Stable Image Quality Research Articles

撮影条件自動適正化機能を用いたルーチン化への検討

Auto mA is a function that automatically controls tube current so as to stabilize image quality. To determine the applicability of this function to routine inspection work, an evaluation was carried out by two doctors in the department of radiology and five technicians in the department of diagnostic radiology using home-made phantoms and phantoms for low contrast resolution determination. The phantom experiment provided an almost constant level of SD values in each Auto mA mode tested, independent of scanning type, slice thickness, and phantom shape. In addition, nearly stable low contrast resolution was attained independent of phantom shape, e.g., circle and ellipse. The results suggest that stable image quality is available in the clinical stage for individual patients and regions, independent of the size and shape of targets. As for the evaluation of clinical images, the image quality requested by clinical operations at our hospital was attained even in the low dose mode that provides the lowest dose level. In addition, for variations in tube current values for photographing in individual regions, both sustained image uniformity and exposure reduction were found to be satisfactory in comparison with constant tube current.

Film processing and the environment. Reducing pollution, water consumption, and costs.

X-ray film processing is associated with pollution from photo chemicals and from the water used to rinse the film. We tested a new processing system that was aimed at reducing both environmental pollution and costs through the use of solid photo chemicals and recirculation of the rinsing water. Before and after the installation of new mixers for the solid chemicals and a system for recirculating the rinsing water, we measured: water consumption, processor function quality, image quality, archivability, and the waste-silver content in the rinsing water. After the installation of a simple system for recirculating the rinsing water, there was an 88% reduction in water and film consumption as shown in the amount of water/m2 film that was used. At the same time, the release of silver-contaminated rinsing water directly into the sewers was stopped. Image quality remained unchanged. Archivability was assessed at more than 100 years. The solid photo chemicals and specially designed mixers proved efficient and provided a stable image quality of high standard. It was thus possible to reduce the risk of pollution from the transportation, storage and handling of liquid chemicals. A simple recirculation system for the rinsing water would significantly reduce water consumption and eliminate contamination of the environment by silver. The on-site preparation of photo chemicals proved viable and reduced the costs of film processing.

Variable bit‐rate video transmission under usage parameter control

AbstractThis paper proposes a method of video bit‐rate control for the case where the average transmission bitrate is constrained, considering the usage parameter control in an ATM network. By a simulation, the video quality and the network congestion probability of the variable bit‐rate (VBR) transmission system, with the constrained average bit‐rate, are compared to those of the conventional constant bit‐rate (CBR) transmission system or the VBR transmission system without the rate control. the relations among the length of the sliding window (SW) to monitor the average bit‐rate, the video quality, and the network congestion probability are analyzed.With respect to the video quality, it is shown that the VBR transmission with the average bit‐rate control exhibits a stable image quality when SW is long and exhibits a better image quality than the CBR transmission for the cases of scene change and the panning scene. When the scene changes, the image quality changes and the VBR transmission with the bit‐rate control.With respect to the network congestion probability, it is shown that the probability is decreased greatly by constraining the average bit‐rate and the probability becomes less when SW is made shorter.Finally, it is shown that SW should desirably be long to stabilize the video quality but the permissible length of SW depends on how many video signlas can be multiplexed in the network.

Digital imaging in pediatric hospitals.

Thirty-nine of 65 children's hospitals in North America responded to a questionnaire regarding their use of digital fluoroscopy and computed radiography (CR) systems. Both digital modalities are very favorably rated by institutions that have them. Budget constraints limit purchases in the other institutions. Picture archiving and communication systems (PACS) networking is not the primary reason for installation of digital systems. Fourteen of 39 hospitals have digital fluoroscopy and another 9 plan installation within 12 months. The three most highly rated benefits of digital fluoroscopy were decreased radiation dose, immediate visualization of the acquired image on the monitor, and the ability to alter image contrast and density. Four of 39 hospitals have computed radiography. The three most highly rated benefits of computed radiography were more stable image quality, ability to alter contrast and density, and PACS networking.

Submicrometer lithography using lensless high-efficiency holographic systems

A hologram recording geometry that was total internal reflection of the reference and reconstruction beams from a photosensitive material surface is used to achieve 0.5-microm resolution at lambda = 457 nm in the readout of a reconstructed image on a photoresist. Such a geometry has demonstrated stable image quality for parallel displacement within the illuminated area and diffraction efficiency tolerance within a +/-2 degrees tilt about the axis of the reconstruction beam. The total-internal-reflection recording system provides double-fringe sets for each plane component inside the volume hologram; therefore, a diffraction efficiency as high as 80% was observed. The result is applicable to highvolume submicrometer lithography and can be expanded to a 20-cm (8-in.) semiconductor submicrometer pattern. The use of a large-aperture, well-collimated laser beam provides us with much higher throughput than that of existing lithography machines.