Two Systems for Direct Radiographic Miniaturization
The direct miniaturization of radiographic images is discussed, and two systems are analyzed in detail. The performance and relative advantages of a large, high-performance X-ray image intensifier (¿18-in or 46-cm diameter) and an optically coupled radiographic intensifier are presented. These systems are estimated to have comparable performance and costs. The X-ray image intensifier system is superior in quantum efficiency and gain, while the radiographic intensifier is superior in contrast. While, as expected, the resolution, contrast, and sensitivity of these systems are not as good as a conventional screen-film cassette system under all circumstances, their performance may be adequate for all but the most demanding radiologic applications.
High Performance Continuous Zoom X-Ray Image Intensifiers
This paper discusses the development and performance of a 9-inch X-ray Image Intensifier featuring a continuously variable magnification from a 9-inch useful input diameter to a 5-inch useful input diameter at a fixed 20mm diameter output image. The pentode electron optical structure in this device was designed through utilization of a digital computer electron optics evaluation program. A brief analysis of the design technique is presented, with particular emphasis directed towards techniques used for prediction and optimization of electron optical performance parameters from computer analysis data. The described techniques resulted in a design which not only demonstrates geometric distortion of less than 5 percent and a flat focal plane surface, but also enables a single voltage divider magnification control which continuously varies the magnification while maintaining focus. This particular result enables incorporation of an integral power supply within the intensifier housing that provides complete operating voltages and subsecond zooming between 9-inch and 6-inch modes. Performance parameters of the device are also investigated with particular atten-tion to an MTF evaluation technique which applies to all X-ray image intensifiers. In addition to superior MTF, this new device also exhibits a conversion gain in excess of 5,000 with 125 linepairs per inch limiting resolution in the 6-inch input mode. Nine-inch mode gain is at least 10,000 with a limiting resolution of 90 linepairs per inch. The high gain and resolution of this new intensifier, in conjunction with its capability of rapid zooming with entire control provided by an integral power supply render it an excellent device for use in x-ray diagnostic equipment.
Scaffolds Containing Spirulina sp. LEB 18 Biomass: Development, Characterization and Evaluation of In Vitro Biodegradation.
Polymer nanofibers are nanomaterials that can be used as scaffolds in tissue engineering. The objective of this study was to develop, characterize and evaluate the in vitro degradation of a biomaterial consisting of nanofibers produced from biodegradable and biocompatible polymers with potential applications as a scaffold for tissue regeneration and containing Spirulina sp. LEB 18 biomass as the bioactive compound. The polymers used were poly(hydroxybutyrate-co-hydroxyvalerate) and polycaprolactone. The polymeric solutions exhibited sufficiently high viscosity to produce uniform nanofibers with diameters between 335 and 617 nm. The applied conditions were as follows: a voltage of 25 kV, a distance from the capillary to the collector of 120 mm, a capillary diameter of 0.80 mm, and 12% polycaprolactone and a blend of 5% polycaprolactone and 10% poly(hydroxybutyrate-co-hydroxyvalerate). The biomass was incorporated into the nanofibers at a concentration of 3%, and the incorporation was confirmed using confocal microscopy. The nanofibers were characterized using differential scanning calorimetry and thermogravimetric analysis, which showed that the addition of biomass did not alter the thermal properties of the biomaterial. The addition of biomass improved the tensile strength and elongation of the scaffolds compared with those produced with polymers alone. A biodegradation assay showed enzymatic action toward the biomaterial, simulating the behavior of natural tissue. Based on the analysis, it was concluded that the scaffolds that were produced have the potential to be applied in the field of tissue regeneration as biomaterials with pharmacological properties.