This might be caused by age-related atrophy of main fibers such as the pyramidal tract, possibly resulting in an increase in the relative signal contribution of some crossing fibers in each pixel. Simultaneous decrease of lambda(L) and increase of lambda(T) resulting in decrease of FA and steady MD with aging were observed. Estimates of fractional anisotropy (FA), mean diffusivity (MD), and longitudinal (lambda(L)) and transversal (lambda(T)) eigenvalues showed age-related and location-dependent variation in AL, genu and PL ROIs and at the 10 equally-spaced positions of PL. To address the branching of PL, a procedure was applied to divide the thinned PL ROI into 10 equally-spaced positions. The IC region-of-interest (ROI) was first thinned to reduce contamination from surrounding tissues and then morphologically divided into three regions: anterior limb (AL), genu and posterior limb (PL). In this study, regional heterogeneity and age-related changes in water diffusion parameters were evaluated in sub-regions of IC. However, there is some risk of misdiagnosis when measuring diffusion parameters throughout the whole IC without knowledge of age-related changes, as the thin structure and branching in multiple directions must be expected to produce sub-regional differences. Diffusion tensor imaging (DTI) is useful for the diagnosis of brain diseases related to IC. The internal capsule (IC) includes various fiber tracts supporting sensory, motor and cognitive abilities. The results of our model were in good agreement with the measured forces in contrast with the large values obtained using the passive fingertip force model. Maximum active fingertip forces were measured for three subjects and compared with the forces calculated using the proposed model and the previous model. A further extension of the previous passive fingertip force model is that a nonlinear relationship between muscle length and exerted force is considered. The model selects the smaller force of the following two forces: the maximum force calculated using the musculoskeletal model and the maximum force calculated using the maximum deformation depth of the fingertip that lies within the ranges of motion of all the joints. The proposed model extends a passive fingertip force model by considering the mobility of the fingertip in terms of its deformation. The present paper develops a model of "active" fingertip forces of a human index finger that allows the maximum fingertip force to be calculated for any specified position of the finger.
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