自由呼吸零回波技术在磁共振肺部扫描的可行性分析及基于图像质量的扫描参数最优设置研究初探

Feasibility of zero echo time technique in MRI scan for lung diseases and the optimization of parameters based on image quality

目的探讨自由呼吸状态下磁共振3.0 T零回波(MRI-ZTE)技术应用于肺部成像的可行性,评价不同空间分辨率与层厚参数设置对肺部磁共振图像质量的影响,优化适用于自由呼吸零回波(ZTE)肺部成像的最佳扫描协议。方法选取2018年10月至2019年3月间中国医学科学院肿瘤医院行MRI-ZTE技术扫描的受检者96例。MRI扫描包括常规横轴位屏气T1WI及T2WI序列横轴位MRI-ZTE序列,扫描范围由肺尖到肺底;MRI-ZTE序列根据空间分辨率及层厚组合,扫描8组MRI-ZTE图像,记录MRI-ZTE序列的全肺扫描时间。由2名不同年资胸部影像学放射科医生依据图像质量评分标准评价8组MRI-ZTE图像,并计算一致性。结果8组图像主观评分得分分别为:(SR2.0ST2.0)组(4.4±0.5)分(SR1.5ST2.0)组(4.8±0.3)分(SR1.25ST2.0)组(4.8±0.2)分,(SR1.1ST2.0)组(4.8±0.2)分,(SR2.0ST1.2)组(4.9±0.2)分,(SR1.5ST1.2)组(4.9±0.1)分,(SR1.25ST1.2)组(4.9±0.2)分,(SR1.1ST1.2)组(4.3±0.6)分,其中空间分辨率2.0mm及层厚1.2mm组图像质量最佳,且较其它各组评分差异有统计学意义(P<0.05)。8组不同MRI-ZTE序列扫描时间分别为:(SR2.0ST2.0)组7分7秒、(SR1.5ST2.0)组5分44秒、(SR1.25ST2.0)组4分39秒、(SR1.1ST2.0)组4分18秒、(SR2.0ST1.2)组7分56秒、(SR1.5ST1.2)组6分19秒、(SR1.25ST1.2)组5分5秒和(SR1.1ST1.2)组4分38秒。层厚为2.0mm的4个扫描参数序列组扫描时间多于层厚为1.2mm的4个扫描组差异均有统计学意义(均P<0.05)。2名放射科医师对8组MRI-ZTE图像评价的一致性好(kappa=0.67)。结论ZTE技术可应用于肺部MR扫描,且空间分辨率1.25mm和层厚1.2mm的参数组合图像质量最优。

Objective To discuss the feasibility of zero echo time(ZTE)magnetic resonance imaging(MRI)at 3.0 T applied to lung imaging and the effects of different spatial resolutions and layer thickness parameters on image quality to optimize best scan protocol for ZTE pulmonary imaging.Methods A total of 96 participants who underwent MRI-ZTE scan were recruited at Cancer Hospital,Chinese Academy of Medical Sciences between October 2018 and March 2019.Axial scanning range of all sequences was the whole lung(from the apex to the base)based on the spatial resolution and layer thickness for a set of eight different ZTE sequences.Meanwhile,the acquisition time of ZTE sequence was documented.Eight different ZTE sequences were evaluated and the consistency was estimated by two blinded thoracic radiologists using image quality assessment scale scale.Results The subjective rating score was 4.4±0.5 for SR2.0ST2.0,4.8±0.3 for SR1.5ST2.0,4.8±0.2 for SR1.25ST2.0,4.8±0.2 for SR1.1ST2.0,4.9±0.2 for SR2.0ST1.2,4.9±0.2 for SR1.5ST1.2,4.9±0.1 for SR1.25ST1.2,and 4.3±0.6 for SR1.1ST1.2.The image quality of ZTE sequence with 1.5 mm spatial resolution and 1.2 mm slice thickness was significantly superior to others(P<0.05).The duration of scanning of 8 groups of ZTE sequences were 7 min and 7 s(SR2.0 ST2.0),5 min and 44 s(SR1.5ST2.0),4 min and 39 s(SR1.25ST2.0),4 min and 18 s(SR1.1ST2.0),7 min and 56 s(SR2.0ST1.2),6 min and 19 s(SR1.5ST1.2),5 min and 5 s(SR1.25ST1.2)and 4 min and 38 s(SR1.1ST1.2),respectively.The duration of scanning was longer in 4 sequence groups with layer thickness of 2.0 mm than in 4 sequence groups with layer thickness of 1.2 mm(P<0.05).Intraclass correlation coefficient(ICC)of interrater agreement was excellent between two radiologists(Kappa value=0.67).Conclusion ZTE can be used in magnetic resonance imaging of lung.The optimum image acquisition was sat at the combinations of 1.5 mm spatial resolution and 1.2 mm slice thickness.