The two parameters, K and λ₁ or which were obtained by the two-compartment model analysis of bone scintigraphy show the values specific to individual bone disease in maxillofacial region. We assumed the K to be the saturated accumlation of the tracer in bone blood pools in region of interest (ROT) and the λ₁ to be the transition speed of the radioisotope from bone blood pools to the bone. The formar and the latter reflect the amount of blood flow and bone metabolism, respectively. These two parameters are thought out by mathematical analysis theoretically. Therefore we produced experimental bone disease models and revealed the meaning of the two parameters. The following results were obtained.
1) Femoral arteries and veins in rabbits were ligated by suture to induce tibial bone blood flow. The K was compared with the bone blood flow obtained by clearance of hydrogen gas generated by electrolysis.
(1) The computer-generated curve obtained by the two-compartment model analysis approximately accorded with the time-activity curve by dynamic bone scintigraphy. This rusult suggests the correctness of this two-compartment model analysis.
(2) Both the K ratio (K/K': K' as contralateral accumulation) and the bone blood flow ratio (blood flow at ROT/blood flow at contralateral side) showed significant decrease after the ligation.
(3) The K ratio was correlated with the bone blood flow ratio at less than 1% level (correlation coefficient: 0.75). Therefore, we think the K is a parameter representing bone blood flow as we assumed. 2) Tibial bone in rabbits was inoculated with 4-nitroquinoline-n-oxide to induce tibial bone metabolism. The λ₁ and the bone mineral density (BMD) by quantitative computerized tomography were determined 1, 2, 3 and 4weeks after inoculation, and the λ₁ was compared with BMD.
(1) Both the BMD and the amount of radioisotope transported from bone blood pool to bone from one after inoculation to 4weeks (∫^4week_1week λ₁·Kdt) increased as the week proceeds.
(2) The ∫^4week_1week λ₁·Kdt was correlated with BMD which increased during the same period of time at less than 0.1 % level (correlation coefficient: 0.91). The λ₁ which was assumed to be the transition speed of radioisotope from bone blood pool to bone was found to be an index for an increase in BMD.

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The analytical method was investigated to determine the quantitative parameter which reflects the regional bone metabolism using compartment model analysis of dynamic bone scintigraphy. The analyses were carried out using the image data of dynamic bone scintigraphy obtained from patients with maxillo-facial bone lesion except for metabolic bone disease. Two quantitative parameters which were named K and λ₁ were obtained. K represents the saturated accumulation of tracer in bone blood compartment in ROT. λ₁ represents the transmission speed of tracer from bone blood compartment to bone compartment. The subjects were 63 males and 34 females (aged 22-78 years). Analysis was performed at every settled ROT; these locations were the body of the mandible, mental region, alveolar process and inferior orbital regions of the maxilla, zygomatic, frontal, and parietal regions. The normal ranges of K and λ₁ were estimated in every age groups of men and women of these regions. Regression analyses demonstrated the age-dependence of parameters as follows. K decreased significantly with age at parietal region in male. The other part of K showed no significant change. λ₁ showed significant age related increase in zygomatic, frontal and parietal regions in each male and female, and inferior orbital region of the maxilla in female. The tendancy of the increases were more remarkable in female than male in every region. The order of increase in λ₁ was inferior orbital region of the maxilla, zygomatic, frontal, and parietal regions. In the body of the mandible, mental region, and alveolar process of the maxilla no significant increase could be observed regardress of sex, but decreased only in the body of the mandible in female.

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Film processing takes an important role in dental radiography. It should be optimized for both diagnosis and radiation protection. To improve the quality of dental X-ray examination in Nagasaki an actual survey of film processing of intraoral X-ray film in 50 dental clinics was carried out in September, 1987. An equally exposed film of a copper step wedge and a lead tablet was mailed to each dental clinic and asked to be processed in an ordinary procedure. The film processing in dental clincs was evaluated by film density, base plus fog density and image contrast of the processed films. The results were summarized as follows for two types of X-ray film. Non-screen type films were generally under developed and fixed comparatively well. The development of screen type films showed a considerable variation and the fixing of them was incomplete. In average non-screen type films maintained higher image quality than screen type films. The incomplete development and fixing in this result may be due to the requirement of shortening of film processing time in dental clinics. It was suggested that film processing in dental clinics should be improved under the proper guidance or recommendation.

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Taurodont is the tooth which shows the body of the tooth to enlarge at the expense of the root, and wide pulp chamber occulusoapically. Yet, objective criteria to diagnose this condition are not well established.
In this paper, eight representative parameters for the radiological feature of taurodont were chosen and five indices using these parameters were calculated. These indices were statistically evaluated to determine which is the best one to diagnose taurodont. As a result, the most significant index was the ratio of the distance from roof to floor in pulp chamber, and the distance from roof of pulp chamber to apex of the longest root.

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Ninety-four cervical lymph nodes of 28 patients were evaluated by ultrasonography. All lymph nodes were confirmed histologically, and 39 lymph nodes had metastases.
The mean shortest diameter of the metastatic lymph nodes was 16±9mm ultrasonographically, but that of the non-metastatic lymph nodes was 5±2mm. When lymph nodes larger than 8mm in shortest diameter were regarded as metastasis, high sensitivity (94.9%) and specificity (87.3%) were obtained.
Eccentric hyperechoic area, that was thought to represent the hilus of the lymph node was observed in 22 lymph nodes. Those were non-metastatic lymph nodes. Otherwise, all of 30 lymph nodes with inhomogeneous internal echoes or with peripheral hypoechoic zone were metastatic lymph nodes.
Ultrasonography was a useful examination for evaluating cervical lymph nodes.

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Thirty five cases of simple bone cyst were studied radiographically. In 6 cases among them, unusual radiographic features, which differed from the ordinary findings of simple bone cyst, were found. They were 1) presence of diffuse sclerotic margin 2) lack of interdental scalloped margin 3) a different pattern of obliteration of lamina dura 4) presence of root resorption 5) a combination with other lesions simulating a variety of fibro-osseous lesions in the jaw. Furthermore, the age distribution in those 6 cases was obiously higher than that of the other 29 cases and there was a marked predilection for occurrence in females over males. From these results, it was suggested that different disease entities might be comprised in the lesion even if it were diagnosed as simple bone cyst from the operative and/or histopathologic standpoints.

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Calcification in a tumor of the left submandibular gland was found by a roentgenogram and CT images of a 68-year-male patient, who had been aware of the swelling in the region for 19 years. Recent spurt of the tumor growth led the patient to seek the medical examinations and he was diagnosed as adenocarcinoma of the gland at biopsy. Thorough histopathological examination of the resected tumor revealed a bulky poorly-differentiated adenocarcinoma with an encapsulated hyaline nest, in which stroma, an ossified cartilage-like tissue and abundant elastic fibers were found.
Although there were no viable benign pleomorphic adenoma cells, depending on the above mentioned features of the hyaline nest, the final diagnosis was made as carcinoma in pleomorphic adenoma.
Calcification in salivary gland tumors may be a roentgenographic sign to be a malignancy.

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