重建参数对CT肺结节容积测量的影响

Effects of Different Reconstruction Parameters on CT Volumetric Measurement of Pulmonary Nodules

背景与目的已有的研究证明:CT肺结节容积测量能够敏感反映结节容积的微小变化,在未定性肺结节的随访观察及良恶性鉴别方面具有重要应用前景。本研究旨在评估不同重建算法和层厚对CT肺结节容积测量的影响。方法对2009年12月-2011年8月在天津医科大学总医院行未定性肺结节CT随访研究的30例患者的CT图像进行后处理分析。共获取52个肺结节,应用3种不同的算法(骨密度算法、标准算法及肺算法)及层厚(0.625 mm、1.25 mm、2.5 mm)进行9次重建。由一位放射科医师应用肺结节容积分析软件进行容积测量。应用重复测量多元方差分析、相关分析及Bland-Altman法评价结节直径、算法、层厚对容积测量的影响。结果不同重建算法(F=13.6,P<0.001)、层厚(F=4.4,P=0.02)条件下测量所得的结节容积之间具有统计学差异。肺结节9次测量所得容积的变异系数和结节直径之间呈负相关(r=-0.814,P<0.001)。应用2.5mm层厚时,结节容积比1.25mm及0.625 mm层厚的一致性差,1.25 mm和0.625 mm层厚在采用骨算法时一致性最好。结论不同重建算法及层厚对肺结节容积测量有影响,尤其是直径较小的结节。在未定性肺结节尤其是肺小结节的随访过程中建议应用相同的重建参数。

Background and objective It has been proven that volumetric measurements could detect subtle changes in small pulmonary nodules in serial CT scans,and thus may play an important role in the follow-up of indeterminate pulmonary nodules and in differentiating malignant nodules from benign nodules.The current study aims to evaluate the effects of different reconstruction parameters on the volumetric measurements of pulmonary nodules in chest CT scans.Methods Thirty subjects who underwent chest CT scan because of indeterminate pulmonary nodules in General Hospital of Tianjin Medical University from December 2009 to August 2011 were retrospectively analyzed.A total of 52 pulmonary nodules were included,and all CT data were reconstructed using three reconstruction algorithms and three slice thicknesses.The volumetric measurements of the nodules were performed using the advanced lung analysis（ALA） software.The effects of the reconstruction algorithms,slice thicknesses,and nodule diameters on the volumetric measurements were assessed using the multivariate analysis of variance for repeated measures,the correlation analysis,and the Bland-Altman method.Results The reconstruction algorithms（F=13.6,P0.00l） and slice thicknesses（F=4.4,P=0.02） had significant effects on the measured volume of pulmonary modules.In addition,the coefficients of variation of nine measurements were inversely related with nodule diameter （r=-0.814,P0.001）.The volume measured at the 2.5 mm slice thickness had poor agreement with the volumes measured at 1.25 mm and 0.625 mm,respectively.Moreover,the best agreement was achieved between the slice thicknesses of 1.25 mm and 0.625 mm using the bone algorithm.Conclusion Reconstruction algorithms and slice thicknesses have significant impacts on the volumetric measurements of lung nodules,especially for the small nodules.Therefore,the reconstruction setting in serial CT scans should be consistent in the follow-up of indeterminate pulmonary nodules,more importantly for the small nodules.