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目的探讨胸部螺旋CT最大密度投影(MIP)重建合理的扫描和重建参数。方法6例煤工的尸检离体肺脏制成充气固定肺标本,分别行不同参数组合的螺旋CT扫描,包括层厚1.5mm,2mm,4mm及8mm,重建间隔1mm,3mm,5mm;曝光量150mA,100mA;螺距1.5;滤过算法包括标准、锐利和平滑3种。每组图像均行MIP重建,重建厚度为12.5mm～13mm,比较不同参数MIP重建图像对支气管血管束的显示。结果a)曝光量对MIP重建图像的影响甚微,150mA、100mA两组剂量MIP无显著性差异(P>0.05);b)重建算法对MIP重建无显著影响。c)扫描层厚影响MIP图像,以薄层(1.5mm)扫描重建为最佳,1.5mm、2mm、4mm层厚MIP图像之间无显著性差异(P>0.05),8mm层厚与前4者MIP图像有显著性差异(P<0.01)。d)重建间隔影响MIP重建效果,8mm层厚扫描,1mm和5mm重建间隔重建图像MIP之间有显著性差异(P<0.05)。结论影响MIP重建的参数主要为扫描层厚和重建间隔,薄层扫描可获得理想的MIP图像,随层厚的增加,减小重建间隔有利于获得理想的MIP图像。建议以中等层厚(4mm)扫描,小重建间隔(1.5mm,2mm)行MIP重建。
Objective To investigate the reasonable reconstruction and reconstruction parameters of maximum density projection (MIP) reconstruction of chest spiral CT. Methods 6 cases of autopsy in the coal mine were made into fixed lung specimens from inflatable lungs. Spiral CT scans with different parameters were performed, including layer thickness 1.5mm, 2mm, 4mm and 8mm, reconstruction interval 1mm, 3mm, 5mm; exposure 150mA , 100mA; Pitch 1.5; Filtering algorithms include standard, sharp and smooth 3 kinds. MIP reconstruction was performed on each group of images, reconstruction thickness of 12.5mm ~ 13mm, compared with different parameters MIP reconstruction images on the display of bronchovascular bundles. Results (a) Exposure had little effect on MIP reconstruction images. There was no significant difference in MIP between 150mA and 100mA (P> 0.05). B) Reconstruction algorithm had no significant effect on MIP reconstruction. c) Scanned layer thickness affected the MIP image, and the thin layer (1.5mm) scan reconstruction was the best. There was no significant difference (P> 0.05) between the MIP images of 1.5mm, 2mm and 4mm layer thicknesses, MIP images were significantly different (P <0.01). d) Reconstruction interval affected MIP reconstruction. There was a significant difference (P <0.05) between 8mm slice thickness scan and MIP in 1mm and 5mm reconstruction interval reconstruction images. Conclusion The parameters affecting the MIP reconstruction are mainly the scan layer thickness and the reconstruction interval. The ideal MIP image can be obtained by thin layer scanning. With the increase of the layer thickness, reducing the reconstruction interval is favorable for obtaining the ideal MIP image. Recommended medium thickness (4mm) scan, reconstruction interval (1.5mm, 2mm) MIP reconstruction.