X-ray tube assemblies with a 12-degree target angle have increased. We examined the dimensions of the x-ray field and the x-ray intensity distribution according to differences in the focal spot size of the same x-ray source assembly. In the dosemeter method and x-ray film method, the optimal object field of the x-ray source assembly by which a small focal spot touches a large spot on the anode side was almost the same. With the x-ray source assembly that was examined at this time, the range of a uniform x-ray intensity distribution to the displacement point of a small focal spot was wider than that of a large focal spot. The dimension of the x-ray filed on the anode side on the X-axis were determined by the target angle, regardless of the position of the focal spot. Differences in the dimensions of the x-ray field as affected by differences in the focal spot size differences in the x-ray intensity distribution occurred on the cathode side. These differences existed because of the size and position of the focal spot. Therefore, it it necessary to understand the x-ray field of each x-ray source assembly in order to radiography.
We developed a new ordering system specifically for the dental field and have been employing it in practical use since October 1996. The system has the folowing important features:(1)Orders and implementation commands can be input by simply touching the screen, as well as by keyboard and mouse unit. (2)The history of infection input at a clinical department prior to ordering radiography can be ascertained by a terminal device at the department of radiology. (3)Exposed films are managed by providing them with a bar code label that links them to the ordering system. (4)A label printer is used. (5)Radiographic conditions and the method of radiography can be printed on the irradiation record. (6)A bar code system is adopted. This system has been found to be more efficient and user-friendly than ordinary systems.
Dose reduction is one of the important features of digital fluorography systems. Dose reduction was examined by using an added x-ray filter, and its influence on image quality was determined. We concluded that a 0.2mm Cu filter is best, considering the balance of exposure and exposure time, spatial resolution, and density resolution. Using the 0.2mm Cu filter, the entrance exposure to the patient was reduced by 45-55% for radiography and 50-60% for fluoroscopy, but exposure time increased 30-35%, fluoroscopic tube viltage increased 5-6%, and fluoroscopic tube current increased 9-10%. Clinical image quality was not sacrificed by using the added x-ray filter. The use of an added filter is an effective means to reduce patient exposure, but it is important to consider the load on the x-ray system and its influence on the image quality.