Fast Structure from Motion for Planar Image Sequences

Dense three-dimensional reconstruction of a scene from images is a challenging task. Usually, it is achieved by finding correspondences in successive images and computing the distance by means of epipolar geometry. In this paper, we propose a variational framework to solve the depth from motion problem for planar image sequences. We derive camera ego-motion estimation equations and we show how to combine the depth map and ego-motion estimation in a single algorithm. We successfully test our method on synthetic image sequences for general camera translation. Our method is highly parallelizable and thus well adapted for real-time implementation on the GPU

Tracking and Structure from Motion

Dense three-dimensional reconstruction of a scene from images is a very challenging task. In the structure from motion approach one of the key points is to compute depth maps which contain the distance of objects in the scene to a moving camera. Usually, this is achieved by finding correspondences in successive images and computing the distance by means of epipolar geometry. In this Master's thesis, a variational framework to solve the depth from motion problem for planar image sequences is proposed. Camera ego-motion estimation equations are derived and combined with the depth from motion estimation in a single algorithm. The method is successfully tested on synthetic images for general camera translation. Since it does not depend on the correspondance problem and because it is highly parallelizable, it is well adapted for real-time implementation. Further work in this thesis include a review of general variational methods in image processing, and in particular TV-L1 optical flow as well as its real-time implementation on the graphics processing unit

Magnetic Resonance Imaging for the in Vivo Evaluation of Gastric-Retentive Tablets

Purpose. To develop a magnetic resonance imaging (MRI) technique for assessing in vivo properties of orally ingested gastric-retentive tablets under physiologic conditions. Methods. Tablets with different floating characteristics (tablet A-C) were marked with superparamagnetic Fe3O4 particles to analyze intragastric tablet position and residence time in human volunteers. Optimal Fe3O4 concentration was determined in vitro. Intragastric release characteristic of one slow-release tablet (tablet D) was analyzed by embedding gadolinium chelates (Gd-DOTA) as a drug model into the tablet. All volunteers underwent MRI in the sitting position. Tablet performance was analyzed in terms of relative position of tablet to intragastric meal level (with 100% at meal surface), intragastric residence time (min) and Gd-DOTA distribution volume (% of meal volume). Results. Intragastric tablet floating performance and residence time of tablets (tablet A-D) as well as the intragastric Gd-DOTA distribution of tablet D could be monitored using MRI. Tablet floating performance was different between the tablets (A, 93%(95 − 9%); B, 80%(80 − 68%); C, 38%(63 − 32%); p < 0.05). The intragastric distribution volume of Gd-DOTA was 19.9% proximally and 35.5% distally. Conclusions. The use of MRI allows the assessment of galenic properties of orally ingested tablets in humans in seated positio

Safety and tolerability of sirolimus treatment in patients with autosomal dominant polycystic kidney disease

Background. We initiated a randomized controlled clinical trial to assess the effect of sirolimus on disease progression in patients affected by autosomal dominant polycystic kidney disease (ADPKD). Here we report the preliminary safety results of the first 6 months of treatment. Method. A total of 25 patients were randomized to sirolimus 2 mg/day and 25 patients to no treatment except standard care. Treatment adherence was monitored electronically. At baseline and at Month 6, laboratory parameters were analysed and the urinary protein profile in 24-h urine collections was determined. Results. Both treatment groups were well balanced for age, sex and renal function. In 94.1 ± 11.4% of the study days, patients in the sirolimus group were exposed to the drug when assuming a therapeutic efficacy duration of 30 h. At Month 6, the mean sirolimus dose and trough level were 1.28 ± 0.71 mg/day and 3.8 ± 1.9 μg/l, respectively. Glomerular (albumin, transferrin, IgG) and tubular (retinol-binding protein, α1-microglobulin) protein excretion remained unchanged. Glomerular filtration rate also did not change significantly. Haematological parameters were similar in both groups, except for a mild reduction of the mean corpuscular volume of erythrocytes in patients receiving sirolimus. Lipid levels were similar in both groups. Adverse events were transient and mild, and no grade 3 or 4 events occurred. The incidence of infections was similar in the sirolimus group (80%) and the standard group (88%). The most common gastrointestinal adverse events were mucositis (72% in the sirolimus group versus 16% in the standard group, P = 0.0001) and diarrhoea (36% in the sirolimus versus 20% in the standard group, P = 0.345). Conclusion. Treatment of ADPKD patients with sirolimus with a dose of 1-2 mg/day is safe and does not cause proteinuria or impairment of GFR. Treatment adherence was excellent. (ClinicalTrials.gov number, NCT00346918.

Determining Objective Parameters to Assess Gait Quality in Franches-Montagnes Horses for Ground Coverage and Over-Tracking - Part 2: At Trot

In gait quality assessments of horses, stride length (SL) is visually associated with spectacular movements of the front limbs, and described as ground coverage, while the movement of the hind limb under the body is supposedly essential to a longer over-tracking distance (OTD). To identify movement patterns with strong associations to SL and OTD, limb and body kinematics of 24 Franches-Montagnes (FM) stallions were measured with 3D optical motion capture (OMC) on a treadmill during an incremental speed test at trot (3.3–6.5 m/s). These measurements were correlated to the scores of ground coverage and over-tracking from six breeding experts. The amount of explained variance of parameters on SL and OTD were estimated using linear mixed-effect models in two models: a full model with all parameters measurable with OMC, and a reduced model with a subset of parameters measurable with inertial measurement units (IMUs). The front limb stance duration (16%) and OTD (7%) measured with OMC, or the OMC parameters front limb stance duration (24%) and suspension duration (14%) measurable with IMUs explained most variance in SL. However, four of six breeding experts were also significantly correlated (r>|0.41|) to front limb protraction angle. OTD variance was explained with OMC parameters suspension duration (10%) and hind limb contralateral pro-retraction angles (9%) or IMU-measurable parameters suspension duration (20%) and maximal pelvis pitch (5%). Four experts’ scores for over-tracking were correlated to suspension duration. These results underscore the need for precise definitions of gait quality traits

An investigation into the association of the physical fitness of equestrians and their riding performance : a cross-sectional study

Poor riding performance may be due to medical issues with the horse or a variety of other factors, such as inadequate equipment or deficiencies in training. The physical fitness of the equestrian is one of the most unexplained factors of current research. The aim of this study is to investigate the association between the physical fitness of the equestrian and riding performance. 115 equestrians were assessed for physical fitness and riding performance. Seven components of physical fitness (balance, endurance, flexibility, reaction, speed, strength, symmetry) were measured by a physiotherapist using equestrian-specific tests. Based on a video-recorded riding test, individual riding performance was rated by two equestrian judges. The riding test included the horse and rider performing a walk, sitting trot, rising trot and canter in both directions. A linear model for riding performance, including the domains of physical fitness and potential confounders (body-mass-index, riding experience, hours of riding per week, and test-motivation), was fitted to the data. Inter-rater reliability of the judges was investigated by calculating the intraclass correlation coefficient (ICC). Endurance, reaction and strength were positively associated with riding performance, whereas flexibility had a negative association. The final model could explain 16.7% of the variance in riding performance. The effects of endurance and strength were significant (P<0.05), but not that of reaction. No association with riding performance was found for the components of balance, speed and symmetry. The inter-rater reliability of judges was confirmed to be ‘good’ to ‘excellent’ (ICC=0.9, 95% confidence interval: 0.86-0.93). Findings suggest that physical fitness is positively associated with riding performance. Fitness-training for equestrians should be included in current training concepts. Future research should investigate whether similar associations exist for junior and elite athletes

Modelling fore- and hindlimb peak vertical force differences in trotting horses using upper body kinematic asymmetry variables

Differences in peak vertical ground reaction forces (dFzpeak) between contralateral forelimbs and hindlimbs are considered the gold standard for quantifying weight-bearing lameness. However, measuring kinematics for the same purpose is more common and practical. Vertical movement asymmetries (VMA) of the horse's upper body have previously been correlated to fore- and hindlimb lameness. But the combined response of head, withers and pelvis VMA to fore- and hindlimb dFzpeak has not yet been thoroughly investigated. Deriving the kinetic responses from kinematics would help the interpretation and understanding of quantified weight-bearing lameness. In this retrospective study, 103 horses with a wide range of fore- and hindlimb dFzpeak had been trotted on a force-measuring treadmill synchronized with an optical motion capture system. VMA of the head, withers and pelvis as well as dFzpeak were extracted. Multiple linear mixed models and linear regressions of kinematic variables were used to model the dFzpeak. It was hypothesised that all included VMA would have a significant influence on the dFzpeak outcome variables. The results showed a complex relationship between VMA and dFzpeak where both amplitude and timing of the VMA were of importance. On average, the contribution percentage of VMA to fore/hind dFzpeak were 66/34% for head, 76/24% for withers and 33/67% for pelvis. The linear regressions for the fore/hindlimb models achieved mean measurement root mean squared errors of 0.83%/0.82% dFzpeak. These results might help determine the clinical relevance of upper body VMA and distinguish between primary fore, hind, ipsilateral and diagonal weight-bearing lameness

Effects of posture on the physiology of gastric emptying: a magnetic resonance imaging study

The stomach maintains the rate of gastric emptying despite radical changes in body position and intragastric distribution of gastric contents. In SP, hydrostatic pressure (modulated by gastric tone) dictates the gastric emptying. In UDP, gastric emptying also appears to be mediated by continuous adaptation of gastric tone. These findings provide support for the hypothesis that the mechanism of gastric emptying resembles a "pressure pump" rather than a "peristaltic pump"

Magnetic resonance imaging for the in vivo evaluation of gastric-retentive tablets

The use of MRI allows the assessment of galenic properties of orally ingested tablets in humans in seated position