18F-FDG胸部符合线路SPECT/CT半定量分析与PET/CT的对比研究

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（SUV_max）、平均标准化摄取值（SUV_mean）、瘦体质量标准化摄取值（SUL_peak）、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）mmPET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SUV_max、SUV_mean、SUL_peak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SUV_mean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。

Semi-quantitative 18F-FDG Co-SPECT/CT: A competitive study with 18F-FDG PET/CT of chest

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 SUV_max, SUV_mean, SUL_peak 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., SUV_max, SUV_mean, SUL_peak 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 SUV_max, SUV_mean, SUL_peak, 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 SUV_max and SUV for SUV_mean 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.