Key Engineering Materials Vols. 321-323

Abstract: The aim of this study is to develop a new method to measure one-dimensional dose distribution of high-energy electron using a miniature fiber-optic radiation sensor. The measurements are made by a thin plastic optical fiber with an organic scintillating sensor tip. The scintillating light in the visible wavelength range is guided to a silicon photodiode by plastic optical fiber in order to convert light output to electrical signal. The one-dimensional spatial dependence of elctron beam is measured by moving the sensor tip with uniform speed. It is shown that this fiber-optic radiation sensor has better spatial resolution than conventional ion chamber and it needs much less time to measure one-dimensional dose distribution in the high radiation fields.

Abstract: This study aimed to investigate the hypothesis that administration of the air with 30% oxygen compared with normal air (21% oxygen) enhances verbal cognitive functioning through increased activation in the brain. Nine male college students participated in the study. The experiment consisted of two runs, one for verbal cognition task with normal air (21% oxygen) and the other for verbal cognition task with hyperoxic air (30% oxygen). Functional brain images were taken with a 3T MRI using the single-shot EPI method. From the results of the verbal behavioral analysis, the accuracy rate was enhanced with 30% oxygen administration when compared to 21% oxygen. The activities were observed at the occipital, parietal, temporal and frontal lobes during both 21% and 30% oxygen administration. There were more activations observed at the right middle frontal gyrus, right inferior frontal gyrus, right superior frontal gyrus, cingulate gyrus, left middle temporal gyrus, and left fusiform gyrus with 30% oxygen administration. These results suggest that a higher concentration of breathed oxygen increases saturation of blood oxygen in the brain, and facilitates verbal performance.

Abstract: In this study, the femoral cancellous bone angle is estimated in order to design the femoral IM (Intra-Medullary) nail. Generally, it is various in size and curvature of femoral cancellous bone depending on patient’s body dimension and surgeon has difficulty in fitting this femoral IM nail to the patient in surgical procedure. In our study, Femoral lateral curve angle was estimated with more precise method based on CT image of the femur and utilize this information is utilized for the design of femoral IM nail for patients. Through this investigation, it may be possible to calculate each patient’s femoral cancellous bowing angle more precisely. If the bowing angle of the lateral images of each patient can be figured immediately through CT image, it will be easier to choose appropriate nail that is most suitable for each individual. More investigations need to be achieved by collecting more patient’s image data for femoral curvature.

Abstract: In this study, we designed a flat-panel digital X-ray imaging module based upon the amorphous silicon (a-Si) technology and tested potential for medical imaging and nondestructive testing. The module employs a commercially available a-Si photosensor array of a 143 μm x 143 μm pixel size and a 42.9 cm x 42.9 cm active area, coupled with a CsI(Tl) scintillator of a 550 μm thickness, and a readout IC board which can be accessed through our home made GUI software. The experimental test was performed to evaluate the system response with exposure, modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE).

Abstract: The quantitative and objective evaluation of spasticity is desirable in rehabilitation and orthopedics where subjective evaluations are mostly used. In the present study, data from a simple pendulum test are used for the evaluation of the spasticity with the help of biomechanical modeling. The spasticity of a knee joint is modeled as nonlinear feedback of muscle lengthening velocity and the muscle length. Through the optimization of the modeling error, the feedback parameters are determined. The threshold of muscle lengthening velocity in the reflex system is suggested as a severity index of the spasticity.

Abstract: This study aims at developing a comprehensive assessment method of motor function practicable for use at home. The motor function can be thought of as the resultant of many categories of fitness, so that a comprehensive assessment technique is desirable. In this study, the motor function is evaluated in terms of cardiorespiratory fitness and the muscular fitness. The cardiorespiratory fitness is assessed by the estimated maximum O2 consumption rate and the total heart beat index. The muscular fitness is assessed by the maintenance time of the maximum speed cycling. The suggested method is evaluated on the young athletes and also on the non-athletic young subjects. Both the cardiorespiratory and muscular fitness of two groups showed significant difference. It is expected that the suggested method be useful for a comprehensive evaluation of the motor function at home.

Abstract: The aim of this study was to evaluate effects of short-term repetitive-bilateral exercise on the activation of motor network using functional magnetic resonance imaging (fMRI). Eight control subjects and four chronic hemiparetic patients were investigated for the present study. The training program with a symmetrical upper-limb motion trainer was performed at 1 hr/day, 5 days/week during 6 weeks. Fugl-Meyer assessments (FMA) were performed every two weeks during the training. We compared cerebral and cerebellar cortical activations in two different tasks before and after the training program: (1) the only unaffected hand movement (Task 1), and (2) passive movements of the affected hand by the active movement of the unaffected hand (Task 2). fMRI was performed at 3T with wrist flexion-extension movement at 1 Hz during the motor tasks. All patients showed significant improvements of FMA scores in their paretic limbs after training. fMRI studies in Task 1 showed that cortical activations decreased in ipsilateral SMC but increased in contralateral sensorimotor cortex (SMC) and ipsilateral cerebellum (CRB). Task 2 showed cortical reorganizations in bilateral SMC, pre-motor area (PMA), supplementary area (SMA) and CRB. This study demonstrated that plastic changes of motor network occurred as a neural basis of the improvement subsequent to repetitive-bilateral exercises using the symmetrical upper-limb motion trainer.

Abstract: This study investigated effects on foot/ankle roll-over characteristics according to heel heights during walking. Fifteen female volunteers who have neither musculoskeletal nor foot problems participated in gait analyses, wearing totally four pairs of shoes with different heel heights. To obtain roll-over shape of foot/ankle complex, we used trajectories of ankle, knee and the center of pressure (COP) between initial contact(IC) and opposite initial contact(OIC) to represent as circular arc using the least-square method. We found that the entire roll-over shape moved distally as the heel height increased but roll-over characteristics did not change significantly with different heel heights. In addition, we found that nondisabled persons automatically adapt their foot/ankle complex to changes in heel height shoes up to 6cm, by moving the origin of roll-over shape distally to keep the roll-over characteristics uniform. Roll-over characteristics in human walking would provide a new understanding of human walking, and furthermore can be applied to the design of prosthetics and orthotics of the lower extremity.

Abstract: This study aims to examine the effects of aerobic exercises for 8 weeks on vascular contraction with α-adrenaline acceptor in SHR (Spontaneously Hypertensive Rats). The rats of 8 weeks with hypertension (SHR) having the weight of 155
165g were aerobic-exercised with using treadmill for 5 days a week through 8 weeks (20m/min). After 8 weeks, chest artery is extracted, suspended into organ bath and changes of isotonia tension are recorded on vital records. The piece of extracted chest artery showed density depending contraction by norepinephrine and its sensitivity to Emax and norepinephrine was significantly reduced after aerobic exercise for 8 weeks. Contraction reaction was accelerated in both groups after eliminating endothelium cell, but when LNNA was input in the state with endothelium cell, contraction reaction by norepinephrine was increased in exercise group and its aspect was similar to the contraction by norepinephrine in the state eliminating endothelium cell. Relaxation by acetylcholine was significantly increased in exercise group, but there was no difference in relaxation by sodium nitroprusside. In conclusion, vascular endothelium cell isolates niotric oxide and reduces contraction reaction of blood vessel with α exercise group, but there was no difference in relaxation by sodium nitroprusside.

Abstract: The purpose of the present study is to develop a magnetic resonance (MR)-compatible electrocardiogram (ECG) amplifier. If ECG signals are measured simultaneously with the acquisition of MR images, there can be a mutual interference effect. The present system was designed to block noises caused by the main magnetic field, gradient magnetic field and radiofrequency (RF) pulse when MR images are acquired. It uses analogue elements in order to remove any possible effect on MR images. In addition, a radio-frequency-interference (RFI)-free optical data link using the pulse-width modulation (PWM) technique is adopted in order to transmit ECG signals measured inside the MR room.