摘要:
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 pointspread 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.%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(SUMmexn)、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f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f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.