CTA图像后处理技术对血管管径影响的实验研究

Experimental study of the influence of CT angiography post-processing on vascular caliber measurements

目的:探讨CT血管造影(CTangiography,CTA)后处理技术容积重建(volumerendering,VR)中阈值、最大密度投影(maximum intensity projection,MIP)中窗宽及窗位、视野(Field of view,FOV)对血管管径测量的影响及相关关系。方法:建立9个不同密度的血管模型,使用不同的FOV、阈值(VR)、窗宽(MIP)测量不同密度血管模型管径,分析标准阈值、窗宽与血管模型管径的关系,并与CT值进行相关性分析。统计临床脑血管CTA MIP重建病例30例的窗宽及窗位,与实验结果进行比较。结果:VR重建,阈值和血管模型管径呈明显负相关(r=-0.847,P=0.000);MIP重建,窗宽和血管模型管径呈明显正相关(r=0.983,P=0.000);FOV和血管模型管径无相关性(r=-0.042,P=0.381)。临床脑血管CTAMIP重建窗宽明显增宽,夸大了血管真实管径。结论:CTA血管管径测量的准确性受VR重建阈值、MIP重建窗宽窗位的影响,根据血管内对比剂密度对这些参数进行调整,保证测量血管管径的可靠性和准确性。

Objective：To investigate the effects of volume rendering opacity , maximum intensity projection window width and window level ,and field of view on the accuracy of vascular calibre measurements in vessel phantoms for CT angiography. Methods：9 vascular models were filled with contrast material of nine different densities, vascular calibre was measured by different sizes of field of view, opacity in VR,and window width in MIP. Correlations among them were analyzed. 30 groups of randomized data of window width and window level of MIP reconstruction for cerebral CT angiography were compared with experimental results. Results：Standard opacity of volume rendering was negatively correlated with vessel calibre in vascular models（r = - 0.847, P = 0.000 ）. Maximum intensity projection window width was positively correlated with vessel calibre in vascular models（r =0.983, P = 0.000 ）. There was no correlation between field of view and vessel caliber measurement in vascular models （r = -0.042,P = 0.381 ）. There was prominent widening of MIP reconstruction window width , and the actual vessel calibres were exaggerated as noted on CT angiograms. Conclesion：The accuracy of the calibre measurements by vascular model for CT angiography was affected by VR reconstruction opacity and MIP reconstruction window width. In order to ensure the dependability and accuracy of the vascular diameter measurement, it is necessary to adjust these parameters according to intravascular density of the contrast material.