Quantitative Analysis on CT image in maxillofacial Region

CT值在解剖结构中的长度、体积和分布是颌面部CT图像定量分析的基本前提。本研究的目的是分析相邻解剖结构对这些形态测量值的影响。解剖结构的长度：对14具尸体的骨和软组织结构的长度进行了头影测量和CT图像测量。上颌窦的最大宽度和高度的CT图像得到的结果与头颅X线片有很好的相关性。CT测量的下颌骨皮质骨厚度比X线片测量的下颌骨皮质骨厚度小10-30%。CT图像上测量的腭部粘膜厚度比实际测量值小20%左右.腮腺CT值的分布从一具正常萌出的32颗牙齿的尸体上小心地取出腮腺，用石蜡包好后放回原位。对尸体腮腺进行了原位CT扫描，并在水模中进行了扫描。上颌骨颈平面轴位CT平均值与水相当。结果显示，与水中图像相比，腺体后部（靠近乳突）CT值较高，前部（下颌支后）CT值较低，冠状面上腺体上部CT值较高，下部CT值较低。冠状面中平面近中侧位CT值显示，近下颌支1-2mm长度内的CT值高于腺体内的CT值.唾液腺的体积从尸体的CT图像估计的腮腺和下颌下腺的体积比实际测量的提取的腺体的体积大约30%。

The length, volume and distribution of CT values in the anatomical structures are the fundamental prerequisites for quantitative analysis of CT images in the maxillofacial region. The purpose of this investigation is to analyze the effect of the neighboring anatomical structures on these morphometric values.1. Length of Anatomical Structures.The length involved in bone and soft tissue structures of 14 cadavers were measured in both cephalometric and CT images. The maximum width and height of the maxillary sinus obtained from CT images are well correlated to those from cephalograms. The cortical bone thickness of the mandible measured in the CT images are 10-30% less than those in cephalograms. The mucosal thickness of the palate measured in the CT images are about 20% less than that actually measured.2. Distribution of CT Value in ParotidA parotid gland was carefully removed from a cadaver with 32 teeth normally erupted and was placed back after wrapped with a sheet of paraffin wax. CT scan was performed for the parotid gland in the cadaver in situ and also in a water phantom. Average CT value in the axial CT image at the cervival plane of the maxilla was equivalent to that of water. However, the CT values were higher in the posterior portion (close to the mastoid process) and lower in the anterior portion (posterior to the madibular ramus) in the gland than those measured in the images of the gland in water.The CT profile in the coronal plane showed higher CT values for upper portion and lower CT values for lower portion of the gland than those obtained from the images in water. The mesio-lateral profile in the mid-plane of the coronal section indicated that CT values close to the madibular ramus were higher in the 1-2mm length than those measured in the gland in water.3. Volume of Salivary GlandThe volume estimated from CT images of the cadaver was about 30% larger for both parotid and submandibular glands than those actually measured for the extracted glands.