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PubMed2002

Computation and visualization of three-dimensional soft tissue motion in the orbit.

This work presents a method to measure the soft tissue motion in three dimensions in the orbit during gaze. It has been shown that two-dimensional (2-D) quantification of soft tissue motion in the orbit is effective in the study of orbital anatomy and motion disorders. However, soft tissue motion is a three-dimensional (3-D) phenomenon and part of the kinematics is lost in any 2-D measurement. Therefore, T1-weighted magnetic resonance (MR) imaging volume sequences are acquired during gaze and soft tissue motion is quantified using a generalization of the Lucas and Kanade optical flow algorithm to three dimensions. New techniques have been developed for visualizing the 3-D flow field as a series of color-texture mapped 2-D slices or as a combination of volume rendering for display of the anatomy and scintillation rendering for the display of the motion field. We have studied the performance of the algorithm on four-dimensional volume sequences of synthetic motion, simulated motion of a static object imaged by MR, an MR-imaged rotating object and MR-imaged motion in the human orbit during gaze. The accuracy of the analysis is sufficient to characterize motion in the orbit and scintillation rendering is an effective visualization technique for 3-D motion in the orbit.

Algorithms↗
PubMed2005

A voting-based computational framework for visual motion analysis and interpretation.

Most approaches for motion analysis and interpretation rely on restrictive parametric models and involve iterative methods which depend heavily on initial conditions and are subject to instability. Further difficulties are encountered in image regions where motion is not smooth-typically around motion boundaries. This work addresses the problem of visual motion analysis and interpretation by formulating it as an inference of motion layers from a noisy and possibly sparse point set in a 4D space. The core of the method is based on a layered 4D representation of data and a voting scheme for affinity propagation. The inherent problem caused by the ambiguity of 2D to 3D interpretation is usually handled by adding additional constraints, such as rigidity. However, enforcing such a global constraint has been problematic in the combined presence of noise and multiple independent motions. By decoupling the processes of matching, outlier rejection, segmentation, and interpretation, we extract accurate motion layers based on the smoothness of image motion, then locally enforce rigidity for each layer in order to infer its 3D structure and motion. The proposed framework is noniterative and consistently handles both smooth moving regions and motion discontinuities without using any prior knowledge of the motion model.

Algorithms↗
PubMed2005

Effect of motion on tracer activity determination in CT attenuation corrected PET images: a lung phantom study.

Respiratory motion is known to affect the quantitation of 18FDG uptake in lung lesions. The aim of the study was to investigate the magnitude of errors in tracer activity determination due to motion, and its dependence upon CT attenuation at different phases of the motion cycle. To estimate these errors we have compared maximum activity concentrations determined from PET/CT images of a lung phantom at rest and under simulated respiratory motion. The NEMA 2001 IEC body phantom, containing six hollow spheres with diameters 37, 28, 22, 17, 13, and 10 mm, was used in this study. To mimic lung tissue density, the phantom (excluding spheres) was filled with low density polystyrene beads and water. The phantom spheres were filled with 18FDG solution setting the target-to-background activity concentration ratio at 8:1. PET/CT data were acquired with the phantom at rest, and while it was undergoing periodic motion along the longitudinal axis of the scanner with a range of displacement being 2 cm, and a period of 5 s. The phantom at rest and in motion was scanned using manufacturer provided standard helical/clinical protocol, a helical CT scan followed by a PET emission scan. The moving phantom was also scanned using a 4D-CT protocol that provides volume image sets at different phases of the motion cycle. To estimate the effect of motion on quantitation of activities in six spheres, we have examined the activity concentration data for (a) the stationary phantom, (b) the phantom undergoing simulated respiratory motion, and (c) a moving phantom acquired with PET/4D-CT protocol in which attenuation correction was performed with CT images acquired at different phases of motion cycle. The data for the phantom at rest and in motion acquired with the standard helical/clinical protocol showed that the activity concentration in the spheres can be underestimated by as much as 75%, depending on the sphere diameter. We have also demonstrated that fluctuations in sphere's activity concentration from one PET/CT scan to another acquired with standard helical/clinical protocol can arise as a consequence of spatial mismatch between the sphere's location in PET emission and the CT data.

Algorithms↗
PubMed1986

Regional variation in the timing and extent of left ventricular wall motion in normal subjects.

Right anterior oblique cineangiograms from 19 subjects without evidence of heart disease were analysed to assess regional non-uniformity in the time of onset of systolic inward motion, amplitude of systolic motion, time of peak inward motion, and wall motion during the isovolumic relaxation period. The left ventricular silhouette was digitised frame by frame for a full cardiac cycle. These four wall motion variables were quantitatively measured along 40 chords drawn from equally spaced points on the end diastolic silhouette to the nearest point on the end systolic silhouette. Onset of systolic inward motion was significantly non-uniform, being delayed by up to 120 ms in the anterior apical chords compared with the areas of earliest inward motion near the base of the heart. More uniformity was noted in time of peak inward motion; the differences between regions were not statistically significant. Amplitude of systolic motion was significantly less at the apical and mid-anterior segments than elsewhere in the heart. Wall motion during the isovolumic relaxation period is outward and greatest in the mid-anterior segments, but inward in the proximal inferior segments and mitral valve region. These data suggest that contraction of muscle fibres in the anterior apical segments is initially isometric due to the considerable afterload at the onset of contraction, this afterload being the result of earlier contraction elsewhere in the ventricle. This may partly explain the propensity for aneurysms to be located in the anterior apical region. When the timing and extent of wall motion in disease states are analysed, account must be taken of the non-uniformity in the normal heart.

Adult↗
PubMed1997

Cross sectional echocardiographic demonstration of the mechanisms of abnormal interventricular septal motion in congenital total absence of the left pericardium.

OBJECTIVE: To investigate the influence of the absence of the pericardium on the left ventricular wall, particularly on interventricular septal motion, using M mode and cross sectional short axis echocardiography in patients with congenital total absence of the left pericardium. METHODS: 21 patients with, congenital total absence of the left pericardium were divided into three groups according to the interventricular septal motion; systolic type (n = 6) with paradoxical motion during systole, diastolic type (n = 11) with abnormal posterior motion during mid to late diastole, and mixed type (n = 4) with paradoxical motion during systole and abnormal posterior motion during diastole. RESULTS: On cross sectional short axis echocardiograms of the left ventricle, in the diastolic type the degree of angular displacement of the papillary muscles during end diastole to end systole showed excessive anticlockwise rotation about the long axis of the left ventricle without marked anteroposterior displacement. In the systolic type, there was shift of the left ventricle towards the anteromedial portion in systole and towards the posterolateral portion in diastole without significant rotation. There was a significantly positive correlation between the degree of angular displacement and the amplitude of diastolic interventricular septal motion during mid to late diastole in all patients. CONCLUSIONS: There was abnormal interventricular septal motion during systole and diastole in patients with total absence of the left pericardium. Abnormal systolic motion was induced by anteroposterior displacement of the left ventricle, and abnormal diastolic motion by left ventricular rotation about the long axis of the heart during the cardiac cycle. Analysis using cross sectional echocardiography was useful for elucidating the mechanisms of abnormal interventricular septal motion.

Adult↗
PubMed1975

Improvement in left ventricular wall motion following nitroglycerin.

Coronary artery disease patients frequently have left ventricular wall motion abnormalities. Though nitroglycerin is commonly used in ischemic heart disease, its effects on wall motion abnormalities is unknown. In this study we have evaluated the effects of nitroglycerin on wall motion abnormalities and on ejection fraction in 25 patients. Sixteen had coronary artery disease (greater than 70% luminal narrowing). Six had no evidence of heart disease and three had congestive cardiomyopathies with normal coronary arteries. Left ventricular angiography was performed prior to and six minutes after administration of 0.4 mg of sublingual nitroglycerin. Twelve of the 16 coronary artery disease patients had wall motion abnormalities, and in seven of these, segmental wall motion improved after nitroglycerin. In five, all motion did not change. The initial heart rate, left ventricular systolic and end-diastolic pressure, and left ventricular end-diastolic volumes were not different for those whose wall motion improved versus those whose did not. The increase in the former and fall in the latter three hemodynamic parameters were significant (P less than 0.01) and similar for the two groups. In those whose wall motion abnormalities improved after nitroglycerin, ejection fraction (mean plus or minus se) increased significantly (P less than 0.05), from 0.47 plus or minus 0.025 to 0.62 plus or minus 0.046. In those without improvement, the ejection fraction went from 0.55 plus or minus 0.056 to 0.58 plus or minus 0.051 (NS). Three patients with congestive cardiomyopathy showed no improvement in ventricular wall motion or ejection fraction after nitroglycerin. Left ventricular wall motion abnormalities and ejection fraction improved in some coronary artery disease patients following nitroglycerin. The mechanism for this is unknown; however, ventriculography before and after nitroglycerin may be of potential usefulness for identifying areas of reversible wall motion abnormalities.

Adult↗
PubMed1982

Two-dimensional echocardiographic analysis of segmental left ventricular wall motion before and after coronary artery bypass surgery.

Twenty patients with coronary artery disease were studied with two-dimensional echocardiography the day before saphenous vein bypass graft surgery. Serial studies were obtained 7.4 +/- 2.5 (+/- SD) and 43.4 +/- 13.1 days postoperatively to qualitatively assess the effect of bypass surgery on regional wall motion. Changes in segmental wall motion were assessed semiquantitatively by assigning a segmental wall motion score to each of nine echocardiographically defined segments. Preoperatively, 18% of the segments moved abnormally. The mean overall segmental wall motion score did not change significantly, as shown by comparing the postoperative studies with the preoperative study. However, there was a significant worsening in the septal motion (apical and basal) and a significant improvement in posterior wall motion (apical and basal) after bypass surgery. Anterior and lateral wall motion were not significantly changed. Nonseptal segments that were normal preoperatively usually remained normal; abnormal nonseptal segments usually improved or were unchanged by surgery. The motion of septal segments, however, generally worsened postoperatively whether they were normal or abnormal preoperatively. We conclude that segmental wall motion assessed by two-dimensional echocardiography may improve after revascularization surgery, but the interventricular septum shows impaired motion. This effect of coronary artery bypass on wall motion is better demonstrated relatively late after operation than early in the postoperative course, as has been done in some previous studies.

Aged↗
PubMed1984

A comparison of quantitative echocardiographic methods for delineating infarct-induced abnormal wall motion.

Current echocardiographic methods for quantitating abnormal regional left ventricular wall motion rely primarily on changes in endocardial excusion from end-diastole to end-systole. Recent studies demonstrating important spatial and temporal heterogeneity in wall motion within ischemic regions, however, raise questions about the validity of this approach. To determine the optimal method for defining abnormal left ventricular wall motion, we used a canine preparation of acute experimental infarction to examine four quantitative methods of wall motion analysis. The circumferential extent of abnormal wall motion assessed by each method was compared with the circumferential extent of infarction (defined by triphenyltetrazolium chloride staining) and the circumferential extent of reduced transmural blood flow (determined by radiolabeled microsphere techniques) 6 hr after acute coronary occlusion. The following methods of quantitating abnormal wall motion were examined: (1) determination of end-diastolic to end-systolic endocardial excursion (less than 0.20 end-diastolic radius), (2) determination of the extent of maximal dyskinesis (systolic bulging), and (3) and (4) two derived correlation methods that consider the entire course of systolic radial motion by correlating the observed echocardiographic field-by-field (every 16.7 msec) motion of each of 36 evenly spaced endocardial targets with the course of normal motion established from pooled normal data. Results obtained with the correlation methods showed a better correlation with the triphenyltetrazolium chloride-defined circumferential extent of infarction (r = .87 and r = .78) than did determinations of reduced end-diastolic to end-systolic endocardial excursion (r = .35) or the extent of maximal dyskinesis (r = .37). Similarly, the best correlation with the extent of reduced flow was obtained with one of the correlation methods (r = .80). We conclude that correlation methods that "integrate" endocardial motion over the entire systolic contraction sequence provide better definition of ischemic left ventricular dysfunction than do methods that consider motion at only single points in time.

Acute Disease↗
PubMed2002

Detection of relative and uniform motion.

We measured the lowest velocity (velocity threshold) for discriminating motion direction in relative and uniform motion stimuli, varying the contrast and the spatial frequency of the stimulus gratings. The results showed significant differences in the effects of contrast and spatial frequency on the threshold, as well as on the absolute threshold level between the two motion conditions, except when the contrast was 1% or lower. Little effect of spatial frequency was found for uniform motion, whereas a bandpass property with a peak at approximately 5 cycles per degree was found for relative motion. It was also found that contrast had little effect on uniform motion, whereas the threshold decreased with increases in contrast up to 85% for relative motion. These differences cannot be attributed to possible differences in eye movements between the relative and the uniform motion conditions, because the spatial-frequency characteristics differed in the two conditions even when the presentation duration was short enough to prevent eye movements. The differences also cannot be attributed to detecting positional changes, because the velocity threshold was not determined by the total distance of the stimulus movements. These results suggest that there are two different motion pathways: one that specializes in relative motion and one that specializes in uniform or global motion. A simulation showed that the difference in the response functions of the two possible pathways accounts for the differences in the spatial-frequency and contrast dependency of the velocity threshold.

Journal Article↗
PubMed1977

Reappraisal of jugular phlebogram in the diagnosis of tricuspid regurgitation. Relationship between echocardiographic interventricular septal motion and jugular phlebogram.

Little information is available concerning the relationship between the pattern of the jugular phlebogram and interventricular septal motion. We studied 250 patients with various conditons. Abnormal septal motion was observed in only 33% of the patients with tricuspid regurgitation. All the patients having abnormal septal motion and 66% of those having normal septal motion had the jugular pattern of tricuspid regurgitation. After cardiac operation with the incision of cardiac chambers and pericardiotomy, abnormal septal motion was seen from 40 to 89% at early postoperative period. Of the patients studied approximately 1 year after operation, there was reduced incidence of septal abnormality. Septal motion was normal in all the patients who had ligation of a patent ductus arteriosus and who underwent Blalock's operation. Of these, all having paradoxical motion which occurred in the mid-septum at least had the jugular pattern of tricuspid regurgitation. On the other hand, only 20 to 30% of the patients whose septal motion was normal had the jugular pattern of tricuspid regurgitation. Furthermore, all of the 3 patients with coronary artery disease having paradoxical motion of the entire septum had the jugular pattern of tricuspid regurgitation, as well. We conclude that the jugular pattern of tricuspid regurgitation and echocardiographic septal motion abnormality are related to each other and that tricuspid regurgitation should not be diagnosed by jugular phlebogram unless echocardiographic septal motion is examined.

Adolescent↗
PubMed1994

An improved technique for measuring in vivo intervertebral motion in the canine.

STUDY DESIGN: An experimental animal study using an established technique for measuring in vivo motion in canines was designed to improve measurement techniques and to eliminate the effects of the instrument mounting technique on the tissue and subsequently on the motion being measured. OBJECTIVES: The purpose of this study was to improve a technique for measuring in vivo intervertebral motion in canines, so that the measuring technique did not affect the motion being measured. SUMMARY OF BACKGROUND DATA: Biplanar radiography has been used to measure in vivo intervertebral motion, but involves radiation exposure and expensive equipment. Electromechanical devices have been used more recently but have had significant effects on the motion over extended time periods. METHODS: Intervertebral motion was measured using an instrumented spatial linkage in eight adult canines divided into two groups that differed regarding the method of "mounting pin" placement. Group I had open surgical placement of the pins and Group II had pins placed into the spinous processes. After pin implantation, the instrumented spatial linkage was attached and motion data were recorded during walking. This testing sequence was repeated 3 weeks later. Animals were killed and intervertebral and facet motion were calculated from the experimental data and compared statistically. RESULTS: Facet motion decreased 1 to 3 weeks after pin implantation for animals of group I (3.4 +/- 0.2 mm to 1.1 +/- 0.3 mm), whereas the facet excursion of animals in Group II showed no change (3.0 +/- 0.2 mm and 3.1 +/- 0.3 mm). CONCLUSIONS: A new method of measuring in vivo intervertebral motion in canines has been developed and shown to have no significant affect on the segment mechanics.

Animals↗
PubMed1993

[Usefulness of electrocardiogram gated 99mTc-methoxy isobutyl isonitrile (MIBI) single photon emission computed tomography for detection of wall motion abnormality of left ventricle].

We evaluated whether the newly developed perfusion imaging agent "99mTc-methoxy isobutyl isonitrile (MIBI)" has a possibility to detect wall motion abnormality of left ventricle. Electrocardiogram (ECG) gated single photon emission computed tomography (SPECT) was performed in 6 patients with myocardial infarction (anterior: 3 and inferior: 3). Apical and basal short axis images were selected from each patient and circumferential analysis was performed on end-diastolic (ED) and end-systolic (ES) images respectively. Count in end-diastole (EDC) and count in end-systole (ESC) were obtained, then % (ESC-EDC) and (ESC-EDC)/EDC were calculated. Wall motion of left ventricle was evaluated by either ultrasonic cardiogram or left ventriculography. Left ventricle was divided into anterior, septal, posterior and lateral areas and then each area was divided into apical and basal segments (finally the heart was divided into 8 segments). Of 48 segments, 33 segments showed normal wall motion and 15 segments showed abnormal wall motion: hypokinesis, akinesis and dyskinesis. % (ESC-EDC) was 74.39 +/- 16.85% in segment of normal wall motion and 33.27 +/- 23.56% in segment of abnormal wall motion (p < 0.001). (ESC-EDC)/EDC was 48.67 +/- 13.35% in segment of normal wall motion and 23.33 +/- 18.83% in segment of abnormal wall motion (p < 0.001). From these data, lower limit of % (ESC-EDC) and (ESC-EDC)/EDC in normal wall motion was defined as 40 and 22 respectively: mean -2SD of normal wall motion. Sensitivity of diagnosis of abnormal wall motion was 73% in % (ESC-EDC) and 60% in (ESC-EDC)/EDC (n.s.). Specificity was 94% and 97% (n.s.).(ABSTRACT TRUNCATED AT 250 WORDS)

Electrocardiography↗
PubMed1997

[Effects of repetitive myocardial ischemia on collateral circulation, ST deviation and epicardial wall motion].

The effects of repetitive myocardial ischemia on collateral circulation, ST deviation and epicardial wall motion were examined in 12 patients undergoing percutaneous transluminal coronary angioplasty (PTCA) for single left anterior descending artery disease. Rentrop collateral filling grade was assessed using contrast injection to the contralateral artery during the first and final episodes of coronary occlusion. ST deviation was measured by intracoronary electrocardiography. Epicardial wall motion (%pre PTCA) was measured by guide wire motion analysis according to the centerline method. Collateral filling grade was assessed 30 sec after balloon inflation. The ST segment and the epicardial wall motion were measured 60 sec after balloon inflation and deflation, respectively. There was no change in the collateral filling grade between the first and final episode of coronary occlusion. Patients with collateral filling grade I (R-I group, n = 4), II (R-II group, n = 3) and III (R-III group, n = 5) during coronary occlusion showed mean ST segment shifts of 13.2, 9.4, and 0.9 mm, respectively, and mean epicardial wall motion of 41.4%, 67.2%, and 78.5%, respectively. The collateral filling grade correlated with ST deviation and epicardial wall motion, and there was a significant correlation between epicardial wall motion and ST deviation (r = -0.67). Comparison of the R-I group or severe ischemia (n = 4) and the R-III group or slight ischemia (n = 4) during coronary occlusion for the fourth time showed the effect of preconditioning was obtained in R-I group. More R-III group patients than R-I group had hyperkinetic epicardial wall motion during coronary reperfusion. Stunned myocardium was demonstrated in both R-I group and R-III group patients. Epicardial wall motion was poorer in the R-I group than R-III group. We concluded the following: There is no change in the grade of collaterals during repetitive coronary occlusion, and there is a relationship between the grade of collateral and degree of myocardial protection; there is good correlation between ST segment and epicardial wall motion; ischemic preconditioning is obtained during repetitive severe myocardial ischemia; recovery from brief episodes of slight myocardial ischemia is associated with hyperkinesia of epicardial wall motion; the reduction of stunned myocardium is related to the degree of premyocardial ischemia; preconditioning is sufficient to cause myocardial stunning, but myocardial stunning is insufficient to cause preconditioning.

Aged↗
PubMed2003

Automated analysis of repetitive joint motion.

Automated measurement, analysis, and comparison of human motion during performance of workplace tasks or exercise therapy are core competencies required to realize many telemedicine applications. Ergonomic studies and telemonitoring of patients performing rehabilitation exercises are examples of applications that would benefit from a representation of complex human motion in a form amenable to comparison. We present a representation of joint motion suitable for the analysis of multidimensional angular joint motion time series data. Complex motion is reduced to a concatenation motion segments, where simple dynamic models approximate the observed motion on each segment. This compact representation still enables measurement of statistics familiar to ergonomics practitioners such as cycle length and task duration. An algorithm to obtain this representation from observed motion data (time series) is given. We introduce a metric, based on a kinetic energy-like measure, to compare motions. Experiments are presented to demonstrate the representation, its relationship to previous measures and the applicability of the kinetic energy metric for motion comparison.

Algorithms↗
PubMed2002

Importance of nonlinear and multivariable flexibility coefficients in the prediction of human cervical spine motion.

The flexibility matrix currently forms the basis for multibody dynamics models of cervical spine motion. While studies have aimed to determine cervical motion segment behavior, their accuracy and utility have been limited by both experimental and analytical assumptions. Flexibility terms have been primarily represented as constants despite the spine's nonlinear stiffening response. Also, nondiagonal terms, describing coupled motions, of the matrices are often omitted. Currently, no study validates the flexibility approach for predicting vertebral motions; nor have the effects of matrix approximations and simplifications been quantified. Therefore, the purpose of this study is to quantify flexibility relationships for cervical motion segments, examine the importance of nonlinear components of the flexibility matrix, and determine the extent to which multivariable relationships may alter motion prediction. To that end, using unembalmed human cervical spine motion segments, a full battery of flexibility tests were performed for a neutral orientation and also following an axial pretorque. Primary and coupled matrix components were described using linear and piecewise nonlinear incremental constants. A third matrix approach utilized multivariable incremental relationships. Measured motions were predicted using structural flexibility methods and evaluated using RMS error between predicted and measured responses. A full set of flexibility relationships describe primary and coupled motions for C3-C4 and C5-C6. A flexibility matrix using piecewise incremental responses offers improved predictions over one using linear methods (p<0.01). However, no significant improvement is obtained using nonlinear terms represented by a multivariable functional approach (p<0.2). Based on these findings, it is suggested that a multivariable approach for flexibility is more demanding experimentally and analytically while not offering improved motion prediction.

Aged↗
PubMed2002

Visually induced motion sickness predicted by postural instability.

We investigated whether postural instability can predict motion sickness and studied relations among instability, motion sickness, and vection. Nine men and 4 women (mean age = 19.85 years) were exposed, while standing, to an optical simulation of body sway. Head motion was recorded using a magnetic tracking system. Postural instabilities were observed prior to the onset of motion sickness. Vection was reported by most participants, including all who became ill. A discriminant analysis revealed that parameters of postural motion accurately predicted motion sickness. The results confirm that postural instability precedes motion sickness and suggest that measures of postural motion may serve as reliable predictors of motion sickness. Potential applications of this research include the development of on-line diagnostic tools that will allow for the prevention of motion sickness in operational and training settings.

Adolescent↗
PubMed2004

Multiple reference frames for motion in the primate cerebellum.

Knowledge of body motion through space is necessary for spatial orientation, self-motion perception, and postural control. Yet, sensory afferent signals may not directly provide such information to the brain. Because motion detected by the vestibular end organs is encoded in a head-fixed frame of reference, a coordinate transformation is thus required to encode body motion. In this study, we investigated whether cerebellar motion-sensitive neurons encode the translation of the body through space. We systematically changed both the direction of motion relative to the body and the static orientation of the head relative to the trunk. The activities of motion-sensitive neurons in the most medial of the deep cerebellar nuclei, the rostral fastigial nucleus, were compared with those in the brainstem vestibular nuclei. We found a distributed representation of reference frames for motion in the rostral fastigial nucleus, in contrast to cells in the vestibular nuclei, which primarily encoded motion in a head-fixed reference frame. This differential representation of motion-related information implies potential differences in the functional roles of these areas.

Acceleration↗
PubMed2002

Effect of frequency and direction of horizontal oscillation on motion sickness.

BACKGROUND: Low frequency horizontal oscillation can cause motion sickness in some transportation systems, but the influence of the frequency, magnitude, direction, and duration of oscillation are poorly understood. HYPOTHESIS: It was hypothesized that motion sickness was independent of the direction of horizontal oscillation (fore-and-aft or lateral) and that there was no difference in the motion sickness produced by different frequencies of horizontal oscillation (between 0.2 and 0.8 Hz) when subjects were exposed to the same peak velocity of motion at each frequency. METHOD: The 192 subjects were exposed within a closed cabin to sinusoidal oscillation with a velocity of +/- 0.50 ms(-1). Each subject experienced up to 30 min of motion while sitting with eyes open on a seat with a low backrest. The 16 conditions involved either fore-and-aft or lateral oscillation at 8 different frequencies: (i) 0.20 Hz, (ii) 0.25 Hz, (iii) 0.315 Hz, (iv) 0.40 Hz, (v) 0.50 Hz, (vi) 0.63 Hz, (vii) 0.80 Hz, or (viii) a stationary control condition. Subjects provided ratings of their motion sickness symptoms at 1-min intervals during the 30-min exposures. RESULTS: Each frequency of oscillation produced significantly more sickness than the static control conditions. Overall, there were no significant differences in the sickness produced by the seven different frequencies or between the sickness produced by fore-and-aft or lateral oscillation. Self-ratings of motion sickness susceptibility provided by subjects before participating in the experiment were positively correlated with their illness ratings during the experiment. CONCLUSIONS: With horizontal oscillation over the range 0.2 to 0.8 Hz, motion sickness is very approximately dependent on the peak velocity of oscillation. An acceleration frequency weighting having a gain inversely proportional to frequency would provide a convenient simple method of evaluating this type of motion in transport. However, the results suggest that a more complex weighting, reflecting decreased nauseogenicity at higher and lower frequencies would be more accurate. The direction of motion (i.e., fore-and-aft or lateral) had no effect on the sickness experienced.

Adolescent↗