高清一体化PET/MRI脑图像分割对比研究

Research on atlas-based brain segmentation for HD integrated PET/MRI image

一体化正电子发射断层成像(Positron Emission Tomography,PET)/磁共振成像(Magnetic Resonance Imaging,MRI)是将PET和MRI有机整合成一体的新型多模态医学影像系统,结合了MRI系统的软组织高分辨率与多参数多功能成像特性和PET系统的放射性示踪剂代谢高灵敏度以及数据定量化特性,常用于脑神经疾病的诊断。在PET/MRI脑部扫描中,脑区分割对脑图像定量研究具有重要的意义。目前行业通用的方法是基于脑图谱的分割方法,该方法既可以用于MRI图像也可以应用于PET图像。在一体化PET/MRI的临床科研中,由于PET和MRI图像同时采集、配准精度高,因此只需选取PET或者MRI图像进行基于图谱的分割,再将分区映射到另一模态图像即可。通过对比实验,将基于PET和MRI两种不同的图谱方案得到的脑区分割结果进行准确性比较。实验结果显示:基于PET的分割结果与金标准的平均dice值为0.64,而基于MRI的分割结果的平均dice值为0.74,表明利用MRI图像进行配准得到的脑区分割结果更精确。

[Background]Integrated positron emission tomography(PET)/magnetic resonance imaging(MRI)is a multimodal imaging system which can acquire PET and MRI images simultaneously.Due to the unique advantages in reflecting the anatomical structure and physiological function,PET/MRI has been widely commonly used in diagnosis of many brain diseases.Brain segmentation is of great significance to the quantitative study of brain images and the common method used in clinical diagnosis is atlas-based brain segmentation,which can be applied to both MRI images and PET images.Brain segmentation based on atlas for integrated PET/MRI image system only needs one modelity as the segmentation results can be mapped to another modelity.[Purpose]This study aims to determine which modality should be used for atlas-based segmentation for high definition(HD)integrated PET/MRI image.[Methods]Comparative experiments with two image groups were designed and performed.In the first group,150 PET images were registered to PET brain template to obtain brain segmentation.In the second group,150 MRI images were registered to MRI brain template to obtain brain segmentation.Six regions were selected to calculate the dice value.Comparing the segmentation results of the two sets of images with their results based on first,the modality with a higher average dice value would be more suitable for atlas-based brain segmentation.[Results]In PET group,the dice values of six regions were 0.62,0.55,0.63,0.62,0.71 and 0.69,respectively.In MRI group,the dice values of six regions were 0.68,0.64,0.79,0.81,0.77 and 0.79.The error coming from registering PET images to PET brain template was larger than that of registering MRI images to MRI brain template.[Conclusions]PETbased segmentation accuracy is lower than MRI-based segmentation precision,hence the MRI image is more suitable for atlas-based brain segmentation.