Investigation of shielding material properties for effective space radiation protection.

Geant4 Monte Carlo simulations were carried out to investigate the possible shielding materials of aluminum, polyethylene, hydrides, complex hydrides and composite materials for radiation protection in spacecraft by considering two physical parameters, stopping power and fragmentation cross section. The dose reduction with shielding materials was investigated for Fe ions with energies of 500 MeV/n, 1 GeV/n and 2 GeV/n which are around the peak of the GCR energy spectrum. Fe ions easily stop in materials such as polyethylene and hydrides as opposed to materials such as aluminum and complex hydrides including high Z metals with contain little or no hydrogen.

Effect of low-intensity pulsed ultrasound stimulation on gap healing in a rabbit osteotomy model evaluated by quantitative micro-computed tomography-based cross-sectional moment of inertia.

Background: It has been previously demonstrated that low-intensity pulsed ultrasound stimulation (LIPUS) enhances formation of the medullary canal and cortex in a gap-healing model of the tibia in rabbits, shortens the time required for remodeling, and enhances mineralization of the callus. In the current study, the mechanical integrity of these models was confirmed. In order to do this, the cross-sectional moment of inertia (CSMI) obtained from quantitative micro-computed tomography scans was calculated, and a comparison was made with a four-point bending test.

Measurement of articular cartilage thickness using a three-dimensional image reconstructed from B-mode ultrasonography mechanical scans feasibility study by comparison with MRI-derived data.

The present study aimed to develop a method to measure three-dimensional (3-D) thickness of cartilage (Tc) at the femoral condyle using B-mode ultrasonography (US) and to clarify the feasibility of US in clinical evaluations of articular cartilage by comparing the results with 3-D measurement values using magnetic resonance imaging (MRI) and assessing repeatability. The medial surface of the right knees of two healthy male volunteers (age, 37 and 59 years) and the knees on affected side of three male patients with osteoarthritis (OA) (age, 73, 81 and 83 years) were scanned using B-mode US with the knee flexed at 120°. The range of the angle of probe rotation for the arm was 0-80° and B-mode images (total, 101 images) were acquired every 0.

Evaluation of the accuracy of articular cartilage thickness measurement by B-mode ultrasonography with conventional imaging and real-time spatial compound ultrasonography imaging.

The present study aimed to quantify the thickness of articular cartilage (Tc) in vitro using both conventional and real-time spatial compound B-mode ultrasonography (US) with a clinically used transducer and to evaluate the accuracy of measurement by comparing the results with values obtained microscopically. Femoral condyle samples were obtained from a 6-month-old pig and a 3-year-old pig. B-mode US images with conventional imaging and real-time spatial compound imaging (RTSCI) of osteochondral blocks were acquired.

Measurement of mechanical properties with respect to gap healing in a rabbit osteotomy model using echo tracking.

The most important issue in the assessment of fracture healing is to acquire information about the restoration of the mechanical integrity of bone. Echo tracking (ET) can noninvasively measure the displacement of a certain point on the bone surface under a load. Echo tracking has been used to assess the bone deformation angle of the fracture healing site.

Comparison of ultrasound speed in articular cartilage measured by different time-of-flight methods.

The purpose of this study was to investigate whether different time-of-flight (TOF) methods including amplitude-related methods, which determine tissue borders from the reflected wave itself, and the cross-correlation method, which requires reference signals to determine borders, influence speed of sound (SOS) values for articular cartilage. Left femoral condyle samples from a 6-month-old pig and a 3-year-old pig were used. Radiofrequency signals from the cartilage surface and cartilage-bone interface were acquired using the ultrasound transducer for nine points in each sample.

Measurement of mechanical properties on gap healing in a rabbit osteotomy model until the remodeling stage.

Background: The most important issue in the assessment of fracture healing is to acquire information about the restoration of the mechanical integrity of bone. Many researchers have attempted to monitor stiffness either directly or indirectly for the purpose of assessing strength, as strength has been impossible to assess directly in clinical practice. The purpose of this study was thus to determine the relationship between bending stiffness and strength using mechanical testing at different times during the healing process.

[Prediction of bone strength using a quantitative computed tomography based finite element method].

Clinically available methods for estimating bone strength include bone densitometry techniques such as dual energy X-ray absorptiometry and quantitative computed tomography, and other diagnostic imaging procedures such as radiographic imaging. These techniques evaluate regional bone density and morphology, which are partly related to fracture risk, but are of limited value for quantifying structural strength. Therefore, it is necessary to develop a noninvasive method for accurate quantitative structural analysis that incorporates information on both morphology and bone density in a three-dimensional distribution.

Prediction of proximal femur strength using a CT-based nonlinear finite element method: differences in predicted fracture load and site with changing load and boundary conditions.

The annual occurrence of hip fracture due to osteoporosis as of 2002 had reached 120,000 in Japan. The increase has been very rapid. From a biomechanical perspective, hip fractures are thought to be caused in real settings by different directions of loading.

Effects of circulating energetic ions on sawtooth oscillations.

In contrast to the well-known result that the effects of the trapped energetic ions (TEI) on the internal kink mode are due to the toroidal precession of the TEI, it is found that the effects of the circulating energetic ions (CEI) on sawtooth are due to the toroidal circulation of the CEI. The effects of the CEI on sawtooth oscillations are found to be different from the well-known purely stabilizing effects of the TEI on sawtooth oscillations; the toroidal circulation of the co-CEI provides an additional sink of free energy and stabilizes the mode; the toroidal circulation of the counter-CEI provides an additional source of free energy and destabilizes the mode.