Purposes: To reduce patient dose without deterioration of image quality and to improve measurement accuracy in radiographic swallowing studies.
Materials and methods: In our hospital, swallowing studies are carried out using cine film with simultaneous digital image (CFSD) mode using a digital subtraction angiography system. The resultant image must be processed by an image intensifier because the detector has an inherent distortion problem.
(1) Exposure parameters were determined based on data obtained by CFSD mode imaging. The patient dose was measured using Rando-phantom and thermoluminescent dosimeter.
(2) A cine film image obtained by CFSD mode was compared with digital cine (DC) mode under routine exposure conditions for sharpness, incident patient dose and image contrast.
(3) As a phantom, lead circular grains of 1mm diameter were placed at the intersections of a 40mm grid. After radiographing this phantom, the distances for 32 positions was measured. The image distortion correction software was developed from commercially available software.
Results: (1) The total absorbed dose in CFSD mode was 2 to 6 times higher than that of videofluorography for each examined region.
(2) Though the sharpness of the DC image was slightly inferior to the cine film image, patient dose could be reduced to 45% by additional filter and exposure parameters.
(3) The mean length in the images without correction was 94.1±3.7 (87.0∼102.8) pixels, and 99.0±1.5 (94.5∼102.5) pixels in the corrected images. The effect of the correction was satisfactory.
Conclusion: This DC system may replace the cine film system because the patient dose can be decreased while maintaining the image quality. Additionally, the use of cine film costs more and the system occupies more physical space. In summary, patient dose reduction and improved measurement precision with lower cost suggest that shifting from a cine film system to the DC system would be advantageous.

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Recently, patients with radiopaque lesions in the jaw bones are sometimes referred to the Hospital of Nihon University School of Dentistry for diagnosis. After examination by rotational panoramic radiography, limited cone beam X-ray CT (dental CT) is usually applied to clarify the internal conditions of radiopaque lesions. This procedure often reveals pearl shell structure (PSS) in the radiopaque lesions. The purpose of this study was to clarify the diagnostic relevance of PSS through the relation between the tooth and the origin of this structure.
We analyzed 100 radiopaque lesions revealed by rotational panoramic radiography and found that PSS most frequently arose in the premolar and molar regions of the mandible. Regarding the site, 60% of lesions were in contact with the root of a tooth, but 24% were localized in the body of the mandible. We found PSS in 34% of all lesions and these were localized at a higher frequency fully enclosed within the roots of teeth than in contact with them.
We show in this study that the PSS in some radiopaque lesions was diagnosed as condensing osteomyelitis histopathologically. Moreover we must follow up PSS to clarify under both conditions, indicating that it is either the starting point of bone sclerosis due to inframmation or the center of increasing bone sclerosis for a long periods.

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The exact location of the mandibular canal and mental foramen should be identified before endosseous implant surgery in the mandible. In this study we used reformatted CT images to assess and classify mental foramina into several patterns based on the morphology, and estimated the length of the anterior loop of the canal. [Material & Methods] A total of 137 sites in 69 patients were examined in this study. The patients consisted of 33 males and 36 females who were referred to our Radiology Clinic for presurgical CT examination of the mandible. After the CT, reformatted images both perpendicular and parallel to the dental arch were created by the multiplanar software supplied with the CT apparatus (GE-Yokogawa, Tokyo). The vertical location of the mental foramen was determined by the distance from the mental foramen to the alveolar ridge, and the height of the mandible was also measured on MPR-CT images. Because the presence of teeth may affect the mandibular morphology around the mental foramen, the sites examined were divided into the following 3 groups: 1) those with both premolar (s) and molar (s), 2) those with premolar (s) but without molar (s), and 3) those without either premolars or molars. Also, the morphology of the mental foramen was classified by shape into four types on MPR-CT images. Then, a total of 80 canals of 40 patients were examined. The length of the anterior loop was calculated from measurements in the MPR-CT images both perpendicular and parallel to the dental arch, and the length of the anterior loop was measured on panoramic images. [Results] Regarding the distance from the alveolar ridge to the mental foramen in the mental foramen area, the male's were larger than the female's. Moreover, when a residual tooth was present in a molar position, this value increased. In the mental foramen areas, the path of the mandibular canal varied, and it was confirmed that the length of the anterior loop also showed individual differences. These findings showed that the both the path and morphology of the mandibular canal and the mental foramen vary widely. [Conclusion] These findings may assist surgeons in planning the surgical approach for placement of the implants, reducing the risk to the inferior alveolar nerve and vessels, especially in the anterior region.

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Japanese diagnostic criteria for Sjögren's syndrome (SS) was revised in 1999. The content of the revised criteria with referring oral examination is explained. The sensitivity and specificity for diagnosing SS and characteristics of the revised criteria is described. The revised criteria consists of 4 major items; histopathology, oral examination, ocular examination and serological examination. The diagnosis of SS can be made when the patients meets at least two of the above 4 items.
The first item consists of histopathology of biopsy specimen either from A) labial salivary glands or from B) lachrymal glands. The number of cells in periductal lymphoid cell infiltration shows over 50 can be regarded as a focus. When the focus score which is defined as the number of focus per 4mm² tissue area shows 1 or more the histopathology can be regarded as positive. The second item, oral examination consists of A) sialography or B) sialometry and salivary scintigraphy. The positive cut-off level in sialographic findings was revised to Stage I by Rubin and Holt classification which means small punctuate shadows less than 1mm in diameter diffuse distributed in whole gland. Both positive findings are required in the reduction of sialometry proven by either chewing gum test (10ml per 10 minutes or less) or the Saxon test (2 grams per 2 minutes or less) and decreased function in salivary gland scintigraphy.
The third item is the ocular examination. A) consists of the combination of Schirmer test and the rose bengal test, and B) consists of the combination of Schirmer test and fluorescein staining test.
The forth item consists of either A) anti-Ro/SS-A antibody positive or B) anti-La/SS-B antibody positive by the serologic test.
The revised diagnostic criteria was proven to show high 96.0% in sensitivity, 90.5% in specificity, 94.5% in accuracy for diagnosing SS when the criteria was examined in 900 sample patients from country wide in the survey research performed by a Grant-in-Aids for Scientific Research supported by Japan Society for the Promotion of Science. The wide recognition and practical use of the revised criteria is desirable.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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