迭代重建对肺肿块低剂量CT灌注成像参数的影响

Functional parameters of pulmonary tumors in low-dose perfusion CT with different reconstruction techniques:comparison of ASIR and FBP

目的:探讨自适应统计迭代重建(ASIR)算法对低剂量CT首次通过法肺肿块灌注成像参数的影响。方法:28例肺肿块患者行首次通过法低剂量CT灌注成像检查,所得原始数据采用滤波反投影(FBP)和30%ASIR两种方法进行重建(重建层厚2.5mm),测量两种算法重建图像上主动脉CT值、图像噪声及肺肿块灌注成像参数,包括表面通透性(PS)、平均通过时间(MTT)、血流量(BF)和血容量(BV),采用配对t检验分析两种重建算法所测量的各参数值的差异。结果:FBP和30%ASIR重建算法比较:主动脉CT值分别为(35.32±2.39)和(35.54±2.71)HU,差异无统计学意义(P=0.617);FBP组图像噪声(51.60±5.34)明显高于30%ASIR组(40.42±3.10),差异有高度统计学意义(P<0.01)。两种重建算法测量的各项灌注参数(PS、MTT、BV和BF)值差异均无统计学意义(P>0.05)。结论:在低剂量CT首次通过法肺肿块灌注成像中,30%ASIR算法测量的各项参数与FBP重建算法相比无明显差异,但图像噪声明显降低。

Objective：To compare the difference of filtered back projection （FBP） and adaptive statistical iterative reconstruction （ASIR） in functional parameters of first-pass perfusion CT in pulmonary tumors with volume helical shuttle scan. Methods：Twenty-eight consecutive patients with pulmonary tumors underwent first-pass perfusion CT with volume helical shuttle technique. All the raw data had been reconstructed with different reconstruction techniques：FBP and 30% ASIR,the slice thickness being 2.5mm. The CT values of aorta and image noise were recorded for both groups. The Para metric maps for the permeability surface （PS）,blood flow （BF）, blood volume （BV） and mean transit time （MTT） were calculated. Paired samples t test was used to analyze the difference. Results：Compared with FBP reconstruction technique, 30% ASIR demonstrates lower image noise E（51. 60±5. 34） vs （40.42±3.10） ,P〈0. 012 ,with no statistical difference in CT values of aorta [ （35.32 ± 2.39） HU vs （ 35.54 ± 2. 71 ） HU, P ： 0.61 ]. All the functional parameters of CT perfusion between two groups, including PS, MTT, BV and BF, showed no statistical difference （P〉 0.05）. Conclusion： Application of ASIR demonstrates no influence in functional parameters acquired from CT perfusion with volume helical shuttle technique, though the noise is lower than FBP.