Reducing of Craniofacial Radiation Dose Using Automatic Exposure Control Technique in the 64 Multi-Detector Computed Tomography

Seoung, Youl Hun; Kim, Yong Ok; Choe, Bo Young

Abstract

The purpose of this study was to evaluate the usefulness of reducing of craniofacial radiation dose using automatic exposure control (AEC) technique in the 64 multi-detector computed tomography (MDCT). We used SOMATOM Definition 64 multi-detector CT, and head of whole body phantom (KUPBU-50, Kyoto Kagaku CO. Ltd). The protocol were helical scan method with 120 kVp, 1 sec of rotation time, 5 mm of slice thickness and increment, 250 mm of FOV, 512x512 of matrix size, 64x0.625 mm of collimation, and 1 of pitch. The evaluation of dose reducing effect was compared the fixed tube current of 350 with AEC technique. The image quality was measured the noise using standard deviation of CT number. The range of craniofacial bone was to mentum end from calvaria apex, which devided three regions: calvaria~superciliary ridge (1 segment), superciliary ridge~acanthion (2 segment), and acanthion~mentum (3 segment). In the fixed tube current technique, CTDIvol was 57.7 mGy, DLP was 640.2 mGy.cm in the all regions. The AEC technique was showed that 1 segment were 30.7 mGy of CTDIvol, 340.7 mGy.cm of DLP, 2 segment were 46.5 mGy of CTDIvol, 515.0 mGy.cm of DLP, and 3 segment were 30.3 mGy of CTDIvol, 337.0 mGy.cm of DLP. The standard deviation of CT number was 2.622 with the fixed tube current technique and 3.023 with the AEC technique in the 1 segment, was 3.118 with the fixed tube current technique and 3.379 with the AEC technique in the 2 segment, was 2.670 with the fixed tube current technique and 3.186 with the AEC technique in the 3 segment. The craniofacial radiation dose using AEC Technique in the 64 MDCT was evaluated the usefulness of reducing for the eye, the parotid and thyroid with high radiation sensitivity particularly.