Objective To study the effects of breath holding during mid-expiration of CT scan on PET/CT and SUV of lung.Methods From September 2010 to December 2010,200 patients including 120males and 80 females (23-87 (55.01± 11.60) years),who underwent 18 F-FDG PET/CT studies were included.Patients were randomly divided into 2 groups using random number table.In breath holding (BH)group (52 males,48 females,age ranging from 29-83 (55.43±10.38) years),all underwent PET/CT studies with BH CT during mid-expiration.In free breath (FB) group (68 males,32 females,age ranging from 23-87 (55.68± 12.72) years),all underwent PET/CT studies with FB CT.PET/CT images were analyzed by 1 senior technologist and 2 nuclear physicians.Analysis was carried out for the special registration of PET and CT,SUV of lung tissue on the bottom of lung and respiratory motion artifacts of lung on CT scanning.The diaphragmatic dome showed on the same layer of PET and CT was considered as well-registration between CT and PET.Two-sample t test,x2 test and one-way analysis of variance were used to analyze data.Results In BH group,28％ (28/100) of expiratory motion artifacts was observed,which was significantly lower than that of FB group (96％,96/100; x2 =98.132,P＜0.01).In BH group,40％ (80/200) was considered well-registration between CT and PET,which was significantly higher than that of FB group (30％,60/200; x2 =4.396,P＜0.05).There were 3 types of registration between CT and PET:location of diaphragm on CT higher than that on PET,matching between PET and CT,location of diaphragm on PET higher than that on CT.SUV in low lung tissue of these different types were increased one by one,with more significant difference found in BH group (SUVmax:0.73±0.28,1.00±0.29,1.60±0.68; SUVmean:0.59±0.23,0.81±0.22,1.33±0.34;F=21.93,24.57,both P＜0.01) than those in FB group (SUVmax:0.84±0.36,1.08±0.27,1.16±0.24; SUVmean:0.69±0.29,0.85±0.20,0.94±0.24; F=7.23,6.29,both P＜0.01).Conclusion Artifacts of respiratory motion on CT could be reduced significantly by BH CT scanning during mid-expiration,while the rate of well-registration between PET and CT is increased.%目的 探讨呼气中期屏气CT扫描模式对PET/CT图像质量及肺组织SUV的影响.方法 将2010年9月至12月间序列完成18F-FDG PET/CT显像的200例常规受检者纳入研究,其中男120例,女80例,年龄23～87(55.01±11.60)岁.所有受检者按随机数字表法分成2组:平静呼气中期屏气行PET/CT之同机CT采集组[屏气组,男52例,女48例,29～ 83(55.43±10.38)岁]和自由平静呼吸行PET/CT之同机CT采集组[自由呼吸组,男68例,女32例,23 ～ 87(55.68± 12.72)岁],每组各100例.图像分析由核医学科1位资深技师和2位资深医师评判.分析所有PET/CT的PET和CT空间配准、肺底部肺组织SUV和CT图像中肺部呼吸运动伪影等.以PET和CT在同一层面出现膈顶为两者空间配准良好,反之为配准不良.采用SPSS 17.0软件对数据进行统计分析,不同组SUV间差异比较采用两样本t检验或单因素方差分析,率的比较采用x2检验.结果 屏气组同机CT肺组织呼吸伪影发生率(28％,28/100)明显低于自由呼吸组(96％,96/100; x2=98.132,P＜0.01).屏气组PET/CT的PET和CT空间配准良好率(40％,80/200)明显高于自由呼吸组(30％,60/200;x2=4.396,P＜0.05).CT图像上出现膈顶先于PET、PET和CT膈顶位置配准良好和PET图像上出现膈顶先于CT 3种情况的肺底部组织的SUV逐项递增,屏气组(对应的SUVmax分别为0.73±0.28、1.00±0.29和1.60±0.68,SUVmean分别为0.59±0.23、0.81±0.22和1.33±0.34;F=21.93和24.57,均P＜0.01)此现象较自由呼吸组明显(对应的SUVmax分别为0.84±0.36、1.08±0.27和1.16±0.24,SUVmean分别为0.69±0.29、0.85±0.20和0.94±0.24;F=7.23和6.29,均P＜0.01).结论 呼气中期屏气CT扫描简便易行,不增加辐射剂量,可明显降低同机CT呼吸运动伪影发生率,在一定程度上提高PET和CT图像空间配准率.PET和CT失配准膈肌位置不同可导致低估或高估肺组织SUV.
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