The patients exposure dose is usually expressed with reference to the detrimental health effects. The effective dose may be accepted as such a dose. To calculate effective dose, it is necessary to know the radiation doses in various organs, but this is almost impossible. The effective dose was thus estimated for intraoral examinations using organ doses determined by the Monte Carlo simulation. In addition, the mean energy imparted was also calculated. The mean energy imparted represents a useful practical quantity for estimating detrimental effects in patients. The purpose of this study was to determine patient exposure from the dose which can be easily measured in the X-ray room. Dose-area product was proved to be the best quantity for estimating mean energy imparted under appropriate conditions. The mean energy imparted could be estimated with reasonable accuracy (about 30%) from dose-area product at the same beam quality. There is a reasonable correlation between mean energy imparted and detrimental health effects for a wide range of x-ray examinations. The effective dose can be estimated from dose-area product with reasonable accuracy at the same beam quality and the same projection site. The effective dose should be estimated only at the same beam quality if the uncertainty factor of two is permissible. Effective dose for intraoral examination can be calculated practically only from the equivalent doses of the thyroid, red bone marrow, brain, bone surface, skin, upper esophagus and muscular substance. Of those, equivalent dose for the thyroid was the most effective. As the average absorbed dose for the thyroid is influenced significantly by positioning in the same site for the small field size as in intraoral examinations, this might result in a unstable effective dose. There is no such instability in the mean energy imparted. In an ideal x-ray department, patient dose measurement should be always carried out on every patient, including for the purpose of quality assurance procedures. The dose-area product method is more convenient for this purpose.

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In recent years, advances in imaging diagnosis have clarified the clinical details of temporomandibular joint (TMJ) arthrosis. Especially, arthrotomography is very useful for the detection of displacement, deformity and perforation of the TMJ disc. However, it remains impossible to detect capsular adhesion or synovitis by X-ray examination alone. Arthroscopy is of great value in diagnosing intracapsular TMJ lesion and fine needle fiber-arthroscopy which causes less damage than an ordinary arthroscopy, has been applied to the TMJ region recently. However, it is unreasonable to apply classifications used with ordinary arthroscopy to fine needl (fiber-arthroscopy. In this study, we diagnosed the TMJ based on the findings of fine needle fiber-arthroscopy, and compared this with the findings on arthrography. The subjects were ten patients (5 men and 5 women, mean age 35.4years) these cases were diagnosed with anterior disc displacement without reduction by clinical findings and arthrotomographic examination. We performed fine needle fiber-arthroscopic examination at the same time as single-contrast arthrotomographic examination in these patients. Findings of arthrography and fine needle fiber-arthroscopy were compared. The results were as follows. 1) According to single-contrast arthrographic examination, abnormal findings of disc configuration were revealed in 7 cases while 3 cases appeared normal. Ten cases showed anterior displacement of the disc, 1 case showed perforation of the disc. 2) As a result of fine needle fiber-arthroscopic examination, abnormalities of the articular eminence were observed in 3 cases. Four cases showed abnormal disc and retrodiscal tissue surfaces, while 4 cases showed abnormal synovial surfaces. 3) Comparison between the findings on arthrography and those on fine-needle fiber-arthroscopy revealed that disc configuration and anterior disc displacement were related to the surface abnomalities described above. This diagnostic arthroscopic system using a fine needle fiber-scope (0.8mm or 1.0mm) could be used with arthrography simultaneously. Therefore, the risk of injury to the patient could be minimized. There were no complications in any case.

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Radiographic features of Ameloblastoma and odontogenic keratocyst are similar although their biological behaviors are different. Therefore, it is very important to differentiate these lesions before treatment. The aim of this study was to differentiate between the two lesions based on characteristic CT findings. Fifty-three patients diagnosed histopathologically as having ameloblastoma (29 cases) or odontogenic keratocyst (24 cases) and who underwent CT were evaluated radiologically, and some characteristic radiological features to differentiate both lesions were assessed. 1) Ameloblastomas tended to be more than 40mm in long diameter and 0.5 short/long diameter ratio, whereas odontogenic keratocysts were less than 40mm and 0.5, respectively (P<0.05: Chi-square test). 2) Buccal expansion of the cortex was seen more often in amelob-lastomas than in odontogenic keratocysts (P<0.05: Chisquare test). 3) Together with these features and internal high density structure, which was only seen in odontogenic keratocysts, differential diagnostic criteria between ameloblastomas and odontogenic keratocysts were proposed. Diagnostic accuracy based on these criteria was 84.9%. These results that our criteria to differentiate ameloblastomas from odontogenic keratocysts using CT are clinically useful prior to treatment.

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The aim of this study was to investigate the changes in the immune organs after head and neck irradiation. The numbers of lymphocytes in peripheral blood, the spleen and the thymus following local irradiation (10Gy) of a portion of the maxilla in mice were studied using three-color fluorometry (anti-CD3, CD4, CD8 and TCR αβ^-monoclonal antibodies), and were compared with a non-irradiation group. The following results were obtained: 1) In the peripheral blood, the absolute numbers of T cells, CD4⁺SP cells and CD8⁺SP cells decreased after irradiation, and the period of the decrease was longer than the decreases in number of leukocytes and lymphocytes. The ratio of CD4⁺SP cells showed a significant decrease, and the ratio of CD8⁺SP cells showed a significant increase 1 day after irradiation. 2) In the spleen, the absolute number of T cells, the radio of CD4⁺SP and CD8⁺SP cell subsets showed a decrease, and the period of the decrease was longer than the decrease of the wet-weight of the spleen, and also longer than the decrease of the number of leukocytes. The number of CD4⁺SP cells showed a significant increase, and CD8⁺SP cells showed a significant decrease 21 days after irradiation. 3) In the thymus, the absolute number of TCR αβ^-thymocytes did not show a significant decrease. However, the number of DN thymocytes showed a marked decrease. These results indicate that the numbers of T cells in peripheral blood, the spleen and the thymus change immediately after irradiation, and the numbers of lymphocytes and the T cells in the spleen recover more slowly than that in the peripheral blood. As lymphoid tissues showed the suppression of immunological response for a long period, it was suggested that lymphoid tissues have to be observed carefully after irradiation to prevent cancer metastasis.

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First and second branchial arch syndrome is a rare congenital disease characterized by anomalies developing in first and second branchial arches during the embryonic stage. Major manifestations are found in tissue and organs originating from first and second branchial arches. We encountered a 7-year-old girl with first and second branchial arch syndrome accompanied by absence of the parotid gland. The following findings were obtained on examination. 1) A markedly asymmetrical face was noted due to hypoplasia of the middle and lower parts of the right face. 2) Right external auditory canal atresia and auricular deformity were noted. Accessory ear or deafness was not noted. 3) Plain and panoramic radiographs showed hypoplasia of the mandiblar joint and partial aplasia of the zygomatic process on the right side. 4) Cephalometric analysis revealed a remarkable underdevelopment of the mandible. 5) A CT scan showed hypoplasia of the right lateral pterygoid muscle and absence of the right masseter muscle. 6) No systemic disease, including cardiac or renal disorder, was noted. 7) Hereditary factors were not evident. 8) Absence of the right parotid gland was noted. Similar findings have been reported in patients with Treacher Collins syndrome and Goldenhar syndrome. In the present case, however, diagnosis of first and second branchial arch syndrome was established on the basis of the unilateral abnormal findings and lack of spinal deformity or hereditary factors. Radiological findings have never been reported in patients with first and second branchial arch syndrome accompanied by the absence of the parotid gland, a very rare condition.

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