基于UTE序列和CT的衰减校正方法在脑部PET应用比较

Comparison of ultrashort echo time-based and CT attenuation correction in the application of PET brain

目的 通过与CT衰减校正方法的比较，探讨超短回波时间（UTE）序列作为脑部PET衰减校正方法的准确性。方法 随机选取10名先后接受PET/CT和PET/MR脑部检查的受检者，基于MRI-UTE和CT方法对PET/MR采集的PET数据进行衰减校正，获得PETUTE与PETCT图像。基于阈值分割法对UET、CT衰减校正图（μ map）行体素分割，使用配对t检验比较两者在颅脑骨、脑实质及空气的差异；并用统计参数图分析PETUTE、PETCT的区别。结果 UTE_μ map和CT_μ map在颅脑骨（t=-23.45，P〈0.05）和空气（t=5.29，P〈0.05）中的差异有统计学意义，差别分别为-64.8%±8.7%和74.8%±44.7%，在脑实质中的差异无统计学意义（t=-1.24，P〉0.05），差别为-1.5%±3.9%；且PETUTE脑实质相对于PETCT在越接近颅骨和空气区代谢低估越大。结论 UTE序列能够准确评估脑实质的μ map，但对于接近颅骨和空气区的局部脑实质存在一定程度PET定量分析的低估。

Objective To compare the accuracy of MR-ultrashort echo time（UTE） attenuation correction （AC） methods with that of CT AC methods in brain PET examination. Methods Ten patients who underwent the brain 18F-FDG examination of PET/CT and PET/MR were selected randomly. The PET data were attenuation corrected by MRI-UTE and CT methods, and PETUTE and PETCT images were obtained. With the threshold segmentation method, the UET and CT attenuation correction maps（μ Maps） were segmented, and their differences in the neurocranium, brain tissue, and air were compared using paired t test. The difference between PETUTE and PETCT was analyzed by the statistical parametric map. Results A significant difference was found between the UTE_μ maps and CT_μ maps in the neurocranium （t=-23.45, P〈0.05） and air（t=5.29, P〈0.05）. The difference rates were -64.8%±8.7% and 74.8%±44.7%, respectively. No significant difference（-1.5%±3.9%） in the brain tissue was found between the two maps （t=-1.24, P〉0.05）. The closer the brain was to the skull and the air, the more metabolism was reduced. Conclusions The UTE sequence can accurately evaluate the μ map of brain tissue, but there was a certain underestimation of PET quantitative analysis in areas close to skull and air area.