Identification of the relationship of a lesion in the sublingual space to the mylohyoid muscle using MDCT and high-resolution MRI is a key part of the imaging assessment of the oral cavity and upper neck.

Objectives To investigate whether CT images reflect the anatomical condition of mylohyoid muscle defects by confirmation with subsequent dissection of cadavers, and to evaluate whether CT images are useful for detecting such defects. Methods CT scans of the head and upper neck were performed in six cadavers. Multiplanar reconstruction was carried out to obtain 2-mm-thick axial and coronal images of the mylohyoid muscle. The number of defects was determined. All the cadavers were subsequently dissected for comparison with the CT findings. The contents of the defects were also identified. Results CT demonstrated the presence of one or more mylohyoid defects in four of the six cadavers. Defects were seen bilaterally in three of the four cadavers. Five of eight defects were observed on both axial and coronal images, whereas two were not observed on coronal images and one was not observed on axial images. The defects contained part of the sublingual gland bilaterally in one cadaver and unilaterally in another. In one cadaver, the submental artery passed through the defect bilaterally. In the other cadaver, there were bilateral defects without any substantial contents. Conclusions Our results indicate that mylohyoid defects are commonly seen anatomically, and that some of them show herniation of the sublingual gland. CT images can demonstrate mylohyoid defects on multiplanar reconstructed images.

In cephalometric radiography, removal of the antiscatter grid yields a significant reduction in exposure with no significant loss of information.

orthodontic patients are children and adolescents, who are more sensitive to ionizing radiation than adults. In many cases, several cephalometric radiographs are taken during treatment and follow-up. Therefore, it is important that these patients be exposed to as little radiation as possible. In many facilities, cephalometric radiography is still performed using a grid to prevent image degradation, such as the decreased contrast caused by scatter radiation. The use of a grid results in increased exposure to compensate for the reduction in the radiation that reaches the detector plane. Some authors have removed the grid, 1 and introduced the air-gap technique 2 in cephalometric radiography. However, the scatter fraction, the ratio of the scatter radiation reaching the film plane to the primary radiation, with and without a grid, have been studied in cephalometric radiography in only one case. 2 In 1976, Muntz et al. 3 suggested that scatter rejection resulting from air gaps could be described using an empirical model in which the scattered radiation behaved as if it originated from an effective scatter point source (ESPS) located between the focal spot of the X-ray tube and the exit surface of the phantom (Fig. 1). Their suggestion was based on chest phantom experiments. In a subsequent paper, 4 they showed a similar tendency on mammography. In 1985, Sorenson and Floch 5 reported the effectiveness of ESPS models for various field sizes, tube voltages, and phantom thicknesses. However, these experiments did not include the parameters used in cephalometric radiography. These parameters could be explored from their results, but it is better to experiment using cephalometric radiography conditions directly. If this model is applicable to cephalometric radiography, the effectiveness of the scatter reduction for any distance of air gap could be estimated.In this study, we evaluated the use of the ESPS model for the scatter property in cephalometric radiography and estimated the scatter rejection effect of the air gap to optimize the air-gap distance. AbstractObjectives. The scatter radiation and scatter rejection effect of air gaps in cephalometric radiography were evaluated using an effective scatter point source (ESPS) model. Methods.A 16-cm-thick water-equivalent phantom was used to measure the scatter fraction. The distance from the source to the center of the object (SOD) was 150, 200, or 300 cm. The air gap was varied from 0 to 96 cm for each SOD. A photostimulable phosphor plate was used as the X-ray sensor. The measured scatter fraction ESPS model was used to simulate the scatter rejection by the air gap, and the predictions were compared with the grid. Results. There was excellent agreement between the ESPS model and the scatter measurements. The air gap reduced the scatter radiation, especially for an SOD of 200 or 300 cm, while keeping an object magnification of 1.1 in view of the signal-to-noise ratio improvement factor. Conclusions. The results suggest that a grid should not be used in cephalometric radiogr...