Longitudinal Translation Research Articles

SU-FF-J-65: Intrinsic Accuracy of I-Beam's Coordinate Positioning System Technology

Purpose: I-Beam, a 3D-ultrasound guided prostate localization system, uses Coordinate Positioning System (CPS) Technology in registering live ultrasound images of the patient to the treatment machine coordinate system. The goal of this study is to verify the accuracy of I-Beam's camera system and its precision in localizing the US images to the isocenter. Method and Materials: The first part of the study was to examine the I-Beam camera system for integrity in tracking the probe position while translating the US probe in 3D-space. We then examined alignment correctness when registering the captured US images and contours. A robotic arm of the Nomos BAT system was used for accurate translations. Both the arm and camera system were fixed to the treatment couch. Longitudinal translations of the camera system were confirmed by the Nomos Auto-crane. An ultrasound phantom mimicking pelvic anatomy was employed in quantifying the precision of the image localization and contour alignment. The phantom was translated to known distances, recapturing the 3D-ultrasound volume, and aligned the contours to determine the shifts computed by the I-Beam system. Results: X-, Y- and Z- translations recorded by the robotic system were subtracted from the coordinates of the camera system in computing the errors. When the camera system was repositioned within ±10 cm of the 3D-space, the CPS technology predicted the ultrasound probe position within ±0.5 mm. The absolute deviations were (mean ± SD): 0.3±0.2, 0.2±0.2 and 0.2±0.2 in lateral, longitudinal and vertical directions, respectively. I-Beam's image registration and contour alignment were accurate within ±1mm. Conclusion: The I-Beam camera system is accurate to within ± 0.5mm in tracking the US probe position. Phantom measurement showed the US image acquisition and the contour alignment is also accurate within ±1mm. These new tests assured that the I-Beam system is accurate in tracking, image-registration and alignment.

A cam-displacement transducer device for measuring small two-degree of freedom inter-component motion in a prosthesis

An electromechanical system is described that comprises a cam and two linear displacement transducers for measuring two-degree of freedom. This is aimed at quantifying the extent and pattern of both transverse rotation and longitudinal translation that takes place during amputee gait at what is sometimes termed a “torque-shock absorbing adapter” located between the prosthetic socket and foot. Both types of motion are measured independently by mounting the cam around the adapter and the two transducers orthogonal to one another with their spring loaded plungers moving separately against the cam’s perimeter and distal, flat face. The cam geometry should be an arc of a spiral and not a circle for the angular displacement measurement to be linear in response to rotation. Over a range of ±18° for transverse rotation the maximum deviation of the ideal cam geometry away from an arc of a circle is less than ±0.5% of the transducers’ 10 mm stroke. The transducer’s linearity is ±2% and it could therefore be assumed that this would be the dominant source of error. The theoretical predictions are supported by the calibration results, in which the pattern of errors that are found in the transducers’ calibration can also be seen in the calibration of the cam.

Simulation of minimally invasive vascular interventions for training purposes

Objective: To master the skills required to perform minimally invasive vascular interventions, proper training is essential. A computer simulation environment has been developed to provide such training. The simulation is based on an algorithm specifically developed to simulate the motion of a guide wire—the main instrument used during these interventions—in the human vasculature. In this paper, the design and model of the computer simulation environment is described and first results obtained with phantom and patient data are presented.Materials and methods: To simulate minimally invasive vascular interventions, a discrete representation of a guide wire is used which allows modeling of guide wires with different physical properties. An algorithm for simulating the propagation of a guide wire within a vascular system, on the basis of the principle of minimization of energy, has been developed. Both longitudinal translation and rotation are incorporated as possibilities for manipulating the guide wire. The simulation is based on quasi-static mechanics. Two types of energy are introduced: internal energy related to the bending of the guide wire, and external energy resulting from the elastic deformation of the vessel wall.Results: A series of experiments were performed on phantom and patient data. Simulation results are qualitatively compared with 3D rotational angiography data.Conclusions: The results indicate plausible behavior of the simulation.

Cine MRI assessment of aortic aneurysm dynamics before and after endovascular repair.

To evaluate stent-graft and aneurysm wall motions during the cardiac cycle using cine magnetic resonance imaging (MRI) to identify mechanisms of long-term failure of endovascular aneurysm repair (EVAR). Prior to and after EVAR in 7 patients with abdominal aortic aneurysms (AAA), 12 MRI images per cardiac cycle were acquired in transverse, sagittal, and coronal planes of the aneurysm. Two independent observers blinded to the aim of the study manually traced stent-graft and aneurysm wall contours. Translation was defined as the maximal displacement of the contours in the peak-systolic image compared to the end-diastolic image. Aneurysm wall motions before and after repair were compared. Stent-graft and aneurysm configuration changes during the cardiac cycle were evaluated. The relation between translation and the degree of angulation of the stent-graft was calculated. The anteroposterior translation of the aneurysm decreased from a median 1.05 mm (range <0.5-1.29) before EVAR to within pixel size (<0.5 mm) after EVAR (p=0.04). The cranial-caudal translation of the aneurysm increased from a median 1.01 mm (range <0.5-1.51) before to 1.69 mm (range 1.1-1.99) after EVAR (p=0.02). In 4 stent-grafts, bending during cardiac systole was observed at the site of maximal angulation of the device. In transverse sections, 2-dimensional pulsatile wall motion of the aneurysm was 0.25 cm(2) (range 0.07-0.29) before and 0.17 cm(2) (range 0.07-0.42) after EVAR (p=0.79). No pulsatility of the stent-graft itself was observed. The correlation coefficient between angulation of the stent-graft and the increase in cranial-caudal translation after EVAR was 0.67 (p>0.05). After EVAR, increased longitudinal translation of both the aneurysm and stent-graft was observed, indicating downward pulling forces at the proximal fixation site. Secondly, increased bending was seen at the site of maximal angulation, which implies a risk of metal fatigue and fabric damage at sites of stent-graft angulation.

Multilayer storage in a shift-multiplexed holographic disk

Multilayer storage in a shift-multiplexed holo- graphic disk is proposed. We consider the longitudinal shift- ing selectivity of the reference beam as another degree of freedom available for multilayer multiplexing storage. A novel optical readout head comprising a fiber array is designed to replace the longitudinal translation stage. © 2003 Society of

Waveguide fabrication in phosphate glasses using femtosecond laser pulses

We report on the response of glass to focused femtosecond (fs) laser pulses during waveguide fabrication in a commercial sodium aluminum phosphate glass (Schott IOG-1). Single-pass longitudinal translation of IOG-1 glass with respect to the focused laser beam at a rate of 20 μm/s and pulse energies of 3.5 μJ results in the formation of two waveguides located on opposite sides of the laser-exposed region, which itself does not guide light. This behavior is different from that of the more widely studied silica glass system. The precise location of the waveguides in IOG-1 glass depends on the relative tilt of the fs laser beam with respect to the sample translation direction. Fluorescence imaging of the modified glass using a confocal microscope setup reveals the formation of color center defects in the exposed region but not within the waveguides.

Transverse rotation and longitudinal translation during prosthetic gait--a literature review.

Improved technology allows for more accurate gait analysis to increase awareness of nonoptimized prosthetic gait patterns and for the manufacture of sophisticated prosthetic components to improve nonoptimized gait patterns. However, prescriptions are often based on intuition rather than rigorous research findings for evidence-based practice. The number of studies found in the literature that are based on prosthetic research regarding transverse rotation and longitudinal translation is small when compared to topics regarding other types of movements. Some design criteria for prosthetic components described in those studies that permit transverse rotation and longitudinal translation can be found in current designs. However, little research has been conducted to establish their effectiveness on the gait parameters and residual limb. This literature review is an investigation into these motions between the socket and the prosthetic foot, with particular reference to gait characteristics and prosthetic design criteria.

Modeling and Simulation of a PC-Based Driving Simulator

This paper describes the simulation and control of a PC-based driving simulator that is constructed by five hydraulic cylinders and can perform five degree-of-freedom(DOF) motions. The mathematical equations of vehicle dynamics are derived from the 2-DOF bicycle model and incorporated with the tire, steering and suspension sub-systems. These equations of motion are then programmed by MATLAB, transferred into C++ code in MIDEVA environment, and further developed into motion platform control program by C++ Builder. In addition, virtual reality environment is projected onto a 72 screen to present the street scene and simulate the sixth DOF motion of a vehicle, and can be employed either in off-line analysis and simulations or on-line simulations. In the future, a road surface model and other more complicated vehicle dynamics models will be incorporated, and a pressure vest will be installed to stimulate the driver to feel the longitudinal translation.

Molecular Behaviors of n-Fatty Acids in Liquid State.

Through near infrared spectroscopy and 13C-NMR spin-lattice relaxation time measurements it was revealed that the molecules of the normal fatty acids in the liquid state are strongly dimerized even at 363K by hydrogen bonding between their carboxylic groups. Thus, dimer molecules for the acids are the units in their intra- and intermolecular movements. The dynamic molecular and aggregate structures of the fatty acids (C8-C18) in the liquid state were estimated through the analyses of their self-diffusion coefficient D, viscosity η, molar volume and X-ray diffraction. The apparent hydrodynamic radius evaluated from D and η for the fatty acid was almost constant, irrespective of the hydrocarbon chain length. This suggests that only a longitudinal translation (translational movement along molecular axes) would be allowed for the dimer molecules of fatty acids. In addition, the distribution function curves obtained from the X-ray diffraction data suggest that, in the pure liquid state, rod-like fatty acid dimers highly aggregate in parallel and probably make clusters that would be randomly aligned.

WAVEGUIDES COUPLED THROUGH A SEMITRANSPARENT BARRIER: A BIRMAN–SCHWINGER ANALYSIS

The paper is devoted to a model of a mesoscopic system consisting of a pair of parallel planar waveguides separated by an infinitely thin semitransparent boundary modeled by a transverse δ interaction. We develop the Birman–Schwinger theory for the corresponding generalized Schrödinger operator. The spectral properties become nontrivial if the barrier coupling is not invariant with respect to longitudinal translations, in particular, there are bound states if the barrier is locally more transparent in the mean and the coupling parameter reaches the same asymptotic value in both directions along the guide axis. We derive the weak-coupling expansion of the ground-state eigenvalue for the cases when the perturbation is small in the supremum and the L 1-norms. The last named result applies to the situation when the support of the leaky part shrinks: the obtained asymptotics differs from that of a double guide divided by a pierced Dirichlet barrier. We also derive an upper bound on the number of bound states.

Adaptive gait planning for multi-legged robots with an adjustment of center-of-gravity

Adaptive gait planning is an important aspect in the development of control systems for multi-legged robots traversing on rough terrain. The problem of adaptive gait generation can be viewed as one of finding a sequence of suitable foothold on rough terrain so that legged systems maintain static stability and motion continuity. Due to the limit of static stability, deadlock situation may occur in the process of searching for a suitable foothold, if terrain contains a large number of forbidden zones. In this paper, an improved method for adaptive gait planning is presented by active compensation of stability margin, through center of gravity (CG) adjustment in the longitudinal axis and/or body translation in the lateral direction. An algorithm for the proposed method is developed and embedded in a computer program. Simulation results show that the method provides legged machines with a much larger terrain adaptivity and better deadlock-avoidance ability.

The nonlinear viscoelastic cosserat model for the wave propagation with generation of subharmonics

A Cosserat model is developed in nonlinear form to describe the appearance of lower frequencies in seismic waves spectra. As in the Ericksen theory of liquid crystals, elastic and viscous rheological elements are combined to get sensible results. The translational degrees of freedom are described by linear elasticity but the rotational kinematically independent motion is governed by the nonlinear elastic potential and linear viscosity. The dynamics of linear perturbations show that the longitudinal translations and rotations both decouple completely from other motions. These rotations represent local oscillations due to the existence of the potential and they do not propagate. However, the linear transverse translations and microrotations are coupled. It is shown that they describe seismic and acoustic waves. In the nonlinear case these motions demonstrate some new interesting phenomena. For instance, if the propagation of the harmonic elastic wave is considered the microrotations behave like nonlinear oscillators excited by the external harmonic force. Thus the system produces the same effects as those obtained recently for the Duffing type equation with the help of the theory of attractors. This means that the initial harmonic wave generates secondary waves with lower frequencies. These secondary frequencies are usually commensurable with the initial ones. Numerical results show that the phenomenon still takes place if the initial wave consists of continuously distributed harmonics. The generation of lower frequencies in granular media has been observed and reported but the theoretical explanation was lacking since it was thought conventionally that weak nonlinearities were able to produce higher frequencies only.

Measurement of current density distribution in high T/sub c/ Ag-sheathed superconducting tapes

Flux history and local inhomogeneities in j/sub c/ govern the current distribution in measured Ag-sheathed TlBaCaCuO-2212 and Bi(Pb)SrCaCuO-2223 tapes. The sausage effect and local grain density and coupling fluctuations result in inhomogeneity in j/sub c/ distribution. This is reflected in violation of axial symmetry across the tape as well as longitudinal translation symmetry along the tape. Hall probe mapping of self field component with or without presence of external field was used to achieve the data for inverse calculation of current distribution and its dynamics in response to time variation of flux. To reveal the asymmetry in j/sub c/ distribution across the tape width the method of gradient field scanning/reversing was applied.

Digital distal lower limb angiography: comparison of selective iliac injection with vasodilators and bolus chasing technique

From October 1992 to May 1993 we carried out a prospective study on 30 patients, mean age 70 years, suffering from lower limb ischaemia (mild,n = 12; moderate,n = 9; severe,n = 9). Four masked investigators compared the outcome of two techniques for the preoperative evaluation of distal vessels of the lower limbs. The reference technique was digital subtraction angiography (DSA) with selective iliac injection, fixed centring on one ankle, and use so vasodilators. The new method was DSA with the so-called bolus chasing technique: after an injection above the aortic bifurcation, an acquisition during a continuous longitudinal translation movement allows all the arteries of the lower limbs to be visualised down to the most distal point. Both techniques are well tolerated and we found no significant difference in the number of distal arteries seen with the two methods. To assess the permeability of the distal lower limb network, the bolus tracking technique is as informative as an iliac selective injection, without its constraints. Consequently, we will routinely use it as the technique of choice.

On some representations of solutions of dynamical problems in elasticity theory

The divergence and rotation of a translation vector field, which are solutions of wave equations, are used as auxiliary potentials for numerical solution of dynamical problems in elasticity theory. In a particular case, the problems of longitudinal translation are tested in two variants of numerical algorithms with their programming realization, some suggestions are given regarding the choice of the optimal algorithm for achieving highly precise calculations with a small number of discretization points.

Validation of tagging with MR imaging to estimate material deformation.

Myocardial tagging with magnetic resonance imaging is useful for non-invasive estimation of in vivo heart wall deformation. To validate the method of strain estimation and quantify the error of deformation estimates, a deformable silicone gel phantom in the shape of a cylindrical anulus was built and imaged. Four observers digitized the displacement of magnetic tags in two deformation modes: axial shear, caused by a 45 degrees rotation of the inner cylinder, and azimuthal shear, caused by a 13.5-mm longitudinal translation of the inner cylinder. In axial shear, good agreement was found between the angular displacement of stripes painted on the gel and an analytic solution. Displacement of magnetic tags also agreed with that solution. Interobserver and observer-model errors in deformation estimates were quantified for homogeneous and nonhomogeneous strain analysis. In homogeneous strain analysis, errors in point localization produced relatively large errors, which were reduced in nonhomogeneous strain analysis. Both estimates were unbiased across the range of deformations.

Surfactants and cosurfactants in lamellar liquid crystals and adsorbed on solid surfaces: I. The model system sodium dodecyl sulfate/butanol or sodium dodecyl sulfate/benzyl alcohol and α-alumina

Phase diagrams of the model systems sodium dodecyl sulfate (SDS)/1-butanol/water and SDS/benzyl alcohol/water have been determined. In both model systems we have found a lamellar lyotropic liquid crystalline phase D with regular molecular packing of the surfactant/cosurfactant. The model systems have also been used for adsorption studies on solid A1 2O 3 in 0.3 M NaCl. At the adsorption plateau SDS is found to cover an area of 0.40 nm 2, 1-butanol an area of 0.30 nm 2, and benzyl alcohol an area of 0.24 nm 2. Corresponding values in the lamellar D phase (without NaCl) are 0.40 (average value), 0.14, and 0.20 nm 2. The good agreement between the area requirements of SDS under these conditions reveals a close connection of an ion-condensation model for the lamellar phase and the surface charge distribution on the solid alumina surface. The discrepancy in the areas for the butanol is attributed to differing water solubilities, which affect the structuring in the monolayer at the solid surface more than in the bilayer in the D phase and/or longitudinal translation of the alcohol molecules in molecular bilayers. For long-chain alcohols a value of around 0.20 nm 2 is obtained in both cases.

Dynamical Structures of Normal Alkanes, Alcohols, and Fatty Acids in the Liquid State as Determined by Viscosity, Self-Diffusion Coefficient, Infrared Spectra, and 13CNMR Spin-Lattice Relaxation Time Measurements

Abstract The dynamical structures of molecules of normal alkanes (C5–C14) and normal fatty acids (C8 and C9) in the liquid state were estimated through analyses of their self-diffusion coefficients (D), viscosities (η), molar volumes, and 13CNMR spin-lattice relaxation time (T1). The apparent hydrodynamic radius evaluated from D and η for the alkanes was ca. 2.5×10−10 m and that for the fatty acids, ca. 3.1×10−10 m, irrespective of their hydrocarbon chain length: The former value is almost equal to that of the van der Waals radius (2.4×10−10 m) of the cross section of a hydrocarbon chain; the latter is in agreement with that of the normal alcohols reported in a previous paper. It is thus concluded that in the pure liquid of a rod-like compound such as normal alkane, alcohol, and fatty acid, the free rotational (end-over-end) as well as the transverse motion of the rod-like molecule is severely restricted due to the entanglements of the molecules; only a longitudinal translation is allowed. In addition, the infrared-spectrum results suggest that a unit in translational motion for a normal fatty acid is a dimer.

Phase transformation and structure of n‐C50H102/n‐C60H122 solid solutions formed from the vapor phase

AbstractBinary solid solutions of n‐paraffins (n‐C50H102/n‐C60H122) epitaxially prepared on potassium hydrogen phthalate substrate from the vapor phase have been studied by electron diffraction to characterize their phase transitions and structure. The continuity of solid solution in the n‐C50H102/n‐C60H122 system is demonstrated once lamellar ordering of the crystal packing is achieved. However, such ordering is achieved only by annealing and proceeds through a series of intermediate chain packings. At first, the electron diffraction patterns from all samples prepared at room temperature resemble those from polyethylene, in which no spots corresponding to the interlayer spacings appear. Longitudinal chain translations are induced by annealing to cause the lamellar reflections to appear, while the “polyethylene” subcell reflections remain unsplit until the crystal structure with well‐defined methyl end planes is reached.

Fresnel-field analysis of double-grating systems and their application in phase-stepping grating interferometers

A new approach to the analysis of grating systems, based on an investigation of the changes of the Fourier spectrum during field propagation through the gratings, is applied to analyze the Fresnel field of an arbitrary system. Detailed considerations of Talbot and grating-shearing interferometers used in various metrological problems are presented. A qualitative analysis of the output fringe patterns is given. The application of the phase-stepping method with the phase shift introduced by lateral and longitudinal translations of gratings is discussed. These theoretical considerations are checked by experiment.