18F-FDG PET/CT显像中连续进床采集和步进采集模式的比较

Comparison of continuous bed motion and step-and-shoot acquisition modes in 18F-FDG PET/CT imaging

目的探讨18F-脱氧葡萄糖(FDG) PET/CT显像连续进床(CBM)和步进(SS)采集模式中采集方案的差异及其对图像质量和标准摄取值(SUV)的影响。方法选择30例(男13例,女17例,年龄40~71岁)2017年6月至9月间于本科行18F-FDG PET/CT显像的患者,分别采用CBM和SS模式进行特定范围(颅顶上缘至坐骨下缘)的模拟采集方案设置,比较2种模式所需的实际采集长度及CT辐射剂量的差异;再分别采用CBM和SS行PET/CT采集,比较2种模式图像质量及SUV差异。采用配对t检验及X^2检验分析数据。结果对于特定采集范围,平均每例患者CBM模式所需实际采集长度比 SS 模式减少 6.65%[(87.11±3.78)和(93.32±6.02) cm;t=-7.737,P<0.001],CT 辐射剂量减少 6.88%[(812+170)和(872±192) mGy·cm;T=-6.432,P<0.001 ]。正常组织中肝脏、骨骼及腰部肌肉最大SUV(SUVmax)和平均SUV(SUVmax)在SS和CBM模式下的差异没有统计学意义(t值:-1.895-0.132,均P>0.05);图像末端腿部肌肉SUVmax在SS模式下明显高于CBM(1.24±0.53 和 1,06±0.42;t=3.450,P<0.01)。40个FDG高摄取病灶的SUVmax和SUVmean在两者间差异亦无统计学意义(t值:0.420和-0.260,均P>0.05)。SS和CBM模式下分别有73.33%(22/30)和80.00%(24/30)的患者整休图像质量为优(X^2=0.373,P>0.05);SS模式下有16.67%(5/30)的患者末端图像质量为优,明显少于CBM[63.33%(19/30);X^2=13.611, P<0.001]。结论在特定采集范围内,CBM可较SS减少不必要的CT扫描范围和CT辐射剂量;除末端图像外,两者正常组织和病灶的图像质量和SUV无明显差异。

Objective To investigate the differences of acquisition protocols from continuous bed motion (CBM) and step-and-shoot (SS) modes and to observe their effects on image quality and standard uptake value (SUV) in 18F-fluorodeoxyglucose (FDG) PET/CT. Methods A total of 30 patients (13 males, 17 females;40-71 years) who underwent 18F-FDG PET/CT from June 2017 to September 2017 were selected. Simulated acquisition protocols for a specific range (upper margin of the skull to the lower edge of sciatic bone) were established with CBM and SS modes. The differences between 2 modes for actual length requiring for a specific acquisition range and the differences in CT radiation dose were compared. Real PET/CT scans were performed using CBM and SS modes consecutively, and the differences in image quality and SUV were compared. Paired t test and X^2 test were used to analyze the data. Results For the specific acquisition range, the average acquisition length of CBM was reduced by 6.65%((87. 11 ±3.78) vs (93.32± 6. 02) cm;t=-7.737, P<0.001) and the CT radiation dose was reduced by 6.88%((812± 170) vs (872± 192) mGy·cm;t=-6.432, P<0. 001) for each patient compared with the results of SS. There were no significant differences in maximum SUV (SUVmax) and mean SUV (SUVmean) between SS and CBM in normal tissues including liver, bone and waist muscles (t values: from - 1.895 to 0.132, all P>0.05). The SUVmax of leg muscles at the end of the image was significantly higher in SS than that in CBM (1.24±0.53 vs 1.06±0.42;t=3.450, P<0.01). There were no statistically significant differences in SUVmax and SUVmean between SS and CBM in 40 FDG high uptake lesions (t values: 0.420 and -0.260, both P〉0.05). There were 73.33%(22/30) patients had images with overall high quality during SS and the percentage was 80. 00%(24/30) during CBM (X^2=0. 373, P〉0.05).The percentage of patients with images of high quality at the end was 16.67%(5/30) during SS, which was significantly less than that during CBM (63.33%, 19/30;X^2=13.611, P<0.001). Conclusions For the specific acquisition range, CBM can reduce unnecessary CT scan range and radiation dose compared with SS. There is no significant difference in image quality and SUV from normal tissue and lesion except for the end of the image.