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G Shechter

Publications and source records attributed to G Shechter.

5 recordsLinked to original sources
PubMed2004

The frequency split method for helical cone-beam reconstruction.

A new approximate method for the utilization of redundant data in helical cone-beam CT is presented. It is based on the observation that the original WEDGE method provides excellent image quality if only little more than 180 degrees data are used for back-projection, and that significant low-frequency artifacts appear if a larger amount of redundant data are used. This degradation is compensated by the frequency split method: The low-frequency part of the image is reconstructed using little more than 180 degrees of data, while the high frequency part is reconstructed using all data. The resulting algorithm shows no cone-beam artifacts in a simulation of a 64-row scanner. It is further shown that the frequency split method hardly degrades the signal-to-noise ratio of the reconstructed images and that it behaves robustly in the presence of motion.

Algorithms↗
PubMed2003

Helical cardiac cone beam reconstruction using retrospective ECG gating.

In modern computer tomography (CT) systems, the fast rotating gantry and the increased detector width enable 3D imaging of the heart. Cardiac volume CT has a high potential for non-invasive coronary angiography with high spatial resolution and short scan time. Due to the increased detector width, true cone beam reconstruction methods are needed instead of adapted 2D reconstruction schemes. In this paper, the extended cardiac reconstruction method is introduced. It integrates the idea of retrospectively gated cardiac reconstruction for helical data acquisition into a cone beam reconstruction framework. It leads to an efficient and flexible algorithmic scheme for the reconstruction of single- and multi-phase cardiac volume datasets. The method automatically adapts the number of cardiac cycles used for the reconstruction. The cone beam geometry is fully taken into account during the reconstruction process. Within this paper, results are presented on patient datasets which have been acquired using a 16-slice cone beam CT system.

Algorithms↗
PubMed2003

Adaptive temporal resolution optimization in helical cardiac cone beam CT reconstruction.

Cone beam computed tomography scanners in combination with heart rate adaptive reconstruction schemes have the potential to enable cardiac volumetric computed tomography (CT) imaging for a larger number of patients and applications. In this publication, an adaptive scheme for the automatic and patient-specific reconstruction optimization is introduced to improve the temporal resolution and image quality. The optimization method permits the automatic determination of the required amount of gated helical cone beam projection data for the reconstruction volume. It furthermore allows one to optimize subvolume reconstruction yielding an increased temporal resolution. In addition, methods for the assessment of the temporal resolution are given which enable a quantitative documentation of the reconstruction improvements. Results are presented for patient data sets acquired in low pitch helical mode using a 16-slice cone beam CT system with parallel ECG recording.

Algorithms↗
PubMed1983

Lipoxygenase from baker's yeast: purification and properties.

Lipoxygenase activity was extracted from the mitochondrial fraction of baker's yeast and was purified by affinity chromatography on a linoleyl aminoethyl sepharose column. Two lipoxygenases were eluted from the affinity column. The second enzyme eluted was characterized as a true lipoxygenase. The lipoxygenase eluted showed maximum activity at pH 6.5 with a Km of 2.68 X 10(-4) M on linoleate. The reaction products of the second lipoxygenase with linoleate were characterized by u.v., i.r., NMR spectra and mass spectrometry and were found to be: 9-hydroperoxy-octadeca-trans-10,cis-12-dienoic acid and 13-hydroperoxy-octadeca-cis-9,trans-11-dienoic acid.

Hydrogen-Ion Concentration↗