Three-dimensional Matching Research Articles

Passive navigation from image sequences by use of a volumetric approach.

The paper describes a volumetric approach to depth estimation for robot navigation with use of only an approximately calibrated translating camera. Our approach is related to techniques for photo-realistic object reconstruction but with the emphasis on issues associated with navigation. The technique performs three-dimensional matching by a process of image interpolation and can adjust for errors in camera position. The reconstruction is achieved from a small angular range of scene views, and the technique is demonstrated to be insensitive to large errors in the camera positions. The ability to correct for more critical errors such as the camera orientation is shown to significantly improve the algorithm's performance. Our technique is demonstrated on real image sequences and compares favorably with techniques based on optical flow.

Monozygotic Twins Discordant for Chronic Fatigue Syndrome: Regional Cerebral Blood Flow SPECT

To evaluate the relationship between regional cerebral blood flow (rCBF) and chronic fatigue syndrome (CFS) in monozygotic twins discordant for CFS. The authors conducted a co-twin control study of 22 monozygotic twins in which one twin met criteria for CFS and the other was healthy. Twins underwent a structured psychiatric interview and resting technetium 99m-hexamethyl-propyleneamine oxime single photon emission computed tomography of the brain. They also rated their mental status before the procedure. Scans were interpreted independently by two physicians blinded to illness status and then at a blinded consensus reading. Imaging fusion software with automated three-dimensional matching of rCBF images was used to coregister and quantify results. Outcomes were the number and distribution of abnormalities at both reader consensus and automated quantification. Mean rCBF levels were compared by using random effects regression models to account for the effects of twin matching and potential confounding factors. The twins with and those without CFS were similar in mean number of visually detected abnormalities and in mean differences quantified by using image registration software. These results were unaltered with adjustments for fitness level, depression, and mood before imaging. The study results did not provide evidence of a distinctive pattern of resting rCBF abnormalities associated with CFS. The described method highlights the importance of selecting well-matched control subjects.

2.1 Operating characteristics of a three-dimensional matching and quatitation algorithm for myocardial perfusion studies

2.1 Operating characteristics of a three-dimensional matching and quatitation algorithm for myocardial perfusion studies

Three-dimensional matching by use of phase-only holographic information and the Wigner distribution.

Matching of three-dimensional (3-D) objects is achieved by Wigner analysis of the correlation pattern between the phase-only holographic information of a reference object and that of a target object. First, holographic information on the reference object and on the target object is extracted by use of optical scanning holography as a form of electrical signal. This electrical information is then stored in a computer for digital processing. In the digital computer, the correlation between the phase-only information of the hologram of the reference object and that of the target object is calculated and analyzed by use of a Wigner distribution. The Wigner distribution yields a space-frequency map of the correlation pattern that indicates whether the 3-D image of the target object matches that of the reference object. When the 3-D image of the target object matches that of the reference object, the Wigner distribution gives a well-defined line that directly indicates the 3-D location of the matched target object. Optical experiments with digital processing are described to demonstrate the proposed matching technique.

A three-dimensional matching model for perishable production scheduling

In the production of perishable goods, particular stress is often given to performance indicators generally less critical in such manufacturing settings as metal-cutting, or mechanical/electronic assembly. For instance, in food or biochemical productions, a prominent interest of the producer is to reduce the time from distribution to the so-called best-before end. A scheduling problem with a goal of this sort is here addressed. The decision variables considered are launching and completion times of parts in a production line with critical aspects in the initial and/or final stages. The basic problem is to find an assignment of a maximum number of products to launching and completion times, so that no two products are assigned the same launching or completion time: feasible solutions have therefore the form of three-dimensional matchings. The problem is studied under two independent respects, assuming either (i) the relative perishability of products or (ii) the feasibility of launching/completion time pairs not affected by the intermediate transformation stage. We show that the problem is NP-Complete, even under such a ranking assumption as (i), whereas is in P under assumption (ii). Polynomial-time algorithms are also proposed to solve other optimization versions of the problem (in two cases, based on the identification of a matroid structure).

The Parametrized Complexity of Some Fundamental Problems in Coding Theory

The parametrized complexity of a number of fundamental problems in the theory of linear codes and integer lattices is explored. Concerning codes, the main results are that MAXIMUM-LIKELIHOOD DECODING and WEIGHT DISTRUBUTION are hard for the parametrized complexity class W[1]. The NP-completeness of these two problems was established by Berlekamp, McEliece, and van Tilborg in 1978 using by means of a reduction from THREE-DIMENSIONAL MATCHING. On the other hand, our proof of hardness for W[1] is based on a parametric polynomial-time transformation from PERFECT CODE in graphs. An immediate consequence of our results is that bounded-distance decoding is likely to be hard for binary linear codes. Concerning lattices, we address the THETA SERIES problem of determining for an integer lattice $\L$ %given by a set of generators, and a positive integer k whether there is a vector $x \in \L$ of Euclidean norm k. We prove here for the first time that THETA SERIES is NP-complete and show that it is also hard for W[1]. Furthermore, we prove that the NEAREST VECTOR problem for integer lattices is hard for W[1]. These problems are the counterparts of WEIGHT DISTRUBUTION and MAXIMUM-LIKELIHOOD DECODING for lattices. Relations between all these problems and combinatorial problems in graphs are discussed.

Within-Subject Reproducibility of Visual Activation Patterns With Functional Magnetic Resonance Imaging Using Multislice Echo Planar Imaging

Within-subject reproducibility of visual brain activation using multislice echo planar functional magnetic resonance imaging (fMRI) was tested. Ten healthy subjects underwent fMRI with visual stimulation on three occasions: two studies in one scanning session (without repositioning); and a third study 1 h to 2 weeks later. Following a three-dimensional matching procedure, activation was measured and compared between sessions on a voxel-by-voxel basis. Data were filtered to full-width-at-half-maximum of 4.0 × 4.0 × 5.0 mm and a conservative Bonferroni-corrected significance threshold was applied to correlation maps. For reproducibility, change in centre of mass of the activated volume, a ratio of the number of pixels and a ratio of the number of overlapping pixels was calculated. Further, reproducibility was tested varying significance thresholds and at different filter widths. Average changes in centre of mass of the activated volume were 2.63 and 3.96 mm between Studies 1 and 2 and 1 and 3, respectively. The reproducibility of the number of activated voxels was 90% and 88% (Studies 1 and 2 and 1 and 3). The ratio of overlapping pixels was 74% between Studies 1 and 2 and 64% between Studies 1 and 3. Varying the significance threshold showed that at a certain range, the overlap reached a maximum, and increasing the filter widths increased reproducibility. It is concluded that fMRI with visual stimulation can be used to measure brain activity with reasonably good reproducibility on a routine clinical system equipped with echo planar imaging. Difficulties remain in separating the contribution of motion, repositioning errors, and true physiological changes.

O-29-423 - The effect of ICP on myelination and the relationship with neurodevelopment in infantile hydrocephalus

To assess the accuracy of ultrasound-based repositioning (BAT) before prostate radiation with fiducial-based three-dimensional matching with cone-beam computed tomography (CBCT).Fifty-four positionings in 8 patients with 125I seeds/intraprostatic calcifications as fiducials were evaluated. Patients were initially positioned according to skin marks and after this according to bony structures based on CBCT. Prostate position correction was then performed with BAT. Residual error after repositioning based on skin marks, bony anatomy, and BAT was estimated by a second CBCT based on user-independent automatic fiducial registration.Overall mean value (MV ± SD) residual error after BAT based on fiducial registration by CBCT was 0.7 ± 1.7 mm in x (group systematic error [M] = 0.5 mm; SD of systematic error [Σ] = 0.8 mm; SD of random error [σ] = 1.4 mm), 0.9 ± 3.3 mm in y (M = 0.5 mm, Σ = 2.2 mm, σ = 2.8 mm), and −1.7 ± 3.4 mm in z (M = −1.7 mm, Σ = 2.3 mm, σ = 3.0 mm) directions, whereas residual error relative to positioning based on skin marks was 2.1 ± 4.6 mm in x (M = 2.6 mm, Σ = 3.3 mm, σ = 3.9 mm), −4.8 ± 8.5 mm in y (M = −4.4 mm, Σ = 3.7 mm, σ = 6.7 mm), and −5.2 ± 3.6 mm in z (M = −4.8 mm, Σ = 1.7 mm, σ = 3.5mm) directions and relative to positioning based on bony anatomy was 0 ± 1.8 mm in x (M = 0.2 mm, Σ = 0.9 mm, σ = 1.1 mm), −3.5 ± 6.8 mm in y (M = −3.0 mm, Σ = 1.8 mm, σ = 3.7 mm), and −1.9 ± 5.2 mm in z (M = −2.0 mm, Σ = 1.3 mm, σ = 4.0 mm) directions.BAT improved the daily repositioning accuracy over skin marks or even bony anatomy. The results obtained with BAT are within the precision of extracranial stereotactic procedures and represent values that can be achieved with several users with different education levels. If sonographic visibility is insufficient, CBCT or kV/MV portal imaging with implanted fiducials are recommended.

SURFACE MATCHING AND DIFFERENCE DETECTION WITHOUT THE AID OF CONTROL POINTS

Abstract If photogrammetry is to be applied to applications such as machine vision, industrial inspection, or medical analysis, more diverse three-dimensional model matching procedures need to be developed. Further, automatic surface difference detection should also be incorporated into the derived algorithms in order to accommodate the requirements of these new applications.This paper reviews a wide range of literature and presents the current status of three-dimensional model matching. A comparison is made between two-dimensional and three-dimensional matching for the purpose of delineating and similarities and differences. Finally, an algorithm developed by the author for surface matching is also discussed.

SURFACE MATCHING AND DIFFERENCE DETECTION WITHOUT THE AID OF CONTROL POINTS

If photogrammetry is to be applied to applications such as machine vision, industrial inspection, or medical analysis, more diverse three-dimensional model matching procedures need to be developed. Further, automatic surface difference detection should also be incorporated into the derived algorithms in order to accommodate the requirements of these new applications.This paper reviews a wide range of literature and presents the current status of three-dimensional model matching. A comparison is made between two-dimensional and three-dimensional matching for the purpose of delineating and similarities and differences. Finally, an algorithm developed by the author for surface matching is also discussed.

MOLGEN: Personal computer-based modeling system

MOLGEN is a comprehensive molecular modeling package that runs on personal computers and allows building, drawing, storing, and comparison of molecular structures. The system contains modules for geometry optimization and conformational analysis, and modules for calculation and description of lipophilicity and electrostatic potentials and for their three-dimensional matching based on gnomonic projection. Described here are a systematic conformation search running on PCs and a new approach to 3D similarity analysis of lipophilic potentials. The drug design applicability of the program is further enhanced by database facilities for retrieving and storing any structure data sets. The program features and examples of its applications are presented.

Finding flexible patterns in a text: an application to three-dimensional molecular matching.

Finding certain regularities in a text is an important problem in many areas, e.g. in the analysis of biological molecules such as nucleic acids or proteins. In the latter case, the text may be sequences of amino acids or a linear coding of three-dimensional structures, and the regularities then correspond to lexical or structural motifs common to two, or more, proteins. We first recall an earlier algorithm that found these regularities in a flexible way. Then we introduce a generalized version of this algorithm designed for the particular case of protein three-dimensional structures, since these structures present a few peculiarities that make them computationally harder to process. Finally, we give some applications of our new algorithm on concrete examples.

Three-dimensional matching of macromolecular structures obtained from electron microscopy: an application to the 70S and 50S E.Coli ribosomal particles

In this work we present a general computational method capable of finding the relative orientation of two structures represented by samples on a three-dimensional grid. It is shown that the three-dimensional shift and the three independent rotations necessary for the correct relative spatial placement of the two volumes can be obtained either from the auto-correlation function of the volumes or from a direct cross-correlation, depending on the specific problem to be solved. This method has been applied to the problem of fitting the 50S ribosomal subunit into the 70S monosome from E.coli, structures that were available as three-dimensional reconstructions from electron microscopical data.

Growth anisotropy in the GaN/Al 2O 3 system

The crystallographic aspect of gallium nitride epitaxy on sapphire were investigated for the vapor phase epitaxy system GaCl/NH 3/HCl/N 2. For this purpose, thick layers of doped gallium nitride were deposited on hemispheres of Al 2O 3 single crystal with the three fold axis of the corundum structure perpendicular to the basal plane. Complete characterization of these layers has been carried out including Laue back diffraction, scanning electron microscopy and cathodoluminescence. After growth, sections were cut along the main crystallographic planes and the growth rate was measured as a function of the substrate orientation. The observed relationship for epitaxy has been interpreted in terms of three-dimensional matching between the gallium nitride and corundum structures.

Silicon/Corundum Epitaxy

The crystallographic aspects of silicon/corundum epitaxy were investigated. Epitaxial deposition was carried out on corundum substrates of two orientations, and the observed crystallographic relationships were shown to be determined by three-dimensional matching between the silicon structure and the sublattice of possible cation sites in corundum. Single-crystal silicon layers were deposited onto (0001) and (8̄629) corundum substrates. For growth on (0001) corundum, (111) silicon is parallel to the interface with [1̄10] silicon parallel to [2̄110] corundum. For growth on (8̄629) corundum, the silicon plane parallel to the interface is irrational, but the epitaxial relationship closely approximates to the following: (001) silicon parallel to (0001) corundum with [1̄10] silicon parallel to [2̄110] corundum. These two epitaxial relationships are the only ones which permit three noncoplanar symmetry axes of the silicon to coincide with three such axes of the cation site sublattice of the corundum. They insure compatible surface symmetries and similar surface densities on an arbitrary deposit/substrate interface. In general, the silicon atom density on the interface does not exceed the cation site density. When it does so, however, the rational crystallographic relationship is modified slightly in order to lower the density of silicon atoms below that of the possible cation sites.