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Background: Three-dimensional gait analysis is often used to assess kinematics and kinetics to discriminate gait patterns and examine change over time. Test-retest reliability is therefore imperative; however, many variations of gait models currently exist.Research Question: This study examined the test-retest reliability of, and agreement between, two commonly used methods of gait modelling, a modified Conventional Gait Model and cluster-based model, using both six degrees-of-freedom or inverse kinematics computational methods in Visual3D.Methods: Thirty healthy participants attended two identical sessions. The data for both models were collected concurrently and analysed in Visual3D using either six degrees-of-freedom or inverse kinematics computational methods. Outcomes were taken as the peak measurements for kinematics (joint angles and angular velocity) and kinetics (joint moments and power) for the hip, knee and ankle. Intraclass correlation coefficients were used to examine reliability, with the standard error of measurement and minimal detectable change also calculated. Agreement between models was examined with Pearson correlations and intraclass correlation coefficients.Results: Test-retest reliability was good to excellent for all models for lower limb kinematics and kinetics. The inverse kinematic models had slightly lower reliability across outcomes compared to the six degrees-of-freedom models. Agreement between the Conventional Gait Model and cluster model was mostly good to excellent. Comparison of the two modified CGMs (with six degrees-of-freedom and inverse kinematics) showed much higher agreement against the comparison of the two cluster-based models (with six degrees-of-freedom and inverse kinematics).Significance: This study provides a comprehensive assessment of the test-retest reliability and agreement between two gait models with various computational methods. Future research may use these results to guide their decision making for the gait model and outcomes of interest to be used. [ABSTRACT FROM AUTHOR]

Background and purpose To perform a quantitative analysis of the accuracy and precision of Kilovoltage Intrafraction Monitoring (KIM) six degree-of-freedom (6DoF) prostate motion measurements during treatments. Material and methods Real-time 6DoF prostate motion was acquired using KIM for 14 prostate cancer patients (377 fractions). KIM outputs the 6DoF prostate motion, combining 3D translation and 3D rotational motion information relative to its planning position. The corresponding groundtruth target motion was obtained post-treatment based on kV/MV triangulation. The accuracy and precision of the 6DoF KIM motion estimates were calculated as the mean and standard deviation differences compared with the ground-truth. Results The accuracy ± precision of real-time 6DoF KIM−measured prostate motion were 0.2 ± 1.3° for rotations and 0.1 ± 0.5 mm for translations, respectively. The magnitude of KIM-measured motion was well-correlated with the magnitude of ground-truth motion resulting in Pearson correlation coefficients of  ≥0.88 in all DoF. Conclusions The results demonstrate that KIM is capable of providing the real-time 6DoF prostate target motion during patient treatments with an accuracy ± precision of within 0.2 ± 1.3° and 0.1 ± 0.5 mm for rotation and translation, respectively. As KIM only requires a single X-ray imager, which is available on most modern cancer radiotherapy devices, there is potential for widespread adoption of this technology. [ABSTRACT FROM AUTHOR]

Abstract: Purpose: To establish a streamlined end‐to‐end test of a 6 degrees‐of‐freedom (6DoF) robotic table using a 3D printed phantom for periodic quality assurance. Methods: A 3D printed phantom was fabricated with translational and rotational offsets and an imbedded central ball‐bearing (BB). The phantom underwent each step of the radiation therapy process: CT simulation in a straight orientation, plan generation using the treatment planning software, setup to offset marks at the linac, registration and corrected 6DoF table adjustments via hidden target test, delivery of a Winston‐Lutz test to the BB, and verification of table positioning via field and laser lights. The registration values, maximum total displacement of the combined Winston‐Lutz fields, and a pass or fail criterion of the laser and field lights were recorded. The quality assurance process for each of the three linacs were performed for the first 30 days. Results: Within a 95% confidence interval, the overall uncertainty values for both translation and rotation were below 1.0 mm and 0.5° for each linac respectively. When combining the registration values and other uncertainties for all three linacs, the average deviations were within 2.0 mm and 1.0° of the designed translation and rotation offsets of the 3D print respectively. For all three linacs, the maximum total deviation for the Winston‐Lutz test did not exceed 1.0 mm. Laser and light field verification was within tolerance every day for all three linacs given the latest guidance documentation for table repositioning. Conclusion: The 3D printer is capable of accurately fabricating a quality assurance phantom for 6DoF positioning verification. The end‐to‐end workflow allows for a more efficient test of the 6DoF mechanics while including other important tests needed for routine quality assurance. [ABSTRACT FROM AUTHOR]

We report on the development of an all-interferometric optomechatronic sensor for the detection of multi-degrees-of-freedom displacements of a remote target. The prototype system exploits the self-mixing technique and consists only of a laser head, equipped with six laser sources, and a suitably designed reflective target. The feasibility of the system was validated experimentally for both single or multi-degrees-of-freedom measurements, thus demonstrating a simple and inexpensive alternative to costly and bulky existing systems.

Abstract: In this paper a design is presented for a precision MEMS-based six degrees-of-freedom (DOFs) manipulator. The purpose of the manipulator is to position a small sample (10μm×20μm×0.2μm) in a transmission electron microscope. A parallel kinematic mechanism with slanted leaf-springs is used to convert the motion of six in-plane electrostatic comb-drives into six DOFs at the end-effector. The manipulator design is based on the principles of exact constraint design, resulting in a high actuation compliance (flexibility) combined with a relatively high suspension stiffness. However, due to fabrication limitations overconstrained design has been applied to increase the stiffness in the out-of-plane direction. The result is a relatively large manipulator stroke of 20μm in all directions combined with a high first vibration mode frequency of 3.8kHz in relation to the used area of 4.9mm×5.2mm. The motion of the manipulator is guided by elastic elements to avoid backlash, friction, hysteresis and wear, resulting in nanometer resolution position control. The fabrication of the slanted leaf-springs is based on the deposition of silicon nitride (Si x N y ) on a silicon pyramid, which in turn is obtained by selective crystal plane etching by potassium hydroxide (KOH). The design has been analyzed and optimized with a multibody program using flexible beam theory. A previously developed flexible beam element has been used for modeling the typical relatively large deflections and the resulting position-dependent behavior of compliant mechanisms in MEMS. The multibody modeling has been verified by FEM modeling. Presently only parts of the manipulator have been fabricated. Therefore, a scaled-up version of the manipulator has been fabricated to obtain experimental data and to verify the design and modeling. [Copyright &y& Elsevier]

We report on the development of an all-interferometric optomechatronic sensor for the detection of multi-degrees-of-freedom displacements of a remote target. The prototype system exploits the self-mixing technique and consists only of a laser head, equipped with six laser sources, and a suitably designed reflective target. The feasibility of the system was validated experimentally for both single or multi-degrees-of-freedom measurements, thus demonstrating a simple and inexpensive alternative to costly and bulky existing systems. [ABSTRACT FROM AUTHOR]

This paper presents a new magnetic levitation system, MagTable, which provides six-degrees-of-freedom (6-DOF) and completely contactless operation of a magnetized object. The MagTable consists of a planar array of square coils and a permanent magnet type carrier. The maximum levitation height of the carrier is 30mm within a 400mm × 200mm horizontal translation range. The novelty of this research lies in the fully untethered manipulation of levitated carriers in such a large area, and in the fast and accurate computation of wrench matrix using the magnetic nodes method and the Lorentz force law. In this paper, the design method is firstly provided. Then, the optimization of the carrier's magnet topology, based on better controllability and minimum power consumption, is documented. Experimental results of the 5-DOF motion control of two single-permanent-magnet carriers and the 6-DOF motion control of a three-permanent-magnets carrier are presented. The results demonstrate the performance of the MagTable in 100mm × 40mm horizontal translation range with maximum levitation height of 20mm. The rotation range are ±6° in both roll and pitch, and ±12° yaw motion about the vertical axis. The proposed system has potential applications in fast and high precision manipulation tasks. [ABSTRACT FROM AUTHOR]