Arterial Spin Labeling Perfusion Study in the Patients with Subacute Mild Traumatic Brain Injury

by Che-Ming Lin, Ying-Chi Tseng, Hui-Ling Hsu, Chi-Jen Chen, David Yen-Ting Chen, Feng-Xian Yan, Wen-Ta Chiu

Background

This study uses a MRI technique, three-dimension pulse continuous arterial spin labeling (3D-PCASL), to measure the patient’s cerebral blood flow (CBF) at the subacute stage of mild traumatic brain injury (MTBI) in order to analyze the relationship between cerebral blood flow and neurocognitive deficits.

Objective

To provide the relationship between cortical CBF and neuropsychological dysfunction for the subacute MTBI patients.

Methods

After MTBI, perfusion MR imaging technique (3D-PCASL) measures the CBF of MTBI patients (n = 23) within 1 month and that of normal controls (n = 22) to determine the quantity and location of perfusion defect. The correlation between CBF abnormalities and cognitive deficits was elucidated by combining the results of the neuropsychological tests of the patients.

Result

We observed a substantial reduction in CBF in the bilateral frontal and left occipital cortex as compared with the normal persons. In addition, there were correlation between post concussive symptoms (including dizziness and simulator sickness) and CBF in the hypoperfused areas. The more severe symptom was correlated with higher CBF in bilateral frontal and left occipital lobes.

Conclusion

First, this study determined that despite no significant abnormality detected on conventional CT and MRI studies, hypoperfusion was observed in MTBI group using 3D-PCASL technique in subacute stage, which suggested that this approach may increase sensitivity to MTBI. Second, the correlation between CBF and the severity of post concussive symptoms suggested that changes in cerebral hemodynamics may play a role in pathophysiology underlies the symptoms.

from #Audiology via xlomafota13 on Inoreader http://ift.tt/1RwMi3y
via IFTTT

Stress-dependent ultrasonic scattering in polycrystalline materials

Stress-dependent elastic moduli of polycrystalline materials are used in a statistically based model for the scattering of ultrasonicwaves from randomly oriented grains that are members of a stressed polycrystal. The stress is assumed to be homogeneous and can be either residual or generated from external loads. The stress-dependent elastic properties are incorporated into the definition of the differential scattering cross-section, which defines how strongly an incident wave is scattered into various directions. Nine stress-dependent differential scattering cross-sections or scattering coefficients are defined to include all possibilities of incident and scatteredwaves, which can be either longitudinal or (two) transverse wave types. The evaluation of the scattering coefficients considers polycrystalline aluminum that is uniaxially stressed. An analysis of the influence of incident wave propagation direction, scattering direction, frequency, and grain size on the stress-dependency of the scattering coefficients follows. Scattering coefficients for aluminum indicate that ultrasonic scattering is much more sensitive to a uniaxial stress than ultrasonic phase velocities. By developing the stress-dependent scatteringproperties of polycrystals, the influence of acoustoelasticity on the amplitudes of waves propagating in stressed polycrystalline materials can be better understood. This work supports the ongoing development of a technique for monitoring and measuring stresses in metallic materials.

from #Audiology via xlomafota13 on Inoreader http://ift.tt/1QwxFbF
via IFTTT

Cochlear implant speech intelligibility outcomes with structured and unstructured binary mask errors

It has been shown that intelligibility can be improved for cochlear implant(CI) recipients with the ideal binary mask (IBM). In realistic scenarios where prior information is unavailable, however, the IBM must be estimated, and these estimations will inevitably contain errors. Although the effects of both unstructured and structured binary mask errors have been investigated with normal-hearing (NH) listeners, they have not been investigated with CI recipients. This study assesses these effects with CI recipients using masks that have been generated systematically with a statistical model. The results demonstrate that clustering of mask errors substantially decreases the tolerance of errors, that incorrectly removing target-dominated regions can be as detrimental to intelligibility as incorrectly adding interferer-dominated regions, and that the individual tolerances of the different types of errors can change when both are present. These trends follow those of NH listeners. However, analysis with a mixed effects model suggests that CI recipients tend to be less tolerant than NH listeners to mask errors in most conditions, at least with respect to the testing methods in each of the studies. This study clearly demonstrates that structure influences the tolerance of errors and therefore should be considered when analyzing binary-masking algorithms.

from #Audiology via xlomafota13 on Inoreader http://ift.tt/1SlWtZO
via IFTTT

Three dimensional multi-segmental trunk kinematics and kinetics during gait: Test-retest reliability and minimal detectable change

Publication date: Available online 11 February 2016
Source:Gait & Posture
Author(s): Rita Fernandes, Paulo Armada-da-Silva, Annelies Pool-Goudaazward, Vera Moniz-Pereira, António P. Veloso
Background and AimTrunk kinematics and kinetics can contribute to more detailed information on gait impairment, however data about reliability and measurement error of multi-segment trunk on three-dimensional gait analysis (3DGA) is lacking. The aim of this study is to investigate test-retest reliability and MDC of 3DGA kinematic and kinetic data in a sample of healthy individuals, using a two rigid segment model for the trunk.Methods A test-retest study with a median interval of 7 days and a sample of 23 healthy individuals was conducted. Anthropometric, time-distance parameters and peak values for lower limb and trunk joint angles/moments were computed. The intraclass correlation coefficient (ICC3,k), standard error of measurement (SEM), minimal detectable change (MDC) and 95% limits of agreement (LOA) were calculated.ResultsAcceptable test-retest reliability for most joint angles and a SEM ≤4°. The ICCs were above 0.7 for joint moments and the SEM and MDC were ≤0.2 Nm/kg and ≤0.6 Nm/kg, respectively. Bland-Altman plots with 95% LOA revealed a good agreement and time-distance parameters were all highly repeatable (majority ICCs>0.90).ConclusionsThe results of this study suggest varied reliability indices for multi-segment trunk joint angles and moments during gait and an acceptable level of error, particularly for sagittal plane parameters. Some parameters showed wide 95% CIs for ICCs and higher SEM%. However, we believe this study provide preliminary data regarding reliability indices for multi-segment trunk during gait, which may be valuable for clinical reasoning and decision making when dealing with musculoskeletal disorders.



from #Audiology via ola Kala on Inoreader http://ift.tt/1PqPjQo
via IFTTT

From Normal to Fast Walking: Impact of Cadence and Stride Length on Lower Extremity Joint Moments

Publication date: Available online 11 February 2016
Source:Gait & Posture
Author(s): Marzieh M. Ardestani, Christopher Ferrigno, Mehran Moazen, Markus A. Wimmer
This study aimed to clarify the influence of various speeding strategies (i.e. adjustments of cadence and stride length) on external joint moments. This study investigated the gait of 52 healthy subjects who performed self-selected normal and fast speed walking trials in a motion analysis laboratory. Subjects were classified into three separate groups based on how they increased their speed from normal to fast walking: (i) subjects who increased their cadence, (ii) subjects who increased their stride length and (iii) subjects who simultaneously increased both stride length and cadence. Joint moments were calculated using inverse dynamics and then compared between normal and fast speed trials within and between three groups using spatial parameter mapping.Individuals who increased cadence, but not stride length, to walk faster did not experience a significant increase in the lower limb joint moments. Conversely, subjects who increased their stride length or both stride length and cadence, experienced a significant increase in all joint moments. Additionally, our findings revealed that increasing the stride length had a higher impact on joint moments in the sagittal plane than those in the frontal plane. However, both sagittal and frontal plane moments were still more responsive to the gait speed change than transverse plane moments. This study suggests that the role of speed in altering the joint moment patterns depends on the individual's speed-regulating strategy, i.e. an increase in cadence or stride length. Since the confounding effect of walking speed is a major consideration in human gait research, future studies may investigate whether stride length is the confounding variable of interest.



from #Audiology via ola Kala on Inoreader http://ift.tt/1TWojLG
via IFTTT

Lower limb joint forces during walking on the level and slopes at different inclinations

Publication date: March 2016
Source:Gait & Posture, Volume 45
Author(s): Nathalie Alexander, Hermann Schwameder
Sloped walking is associated with an increase of lower extremity joint loading compared to level walking. Therefore, the aim of this study was to analyse lower limb joint compression forces as well as tibiofemoral joint shear forces during sloped walking at different inclinations. Eighteen healthy male participants (age: 27.0±4.7 years, height: 1.80±0.05m, mass: 74.5±8.2kg) were asked to walk at a pre-set speed of 1.1m/s on a ramp (6m×1.5m) at the slopes of −18°, −12°, −6°, 0°, 6°, 12° and 18°. Kinematic data were captured with a twelve-camera motion capture system (Vicon). Kinetic data were recorded with two force plates (AMTI) imbedded into a ramp. A musculoskeletal model (AnyBody) was used to compute lower limb joint forces. Results showed that downhill walking led to significantly increased hip, tibiofemoral and patellofemoral joint compression forces (p<0.05) and to significantly decreased ankle joint compression forces (p<0.05). Uphill walking significantly increased all lower limb joint compression forces with increasing inclination (p<0.05). Findings that downhill walking is a stressful task for the anterior cruciate ligament could not be supported in the current study, since anterior tibiofemoral joint shear forces did not increase with the gradient. Due to diverse tibiofemoral joint shear force patterns in the literature, results should be treated with caution in general. Finally, lower limb joint force analyses provided more insight in the structure loading conditions during sloped walking than joint moment analyses.



from #Audiology via ola Kala on Inoreader http://ift.tt/1PqPjzZ
via IFTTT

Three dimensional multi-segmental trunk kinematics and kinetics during gait: Test-retest reliability and minimal detectable change

Publication date: Available online 11 February 2016
Source:Gait & Posture
Author(s): Rita Fernandes, Paulo Armada-da-Silva, Annelies Pool-Goudaazward, Vera Moniz-Pereira, António P. Veloso
Background and AimTrunk kinematics and kinetics can contribute to more detailed information on gait impairment, however data about reliability and measurement error of multi-segment trunk on three-dimensional gait analysis (3DGA) is lacking. The aim of this study is to investigate test-retest reliability and MDC of 3DGA kinematic and kinetic data in a sample of healthy individuals, using a two rigid segment model for the trunk.Methods A test-retest study with a median interval of 7 days and a sample of 23 healthy individuals was conducted. Anthropometric, time-distance parameters and peak values for lower limb and trunk joint angles/moments were computed. The intraclass correlation coefficient (ICC3,k), standard error of measurement (SEM), minimal detectable change (MDC) and 95% limits of agreement (LOA) were calculated.ResultsAcceptable test-retest reliability for most joint angles and a SEM ≤4°. The ICCs were above 0.7 for joint moments and the SEM and MDC were ≤0.2 Nm/kg and ≤0.6 Nm/kg, respectively. Bland-Altman plots with 95% LOA revealed a good agreement and time-distance parameters were all highly repeatable (majority ICCs>0.90).ConclusionsThe results of this study suggest varied reliability indices for multi-segment trunk joint angles and moments during gait and an acceptable level of error, particularly for sagittal plane parameters. Some parameters showed wide 95% CIs for ICCs and higher SEM%. However, we believe this study provide preliminary data regarding reliability indices for multi-segment trunk during gait, which may be valuable for clinical reasoning and decision making when dealing with musculoskeletal disorders.



from #Audiology via xlomafota13 on Inoreader http://ift.tt/1PqPjQo
via IFTTT

From Normal to Fast Walking: Impact of Cadence and Stride Length on Lower Extremity Joint Moments

Publication date: Available online 11 February 2016
Source:Gait & Posture
Author(s): Marzieh M. Ardestani, Christopher Ferrigno, Mehran Moazen, Markus A. Wimmer
This study aimed to clarify the influence of various speeding strategies (i.e. adjustments of cadence and stride length) on external joint moments. This study investigated the gait of 52 healthy subjects who performed self-selected normal and fast speed walking trials in a motion analysis laboratory. Subjects were classified into three separate groups based on how they increased their speed from normal to fast walking: (i) subjects who increased their cadence, (ii) subjects who increased their stride length and (iii) subjects who simultaneously increased both stride length and cadence. Joint moments were calculated using inverse dynamics and then compared between normal and fast speed trials within and between three groups using spatial parameter mapping.Individuals who increased cadence, but not stride length, to walk faster did not experience a significant increase in the lower limb joint moments. Conversely, subjects who increased their stride length or both stride length and cadence, experienced a significant increase in all joint moments. Additionally, our findings revealed that increasing the stride length had a higher impact on joint moments in the sagittal plane than those in the frontal plane. However, both sagittal and frontal plane moments were still more responsive to the gait speed change than transverse plane moments. This study suggests that the role of speed in altering the joint moment patterns depends on the individual's speed-regulating strategy, i.e. an increase in cadence or stride length. Since the confounding effect of walking speed is a major consideration in human gait research, future studies may investigate whether stride length is the confounding variable of interest.



from #Audiology via xlomafota13 on Inoreader http://ift.tt/1TWojLG
via IFTTT

Lower limb joint forces during walking on the level and slopes at different inclinations

Publication date: March 2016
Source:Gait & Posture, Volume 45
Author(s): Nathalie Alexander, Hermann Schwameder
Sloped walking is associated with an increase of lower extremity joint loading compared to level walking. Therefore, the aim of this study was to analyse lower limb joint compression forces as well as tibiofemoral joint shear forces during sloped walking at different inclinations. Eighteen healthy male participants (age: 27.0±4.7 years, height: 1.80±0.05m, mass: 74.5±8.2kg) were asked to walk at a pre-set speed of 1.1m/s on a ramp (6m×1.5m) at the slopes of −18°, −12°, −6°, 0°, 6°, 12° and 18°. Kinematic data were captured with a twelve-camera motion capture system (Vicon). Kinetic data were recorded with two force plates (AMTI) imbedded into a ramp. A musculoskeletal model (AnyBody) was used to compute lower limb joint forces. Results showed that downhill walking led to significantly increased hip, tibiofemoral and patellofemoral joint compression forces (p<0.05) and to significantly decreased ankle joint compression forces (p<0.05). Uphill walking significantly increased all lower limb joint compression forces with increasing inclination (p<0.05). Findings that downhill walking is a stressful task for the anterior cruciate ligament could not be supported in the current study, since anterior tibiofemoral joint shear forces did not increase with the gradient. Due to diverse tibiofemoral joint shear force patterns in the literature, results should be treated with caution in general. Finally, lower limb joint force analyses provided more insight in the structure loading conditions during sloped walking than joint moment analyses.



from #Audiology via xlomafota13 on Inoreader http://ift.tt/1PqPjzZ
via IFTTT

Development of adaptive sensorimotor control in infant sitting posture

Publication date: March 2016
Source:Gait & Posture, Volume 45
Author(s): Li-Chiou Chen, John Jeka, Jane E. Clark
A reliable and adaptive relationship between action and perception is necessary for postural control. Our understanding of how this adaptive sensorimotor control develops during infancy is very limited. This study examines the dynamic visual–postural relationship during early development. Twenty healthy infants were divided into 4 developmental groups (each n=5): sitting onset, standing alone, walking onset, and 1-year post-walking. During the experiment, the infant sat independently in a virtual moving-room in which anterior-posterior oscillations of visual motion were presented using a sum-of-sines technique with five input frequencies (from 0.12 to 1.24Hz). Infants were tested in five conditions that varied in the amplitude of visual motion (from 0 to 8.64cm). Gain and phase responses of infants’ postural sway were analyzed. Our results showed that infants, from a few months post-sitting to 1 year post-walking, were able to control their sitting posture in response to various frequency and amplitude properties of the visual motion. Infants showed an adult-like inverted-U pattern for the frequency response to visual inputs with the highest gain at 0.52 and 0.76Hz. As the visual motion amplitude increased, the gain response decreased. For the phase response, an adult-like frequency-dependent pattern was observed in all amplitude conditions for the experienced walkers. Newly sitting infants, however, showed variable postural behavior and did not systemically respond to the visual stimulus. Our results suggest that visual–postural entrainment and sensory re-weighting are fundamental processes that are present after a few months post sitting. Sensorimotor refinement during early postural development may result from the interactions of improved self-motion control and enhanced perceptual abilities.



from #Audiology via xlomafota13 on Inoreader http://ift.tt/1TWojeW
via IFTTT

Three dimensional multi-segmental trunk kinematics and kinetics during gait: Test-retest reliability and minimal detectable change

Publication date: Available online 11 February 2016
Source:Gait & Posture
Author(s): Rita Fernandes, Paulo Armada-da-Silva, Annelies Pool-Goudaazward, Vera Moniz-Pereira, António P. Veloso
Background and AimTrunk kinematics and kinetics can contribute to more detailed information on gait impairment, however data about reliability and measurement error of multi-segment trunk on three-dimensional gait analysis (3DGA) is lacking. The aim of this study is to investigate test-retest reliability and MDC of 3DGA kinematic and kinetic data in a sample of healthy individuals, using a two rigid segment model for the trunk.Methods A test-retest study with a median interval of 7 days and a sample of 23 healthy individuals was conducted. Anthropometric, time-distance parameters and peak values for lower limb and trunk joint angles/moments were computed. The intraclass correlation coefficient (ICC3,k), standard error of measurement (SEM), minimal detectable change (MDC) and 95% limits of agreement (LOA) were calculated.ResultsAcceptable test-retest reliability for most joint angles and a SEM ≤4°. The ICCs were above 0.7 for joint moments and the SEM and MDC were ≤0.2 Nm/kg and ≤0.6 Nm/kg, respectively. Bland-Altman plots with 95% LOA revealed a good agreement and time-distance parameters were all highly repeatable (majority ICCs>0.90).ConclusionsThe results of this study suggest varied reliability indices for multi-segment trunk joint angles and moments during gait and an acceptable level of error, particularly for sagittal plane parameters. Some parameters showed wide 95% CIs for ICCs and higher SEM%. However, we believe this study provide preliminary data regarding reliability indices for multi-segment trunk during gait, which may be valuable for clinical reasoning and decision making when dealing with musculoskeletal disorders.



from #Audiology via ola Kala on Inoreader http://ift.tt/1PqPjQo
via IFTTT

From Normal to Fast Walking: Impact of Cadence and Stride Length on Lower Extremity Joint Moments

Publication date: Available online 11 February 2016
Source:Gait & Posture
Author(s): Marzieh M. Ardestani, Christopher Ferrigno, Mehran Moazen, Markus A. Wimmer
This study aimed to clarify the influence of various speeding strategies (i.e. adjustments of cadence and stride length) on external joint moments. This study investigated the gait of 52 healthy subjects who performed self-selected normal and fast speed walking trials in a motion analysis laboratory. Subjects were classified into three separate groups based on how they increased their speed from normal to fast walking: (i) subjects who increased their cadence, (ii) subjects who increased their stride length and (iii) subjects who simultaneously increased both stride length and cadence. Joint moments were calculated using inverse dynamics and then compared between normal and fast speed trials within and between three groups using spatial parameter mapping.Individuals who increased cadence, but not stride length, to walk faster did not experience a significant increase in the lower limb joint moments. Conversely, subjects who increased their stride length or both stride length and cadence, experienced a significant increase in all joint moments. Additionally, our findings revealed that increasing the stride length had a higher impact on joint moments in the sagittal plane than those in the frontal plane. However, both sagittal and frontal plane moments were still more responsive to the gait speed change than transverse plane moments. This study suggests that the role of speed in altering the joint moment patterns depends on the individual's speed-regulating strategy, i.e. an increase in cadence or stride length. Since the confounding effect of walking speed is a major consideration in human gait research, future studies may investigate whether stride length is the confounding variable of interest.



from #Audiology via ola Kala on Inoreader http://ift.tt/1TWojLG
via IFTTT

Lower limb joint forces during walking on the level and slopes at different inclinations

Publication date: March 2016
Source:Gait & Posture, Volume 45
Author(s): Nathalie Alexander, Hermann Schwameder
Sloped walking is associated with an increase of lower extremity joint loading compared to level walking. Therefore, the aim of this study was to analyse lower limb joint compression forces as well as tibiofemoral joint shear forces during sloped walking at different inclinations. Eighteen healthy male participants (age: 27.0±4.7 years, height: 1.80±0.05m, mass: 74.5±8.2kg) were asked to walk at a pre-set speed of 1.1m/s on a ramp (6m×1.5m) at the slopes of −18°, −12°, −6°, 0°, 6°, 12° and 18°. Kinematic data were captured with a twelve-camera motion capture system (Vicon). Kinetic data were recorded with two force plates (AMTI) imbedded into a ramp. A musculoskeletal model (AnyBody) was used to compute lower limb joint forces. Results showed that downhill walking led to significantly increased hip, tibiofemoral and patellofemoral joint compression forces (p<0.05) and to significantly decreased ankle joint compression forces (p<0.05). Uphill walking significantly increased all lower limb joint compression forces with increasing inclination (p<0.05). Findings that downhill walking is a stressful task for the anterior cruciate ligament could not be supported in the current study, since anterior tibiofemoral joint shear forces did not increase with the gradient. Due to diverse tibiofemoral joint shear force patterns in the literature, results should be treated with caution in general. Finally, lower limb joint force analyses provided more insight in the structure loading conditions during sloped walking than joint moment analyses.



from #Audiology via ola Kala on Inoreader http://ift.tt/1PqPjzZ
via IFTTT

Development of adaptive sensorimotor control in infant sitting posture

Publication date: March 2016
Source:Gait & Posture, Volume 45
Author(s): Li-Chiou Chen, John Jeka, Jane E. Clark
A reliable and adaptive relationship between action and perception is necessary for postural control. Our understanding of how this adaptive sensorimotor control develops during infancy is very limited. This study examines the dynamic visual–postural relationship during early development. Twenty healthy infants were divided into 4 developmental groups (each n=5): sitting onset, standing alone, walking onset, and 1-year post-walking. During the experiment, the infant sat independently in a virtual moving-room in which anterior-posterior oscillations of visual motion were presented using a sum-of-sines technique with five input frequencies (from 0.12 to 1.24Hz). Infants were tested in five conditions that varied in the amplitude of visual motion (from 0 to 8.64cm). Gain and phase responses of infants’ postural sway were analyzed. Our results showed that infants, from a few months post-sitting to 1 year post-walking, were able to control their sitting posture in response to various frequency and amplitude properties of the visual motion. Infants showed an adult-like inverted-U pattern for the frequency response to visual inputs with the highest gain at 0.52 and 0.76Hz. As the visual motion amplitude increased, the gain response decreased. For the phase response, an adult-like frequency-dependent pattern was observed in all amplitude conditions for the experienced walkers. Newly sitting infants, however, showed variable postural behavior and did not systemically respond to the visual stimulus. Our results suggest that visual–postural entrainment and sensory re-weighting are fundamental processes that are present after a few months post sitting. Sensorimotor refinement during early postural development may result from the interactions of improved self-motion control and enhanced perceptual abilities.



from #Audiology via ola Kala on Inoreader http://ift.tt/1TWojeW
via IFTTT

Development of adaptive sensorimotor control in infant sitting posture

Publication date: March 2016
Source:Gait & Posture, Volume 45
Author(s): Li-Chiou Chen, John Jeka, Jane E. Clark
A reliable and adaptive relationship between action and perception is necessary for postural control. Our understanding of how this adaptive sensorimotor control develops during infancy is very limited. This study examines the dynamic visual–postural relationship during early development. Twenty healthy infants were divided into 4 developmental groups (each n=5): sitting onset, standing alone, walking onset, and 1-year post-walking. During the experiment, the infant sat independently in a virtual moving-room in which anterior-posterior oscillations of visual motion were presented using a sum-of-sines technique with five input frequencies (from 0.12 to 1.24Hz). Infants were tested in five conditions that varied in the amplitude of visual motion (from 0 to 8.64cm). Gain and phase responses of infants’ postural sway were analyzed. Our results showed that infants, from a few months post-sitting to 1 year post-walking, were able to control their sitting posture in response to various frequency and amplitude properties of the visual motion. Infants showed an adult-like inverted-U pattern for the frequency response to visual inputs with the highest gain at 0.52 and 0.76Hz. As the visual motion amplitude increased, the gain response decreased. For the phase response, an adult-like frequency-dependent pattern was observed in all amplitude conditions for the experienced walkers. Newly sitting infants, however, showed variable postural behavior and did not systemically respond to the visual stimulus. Our results suggest that visual–postural entrainment and sensory re-weighting are fundamental processes that are present after a few months post sitting. Sensorimotor refinement during early postural development may result from the interactions of improved self-motion control and enhanced perceptual abilities.



from #Audiology via ola Kala on Inoreader http://ift.tt/1TWojeW
via IFTTT