Motion In Human Subjects Research Articles

Reproducibility of cine displacement encoding with stimulated echoes (DENSE) in human subjects

ObjectivesTo test the hypothesis that two-dimensional (2D) displacement encoding via stimulated echoes (DENSE) is a reproducible technique for the depiction of segmental myocardial motion in human subjects. Materials and methodsFollowing the approval of the institutional review board (IRB), 17 healthy volunteers without documented history of cardiovascular disease were recruited. For each participant, 2D DENSE were performed twice (at different days) and the images were obtained at basal, midventricular and apical levels of the left ventricle (LV) with a short-axis view. The radial thickening strain (Err), circumferential strain (Ecc), twist and torsion were calculated. The intra-, inter-observer and inter-study variations of DENSE-derived myocardial motion indices were evaluated using coefficient of variation (CoV) and intra-class correlation coefficient (ICC). ResultsIn total, there are 272 pairs of myocardial segments (data points) for comparison. There is good intra- and inter-observer reproducibility for all DENSE-derived measures in 17 participants. There is good inter-study reproducibility for peak Ecc (CoV=19.64%, ICC=0.8896, p<0.001), twist (CoV=33.11%, ICC=0.9135, p<0.001) and torsion (CoV=13.96%, ICC=0.8684, p<0.001). There is moderate inter-study reproducibility for Err (CoV=38.89%, ICC=0.7022, p<0.001). ConclusionDENSE is a reproducible technique for characterizing LV regional systolic myocardial motion on a per-segment basis in healthy volunteers.

A talking profile to distinguish identical twins

Identical twins pose a great challenge to face recognition due to high similarities in their appearances. Motivated by the psychological findings that facial motion contains identity signatures and the observation that twins may look alike but behave differently, we develop a talking profile to use the identity signatures in the facial motion to distinguish between identical twins. The talking profile for a subject is defined as a collection of multiple types of usual face motions from the video. Given two talking profiles, we compute the similarities of the same type of face motion in both profiles and then perform the classification based on those similarities. To compute the similarity of each type of face motion, we give higher weights to more abnormal motions which are assumed to carry more identity signature information.Our approach, named Exceptional Motion Reporting Model (EMRM), is unrelated with appearance, and can handle realistic facial motion in human subjects, with no restrictions of speed of motion or video frame rate. We first conduct our experiments on a video database containing 39 pairs of twins. The experimental results demonstrate that identical twins can be distinguished better by the talking profiles over the traditional appearance based approach. Moreover, we collected a non-twin YouTube dataset with 99 subjects. The results on this dataset verified that the talking profile can be the potential biometric. We further conducted an experiment to test the robustness of talking profile to the time. Videos from 10 subjects which span across years or even decades in their lives are collected. The results indicated the robustness of talking profile to the aging process.

TU‐C‐M100J‐09: Application of a PARMA Algorithm to Predict Intrafraction Respiratory Motion

Purpose: Accurate motion tracking can decrease normal tissue dose, PTV margins, and shorten treatment times required for radiation therapy. A Periodic Autoregressive Moving Average (PARMA) model was developed to predict one‐dimensional respiratory motion in human subjects. Methods and Materials: A PARMA prediction algorithm was applied to clinical respiration signals from three categories: free‐breathing, audio instruction, and audio‐visual coaching. The PARMA model of the respiration motion is a dual‐component signal, a partially correlated time‐series superimposed onto a periodic pattern. The periodic component was estimated by averaging over the inhale‐exhale cycles in a 60‐second sample of the respiration signal, and the autocorrelation in the residual signal was modeled by linear autoregressive moving average equations. The PARMA predictions were compared to the system latency errors produced when tumor tracking is done without forward predictions. Results: For audio‐visual coaching, the PARMA prediction errors (1σ) were 0.09 mm, 0.23 mm and 0.99 mm at 0.1 s, 0.2 s and 0.5 s respectively. A prediction error of 0.99 mm is equivalent to 7.2% of the average end‐inhale to end‐exhale motion. By comparison, the errors were 0.60 mm, 1.20, and 2.90 mm when the lagged signal is used as an estimate of current position at 0.1 s, 0.2 s and 0.5 s respectively. For free‐breathing respiration, PARMA predictions were accurate to within 0.10 mm (1σ) at 0.1 seconds, 0.24 mm at 0.2 seconds, and 1.07mm at 0.5 seconds. The system latency errors were also similar to the coached signals. Conclusion: Tumor tracking with dynamic MLC can theoretically achieve system latency times of 0.16 seconds with accuracy of about 1 mm. The prediction errors of the PARMA algorithm was well under one‐third of the calculated system latency error for all lag times investigated.

Voluntary head movement and allocentric perception of space.

Although visual input is egocentric, at least some visual perceptions and representations are allocentric, that is, independent of the observer's vantage point or motion. Three experiments investigated the visual perception of three-dimensional object motion during voluntary and involuntary motion in human subjects. The results show that the motor command contributes to the objective perception of space: Observers are more likely to apply, consciously and unconsciously, spatial criteria relative to an allocentric frame of reference when they are executing voluntary head movements than while they are undergoing similar involuntary displacements (which lead to a more egocentric bias). Furthermore, details of the motor command are crucial to spatial vision, as allocentric bias decreases or disappears when self-motion and motor command do not match.

A line imaging system for measurement of eyelid movements

A line scan imaging system which provides a facility for comprehensive measurement and analysis of eyelid motion in human subjects is described. The device obtains parasagittal line images of the eye and eyelids by focusing an image of the eye onto a linear 256-element CCD array. Line images are acquired and digitized at a rate of 200 per second and stored in a buffer memory. The stored data are subsequently analysed on a PC to give measurements of eyelid displacement and velocity. Measurements of eyelid displacement and velocity during normal blinks in five subjects were comparable with published results from other measurement techniques.

Cardiac cycle-dependent variation of integrated backscatter is not distorted by abnormal myocardial wall motion in human subjects with paradoxical septal motion

To define the dependence of cardiac cycle-dependent variation of integrated backscatter on regional myocardial wall motion, 8 children mean age 10.6 ± 1.3 y with congenital cardiac lesions associated with paradoxical septal motion were studied (study group). Six healthy children mean age 9.0 ± 0.3 y with no history of cardiac disease served as controls (control group). Subjects in the study group had paradoxical septal motion but normal septal wall thickening detected by conventional two-dimensional and M-mode echocardiography. The control group had normal septal motion evident by conventional echocardiographic criteria. The percentage of systolic septal thickening was 46 ± 4.5% and 42 ± 5.9% in the study and control groups (p = NS). Cyclic variation was measured in parasternal long-axis views from several septal sites in each subject. Mean values of the magnitude of cyclic variation from independent septal sites were averaged to yield a regional average value for each subject. The average regional magnitude of cyclic variation was 8.3 ± 1.0 dB and 5.7 ± 0.4 dB in the study and control groups (p = NS). The results indicate that the measurement of cyclic variation of integrated backscatter is not distorted by altered regional wall motion, and that it reflects intrinsic contractile function.