多层螺旋CT扫描正常内耳容积再现技术成像参数研究

目的:探讨多层螺旋CT容积再现技术(VRT)正常内耳成像的最佳成像参数。方法:对10例(20耳)健康志愿者进行MSCT扫描,并对双侧耳分别进行重叠放大重建,重建间隔分别采用0.1mm(重叠86.7%)、0.2mm(重叠73.3%)、0.3mm(重叠60%)、0.4mm(重叠46.7%)和0.5mm(重叠33.3%),然后以容积再现技术(VRT)对内耳进行图像重组,比较不同重建间隔对VRT图像质量的影响。调整VR重组的阈值,分别选择-1000～0HU、0～ 1000HU和-1000～ 1000HU,比较3组阈值对图像质量的影响。结果:三组阈值间VRT图像质量有明显差异,其中以-1000～ 1000HU为最佳,其图像内耳结构显示完整、清晰,边缘清晰锐利,立体感较强,无明显伪影;以阈值-1000～0HU所得图像最差,内耳结构显示粗细不均、密度不等,半规管显示不完整。重建间隔为0.1和0.2mm时图像立体感较强,分辨力较高,内耳结构显示清晰。结论:MSCT内耳成像0.75mm准直器宽度时选择0.2mm重建间隔所得VRT图像质量最佳;VR图像重组时阈值-1000～ 1000HU时内耳三维结构显示最佳。

Study of the Parameters for Volume Rendering Technique with Multislice Spiral Computed Tomography for the Imaging of Normal Inner Ear

Objective:To investigate the optimal parameters for the visualization of inner ear with volume rendering technique(VRT)using multislice spiral computed tomography(MSCT).Methods:10 healthy volunteers with 20 normal ears were examined with MSCT.Bilateral ears were scanned and reconstructed with the reconstruction increment of 0.1mm,0.2mm,0.3mm,0.4mm and 0.5mm,respectively.VRT reconstructions were done on the workstation using three different ranges of threshold,which were-1000~0HU,0~ 1000HU and-1000~ 1000HU.The VRT images with different increments and different thresholds were compared.Results:There was significant statistical difference between the different thresholds,with-1000~ 1000HU the best,showing complete and clear inner ear structure,better stereographical images and without obvious artifact.The threshold-1000~0HU was the worst,showing the inner ear with uneventful structure,heterogeneous attenuation and incomplete semi-circular canals.Better resolution,well-delineated inner ear structure and stereographical images could be obtained by using the increment as 0.1mm and 0.2mm for reconstruction.Conclusion:The most optimal VR images of inner ear with MSCT could be obtained when using 0.75mm collimation and 0.2mm increment for reconstruction.When using the threshold-1000~ 1000HU for reconstruction,the 3-dimensional inner ear VR images could be assessed.