety Research Institute Dummy Compared with General Motors Biofidelity Recommendations and the Hybrid II Dummy

Geometric, inertial, and joint characteristics of two part 572 dummies for occupant modeling