[Comparison of absorbed and effective dose from two dental cone beam computed tomography scanners].

OBJECTIVE: This research compared the field of view with the tissue absorbed dose and effective doses using the two dental cone beam computed tomography (CBCT) scanners. MATERIALS AND METHODS: Two CBCT devices, an Alphard VEGA and 3DX multi-image micro CT MCT-1, were used. Measurements were made using an Alderson RANDO phantom and thermoluminescence dosimeters (TLDs). The calculation of the effective dose was carried out according to ICRP Publication 60 and 103. RESULTS: The effective doses for Alphard VEGA D mode, I mode, P mode, and C mode were 86, 238, 413, and 323 µSv, respectively. The effective doses using 3DX for the maxillary incisor, maxillary molar, mandibular incisor, mandibular molar, TMJ, and mandibular molar scout images were 27, 30, 48, 60, 14, and 1 µSv, respectively. CONCLUSIONS: Both Alphard VEGA and 3DX values revealed salivary gland and oral mucosa doses much higher than those required for other tissues. It is necessary to select a small mode suitable in order to realize optimization.

[Absorbed dose and the effective dose of panoramic temporo mandibular joint radiography].

PURPOSE: This study measured the radiation doses absorbed by the patient during Panoramic temporo mandibular joint radiography (Panoramic TMJ), Schüllers method and Orbitoramus projection. The dose of the frontal view in Panoramic TMJ was compared to that with Orbitoramus projection and the lateral view in Panoramic TMJ was compared to that with Schüllers method. METHODS: We measured the doses received by various organs and calculated the effective doses using the guidelines of the International Commission on Radiological Protection in Publication 103. Organ absorbed doses were measured using an anthropomorphic phantom, loaded with thermoluminescent dosimeters (TLD), located at 160 sensitive sites. The dose shows the sum value of irradiation on both the right and left sides. In addition, we set a few different exposure field sizes. RESULT: The effective dose for a frontal view in Panoramic TMJ was 11 µSv, and that for the lateral view was 14 µSv. CONCLUSION: The lens of the Orbitoramus projection was 40 times higher than the frontal view in Panoramic TMJ. Although the effective dose of the lateral view in Panoramic TMJ was 3 times higher than that of the small exposure field (10×10 cm on film) in Schüller's method, it was the same as that of a mid-sized exposure field. When the exposure field in the inferior 1/3 was reduced during panoramic TMJ, the effective doses could be decreased. Therefore we recommend that the size of the exposure field in Panoramic TMJ be decreased.

[Estimation of effective dose to salivary glands at examination of the oral and maxillofacial region].

The salivary glands and the oral mucosa were included in the determination of effective doses of radiography in the new ICRP (International Commission on Radiological Protection) recommendations. These changes will likely result in an upward reassessment of the effective dose during oral and maxillofacial radiographic examination. We measured the dose received by many organs and calculated the effective doses using the guidelines in ICRP Publications 103 and 60. For this study, we used intraoral radiography (incisor, canine, premolar, molar, maxillary, and mandibular areas) and panoramic radiography. The two levels of effective doses were compared. As a result, exposure during intraoral radiography ranged from 4 to 8 microSv and that during panoramic radiography ranged from 16 microSv in Publication 103. Effective doses in Publication 103 were higher than those in Publication 60. The dose was 1.6-4.5 times higher in intraoral radiography and 2.2 times higher in panoramic radiography. In conclusion, the salivary glands markedly influenced the value of the effective doses of radiography in this study.