Intraosseous pressure and strain generated potential of cylindrical bone samples in the drained uniaxial condition for various loading rates.

Cortical bone is a composite material consisting of a porous elastic solid and viscous fluid. It is well known that the intraosseous fluid circulates as a result of a bone fluid pressure gradient in the porous space of the cortical bone. When a time-dependent mechanical load is applied to the bone, intraosseous fluid flow occurs through the interconnected pore space in the bone. Bone fluid flow leads to a strain generated streaming potential (SGP). However, there is no experimental study on the relationship between the generation of intraosseous pressure and the SGP. The purpose of this study was to obtain the relationship between SGP and intraosseous pressure generations in cortical bone. In order to understand the issue, a drained, one-dimensional experimental setup for fluid-filled cortical bone samples with four different strain rates was used to simultaneously measure the intraosseous pressure and SGP. The results revealed a significant correlation (r = 0.98, p = 0.02) between the generation of the SGP and the intraosseous pressure, which indicates that an intraosseous pressure gradient produces a SGP in cortical bone.

Influence of the anisotropic mechanical properties of the skull in low-intensity focused ultrasound towards neuromodulation of the brain.

Lately, neuromodulation of the brain is considered one of the promising applications of ultrasound technology in which low-intensity focused ultrasound (LIFU) is used noninvasively to excite or inhibit neuronal activity. In LIFU, one of critical barriers in the propagation of ultrasound wave is the skull, which is known to be highly anisotropic mechanically: this affects the ultrasound focusing, thereby neuromodulation effects. This study aims to investigate the influence of the anisotropic properties of the skull on the LIFU via finite element head models incorporating the anisotropic properties of the skull. We have examined the pressure and stress distributions within the head in LIFU. Our results show that though most of the pressure that reaches to the brain is due to the longitudinal wave propagation through the skull, the normal stress in the transverse direction of the wave propagation has the main role to control the pressure profile inside the brain more than the shear stress. The results also show that the anisotropic properties of skull contribute in broadening the focal zone in comparison to that of the isotropic skull.

Patient-specific walking pattern simulation in a gait trajectory guiding device.

Repetitive training is of much importance for restoring full-fledged gait ability. At present, task-specific repetitive approach has been proved to be the most effective motor learning concept. In this regard, a gait trajectory guiding device with partial body weight support system can be a solution for gait rehabilitation. This paper presents a complete gait study with an objective to implement the motion of a natural walking pattern in the automated foot-boards of a gait trajectory guiding device. In our developed motion algorithm of foot-boards we have concentrated on adaptation of patient-specific true walking trajectory, determination of variable velocity pattern along different degrees of freedom and time-division for simulating different phases of a complete gait cycle. Gait database, collected from disparate sources and previous gait-studies have been used for kinetic and kinematic analysis of human walking. We have modeled those data based on the previous researches done in this area and adopt them for our motion algorithm. A precise velocity pattern and time-division have been described along different axes so that patient's biofeedback and postural stability in different walking phases can be recorded accordingly and motion-correction of the foot-boards can be done in consecutive cycles through iterative learning control algorithm with the help of motion sensors.

A method for size estimation of amorphous pupil in 3-dimensional geometry.

Measuring pupil size is a noninvasive method for evaluation of autonomic nervous system (ANS) activity because the pupil is exclusively controlled by the autonomic nervous system. To evaluate the activity of ANS, an accurate pupil size calculation method different from those of pupillometer and eye tracker should be suggested. This paper presents a three-dimensional model of eye and pupil and also suggests an accurate estimation method of pupil size from images projected on two-dimensional image plane with distortions.

A study of Korean femoral geometry.

The current authors investigated the anatomic geometry of femurs from Korean subjects and compared the results with those of femurs from American and Japanese subjects. Thirty-eight femurs extracted from cadavers and 200 femurs of healthy subjects were used. The 38 femurs were placed on a horizontal plane to obtain computed tomography images, which then were transformed into bitmap images, and the computed tomography images of the 200 femurs of healthy subjects also were obtained. Three-dimensional images of the femurs were reconstructed and used for measuring the parameters. The measurement results suggested that femurs from Korean subjects were different from femurs from American subjects. The major differences were that femurs from Korean subjects had a larger anteversion angle by approximately 8 degrees, a relatively larger canal flare index, and there was a shorter distance between the lesser trochanter and the isthmus. These differences can provide useful information to the design of a new hip prosthesis for Korean, Japanese, and other Asian patients.