CT imaging of small animals using monochromatized synchrotron x rays

Rats and chicken embryos were imaged in vivo with a prototype Multiple Energy Computed Tomography (MECT) system using monochromatized x rays from the X17 superconducting wiggler at the National Synchrotron Light Source. The CT configuration coated of a horizontal low-divergence, fan-shaped beam, 70 mm wide and 0.5 mm high, and a subject rotating about a vertical aids. A linear-array high-purity Ge detector with 140 elements, each 0.5 mm wide and 6 mm thick, was used with a data acquisition system that provides a linear response over almost six orders of magnitude of detector current. The dual photon absorptiometry (DPA) algorithm was applied to images of the rat head acquired at 20 and 45 keV to obtain two new images, one representing the low-Z, and the other the intermediate-Z clement group. The results indicate that the contrast resolution and the quantification accuracy of the images improve stepwise; first, with the monochromatic beam and, second, the DPA method. The system is a prototype for a brain scanner

Novel Temperature Dependence of the Smectic−C Tilt in the Polymeric Liquid Crystal, C−6 Polysiloxane: A High−Resolution X−Ray Study

High-resolution x-ray scattering measurements of the smectic-C phase of the polymeric liquid crystal, C-6 polysiloxane, show that the smectic-C tilt angle φp decreases continuously upon decreasing temperature. This behavior, opposite to that observed in monomeric liquid crystals, is caused by stiffening in the polymeric backbones and spacers

Nematic−Smectic−C phase transition in the polymeric liquid crystal C−6 polysiloxane: A high resolution x−ray study

We report on the first x-ray scattering measurements of pretransitional smectic-C fluctuations in the nematic phase of a side-chain polymeric liquid crystal, C-6 polysiloxane. The data are well described by the mean-field theory of Chen and Lubensky suggesting that the mesogenic side groups are only weakly coupled to the polymeric backbone. Because of disorder in the polymer backbone, the correlation lengths, in the vicinity of the nematic-smectic-C phase transition, are weak functions of temperature and their magnitudes are smaller than those of conventional monomeric liquid crystals

Monochromatic computed tomography of the human brain using synchrotron x rays: Technical feasibility

A monochromatic computed tomography (CT) scanner is being developed at the X17 superconducting wiggler beamline at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory, to image the human head and neck. The system configuration is one of a horizontal fan beam and an upright seated rotating subject. The purpose of the project are to demonstrate improvement in the image contrast and in the image quantitative accuracy that can be obtained in monochromatic CT and to apply the system to specific clinical research programs in neuroradiology. This paper describes the first phantom studies carried out with a prototype system, using the dual photon absorptiometry (DPA) method at energies of 20 and 39 Kev. The results show that improvements in image contrast and quantitative accuracy are possible with monochromatic DPA CT. Estimates of the clinical performance of the planned CT system are made on the basis of these initial results

Monochromatic computed tomography of the human brain using synchrotron x rays: Technical feasibility

A monochromatic computed tomography (CT) scanner is being developed at the X17 superconducting wiggler beamline at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory, to image the human head and neck. The system configuration is one of a horizontal fan beam and an upright seated rotating subject. The purpose of the project are to demonstrate improvement in the image contrast and in the image quantitative accuracy that can be obtained in monochromatic CT and to apply the system to specific clinical research programs in neuroradiology. This paper describes the first phantom studies carried out with a prototype system, using the dual photon absorptiometry (DPA) method at energies of 20 and 39 Kev. The results show that improvements in image contrast and quantitative accuracy are possible with monochromatic DPA CT. Estimates of the clinical performance of the planned CT system are made on the basis of these initial results