Tomographic reconstruction

Braun, H., Hauck, A. Tomographic reconstruction of vector fields. IEEE Trans, on Signal Processing, 1991, 39(2) fOf-fll. 

Prince, J. Tomographic reconstruction of S-D vector fields. Proc IEEE Int. Gonf. ASSP 93, 1993, V48S-386. 

This new probe design associated with the preprocessings presented in this paper allows efficient flaw detection. The first tests with silicium coils probe give similar results and give great hope in future tomographic reconstruction. 

The mechanical movements and the data aequisition is controlled by a DEC Alpha-Workstation which is also able to perform the tomographic reconstruction and parts of the visualization of the results. 

One can then use the classical algorithm of tomographic reconstruction by summation of filtered back-projections ... 

The system uses a remote controlled manipulator system whieh scans the volume of interest. It also positions the x-ray source and x-ray camera at different angles relative the crack and create projection images of the craek. By using a tomographic reconstruction of these images a 3-D representation of the crack can be used for analysis and sizing. 

Figure 3. Tomographic reconstruction the Projection Slice Theorem.

Initial and tomographic reconstruction of chemically fixed sporozoites of C. parvum have revealed a complex arrangement of membranes both... 

In tomographic reconstructions of fixed sporozoites, a single, highly folded inner membrane (Fig. 2), or multiple internal subcompartments (see Figs. 12-15, Keithly et al. 2005), were visualized within the organelle. As mentioned before, the infoldings of the IM appeared to lack tubular crista... 

Although neither the function nor the origin of this enigmatic organelle is yet known, the three-dimensional structure of the CB visualized by tomographic reconstruction suggested that the closely packed vesicles observed by might actually be a series of interconnected channels (see Fig. 20, Keithly et al. 

Figure 21.14 STEM tomographic reconstruction of the bulk specimen (aluminosilicate bright). Sections taken through the strand layers at depths of 0, 11, 22, and 33 nm, respectively, show successive layers of strands running in alternate directions. The spacing between strands within each layer is dip 23.3 nm while the angle between the direction of strands in successive layers is 4> 75°.36 (Reprinted with permission from G. E. S. Toombes et al., Macromolecules 2008, 41, 852-859. Copyright 2008 American Chemical Society.)...

An objective of this series of experiments is to provide a preliminary assessment of the tomographic reconstruction approach for combustion diagnostics. In order to minimize experimental difficulties introduced by combustion, a simple flow configuration has been chosen for this initial study. It is mathematical truism that any bandlimited function can be accurately reconstructed from its projections if both the number and the signal to noise ratio of these projections approach infinity. In any real combustion situation, both of these conditions will be severely limited. The present results provide insights into the measurement capabilities of the tomographic reconstruction approach under such limitations. 

For practical reasons, the number of LOS measurements is finite, and the tomographic reconstruction problem is ill-posed. Two reconstruction methods have been developed for cases where optical access is restricted, and the number of measurement LOSs is limited. One method, adaptive FDDI, requires 100 or more LOSs [1-3], while the other method. Tomographic Reconstruction via a Karhunen-Loeve Basis, requires far fewer [4, 5]. Because it requires very few LOSs, the authors believe that this latter method has potential for use in sensing for feedback control of combustion systems where optical access is limited however, it requires considerable a priori information in the form of a set of expected distributions, the training set. This set is analyzed via POD to yield a set of basis functions, the Karhunen-Loeve eigenfunctions, that are used for reconstruction. These training sets could come from measurements on prototype equipment or from computational combustion simulations. 

Ha, J., M. Feng, and F.C. Gouldin. 1999. Laser tomographic reconstruction in a complex concentration flow field. AIAA Paper No. 99-0444. 

The NMRI technique uses an induction coil surrounding the sample to image nuclear spin density that results from the nuclear spin system rearrangement. An initial magnetic pulsed field orients the nuclear spin system and then it relaxes back toward a random state. Because of the relaxation time and that tomographic reconstruction is needed to extract the 3-D details, there are time limitations (Altobelli et al., 1992) (currently of the order of 10-ms, at best). Consequently, the technique has been used mostly for steady or quasi-steady laminar flows because of the rather low data acquisition rate. However, modifications to allow turbulent and unsteady flows to be investigated have been reported and new... 

Original image (left) and its tomographic reconstruction (right) of a premixed flame with ER = 0.8. 

P Xj yj) estimated using (a) original images and (b) their tomographic reconstructions. 

The final step is tomographic reconstruction, presently done using filtered backprojection using the IDL Riemann function. Reconstruction times are a few hours for a 512x512x512 3-D data set using a single 450 MHz Pentium PC running Windows NT. Visualization is currently performed in IDL on the local PC at the beamline. 

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