Vision 20/20: Magnetic resonance imaging-guided attenuation correction in PET/MRI: Challenges, solutions, and opportunities
Vision 20/20: Magnetic resonance imaging-guided attenuation correction in PET/MRI: Challenges, solutions, and opportunities
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DOI：
10.1118/1.4941014
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发表时间：
2016-03-01
期刊：
影响因子：
3.8
通讯作者：
Zaidi, Habib
中科院分区：
文献类型：
--
作者：
Mehranian, Abolfazl;Arabi, Hossein;Zaidi, Habib
衰减校正是实现定量正电子发射断层扫描（PET）成像的全部潜力所需的长链数据校正技术的重要组成部分。组合PET/磁共振成像（MRI）系统的发展要求对开发用于导出精确衰减图的新策略的广泛兴趣，目的是提高这些新兴混合成像系统的定量准确性。PET/MRI中的衰减图理想情况下应来自解剖MR图像;然而，MRI强度反映的是生物组织的质子密度和弛豫时间特性，而不是其电子密度和光子衰减特性。因此，与PET/计算机断层扫描相比，在511 keV处MRI信号强度与线性衰减系数之间缺乏标准化的全局映射。此外，在标准MRI序列中，骨骼和肺组织由于其低质子密度和短横向弛豫时间而不产生可测量的信号。MR图像也不可避免地受到降低其质量的伪影的影响，从而损害其对于PET/MRI中的衰减校正任务的适用性。MRI引导的衰减校正策略可以分为三大类：（i）基于分割的方法，（ii）图谱配准和机器学习方法，以及（iii）基于发射/传输的方法。本文总结了PET/MRI衰减校正的过去和现在的最新进展。全面描述了用于解决基于MR的衰减校正的挑战的每种方法的优点和缺点。MRI和PET成像模式为获得准确的衰减图和改善PET定量带来的机会将详细说明。这些技术的未来前景和潜在的临床应用以及它们在商业系统中的集成也将被讨论。(C)2016年美国医学物理学家协会。
Attenuation correction is an essential component of the long chain of data correction techniques required to achieve the full potential of quantitative positron emission tomography (PET) imaging. The development of combined PET/magnetic resonance imaging (MRI) systems mandated the widespread interest in developing novel strategies for deriving accurate attenuation maps with the aim to improve the quantitative accuracy of these emerging hybrid imaging systems. The attenuation map in PET/MRI should ideally be derived from anatomical MR images; however, MRI intensities reflect proton density and relaxation time properties of biological tissues rather than their electron density and photon attenuation properties. Therefore, in contrast to PET/computed tomography, there is a lack of standardized global mapping between the intensities of MRI signal and linear attenuation coefficients at 511 keV. Moreover, in standard MRI sequences, bones and lung tissues do not produce measurable signals owing to their low proton density and short transverse relaxation times. MR images are also inevitably subject to artifacts that degrade their quality, thus compromising their applicability for the task of attenuation correction in PET/MRI. MRI-guided attenuation correction strategies can be classified in three broad categories: (i) segmentation-based approaches, (ii) atlas-registration and machine learning methods, and (iii) emission/transmission-based approaches. This paper summarizes past and current state-of-the-art developments and latest advances in PET/MRI attenuation correction. The advantages and drawbacks of each approach for addressing the challenges of MR-based attenuation correction are comprehensively described. The opportunities brought by both MRI and PET imaging modalities for deriving accurate attenuation maps and improving PET quantification will be elaborated. Future prospects and potential clinical applications of these techniques and their integration in commercial systems will also be discussed. (C) 2016 American Association of Physicists in Medicine.