Tetsuya Nishimoto

Relation Between Diffuse Axonal Injury and Internal Head Structures on Blunt Impact

Diffuse axonal injury (DAI) is a severe head injury, which exhibits symptoms of consciousness disturbance and is thought to occur through rotational angular acceleration. This paper analyzes the occurrence of DAI when direct impacts with translational accelerations are applied to two-dimensional head models. We constructed a human model reproducing the human head structure, as well as modified human models with some internal head structures removed. Blunt direct impacts were applied from a lateral direction to the bottom of the third ventricle, considered to be the center of impact, using an impactor. The analysis was done by comparing the macroscopic manifestation of DAI with the shear stress as the engineering index. In the analytical data obtained from the human model, shear stresses were concentrated on the corpus callosum and the brain stem, in the deep area. This agrees with regions of the DAI indicated by small hemorrhages in the corpus callosum and the brain stem. The analytical data obtained by the modified human models show that the high shear stress on the corpus callosum is influenced by the falx cerebri, while the high shear stress on the brain stem is influenced by the tentorium cerebelli and the shape of the brain. These results indicate that DAI, generally considered to be influenced by angular acceleration, may also occur through direct impact with translational acceleration. We deduced that the injury mechanism of DAI is related to the concentration of shear stress on the core of the brain, since the internal head structures influence the impact stress concentration.

Direct impact simulations of diffuse axonal injury by axial head model

This paper discusses the relation between head injury and the Head Injury Criterion (HIC), which is widely used as a vehicle crash safety standard, and considers the importance in traffic accidents of diffuse axonal injury (DAI), which exhibits symptoms of conscious disturbance. In our analytical study reported in this paper, we constructed a two-dimensional computer model reproducing an axial section of the human head to analyze causes of DAI. Simulation results of applying direct impacts to the head by an impactor are reported. We found that, although DAI has been widely believed to be caused by rotational impacts, it can also be caused by translational direct impacts due to the influence of internal head structures.

Development of high performance drive-recorders for measuring accidents and near misses in the real automobile world

Two types of drive-recorders were developed for recording data on automobile accidents and near misses. The first type was an accident drive-recorder (ADR) to record accident data only. The other type was a near miss and accident drive-recorder (NADR) to record both accident and near miss data. The ADR and NADR were each equipped with a CCD camera to obtain visual data on accidents and near misses from the drivers view. The recordable data items of the ADR and NADR included acceleration, angular velocity, video image, accident avoiding behavior and global position. In this paper, we introduce the design concepts, specifications and data recording methods of the drive-recorders, and report the results of their validation tests. ADR and NADR should provide more accurate data on accidents and near misses to assist in revising the safety regulations, improving the injury criteria and crash test procedures, and in developing new dummies.

Serious injury prediction algorithm based on large-scale data and under-triage control

The present study was undertaken to construct an algorithm for an advanced automatic collision notification system based on national traffic accident data compiled by Japanese police. While US research into the development of a serious-injury prediction algorithm is based on a logistic regression algorithm using the National Automotive Sampling System/Crashworthiness Data System, the present injury prediction algorithm was based on comprehensive police data covering all accidents that occurred across Japan. The particular focus of this research is to improve the rescue of injured vehicle occupants in traffic accidents, and the present algorithm assumes the use of an onboard event data recorder data from which risk factors such as pseudo delta-V, vehicle impact location, seatbelt wearing or non-wearing, involvement in a single impact or multiple impact crash and the occupants age can be derived. As a result, a simple and handy algorithm suited for onboard vehicle installation was constructed from a sample of half of the available police data. The other half of the police data was applied to the validation testing of this new algorithm using receiver operating characteristic analysis. An additional validation was conducted using in-depth investigation of accident injuries in collaboration with prospective host emergency care institutes. The validated algorithm, named the TOYOTA-Nihon University algorithm, proved to be as useful as the US URGENCY and other existing algorithms. Furthermore, an under-triage control analysis found that the present algorithm could achieve an under-triage rate of less than 10% by setting a threshold of 8.3%.

VEHICLE CRASH ANALYSIS BASED ON OWN DATA RECORDING

This paper explains a method of estimating the acceleration of the center of gravity and the trajectory of a vehicle by a drive-recorder which records accident data at the time of a traffic accident. We compared the drive-recorder data with the data of crash tests and verified that the drive-recorder captured the vehicle trajectory at the time of crash. The analytical method described in this paper is useful for collecting accurate accident data by drive-recorders and for providing accident information in accident notification systems.

Impact Injury Analysis of the Human Head

The brain is the most important organ for life activity and humanity and is also an organ that tends to have residual disabilities after an accident because neuron cells cannot repair themselves. Therefore, protecting the brain from serious damage should be one of the most important objectives in automotive safety design for both passengers and pedestrians. For this reason, the Seikei University Graduate School and others have examined head impacts and the subsequent responses.

Critical contact pressure and transferred energy for soft tissue injury by blunt impact in human-robot interaction

The peak mean contact pressure and the total transferred energy are discussed as the dominant parameters of bruise tolerance by blunt impact in order to obtain safety criteria for robot design in human-robot interaction. Impact tests are conducted using live pigs with the permission of the ethical committee. A 25 mm-diameter cylindrical impactor is used to represent moving parts of robots. Samples of soft tissue are stained, and capillary damages are investigated by microscopy. The results show that there is no capillary damage if the peak mean contact pressure is less than 1.3 MPa and the total transferred energy is less than 87 kJ/m2. The probability of injury as a function of these parameters is obtained using logistic regression of the the experiment results.

Three-Dimensional Human-Head Model using VOXEL Approach Developed for Head-Injury Analysis

In this paper, a three-dimensional human-head model was developed using the VOXEL approach. The human-head VOXEL model is based on 433 scanned images (512 x 512 pixels) taken by CT (Computed Tomography). The precision of the head model depends on the resolution of slice images. The number of elements is then defined by the resolution and number of slice images. The maximum number of elements for a human-head VOXEL model developed from slice images is about 40.0 million. This model included the scalp, soft tissue, subarachnoid space, eyes, skull, brain, falx cerebri, dura mater, tentorium cerebelli and ventricles. All of these biological tissues were modeled as tiny cubic elements with one-point integration. To investigate the relation between CPU time and the number of elements, finite-element analysis was conducted using an original finite-element analysis code. Direct-impact analysis was conducted frontally on the human-head VOXEL model by a cylinder to simulate the cadaveric tests.