Presurgical functional MRI in patients with large susceptibility artifacts

项目摘要/摘要 美国和世界各地的大型医疗中心越来越多地进行手术前功能磁共振成像，包括 在约翰·霍普金斯大学。常用于脑肿瘤和癫痫患者的非侵入性定位 皮质感觉运动和语言区域，并在手术前确定语言优势半球， 从而有助于减少对术中皮质刺激等侵入性诊断程序的需求 映射。然而，接受术前功能磁共振检查的患者中有很大一部分人受到 具有以下特性的区域中的几何失真和信号丢失(从而影响灵敏度)问题是众所周知的 使用当前标准的BOLD fMRI方法时的大磁化率效应：梯度回波(GRE) 回声平面成像(EPI)。这些区域包括几个与语言特别相关的额叶和颞叶区域 术前功能磁共振成像中的标测。此外，这种敏感性伪影也可由与以下相关的空洞引起 以前的手术，钙化的结构，出血，和金属植入。例如，大约25%的我们的 手术前转诊的功能磁共振成像已经接受了先前的切除，正在考虑进行第二次切除，世卫组织 将遭受与切除空洞和外科金属开颅硬件相关的易感性伪影。 虽然已经开发了许多方法来缓解这些问题，但大多数方法依赖于地区或需要 额外的数据采集。我们最近开发了一种T2准备(T2prep)的BOLD fMRI方法，它显示了 即使在金属存在的情况下，整个大脑也具有最小的失真和丢失以及足够的大胆敏感度 头部植入物，在受大的敏感伪影影响的区域，比GRE EPI更具大胆的敏感性。 该方法最初是在超强磁场(7特斯拉，7T)下发展起来的。这款R21的目标是优化 并在3T临床MRI扫描仪上验证T2prep BOLD在肿瘤患者术前功能磁共振成像中的价值。目标1：优化 3T临床磁共振全脑T2 prep BOLD功能磁共振成像在健康志愿者术前典型功能磁共振成像中的应用 扫描仪。多频段技术将在T2prep BOLD中实施。图像质量、功能灵敏度 和特异性(在敏感性影响小或大的区域)将与GRE EPI BOLD功能磁共振进行比较 (现行标准)。目的2：确定T2prep BOLD fMRI是否可以作为补充方法 适用于3T有大敏感伪影的脑肿瘤患者的术前计划。函数结果来自 使用典型术前功能磁共振成像范例的患者将在T2prep BOLD和GRE EPI BOLD之间进行比较 FMRI，并将通过术中皮质刺激标测数据进行验证。如果拟议的研究是 如果成功，预计将使接受术前功能磁共振检查的患者中的一大部分受益。作为手术前的 FMRI协议通常由几个功能扫描组成，T2prep BOLD fMRI可以可行地合并到 现有的临床方案。此外，我们还希望T2prep的大胆方法对其他功能 神经科学和临床研究作为一种替代功能磁共振成像工具，可以评估脑功能 以前由于EPI BOLD功能磁共振成像中与易感性相关的信号丢失，较少探索大脑区域。

PROJECT SUMMARY/ABSTRACT Presurgical fMRI is increasingly performed in large medical centers across the US and in the world, including here at Johns Hopkins. It is commonly used in brain tumor and epilepsy patients to noninvasively locate essential cortical sensorimotor and language areas and to determine the language dominant hemisphere prior to surgery, thus helping to reduce the need for invasive diagnostic procedures such as intraoperative cortical stimulation mapping. However, a significant subpopulation of patients undergoing presurgical fMRI are affected by the well-known problems of geometric distortion and signal dropout (thus compromised sensitivity) in regions with large magnetic susceptibility effects when using the current standard BOLD fMRI method: gradient echo (GRE) echo-planar-imaging (EPI). These include several frontal and temporal regions particularly relevant for language mapping in presurgical fMRI. Furthermore, such susceptibility artifacts can also arise from cavities related to previous surgery, calcified structures, hemorrhage, and metal implants. For instance, about 25% of our presurgical fMRI referrals have undergone prior resection and are being considered for a second resection, who will suffer from susceptibility artifacts related to resection cavities and surgical metallic craniotomy hardware. Although many methods have been developed to mitigate these problems, most are region dependent or require extra data acquisition. We have recently developed a T2-prepared (T2prep) BOLD fMRI method, which showed minimal distortion and dropout and sufficient BOLD sensitivity in the entire brain even in the presence of metallic head implants, and superior BOLD sensitivity than GRE EPI in regions affected by large susceptibility artifacts. The method was initially developed at ultra-high magnetic field (7 Tesla, 7T). The goal of this R21 is to optimize and validate T2prep BOLD for presurgical fMRI in tumor patients on 3T clinical MRI scanners. Aim 1: To optimize whole-brain T2prep BOLD fMRI for typical presurgical fMRI paradigms in healthy volunteers on 3T clinical MRI scanners. The multiband techniques will be implemented for T2prep BOLD. Image quality, functional sensitivity and specificity (in regions with small or large susceptibility effects) will be compared with GRE EPI BOLD fMRI (current standard). Aim 2: To determine whether T2prep BOLD fMRI can be used as a complementary method for presurgical planning in brain tumor patients with large susceptibility artifacts at 3T. Functional results from patients using typical presurgical fMRI paradigms will be compared between T2prep BOLD and GRE EPI BOLD fMRI, and will be validated by intraoperative cortical stimulation mapping data. If the proposed research is successful, it is expected to benefit a significant subset of patients undergoing presurgical fMRI. As presurgical fMRI protocols often consist of several functional scans, T2prep BOLD fMRI can be feasibly incorporated into existing clinical protocols. Besides, we also expect the T2prep BOLD approach to be useful for other functional studies in neuroscience and clinical research as an alternative fMRI tool that can assess brain functions in previously less explored brain territories due to susceptibility related signal losses in EPI BOLD fMRI.