A study of clinical appliance of multidetector-row CT in the maxillo-facial region

本研究旨在明确多排螺旋CT在颌面部临床应用中的最佳扫描条件。考虑到应用于评价颌骨畸形或关节紊乱患者的颞下颌关节(TMJ)骨变化，对体模的TMJ区域进行了多种条件的扫描。每次扫描获得的CT数据在4个不同的重建间隔进行重建，然后用重建图像进行多平面重建(MPR)。应用MPR的冠状位和矢状位图像评价TMJ的骨性，是最合适的条件组合。扫描范围：体模(恒定条件)中TMJ区域的扫描范围：50 mm(恒定条件)管电位：120KV(恒定条件)CT束准直：1.25 mm(恒定条件)管电流：80 mA(恒定条件)螺旋螺距：3(非恒定条件)重建间隔：0.25 mm(非恒定条件)在上述条件的组合中，扫描时间为14.8秒，CT剂量指数(CTDI)为25.08mGycm，剂量长度积(DLP)为139.15mGycm。比较相同重建间隔条件下的图像，可以认为管电流并不总是影响图像观察的容易程度。可以认为，重建间隔更有利于MPR图像的清晰显示。

This study was carried out mainly to make clear the optimal scanning conditions in clinical appliance of multidetector-row CT in the maxillo-facial region. Thinking of the appliance to evaluation of bone change of temporomandibular joint(TMJ) in the patients with jaw deformity or temporomandibular joint disorder, the region of TMJs of the phantom was scanned in several conditions. CT data obtained from every scanning was reconstructed in the different reconstruction interval of 4, then multi planar reconstruction(MPR) images were made with the reconstructed images. Coronal and sagittal images of MPR was used to estimate better imagse to evaluate bone in TMJ, the most suitable combination of the conditions i.s. tube current, helical pitch, reconstruction function, and reconstruction interval.Optimal scanning protocol of the region of TMJs was considered as follows.Scanning range : 50mm of the region of TMJ in the phantom (constant condition)Tube potential : 120kV (constant condition)CT beam collimation : 1.25mm (constant condition)Tube current : 80mA (inconstant condition)Helical pitch : 3 (inconstant condition)Reconstruction interval : 0.25mm (inconstant condition)In the combination of the conditions as above, scanning time, computed tomography dose index(CTDI), and dose-length product(DLP) were 14.8 seconds, 25.08mGy, and 139.15mGycm, respectively. Comparing images in the same condition of reconstruction interval, it might be suggested that tube current was not always effect on the ease of observation of images. It could be considered that reconstruction interval is more effective to make clear MPR images.