Sialograms of submandiblar sialolithiasis were analyzed. First, statistics of 192 cases of submandibular sialolithiasis was investigated. Second, sialographic signs were compared with pathological changes of the glands. That is, the relations among the size of sialolith, the degree of sialographic fineness of the gland distal to the sialolith and pathological changes of the gland were examined. The degrees of sialographic fineness were grouped into four types. The results were as follows.
1. The cases with only one sialolith were 85.4%. The cases with the sialolith located in Whalton's duct or at the knee of the gland were 85.9%, and the cases with the sialoliths located in the gland distal to the knee were 12.0%. Four cases were found to have the sialoliths in the diverticulum of whalton's duct. More than 50% of cases had the sialoliths of diameter larger than 5mm.
2. The two sialographic signs, the size of sialolith and the degree of sialographic fineness were related with pathological changes of the glands. That is, most of the cases with the severely damaged gland had the sialoliths of diameter larger than 5mm and the sialograms of lower degrees of fineness. In addition, the size of sialolith was correlated with the degree of sialographic fineness, that is, most of the cases with the sialoliths of larger than 5mm showed lower degrees of sialographic fineness. It is proposed by the present study that the two sialographic signs in the submandibular sialolithiasis, i. e., the size of sialolith and the degree of sialographic fineness provide useful diagnostic findings in addition to conventional findings on the pathological changes of the gland.

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Quality assurance of automated processors for dental X-ray films (dental processors) was performed to establish their quality control in clinical practice. Four (three kinds of) dental processors and one processor for general purpose were examined.
Our quality assurance program has the measurements of temperature and pH of developers, as well as speed indices and contrasts obtained from sensitometric films. Their mean values and standard deviations were calculated. And the correlations between characteristics for each measurement value were illustrated.
The temperature of developers for all dental processors was usually stable and varied within ±0.5°C, if the setting temperature was under the room temperature. Speed indices had no relations to temperature of developers, but had some correlation with pH of developers in routine conditions.
To maintain the good image quality of dental X-ray films, it is more effective to measure the densities of sensitometric strips rather than measure the temperature or pH of developers.

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The purpose of this study was to determine the ideal spatial frequency band for use in intraoral roentgenographical diagnosis.
It is postulated that the results of this study may provide a positive indication of film resolving power using enhanced film speeds for intraoral roentgenography.
The experimantal procedure was as follows: After fixation of the focus-object distance, the object-film distance was kept away. By modifying the object-film distance, varied frequency band reduction images could be obtained. Band reduction images obtained in this manner were duplicated to dental size. Based on these roentgenograms, experienced dentists evaluated whether the periodontal space and laminadura were determinable [Yes] or not [No] in diagnosis. Eleven dentists, each having over five years of clinical experience, participated in this study. Frequency bands having in the object—film distances for which a positive [Yes] answer was obtained from one half of these dentists, and for which a negative [No] answer was obtained from the remaining dentists were regarded as the frequency bands required for diagnosis.
The film used was Ektaspeed ready pack E-2 film (KODAK Co.) for roentgenography and X-Omat duplicating film (KODAK Co.) for the duplicating procedure. Four areas of the jaw, including the dried incisor and molar regions of the upper jaw, and the incisor and molar regions of the lower jaw were used as representative for this study. The scattering material used was water phantom (4cm).
The results obtained can be summarized as below:
1. The cut-off spatial frequency when the periodontal space and laminadura were examined and diagnosed, using roentogenograms obtained from intraoral roentogenographic system, was 6.2lp/mm for the upper incisor region, 4.5lp/mm for the upper molar region, 4.8lp/mm for the lower incisor region and 5.8lp/mm for the lower molar region. The necessary diagnostic information was obtained when the spatial frequency band ranged between 7.0 and 8.0lp/mm in the intraoral roentgenography.
2. It was established that scatter originating from the soft tissue of the jaw decreased image contrast which further negatively affected the diagnostic recognition of spatial frequency.
3. Using the bisecting angle technique, the spatial frequency band mentioned above was obtainable with an angle of tooth axis and film of less than 40°.

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Effects of the exposure and tube voltage on the determination of the cephalometric landmarks were discussed. The skull phantom with soft tissue-equivalent material was exposed using the different exposure times to obtain the images with different optical densities, and using two different tube voltage of 75 and 110kV. The images obtained were showed to the dentists joined to serve as the observers and were evaluated in terms of the visibility. The variance of points determined by ten observers was used as a measure of the visibility of the reference point. The results were as follows. 1) The points situated in the middle of the skull such as S, Or, Ptm, or Ar were better detected in the high density image than in the low density image. On the other hand, the points situated in the boundary of the skull, such as ANS, A, or B were better observed using the relatively low density image. 2) The ratios of the exposure in the both areas mentioned above were 1/7 to 1/10 for 75kV image and 1/5 for 110kV image.
These results showed that the visivility of the reference points depends on the image density and tube voltage. These may contribute in effect to the design of the wedge filter and compensated intensifying screen.

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The medical image processing system was developed. The system was made up of the minicomputer, high resolution laser scanner and laser printer etc.. The pixel size of the laser scanner was variable from 56.6 to 198.1μm by a pitch of 28.3μm. The density resolution of this device was 10 bit, and its density range was 0 to 2 and 0 to 4. It took about 40 seconds to digitize a x-ray film in 1024² matrix and send this image to the computer. The linear relationship between optical density and scanner gray level was verified. The pixel size of the laser printer was 85μm. And the density resolution of this device was 8 bit. Although the sigmoidal relationship was observed between gray level and printed film density, the out put density was corrected with look up table. It took about 40 seconds to send a 1024² matrit image to the computer and 20 seconds to print out this image.
Some of the cilinical radiographs in dentomaxillofacial region were processed and evaluated. Edge enhancement was extremely effective in a blurred image such as a plain tomograph. Using low pass filter in frequency domain, the grid lines were eliminated from the radiograph taken with the antiscatter grid without reduction of the image quality.

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In the panoramic tomography, the X-ray beam passing through a object contains vast informations of the numerous tomographic layers. However, we usually don't use the information of all the other tomographic layers, except that of focus layer. Therefore, a system of digital panoramic tomograph had been introduced, with which any desired tomographic layer was able to obtain as a visible image. The system was composed of screen, I. I. camera, VTR, frame-memory and computer. But it had clinical issues to be improved, i. e. it had (1) prolonged scanning and reconstruction time, because of complicated data input and (2) less resolution than conventional panoramic tomography.
So the author made an attempt to develop a new digital panoramic tomograph system, which was composed of screen, SIT-TV camera, VTR, frame-memory (512×1024×16bit) and 16bit-computer, and these were all assembled on rotating unit of ZONARC® (PALOMEX CO.). At first, the radiographic informations of all tomographic layers were recorded onto the VTR with TV rate (30 frames per second), with a single exposure of panoramic tomography for 30 seconds. The optional tomographic image was picked up and reconstructed by the frame-memory and computer.
Using this system, image reconstruction can be attained in real-time. And any desired image of the panoramic layer can be obtain by repeating the reconstruction of VTR. The image has no less resolution than conventional panoramic tomography.

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Methods to improve the image quality in sialography were investigated.
The factors in xeroradiography (XR) which influence the image quality are entirely different from those in the case of silver-salt film. Images in XR are greatly influenced by the tube voltage, plate voltage, the mode of development and burst number, while those in the case of film are influenced to a great extent by the intensifying screen and the film, followed by the strip density of the grid and field size. These points were examined under conditions similar to clinical procedures, yielding the following results:
(1) In the development mode of XR, both visual latitude and visual evalution of a positive images were better than those of a negative one.
(2) Plate voltage (1300V, 1700V) and tube voltage (70kV, 120kV) should be selected according to the thickness of the subject with no relation to the mode of development. However, it was difficult to determine the optimal combination as the negative image was influenced by complication of many factors involving the burst number. A comparatively good image was obtained by the combination of the above conditions with the burst number (14 times).
(3) Although the Kodak Min-R system showed a low gamma level, it had good granularity and modulation transfer function. It was an adequately sensitivie material.
(4) In order to improve the image quality it was important to reduce the amount of scattered radiation by making the field as small as possible. When grids were used, however, the rate of removing scattered radiation was a maximum at 40lines/cm (grid ratio 8:1), and at 57lines/cm (grid ratio 8:1) the image evalution was best.
(5) The film was evaluted as being slightly better than XR. In conculusion, it is necessary to analyze the objective of sialography, to recognize the sensitive materials used and to select them according to each case.

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We showed in this communication a peculiar case of mucopolysaccharidosis which subtype is unknown in a 16-year-old male.
The symptoms observed in this patient included short stature, kyphosis, joint stiffness, mental retardation, as well as increased excretion of urinary dermatan sulfate.
Radiologic changes of dysostosis multiplex involved the spine, ribs, pelvis, and hands. Acroosteolysis of all distal phalanges, previously undescribed, was seen.
Radiograms of jaw bones showed flattening of bilateral mandibular heads, multiple dentigerous cyst-like radiolucent lesions in both upper and lower molar regions, a number of carious lesions, enlarged pulp chamber and delaceration of the roots.
Cephalometric analysis revealed marked underdevelopment of the mandible.

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The present study is based on clinical and roentgenological observations of 7 cases of nonHodgkin lymphoma that were encountered in past 4.5 years at Okayama University Dental School affiliated Hospital.
The results are summarized as follows:
(1) They included 5 males and 2 females. The age of patients ranged from 30 to 70 years, with a mean of 51.4 years old.
(2) Clinically intraoral swelling and regional lymph node swelling were most common features, but ulcer formation was seen in few cases. These symptoms apparently led to the early, but erroneous, diagnosis of inflammatory disease in most cases.
(3) Radiographically loss of lamina dura and widening of periodontal space were seen in all cases. But destructive appearnces of jaw bone were quite varied, so it was difficult to make a differential diagnosis from other malignant tumors or some inflammatory diseases.

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