Mechanical Modeling and Design for Reduction of Parkinsonian Hand Tremor

Most of the active research in reducing Parkinsonian tremor involves invasive surgeries or medical treatment. In this paper hand tremors associated with Parkinson’s Disease (PD) are studied and passive vibration control methods are developed and tested. Patients with PD are surveyed regarding difficulties with hand tremor during the act of eating. The result leads to design criteria for an enhanced eating utensil and the establishment of meaningful testing methods for measuring hand tremor. Tremor data collected from several PD patients provides insight into the nature of the motion and allows for the development of test fixture and prototypes. This experimental data is coupled with linear model identification testing for the free response of a “healthy” hand undergoing the same motions. The resulting differential equation model, where the system input is realized as actuation through the biomechanics of the forearm and wrist, is used in the design of an eating utensil for vibration reduction. With self-excitation and the existence of harmonics, the tremor data is also used to develop a nonlinear differential equation model, where the complete neurological/mechanical system is realized with an equivalent mechanical system. This nonlinear model is shown to mimic the tremor data and is used to enhance the development of the vibration absorber. A prototype of the vibration absorber is built, validated on the test fixture, and tremor reduction data is collected again with PD patients.

Detection of Arteries by Using Diffuse Reflectance Photoplethysmography

Non-invasive measurement of the arterial pulse wave can be carried out by means of an optical sensor placed at the center of the artery. In this paper, we explore the possibility of using diffuse reflectance photoplethysmography (PPG) for the detection of arteries, a method that allows for the timely detection of changes in the blood pressure. It is believed that the light scattering intensity is affected by the presence of veins in the light path. The purpose of the present study is to elucidate the influence of veins on the accuracy of PPG. In this study, we used light scattering measurements to investigate the difference observed in the performance of PPG (wavelength: 810 and 530 nm) due to the presence of veins. On the basis of these results, we concluded that PPG at a wavelength of 810 nm is more susceptible to the presence of veins than at 530 nm. However, the influence of veins can be reduced by the measurement condition that surrounding veins are being crushed at a wavelength of 810 nm.

Investigation of Stress Wave Propagation in Brain Tissues Through the Use of Finite Element Method

Because axons serve as the conduit for signal transmission within the brain, research related to axon damage during brain injury has received much attention in recent years. Although myelinated axons appear as a uniform white matter, the complex structure of axons has not been thoroughly considered in the study of fundamental structural injury mechanisms. Most axons are surrounded by an insulating sheath of myelin. Furthermore, hollow tube-like microtubules provide a form of structural support as well as a means for transport within the axon. In this work, the effects of microtubule and its surrounding protein mediums inside the axon structure are considered in order to obtain a better understanding of wave propagation within the axon in an attempt to make progress in this area of brain injury modeling. By examining axial wave propagation using a simplified finite element model to represent microtubule and its surrounding proteins assembly, the impact caused by stress wave loads within the brain axon structure can be better understood. Through conducting a transient analysis as the wave propagates, some important characteristics relative to brain tissue injuries are studied.

Enhancement of RF Ablation by Combined Use of Ultra-Low Temperature Fluid Cooling and Magnetic Nanoparticles

Magnetic nanoparticles with high electrical conductivity have been proved to be effective in enhancing the efficacy of RF ablation. However, the possible carbonization of tissues is an unfavorable factor in achieving greater dimensions of necrosis, because carbonized tissue is a poor conductor, increases impedance and limits propagation area of RF energy. To prevent potential carbonization of tissues surrounding to the heating part of RF electrodes during RF ablation, a new method using ultra-low temperature fluid was proposed for cooling RF electrodes and tissues in the vicinity of RF electrodes in this study. To test its feasibility, the corresponding bioheat transfer process during RF ablation simultaneously applying this cooling method and magnetic nanoparticles was studied through numerical simulations. The results indicate that the cooling method by ultra-low temperature fluid can prevent carbonization of tissues resulted by local high temperature, significantly enlarge the effective heating area and thus actualize highly efficient thermal coagulation to tumor tissues during RF ablation with adjuvant use of magnetic nanoparticles.

Biodynamic Modeling of a Pedestrian Impact With a Rigid Frontal Guard of a Utility Vehicle

Accident data reveals that in most pedestrian accidents, the pedestrian head and lower extremity are vulnerable to serious injuries. The vehicle front geometry profile as well as the impact speed are important factors affecting the pedestrian kinematics and injury potential. In the US, accident data also shows that the fatality rate for pedestrian/light trucks and vans (LTV) impact is greater than that for the pedestrian/passenger-car impact. Addition of a front guard on light trucks and sports utility vehicles to mitigate damage during off-road activity or to provide mounting points for extra lights, makes the pedestrian more vulnerable to the impact. In this paper, a computational technique is utilized to study the influence of the added front guard on the impacted pedestrian. A CAD model of a typical commercial frontal guard is developed and converted into a rigid facet model, and attached to the vehicle front. The validated standing dummy model in the MADYMO code is used to simulate a pedestrian, and the rigid facet-surface model of a pickup truck is used to generate a vehicle front surface. This computational model is validated by comparing the pedestrian kinematics with the published data. This study demonstrates that the pedestrian mid body region is more vulnerable with the addition of guard on the vehicle. The result from this study facilitates a better understanding of a guard design and its geometry profile as required to protect vulnerable road users.

Orthogonal Frequency Ultrasound Vibrometry

New vibration pulses are proposed to increase the power of shear waves induced by ultrasound radiation force in a tissue region with a preferred spectral distribution. The new pulses are sparsely sampled from an orthogonal frequency wave composed of several sinusoidal signals. Those sinusoidal signals have different frequencies and are orthogonal to each other. The phase and amplitude of each sinusoidal signal are adjusted to control the shape of the orthogonal frequency wave. Amplitude of the sinusoidal signal is increased as its frequency increases to compensate for higher loss at higher frequency in the tissue region. The new vibration pulses and detection pulses can be interleaved for array transducer applications. The experimental results show that the new vibration pulses significantly increases induced tissue vibration with the same peak ultrasound intensity, compared with the binary vibration pulses.

Finite Element Study of Spinal Cord Mechanics During Biomechanical Response of Middle Cervical Spine

The present study is conducted to develop a detailed FE model of spinal cord and to study its behaviour under various loading conditions. To achieve the goal, a previously developed and validated FE model of the middle cervical spine (C3-C5) is utilized. The model is further modified to investigate the stresses that the spinal cord in experiences during cervical spine motion segment in compression and flexion/extension loading modes. The resulting Von Misses stress and axial strain of the anterior and posterior surfaces of the cervical spinal cord are obtained from a set of elements along the C4-C5 disc space of the dural sheath, CSF and cord. The results show that in compression, the anterior surface of spinal cord experiences larger displacement, stress, and strain than those of the posterior surface. Conversely, the analyses show that in flexion\extension, the stresses, strains, and displacements are more pronounced in posterior segment of the spinal cord. In extension, the posterior disc bulge applies pressure onto the Posterior Longitudinal Ligament and thereby, applying local pressure on the spinal cord. The FE results show a stress concentration at the point of contact between disc and spinal cord. Furthermore, the FE results of flexion test show similar stress concentration characteristic at the point of contact. However, the local stress on spinal cord is more pronounced in flexion than extension at the C4-C5 area of spinal cord. It was also determined the compressive load resulted in the highest stress concentration on the spinal cord.

Integrated System for Soft Tissue Dynamic Simulation

An integrated system is built to model and simulate the dynamic response of soft tissues. The mathematical formulation employs finite element and model order reduction approaches to develop a state space model for soft tissues that allows for time-efficient numerical analysis. The stimulus device and signal processing routines are built in Matlab/Simulink and then integrated with the finite element state space model. This integrated system facilitates expeditious numerical evaluation of different soft tissue models subjected to dynamic excitation. It further elucidates the effect of different stimulus sources, as well as relative influences of different sources of uncertainty.

Single Screw vs. Double Screw Device for Use in Treating Femoral Bone Fractures

Proximal femur fractures commonly occur between the head of the femur and the femoral shaft. As the third most common injury encountered in orthopedic clinics, these fractures are typically treated with medical implants creating internal stabilization of the bone. Over 100 different implants are available for this application. Although the optimal choice for the implants is still controversial, traditional devices which include a single cylindrical screw, such as SHS (Sliding Hip Screw) and IMHS – CP (Intramedullary Hip Screw, Clinically Proven), are widely used to repair the bone fracture. However, the application of the single screw device still suffers technical problems. The head of the femur has the potential to rotate about the screw and the fracture surfaces have potential to slide over each other. In addition, force relaxation can occur, leading to inadequate contact between the fracture surfaces. To attack these problems and prevent possible complications, a new device has been developed. The new device consists of one long screw interlocked with one short screw, creating a cross-sectional figure-eight pattern and offering an integrated, interlocking screw option. The objective of the current study is to compare biomechanical characteristics within the bone caused by the new double screw device verses the traditional single screw device. Experiments were preformed to compare the torsional stiffness of the two devices. 2D and 3D finite element analysis methods were carried out to obtain macroscopic and microscopic responses of each device’s interaction with the fractured bone. The modeled results show a significant difference between the two geometries. The single screw geometry has higher maximum total deformation, equivalent strain, equivalent von Mises stress, and maximum principle stress. The improved rotational stability of the new double screw device may reduce the complication rate of instability of the fracture fragments.

Effects of Starch Volume Expanders on Blood Viscosity and Vascular Endothelial Markers

The intravenous fluid of choice for acute blood volume replacement remains controversial. We focus here on the two hydroxyethyl (HES) available in Canada: HES 130/0.40 (Voluven®) and HES 260/0.45 (Pentaspan®). Although information regarding their pharmacokinetic and risk/benefit profiles are available, how the infusion of these fluids could affect blood viscosity and vascular endothelial function in humans is largely unknown. Dynamic viscosity was measured at 21°C and 37°C through capillary viscometry. The HES solutions were driven through a closed flow loop at room temperature (21°C). Viscosity at 21°C was 7.62 centipoise (cP) for HES 260/0.45 and 2.73 cP for HES 130/0.40 decreasing to 4.23 cP for HES 260/0.45 and 1.72 cP for HES 130/0.40 at 37°C. Analysis of viscous behaviour through pipe flow found that HES 260/0.45 displayed marginal variations in viscosity suggesting Newtonian behaviour across our range of Re measured. HES 130/0.40 displayed an appreciable increase in viscosity at higher Re suggesting the presence of shear thickening behaviour. Human aortic endothelial cells (HAEC) and human microvascular endothelial cells (HMVEC) were exposed to the HES solutions and saline to identify chemical effects on vascular endothelium. Western blot quantification showed that E-selectin was the leukocyte adhesion receptor that was most strongly affected, and this was not dose dependent. Interestingly, HAEC and HMVEC had different responses to HES treatment, suggesting that different vascular tissues may have different outcomes to HES infusion. Protein expression in HMVEC decreased when exposed to both HES solutions.