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18F-FDG PET/CT已在临床应用很多年,随着技术的进步,其在肿瘤诊断与鉴别诊断、分期与再分期以及疗效评估与预测预后方面发挥着越来越重要的作用[1-2]。18F-FDG PET/CT的半定量指标[如SUV、肿瘤代谢体积(metabolic tumor volume,MTV)等]被用于监测化疗效果,对于改善淋巴瘤、乳腺癌、非小细胞肺癌、结直肠癌和食管癌的预后具有重要价值[3],但由于检查费用昂贵,限制了其被广泛应用。18F-FDG符合线路SPECT/CT的检查费用约为PET/CT的1/3,且包含在医疗保险报销范围之内,可以大大减轻肿瘤患者的经济压力[4-6]。在发展中国家,尤其是在中国,18F-FDG SPECT/CT是PET/CT重要的替代检查方法[7-8]。但是传统的符合线路SPECT/CT图像质量差,并且不能进行半定量分析,因此限制了其在肿瘤分期及评价治疗效果等方面的应用[9]。在本研究中,我们通过对符合线路SPECT/CT图像进行物理校正,在改善图像质量的同时,使符合线路图像也能进行半定量分析。通过在模型与胸部实体肿瘤患者中的应用,比较传统符合线路SPECT/CT、校正后半定量符合线路SPECT/CT(以下简称半定量符合线路)与PET/CT的图像,并以PET/CT为标准,评估半定量符合线路的半定量参数(如SUVmax、MTV等)的准确性。
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由图1可见,点源的3种重建图像的分辨率由低到高依次为传统符合线路SPECT/CT、半定量符合线路、PET/CT;由图2可见,NEMA模型的3种重建图像能观测到的最小球体直径分别为:传统符合线路SPECT/CT 28 mm、半定量符合线路22 mm、PET/CT 17 mm,图像分辨率依次提高。
图 1 传统符合线路SPECT/CT(A)、半定量符合线路(B)及PET/CT(C)显像的十字形点源显像图 图中, SPECT/CT:单光子发射计算机体层摄影术;半定量符合线路:校正后半定量符合线路SPECT/CT;PET/CT:正电子发射断层显像计算机体层摄影术。
Figure 1. Images of point sources aligned in a cross shape on traditional Co-SPECT/CT, semi-quantitative Co-SPECT/CT and PET/CT images
图 2 CT(A)、传统符合线路SPECT/CT(B)、半定量符合线路(C)及PET/CT(D)显像的NEMA模型显像图 图中,CT:体层摄影术, 发射型计算机;SPECT/CT:单光子发射计算机体层摄影术;半定量符合线路:校正后半定量符合线路SPECT/CT;PET/CT:正电子发射断层显像计算机体层摄影术;NEMA:美国国家电气制造商协会;。
Figure 2. Images of NEMA phantom on CT, traditional Co-SPECT/CT, semi-quantitative Co-SPECT/CT and PET/CT images
经过物理校正,NEMA模型的传统符合线路SPECT/CT、半定量符合线路、PET/CT图像的平面半高宽分别为(13.1±1.2)、(9.5±0.8)、(7.4±0.4) mm,三者之间两两比较差异均有统计学意义(t=–8.38、–12.93、–12.03,均P<0.0001);轴向半高宽分别为(13.5±1.1)、(9.8±0.7)、(7.6±0.5)mm,三者之间两两比较差异均有统计学意义(t=–8.63、–14.41、–12.59,均P<0.0001);图像对比度分别为1.79、6.32、6.69,三者之间两两比较差异均有统计学意义(t=–8.25、–13.23、–12.01,均P <0.0001),这些数据说明图像的分辨率依次提高。
在直径≥28 mm的球体中,半定量符合线路测量18F-FDG放射性浓度的准确率>97.1%,随着球体体积缩小,部分容积效应增大,其测量准确率也逐渐降低;而PET/CT在直径≥17 mm的球体中,其测量准确率>98.5%(图3)。在NEMA模型的本底区,由于不受部分容积效应的影响,半定量符合线路和PET/CT测量放射性浓度的准确率均高于99%。
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15例患者的PET/CT图像中共发现包括主病灶及转移病灶在内的61个病灶,半定量符合线路发现的病灶数与PET/CT一致,而传统符合线路SPECT/CT共发现病灶57个,未能发现4例患者中的4个转移病灶,典型病例的图像见图4。主病灶与病理结果一致,无误诊病例。
图 4 食管癌患者(男性,65岁)的传统符合线路SPECT/CT(A)、半定量符合线路(B)和PET/CT(C)显像图 图中,A中未见高代谢淋巴结,但在B、C的心脏附近有1枚高代谢淋巴结。SPECT/CT:单光子发射计算机体层摄影术;半定量符合线路:校正后半定量符合线路SPECT/CT;PET/CT:正电子发射断层显像计算机体层摄影术。
Figure 4. The comparison of traditional Co-SPECT/CT (A), semi-quantitative Co-SPECT/CT (B) and PET/CT (C) images for a male patient with esophagus cancer
图5显示了1例肺腺癌患者的传统符合线路SPECT、半定量符合线路和PET图像。从视觉效果可以看出,半定量符合线路的图像分辨率和对比度均高于传统符合线路SPECT/CT图像,更接近PET/CT的图像质量。
图 5 肺腺癌患者(男性,62岁)的传统符合线路SPECT/CT(A)、半定量符合线路(B)和PET/CT(C)显像图 图中,B的分辨率和对比度均高于A,接近C的图像质量。SPECT/CT:单光子发射计算机体层摄影术;半定量符合线路:校正后半定量符合线路SPECT/CT;PET/CT:正电子发射断层显像计算机体层摄影术。
Figure 5. The comparison of traditional Co-SPECT/CT (A), semi-quantitative Co-SPECT/CT (B) and PET/CT (C) images for a male patient with pulmonary adenocarcinoma
配对样本t检验结果显示,在15例患者的61个病灶中,半定量符合线路的各参数与PET各参数之间存在显著差异,SUVmax、SUVmean、SULpeak 以及MTV之间的平均差异(半定量符合线路-PET)分别为–1.822、–1.250、1.808 g/mL和34.97 mL(t=3.16、3.90、3.92和3.98,均P<0.01)。但是,线性回归显示两者之间的各参数存在着很好的相关性(图6):SUVmax的相关系数r=0.8218(95%可信区间:0.7186~0.8895),y=1.0804x–2.7765;SUVmean的相关系数r=0.8390(95%可信区间:0.7444~0.9005),y= 1.0601x–1.679;SULpeak的相关性系数r=0.8171(95%可信区间:0.7116~0.8865),y=0.9736x–1.5318。半定量符合线路和PET的MTV测量值也存在着很好的相关性,r= 0.8791(95%可信区间:0.8056~0.9260),y=1.2021x+20.037。观察SUVmean与MTV设定不同阈值时与PET的相关性,研究证明阈值在30%~50%的范围内变化时,SUVmean均与PET有很好的相关性(r=0.8315~0.8413);当MTV的勾画阈值在SUV2.8~4.0之间变化时,均与PET有较好的相关性,但是当阈值取3.0时,相关性最好(r=0.8801)(表1)。
图 6 半定量符合线路与PET/CT的半定量参数间的相关性分析 图中,线性回归显示两者之间的各参数存在着很好的相关性。PET:正电子发射断层显像术;SUVmax:最大标准化摄取值;SUVmean:平均标准化摄取值;SULpeak:瘦体质量标准化摄取值;MTV:肿瘤代谢体积。
Figure 6. Linear regression for SUVmax, SUVmean, SULpeak and MTV obtained from semi-quantitative Co-SPECT/CT and compared to those of PET/CT
统计结果 SUVmean(不同SUVmax阈值) MTV(不同SUV阈值) 30% 35% 45% 50% 2.8 3.0 3.5 4.0 r值 0.8315 0.8346 0.8408 0.8413 0.8779 0.8801 0.8265 0.8103 95% 可信区间 0.7332~0.8958 0.7379~0.8978 0.7472~0.9017 0.7479~0.9092 0.8038~0.9252 0.8072~0.9266 0.7256~0.8925 0.7016~0.8821 P值 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 注:表中,SPECT:单光子发射计算机体层摄影术;SUVmean:平均标准化摄取值;SUVmax:最大标准化摄取值;MTV:肿瘤代谢体积。 表 1 半定量SPECT设定不同阈值的SUVmean和MTV与PET相关性分析
Table 1. Linear regression for SUVmean and MTV obtained from semi-quantitative Co-SPECT with different thresholds to those of PET
18F-FDG胸部符合线路SPECT/CT半定量分析与PET/CT的对比研究
Semi-quantitative 18F-FDG Co-SPECT/CT: A competitive study with 18F-FDG PET/CT of chest
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摘要:
目的 通过对18F-FDG符合线路SPECT/CT采集的图像进行物理校正,提高其图像分辨率与对比度,并使之可进行半定量分析,并以PET/CT半定量参数为标准,评价校正后半定量符合线路各参数的准确性。 方法 将18F-FDG符合线路SPECT/CT采集的图像经过衰减校正、散射校正、点扩散函数校正等处理过程,去除影像中物理衰减、散射、噪声等干扰,提高图像分辨率与对比度,并通过点源及美国国家电气制造商协会标准模型测试,确定图像分辨率、对比度以及其测定18F-FDG放射性浓度的准确性。于2016年1月至2017年8月收集已确诊胸部肿瘤的患者15例(男性13例),患者均先、后采集胸部18F-FDG符合线路SPECT/CT和胸部PET/CT扫描,并将符合线路图像经第三方软件校正后重建为半定量符合线路图像。对半定量符合线路图像与PET/CT显像的肿瘤病灶分别测量最大化标准摄取值(SUVmax)、平均标准化摄取值(SUVmean)、瘦体质量标准化摄取值(SULpeak)、肿瘤代谢体积(MTV)半定量参数,并采用配对t检验及线性回归做相关分析。 结果 在模型研究中,经过校正的半定量符合线路图像平面半高宽从(13.1±1.2)mm减少至(9.5±0.8)mm [PET为(7.4±0.4)mm],而轴向半高宽从(13.5±1.1)mm减少至(9.8±0.7)mm[PET为(7.6±0.5)mm],同时图像对比度提高到6.32(传统符合线路为1.79,PET为6.69)。在对患者进行的研究中,配对t检验示半定量符合线路的各参数,包括SUVmax、SUVmean、SULpeak以及MTV,与PET各参数的差异均有统计学意义(t=3.16、3.90、3.92和3.98,均P<0.01);但线性回归分析显示两者之间有着很好的相关性,r分别为0.8218、0.8390、0.8171和0.8791。改变SUVmean和MTV的阈值,并不影响其与PET的相关性。 结论 经过校正,18F-FDG符合线路SPECT/CT的图像分辨率与对比度得到显著提高,可显示更小的病灶,同时具备了类似PET/CT的半定量分析能力。 -
关键词:
- 氟脱氧葡萄糖F18 /
- 单光子发射计算机体层摄影术 /
- 正电子发射断层显像计算机体层摄影术 /
- 胸部肿瘤 /
- 图像增强 /
- 功能参数
Abstract:Objective To implement physical corrections in semiquantitative Co-SPECT to improve image resolution and contrast, along with the capability for image semiquantitation. And to evaluate the image performance using 18F-FDG PET/CT as the reference standard. Methods Full physical corrections included attenuation correction, scatter correction, and spatially dependent point-spread functions. Point sources in a cross shape and a standard National Electrical Manufacturers Association phantom were utilized to verify image resolution and contrast, as well as the accuracy in measuring 18F activity concentration. In the patient study, 13 males and 2 females with histologically confirmed thoracic carcinomas were included. All patients were subjected to 18F-FDG Co-SPECT/CT scan followed by 18F-FDG PET/CT scan. The functional parameters SUVmax, SUVmean, SULpeak and MTV from semiquantitative Co-SPECT and PET were analyzed. Results In the phantom study, the image resolution of Co-SPECT improved. The mean image resolution improved from (13.1±1.2) mm to (9.5±0.8) mm in the in-plane direction[(7.4±0.4)mm for PET] and from (13.5±1.1) mm to(9.8±0.7) mm in the axial direction[(7.6±0.5) mm for PET], whereas the image contrast improved from 1.79 to 6.32(6.69 for PET). In the patient study, paired t-test showed that the functional parameters of quantitative Co-SPECT(i.e., SUVmax, SUVmean, SULpeak and MTV) significantly differed from those of PET(t=3.16, 3.90, 3.92, 3.98, respectively; all P<0.0025). Conversely, the correlations of SUVmax, SUVmean, SULpeak, and MTV from semiquantitative Co-SPECT were highly correlated overall with those from PET(r=0.8218, 0.8390, 0.8171 and 0.8791, respectively). Measurements remained stable whereas the threshold adjustment of SUVmax and SUV for SUVmean and MTV determination did not further change the correlations with PET(r=0.8103–0.8801). Conclusion Adding physical corrections to Co-SPECT images can significantly improve image resolution and contrast to reveal smaller tumor lesions, as well as the capability to semiquantify functional parameters such as PET/CT. -
图 4 食管癌患者(男性,65岁)的传统符合线路SPECT/CT(A)、半定量符合线路(B)和PET/CT(C)显像图 图中,A中未见高代谢淋巴结,但在B、C的心脏附近有1枚高代谢淋巴结。SPECT/CT:单光子发射计算机体层摄影术;半定量符合线路:校正后半定量符合线路SPECT/CT;PET/CT:正电子发射断层显像计算机体层摄影术。
Figure 4. The comparison of traditional Co-SPECT/CT (A), semi-quantitative Co-SPECT/CT (B) and PET/CT (C) images for a male patient with esophagus cancer
图 5 肺腺癌患者(男性,62岁)的传统符合线路SPECT/CT(A)、半定量符合线路(B)和PET/CT(C)显像图 图中,B的分辨率和对比度均高于A,接近C的图像质量。SPECT/CT:单光子发射计算机体层摄影术;半定量符合线路:校正后半定量符合线路SPECT/CT;PET/CT:正电子发射断层显像计算机体层摄影术。
Figure 5. The comparison of traditional Co-SPECT/CT (A), semi-quantitative Co-SPECT/CT (B) and PET/CT (C) images for a male patient with pulmonary adenocarcinoma
表 1 半定量SPECT设定不同阈值的SUVmean和MTV与PET相关性分析
Table 1. Linear regression for SUVmean and MTV obtained from semi-quantitative Co-SPECT with different thresholds to those of PET
统计结果 SUVmean(不同SUVmax阈值) MTV(不同SUV阈值) 30% 35% 45% 50% 2.8 3.0 3.5 4.0 r值 0.8315 0.8346 0.8408 0.8413 0.8779 0.8801 0.8265 0.8103 95% 可信区间 0.7332~0.8958 0.7379~0.8978 0.7472~0.9017 0.7479~0.9092 0.8038~0.9252 0.8072~0.9266 0.7256~0.8925 0.7016~0.8821 P值 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 注:表中,SPECT:单光子发射计算机体层摄影术;SUVmean:平均标准化摄取值;SUVmax:最大标准化摄取值;MTV:肿瘤代谢体积。 -
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