Nuclear magnetic resonance (NMR) microscopy with 4-microns resolution, a step closer to the 1-micron resolution with which in vivo cellular imaging would be possible is described. An analysis of the ultimate resolution and voxel size dependent signal-to-noise ratio (SNR) in NMR microscopy is presented and experimentally verified. For microscopic scale objects (less than 1-mm diameter), the SNR based on the geometrical scale factor(s) is found to be proportional to sn where n less than 2, rather than n = 3 as previously supposed. This comes about because of a drastic reduction in sample noise coupled with a significant sensitivity gain realized in small diameter radiofrequency coils. A new pulse sequence which reduces both diffusion dependent resolution degradation and signal attenuation is presented. The selection of optimal bandwidth and acquisition time for maximal SNR is discussed. Experimental results obtained on both a 2.0-T whole-body system and a 7.0-T small bore system adapted for microscopy indicate the potentials of 4-microns resolution microscopy with the existing magnets.
This study investigated the effect of 40% oxygen administration on n-back task performance, blood oxygen saturation and heart rate. Five male (25.8 +/- 1.3 years) and five female (23.0 +/- 1.0 years) college students were selected as the subjects for this study. The experiment consisted of two runs: one was an n-back task with normal air (21% oxygen) administered and the other was with hyperoxic air (40% oxygen) administered. The experimental sequence in each run consisted of Rest1 (1 min), 0-back task (1 min), 2-back task (2 min) and Rest2 (4 min). Blood oxygen saturation and heart rate were measured throughout the four phases. The results of the n-back behavioural analysis reveal that accuracy rates were enhanced with 40% oxygen administration compared to 21% oxygen. When 40% oxygen was supplied, blood oxygen saturation was increased and heart rate was decreased compared to that with 21% oxygen administration. It is suggested that 40% oxygen can stimulate brain activation by increasing actual blood oxygen concentration in the process of cognitive performance, and hyperoxia makes heart rate decrease. This result supports the hypothesis that 40% oxygen administration would lead to increases in n-back task performance.
This study investigated the effect of 30% oxygen administration on verbal cognitive performance, blood oxygen saturation, and heart rate. Five male (24.6(+/-0.9) years) and five female (22.2(+/-1.9) years) college students were selected as the subjects for this study. Two psychological tests were developed to measure the performance level of verbal cognition. The experiment consisted of two runs: one was a verbal cognition task, with normal air (21% oxygen) administered and the other was with hyperoxic air (30% oxygen) administered. The experimental sequence in each run consisted of Rest 1 (1 min), Control (1 min), Task (4 min), and Rest 2 (4 min). Blood oxygen saturation and heart rate were measured throughout the four phases. The results of the verbal behavioural analysis reveal that accuracy rates were enhanced with 30% oxygen administration compared to 21% oxygen. When 30% oxygen was supplied, blood oxygen saturation was increased significantly compared to that with 21% oxygen administration, whereas heart rate showed no significant difference. Significant positive correlations were found between changes in oxygen saturation and cognitive performance. This result supports the hypothesis that 30% oxygen administration would lead to increases in verbal cognitive performance.
The purpose of this study is to develop a more convenient system for measurement of hand rotation, and to validate the system by correlation of performance indices derived from the system with the bradykinesia score of hand rotation movement during on-medication state. Forty patients with Parkinson's disease and 14 age-matched control subjects participated in this study. The measurement system was developed using a ceramic gyroscope that is significantly smaller and lighter than those in the literature. The sensor signal was bandpass filtered and action tremor was eliminated by additional lowpass filtering (fc=5Hz) with automated tremor discrimination. Four performance indices (RMS velocity and RMS angle, peak power and total power) were derived from the angular velocity signal. Correlations of performance indices with clinical scores and difference of performance indices among subject groups were investigated. Correlations of all performance indices were far better with bradykinesia score of hand rotation (best r=-.78) than with the other categorized subscores of UPDRS (bradykinesia subscore, axial symptom subscore, and total motor score; best r=-.64). Elimination of action tremor resulted in improvement in correlations of RMS velocity and total power with bradykinesia score for hand rotation (r=-.84 from -.81). Differences between low scores were greater in total power and differences between high scores were greater in RMS velocity, suggesting that use of more than one PI would be beneficial for diagnosis of a wide range of patients. The convenient sensor system, action tremor elimination, and performance indices suggested in this study are expected to be useful in clinical situations.
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