Aspects of magnetic resonance relaxation measurements in human tissues are discussed. The influence of pulse sequences and parameters are compared and analyzed for different tissues. By controlling the acquisition parameters and data fitting the relaxation rate can be useful in several clinical situations. The influence of repetition and echo time, predicted in sequences of signal acquisition, on measurement of transversal relaxation time (T2) was evaluate using simulated MRI signal.
OBJECTIVE:The aim of this study was to evaluate the multisegmental static postural balance of active eutrophic and obese elderly women using a three-dimensional system under different sensory conditions.METHODS:A cross-sectional study was conducted on 31 elderly women (16 eutrophic and 15 obese) aged 65 to 75 years. The following anthropometric measurements were obtained: weight, height, waist and hip circumference, and handgrip strength. The physical activity level was evaluated using the International Physical Activity Questionnaire. Body composition was measured using the deuterium oxide dilution technique. The Polhemus® Patriot (three-dimensional) equipment was used to measure the parameters of postural balance along the anteroposterior and laterolateral axes. The data acquisition involved one trial of 60 s to test the limit of stability and four trials of 90 s each under the following conditions: (1) eyes open, stable surface; (2) eyes closed, stable surface; (3) eyes open, unstable surface; and (4) eyes closed, unstable surface.RESULTS:For the limit of stability, significant differences were observed in the maximum anteroposterior and laterolateral displacement (p<0.01) and in the parameter maximum anteroposterior displacement in the eyes closed stable surface condition (p<0.01) and maximum anteroposterior and laterolateral displacement in the eyes open unstable surface (p<0.01 and p = 0.03) and eyes closed unstable surface (p<0.01 and p<0.01) conditions. CONCLUSIONS:Obese elderly women exhibited a lower stability limit (lower sway area) compared with eutrophic women, leaving them more vulnerable to falls.
BackgroundTraining in medical education depends on the availability of standardized materials that can reliably mimic the human anatomy and physiology. One alternative to using cadavers or animal bodies is to employ phantoms or mimicking devices. Styrene-ethylene/butylene-styrene (SEBS) gels are biologically inert and present tunable properties, including mechanical properties that resemble the soft tissue. Therefore, SEBS is an alternative to develop a patient-specific phantom, that provides real visual and morphological experience during simulation-based neurosurgical training.ResultsA 3D model was reconstructed and printed based on patient-specific magnetic resonance images. The fused deposition of polyactic acid (PLA) filament and selective laser sintering of polyamid were used for 3D printing. Silicone and SEBS materials were employed to mimic soft tissues. A neuronavigation protocol was performed on the 3D-printed models scaled to three different sizes, 100%, 50%, and 25% of the original dimensions. A neurosurgery team (17 individuals) evaluated the phantom realism as “very good” and “perfect” in 49% and 31% of the cases, respectively, and rated phantom utility as “very good” and “perfect” in 61% and 32% of the cases, respectively. Models in original size (100%) and scaled to 50% provided a quantitative and realistic visual analysis of the patient’s cortical anatomy without distortion. However, reduction to one quarter of the original size (25%) hindered visualization of surface details and identification of anatomical landmarks.ConclusionsA patient-specific phantom was developed with anatomically and spatially accurate shapes, that can be used as an alternative for surgical planning. Printed models scaled to sizes that avoided quality loss might save time and reduce medical training costs.
Abstract:The relationship between the film generation and the coefficient of friction in grease lubricated contacts was investigated. Ball-on-disc tests were performed under different operating conditions: entrainment speed, lubricant temperature and surface roughness. The tests were performed with fully formulated greases and their base oils. The greases were formulated with different thickener types and also different base oils natures and viscosities. Film thickness measurements were performed in ball-on-glass disc tests, and Stribeck curves were measured in ball-on-steel disc tests with discs of different roughness. The role of the thickener and the base oil nature/viscosity on the film thickness and coefficient of friction was addressed and the greases' performance was compared based on their formulation.
Objective:To test the accuracy and reproducibility of ultrasound and computed
tomography (CT) for the quantification of abdominal fat in correlation with
the anthropometric, clinical, and biochemical assessments.Materials and Methods:Using ultrasound and CT, we determined the thickness of subcutaneous and
intra-abdominal fat in 101 subjects-of whom 39 (38.6%) were men and 62
(61.4%) were women-with a mean age of 66.3 years (60-80 years). The
ultrasound data were correlated with the anthropometric, clinical, and
biochemical parameters, as well as with the areas measured by abdominal
CT.Results:Intra-abdominal thickness was the variable for which the correlation with the
areas of abdominal fat was strongest (i.e., the correlation coefficient was
highest). We also tested the reproducibility of ultrasound and CT for the
assessment of abdominal fat and found that CT measurements of abdominal fat
showed greater reproducibility, having higher intraobserver and
interobserver reliability than had the ultrasound measurements. There was a
significant correlation between ultrasound and CT, with a correlation
coefficient of 0.71.Conclusion:In the assessment of abdominal fat, the intraobserver and interobserver
reliability were greater for CT than for ultrasound, although both methods
showed high accuracy and good reproducibility.
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