A Study of Effective Sequences on Micro-CT in the Dent-maxillo-facial Region
2005 Volume 45 Issue 1 Pages 10-16
Details
2005 Volume 45 Issue 1 Pages 10-16
Purpose: Microfocus computed tomography (micro. CT) using cone-beam scan is becoming widely used for various studies of oral structures. However, this machine has not been used to evaluate the effective parameters for two-dimensional (2D) or three-dimen-sional (3D) images. This study evaluated the effective parameters of micro-CT for 2D or 3D images of oral hard tissue structures.
Subject and method:
1) Study of 2D images
We evaluated the CT value of 5 human teeth (upper first molars) to determine suitable CT value examined according to several X-ray parameters using CRT on a work station. CT information from the specimens was obtained using a micro-CT (Toscaner-31300μ, Toshiba ITC), under the conditions of tube voltage of 75kV, tube current of 120μA, 100∼1600 views, the number of times of addition, 512×512 pixel matrix, and 0.2 slice thickness.
2) Study of reconstruction images
We made 3D-reconstruction images from the micro-CT data. Three-dimensional reconstruction was performed using 2D images processed by the volume-rendering method using 3D-reconstruction soffware (TRI/3D BON, RATOC system engineering). Then, we evaluate the 3D tooth images. In the assessment of images, three dental radiologists evaluated several 3D tooth images using 3D-reconstruction images. Each image was scored on a five-level scale by Scheffé one-pair comparison method as follows: 5: much easier to evaluate, 4: easier to evaluate, 3: equivalent, 2: harder to evaluate, 1: much harder to evaluate. In scoring, each of the three dental radiologists made an individual assessment, and when differences among individual scores occurred, the score was ultimately assigned by consensus among the three individuals. Statistical analysis of the scores assigned by the three dental radiologists as described above was carried out using Stat View-J 5.0 (Abacus Concepts, Inc, USA) statistical software and Tukey-Kramer multiplecomparlson testlng.
Result & conclusion: The optimal CT value for evaluating the human tooth by micro-CT is 600 on 2D images. On 3D images, the optimal value is 600 for tooth and 400 for the mandible (p<0.01). Micro-CT of the tooth is useful for evaluation of dent-maxillo facial structures such as the tooth and mandible.
