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At least 379 records · Page 21Linked to original sources
PubMed1997

Motion-adapted gating based on k-space weighting for reduction of respiratory motion artifacts.

A new modified type of gating is presented that shows the ability to reduce the total scan time with almost conserved image quality compared with conventional gating. This new motion-adapted gating approach is based on a k-space-dependent gating threshold function. MR data acquired are only accepted if the motion-induced displacements measured from a reference position are below the chosen gating threshold function. During the MR measurement the scanner analyses respiratory motion decides in real-time which data in k-space could be measured according to the gating threshold function and performs data acquisition. In the present paper the approach will be described and discussed. Simulations based on in vivo data and initial in vivo experiments are presented to compare different variants of the new approach mutually and to the conventional technique. The analysis given is focused on spin warp type sequences, which are the best candidates for this approach.

Abdomen↗
PubMed2004

Segmental vertebral motion in the assessment of neck range of motion in whiplash patients.

The purpose of this study was to obtain comparative data concerning the relative contribution of segmental cervical vertebral motion to the cervical range of motion (ROM) in whiplash and healthy subjects in an effort to evaluate the usefulness of X-ray analysis in future forensic and research efforts. Each subject's neck ROM was measured with an optoelectronic system and also by X-ray measurements of the angular rotation in flexion and extension. The X-rays were examined to calculate the angular movement in the sagittal plane of each of the functional units C2-C3 to C6-C7. The chronic whiplash subjects showed reduced total neck range in all directions as compared to healthy subjects (p<0.001). There was a reduced total angular rotation from flexion to extension between these two groups (p<0.01), but no significant difference, however, between chronic whiplash subjects and controls in the percentage contribution of each of the functional units C2-C3 to C6-C7 to this rotation. This data will now allow a design of trials where healthy subjects are asked to simulate restricted neck ROM while undergoing optokinetic and X-ray evaluation of segmental vertebral motion. We will be able to determine if simulators produce a similar pattern to chronic whiplash and healthy, non-simulating subjects, and thus determine if, at least for forensic and research purposes, this technique is useful in validating reported restricted neck range.

Adolescent↗
PubMedDate not supplied

Analysis of imaging axes significance in motion artifact suppression technique (MAST): MRI of turbulent flow and motion.

Recently, a new technique has been demonstrated which effectively refocusses the dephasing effects of spins moving during application of MR imaging gradients. This paper presents an analysis of imaging axes significance in spin dephasing for motion occurring along the slice select, read and phase-encoding directions. A flow phantom under constant flow conditions in all experiments was used to provide complete spin dephasing when "traditional" imaging gradients were used. The MAST technique was used to refocus along various combinations of imaging axes, and variable number of terms from the Taylor expansion of motion along them. Results indicate that motion along any imaging axis can be refocussed effectively when MAST gradients are used along only the slice select and read axis.

Abdomen↗
PubMed2003

Mitral annulus motion compared with wall motion scoring index in the assessment of left ventricular ejection fraction.

The biplane disc summation method is the recommended echocardiographic procedure to determine left ventricular (LV) ejection fraction (EF). Assessment of mitral annulus motion (MAM) or wall motion scoring index (WMI) has been reported to be less dependent on image quality compared with the recommended method, and proposed as a surrogate to the disc summation method in calculation of LVEF. We aimed to compare MAM and WMI in the echocardiographic assessment of LVEF. In a randomly selected population-based sample of 75-year-old men and women in sinus rhythm (n = 409) MAM, as measured by M-mode, was compared with WMI, calculated as the mean value of wall motion scoring in 9 LV segments. LVEF, as measured by the biplane disc summation method was used as reference. The limits of agreement (mean difference +/- 1.96 SD) between LVEF and corresponding MAM values were -18 to +13 LVEF%, and between LVEF and corresponding WMI values were -12 to +13 LVEF%. The areas under the receiver operating characteristic curves for MAM and WMI to predict a LVEF < 50% were 0.892 and 0.998, respectively (95% confidence interval of the difference 0.062-0.149). The corresponding areas for MAM and WMI to predict a LVEF < 40% were 0.955 and 0.998, respectively (95% confidence interval of the difference 0.017-0.069). In conclusion, the ability of WMI to estimate LVEF was more favorable than MAM in this population-based sample of 75-year-old participants. The findings suggest that the WMI is preferable to MAM in estimating LVEF.

Aged↗
PubMed2003

Probing motions between equivalent RNA domains using magnetic field induced residual dipolar couplings: accounting for correlations between motions and alignment.

Approaches developed thus for extracting structural and dynamical information from RDCs have rested on the assumption that motions do not affect molecular alignment. However, it is well established that molecular alignment in ordered media is dependent on conformation, and slowly interconverting conformational substates may exhibit different alignment properties. Neglecting these correlation effects can lead to aberrations in the structural and dynamical analysis of RDCs and diminish the utility of RDCs in probing motions between domains having similar alignment propensities. Here, we introduce a new approach based on measurement of magnetic field induced residual dipolar couplings in nucleic acids which can explicitly take into account such correlations and demonstrate measurements of motions between two "magnetically equivalent" domains in the transactivation response element (TAR) RNA.

Magnetics↗
PubMed1995

Effects of electrically-stimulated exercise and passive motion on echocardiographically-derived wall motion and cardiodynamic function in tetraplegic persons.

The purposes of the study were (1) to characterize left ventricular wall motion, and the cardiodynamic and metabolic responses during electrical stimulation cycle ergometry (ESCE) exercise in tetraplegic people; (2) to test whether these responses linger into the post-exercise recovery period; and (3) to test whether they differ from those imposed by lower extremity continuous passive motion (CPM). Subjects were six tetraplegic males aged 25.8 +/- 3.1 (mean +/- SD) years with spinal cord injuries of 6.7 +/- 3.5 years' duration at the C5 and C6 levels (Frankel classifications A and B). On randomized non-consecutive days, subjects underwent either 30 min of steady-state exercise using transcutaneous electrically-stimulated contractions of bilateral quadriceps, hamstring, and gluteus muscle groups, or 30 min of continuous passive motion at 50 rpm. Data were taken at rest, min 15 and 30 of treatment, and min 5, 15, and 30 post-treatment. Stroke volume (SV) was measured echocardiographically as the product of the left ventricular outflow tract area and the integrated area under the left ventricular outflow tract flow-velocity curve acquired by doppler ultrasound. This value was multiplied by heart rate (HR) to determine the cardiac output (CO). Oxygen consumption (VO2) was monitored spirometrically, with arteriovenous oxygen difference (a-vO2DIFF) computed algebraically. Data were analyzed using repeated measures within-subjects design anaysis of variance, with significance accepted at the 0.05 level. Results showed five subjects had small hyperkinetic ventricles at rest that became more dynamic during ESCE than CPM. Though no systolic dysfunction was noted, all but one subject exhibited some degree of septal hypokinesis at rest and during exercise, possibly indicative of left ventricular noncompliance. Significant effects of condition (ESCE vs CPM), trial (measurement time point), and their interaction, were observed for CO (P < 0.05, 0.01, and 0.0001, respectively), HR (P < 0.0001, 0.05 and 0.005, respectively), and VO2 (P < 0.001, 0.05 and 0.005, respectively). A significant trial and condition by trial interaction was found for a-vO2DIFF (P < 0.05 and 0.0001, respectively). No effects for condition, trial or their interaction were found for SV or BPDIAS. Electrical stimulation cycle ergometry-treated subjects achieved peak VO2 of 712 +/- 300 ml min-1, 2.63 times baseline, with 56% elevation of a-vO2DIFF. Cardiac output increased from 3.5 +/- 1.51 min-1 to 6.0 +/- 2.11 min-1, an elevation solely attributable to a 57% increase in HR. Thus, both CO and a-vO2DIFF accounted for elevated VO2 during ESCE.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1989

Two motion perception mechanisms revealed through distance-driven reversal of apparent motion.

We demonstrate two kinds of visual stimuli that exhibit motion in one direction when viewed from near and in the opposite direction from afar. These striking reversals occur because each kind of stimulus is constructed to simultaneously activate two different mechanisms: a short-range mechanism that computes motion from space-time correspondences in stimulus luminance and a long-range mechanism in which motion computations are performed, instead, on stimulus contrast that has been full-wave rectified (e.g., on the absolute value of contrast).

Journal Article↗
PubMed1995

Use of a spinal model to quantify the forces and motion that occur during therapists' tests of spinal motion.

BACKGROUND AND PURPOSE: Despite the widespread use of spinal mobilization, little is known about the forces used or the accuracy of therapists in estimating the forces they use in administering the technique. The purposes of this study were to quantify the forces used and to determine the accuracy of therapists in applying forces on a mechanical model. SUBJECTS: Ten physical therapists participated. METHODS: A spinal model was used to measure applied force and displacement under different conditions of stiffness. The therapists applied oscillatory posteroanterior mobilizations to the model under three different conditions of stiffness. RESULTS: Mean peak forces across grades and stiffness levels ranged between 57.59 and 178.27 N. The forces were generally lower in the least stiff condition. Displacement varied with stiffness and mobilization grade. In the least stiff condition, the mean displacement varied between 2.25 and 3.45 mm for grades 1 to 4, respectively. CONCLUSION AND DISCUSSION: Inter-therapist variability was high, and there was a systematic bias in underestimating the magnitude of applied force and in overestimating motion. The variability in force application and the general overestimation of motion detection may explain the poor reliability of measurements obtained with clinical tests based on motion palpation.

Adult↗
PubMed2007

Effects of the mechanical load on forward bending motion of the trunk: comparison between patients with motion-induced intermittent low back pain and healthy subjects.

STUDY DESIGN: Postural changes and trunk muscle activities were examined in patients with motion-induced intermittent low back pain (MILBP) and healthy controls. OBJECTIVES: To assess the ability to maintain an upright standing position. SUMMARY OF BACKGROUND DATA: Since MILBP is not observed at rest, its pathophysiology is complicated to investigate. METHODS.: Postural changes were measured with a 3-dimensional motion analyzer, and muscle activities with a surface electromyography while 10 female patients at an average age of 76 years (MILBP group) and 10 healthy controls at an average age of 74 years (Control Group) were standing upright and loaded with 10-kg weights. RESULTS: In the Control Group, no significant forward bending motion occurred. In the MILBP group, there was a temporal increase in forward bending at various speeds and at various time phases. In the MILBP group but not in the Control Group, the rate of changes in median power frequency of erector spinae muscle declined significantly as compared with that in the Control Group (P < 0.05). CONCLUSIONS: These results indicated that fatigue of the back muscles occurred in MILBP patients and could be a pain generator in low back pain.

Abdominal Muscles↗
PubMed2001

Coronary MR angiography: selection of acquisition window of minimal cardiac motion with electrocardiography-triggered navigator cardiac motion prescanning--initial results.

The authors developed an electrocardiography-triggered M-mode navigator-echo technique to help monitor cardiac motion and identify the period of minimal cardiac motion in the cardiac cycle. Coronary magnetic resonance angiography was performed in eight healthy adult volunteers and one patient with heart disease. To minimize cardiac motion effects, trigger delays were estimated with the navigator-echo technique and two empirical formulas. The quality of images obtained with the different delay times was compared for clarity of depiction of the coronary arteries. Image quality was best with the delay calculated with the navigator-echo technique.

Adult↗
PubMed1980

Systolic anterior motion of the mitral valve with and without asymmetric septal hypertrophy. Role of left ventricular posterior wall motion.

Abnormal systolic anterior (SAM) motion of the mitral valve without asymmetric hypertrophy of the interventricular septum was observed in 16 patients (group 1). 5 of the 16 patients had no other evidence of heart disease and the remaining 11 had a variety of cardiac disorders. Left ventricular dimensions, septal and posterior wall thickness, left ventricular ejection fraction, the mean velocity of circumferential fiber shortening, and the mean velocity of the posterior wall and septal contraction was measured by echocardiography in all patients in group 1. These measurements were compared with similar measurements in 14 patients with idiopathic hypertrophic subaortic stenosis (group 2) and in 11 normal subjects (group 3) to evaluate the role of the left ventricular contractility with particular reference to the left ventricular posterior wall motion in production of SAM. All patients with SAM (groups 1 and 2) showed significantly higher indexes of left ventricular contractility, particularly posterior wall velocity, and normalized mean posterior wall velocity, when compared to the normal subjects. The significantly higher posterior wall and the normalized mean posterior wall velocities in all patients with SAM suggest that the exaggerated systolic anterior motion of the left ventricular posterior wall plays an important role in production of SAM in the presence or absence of asymmetric septal hypertrophy.

Adult↗
PubMed1990

Cervical spine motion in the sagittal plane (I) range of motion of actually performed movements, an X-ray cinematographic study.

A fast method has been developed to determine the position of the outlines of bony structures on X-ray photographs of the cervical spine movements in the sagittal plane (105 mm spot film camera; 4 frames per second; about 10 seconds per complete anteflexion-retroflexion or vice versa). This method corrects for incongruity of the vertebral contours on consecutive frames due to motion in another than the sagittal plane. It also automatically corrects erroneously marked points. This method has been used to determine segmental range of motion (SROM) and total range of motion of the head with respect to the seventh cervical vertebra (TROM). It is shown that SROM may be larger when frames of intermediate instead of extreme positions of the film are considered. In ten test persons without cervical complaints the interindividual variability of SROM turned out to be comparable to the ones found with older methods. Intraindividual variability of SROM and TROM was determined by registration at three different measuring sessions (0, 2 and 10 weeks). This intraindividual variability is high, especially in the cranial and caudal parts of the cervical spine. It is concluded that SROM and TROM are unsuitable to be used as a parameter of cervical spine mobility.

Adult↗
PubMed2003

Cells in monkey STS responsive to articulated body motions and consequent static posture: a case of implied motion?

We show that populations of visually responsive cells in the anterior part of the superior temporal sulcus (STSa) of the macaque monkey code for the sight of both specific articulated body actions and the consequent articulated static body postures. We define articulated actions as actions where one body part (e.g. a limb or head) moves with respect to the remainder of the body which remains static; conversely non-articulated actions are actions where the equivalent body parts do not move with respect to each other but move as one. Similarly, articulated static body postures contain a torsion or rotation between parts, while non-articulated postures do not. Cells were tested with the sight of articulated and non-articulated actions followed by the resultant articulated or non-articulated static body postures. In addition, the static body postures that formed the start and end of the actions were tested in isolation. The cells studied did not respond to the sight of non-articulated static posture, which formed the starting-point of the action, but responded vigorously to the articulated static posture that formed the end-point of the action. Other static postures resembling the articulated end-point posture, but which were in a more relaxed muscular state (i.e. non-articulated), did not evoke responses. The cells did not respond to body actions that were less often associated with the effective static articulated postures. Our results suggest that the cells' responses were related to the implied action rather than the static posture per se. We propose that the neural representations in STSa for actual biological motion may also extend to biological motion implied from static postures. These representations could play a role in producing the activity in the medial temporal/medial superior temporal (V5(MT)/MST) areas reported in fMRI studies when subjects view still photographs of people in action.

Action Potentials↗
PubMed1997

The effect of continuous passive motion duration and increment on range of motion in total knee arthroplasty patients.

There is insufficient information on continuous passive motion (CPM) parameters in total knee arthroplasty patients for optimal patient outcomes. We compared CPM duration and increments on active and passive range of motion (ROM) in patients who underwent a unilateral total knee arthroplasty due to degenerative joint disease. Forty-five total knee arthroplasty patients were randomly assigned to either a control group, a short CPM duration (3-5 hours per day) group with CPM ROM increased 5 degrees twice daily, a short CPM duration group with CPM ROM increased daily to patient tolerance, a long CPM duration (10-12 hours per day) group with CPM ROM increased 5 degrees twice daily, or a long CPM duration group with CPM ROM increased daily to patient tolerance. Active and passive flexion and extension were measured goniometrically on each postoperative day that the patient was treated by physical therapy. No statistically significant differences between groups were found for baseline and final postoperative ROM. The CPM groups did not maintain the parameters assigned and were combined, revealing an enhanced rate of change of flexion. Most patients opted for a CPM duration of between 4 and 8 hours per day and the patient-preferred CPM incremental increase in ROM was 6-7 degrees/day.

Aged↗
PubMed1982

Effect of motion sweep duration and number of stations upon interpolation in discontinuous motion.

Spatial and temporal vernier offset thresholds were determined for a target moving in discrete spatial steps between stations. In the spatial case, the two bars comprising the target had a relative spatial offset at each station but were synchronous. In the temporal case the two bars appeared at aligning stations with a temporal asynchrony. Temporal thresholds were converted into spatial units by calculating the distance the target would have travelled during the temporal delay. When compared in this way, temporal and spatial thresholds were very similar if the duration of the motion sequence was 300 msec or greater, but at briefer durations temporal thresholds became progressively higher. The possibility that eye pursuit might account for these data was ruled out by recording eye movements and rejecting trials on which tracking occurred. Analysis of eye records revealed the surprising fact that some tracking can occur even when the duration of the motion sequence is as little as 150 msec and random in direction.

Eye Movements↗
PubMed1990

The temporal range of motion sensing and motion perception.

Apparent motion (AM) was studied using the missing-fundamental square-wave grating, displaced discretely over time. At inter-stimulus intervals (ISIs) greater than about 40 msec, AM was seen in the direction of displacement of the visible features of the pattern, while at shorter ISIs AM was seen in the reversed direction, following the displacement of the third harmonic spatial frequency component. This confirms (a) that the "long-range", feature-based process can bridge much greater time-gaps than the "short-range" motion sensors and (b) that the missing-fundamental pattern is a particularly useful tool for teasing the two processes apart.

Humans↗
PubMed1994

Recovery from motion adaptation is delayed by successively presented orthogonal motion.

Following a period of adaptation to a pattern moving in a particular direction, a subsequently viewed stationary pattern appears to move in the opposite direction for some time: the movement after effect (MAE). The MAE lasts longer when the test pattern is not immediately or not continuously presented after adaptation. This phenomenon is called storage. So far research indicates that storage only occurs when textured visual stimulation is absent during part of the test phase or if the processing of a stationary test stimulus is prevented (e.g. by binocular rivalry). We present evidence that storage-like phenomena can occur even while a textured and moving visual stimulus is phenomenally present. We adapted binocularly to uni-directional motion of a random-pixel array M1 for 60 sec. This stimulus was immediately followed by another moving pattern M2. Its motion direction was orthogonal to that of M1. The presentation time of M2 was the independent variable. A stationary pattern was presented immediately after presentation of M2. The direction of the resulting integrated uni-directional MAE was measured. For short presentation times of M2 there is an integrated uni-directional MAE, which shows an interaction of the output of units stimulated by both moving patterns. However, it appeared that the effect of M1 on the direction of this combined uni-directional MAE is much longer present than would be expected from the MAE duration of M1, when tested in isolation.

Adaptation, Ocular↗
PubMed1996

Directional motion sensitivity under transparent motion conditions.

We measured directional sensitivity to a foreground pattern while an orthogonally directed background pattern was present under transparent motion conditions. For both foreground and background pattern, the speed was varied between 0.5 and 28 deg sec-1. A multi-step paradigm was employed which results in a better estimation of the suppressive or facilitatory effects than previously applied single-step methods (e.g. measuring Dmax or Dmin). Moreover, our method gives insight into the interactions for a wide range of speed and not just the extreme motion thresholds (the D-values). We found that high background speeds have an inhibitory effect on the detection of a range of high foreground speeds and low background speeds have an inhibitory effect on a range of low foreground speeds. Intermediate background pattern speeds inhibit the detection of both low and high foreground pattern speeds and do so in a systemic manner.

Depth Perception↗