Presurgical functional MRI in patients with large susceptibility artifacts

项目总结/摘要 术前功能磁共振成像越来越多地在美国和世界各地的大型医疗中心进行，包括 在约翰霍普金斯。它通常用于脑肿瘤和癫痫患者，以非侵入性地定位基本的 皮层感觉运动和语言区并在手术前确定语言优势半球， 从而有助于减少对侵入性诊断程序的需要 映射.然而，接受术前功能磁共振成像的患者中有一个重要的亚群受到 已知的问题的几何失真和信号丢失（从而妥协的灵敏度）的区域， 使用当前标准BOLD fMRI方法时的大磁化率效应：梯度回波（GRE） 回波平面成像（EPI）。其中包括几个与语言特别相关的额叶和颞叶区域 功能性磁共振成像中的映射。此外，这样的磁化率伪影也可以由与以下有关的腔引起： 既往手术、钙化结构、出血和金属植入物。例如，大约25%的 术前功能磁共振转介已经经历了先前的切除，并正在考虑第二次切除，谁 将遭受与切除腔和外科金属开颅硬件相关的敏感性伪影。 尽管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区域或需要 额外的数据采集。我们最近开发了一种T2-prepared（T2 prep）BOLD fMRI方法， 即使在金属存在的情况下，整个大脑的失真和丢失也最小， 头部植入物，在受大敏感性伪影影响的区域，BOLD灵敏度上级GRE EPI。 该方法最初是在超高磁场（7特斯拉，7 T）下开发的。R21的目标是优化 并在3 T临床MRI扫描仪上验证T2 prep BOLD用于肿瘤患者的术前fMRI。目标1：优化 3 T临床MRI上健康志愿者典型术前fMRI范例的全脑T2 prep BOLD fMRI 扫描仪多波段技术将用于T2 prep BOLD。图像质量、功能灵敏度 和特异性（在具有小或大的易感性效应的区域中）将与GRE EPI BOLD fMRI进行比较。 （现行标准）。目的2：确定T2 prep BOLD功能磁共振成像是否可以作为一种补充方法 用于3 T下具有较大敏感性伪影的脑肿瘤患者的手术前计划。功能结果来自 使用典型术前fMRI范例的患者将在T2 prep BOLD和GRE EPI BOLD之间进行比较 fMRI，并将通过术中皮层刺激映射数据进行验证。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成像的患者中的一个重要子集受益。作为术前 fMRI协议通常由几个功能扫描组成，T2 prep BOLD fMRI可以可行地并入到 现有的临床协议。此外，我们还希望T2 prep BOLD方法对其他功能性 神经科学和临床研究作为一种替代的功能磁共振成像工具，可以评估大脑功能， 由于EPI BOLD fMRI中与易感性相关的信号损失，以前较少探索的大脑区域。

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.