Rapid, robust and non-invasive cerebral oxygenation measurements using MRI

描述（由申请人提供）：氧提取分数（OEF）是一项重要的脑氧代谢参数，为了解脑血管疾病的病理生理学、预测组织梗死和患者预后提供关键信息，并可能确定将从治疗干预中受益的患者。已经证明，脑组织中氧提取分数（OEF）的升高预示着慢性动脉粥样硬化性颈动脉闭塞患者随后中风的风险增加6-7倍。此外，在急性缺血性中风期间，以OEF升高和血流减少为特征的“悲惨灌注”已被用作“危险”组织的指标，这是治疗治疗的目标。另一方面，不筛查“危险”组织的不加区分的治疗可能导致严重的治疗相关并发症。因此，在常规临床设置中获得可靠且无创的OEF测量将对患者的适当诊断和治疗产生重大影响。尽管脑氧合很重要，但它只能通过15O正电子发射断层扫描（PET）来量化。然而，现场回旋加速器的要求限制了15O PET测量，只有世界各地的几个医疗中心。在过去的十年中，使用磁共振成像（MRI）进行无创定量OEF测量的技术取得了重大进展。虽然已经成功地在健康的人类受试者中获得了绝对的OEF测量，但由于在患者研究中存在许多未解决的问题，这些方法的临床应用仍然很小。此外，尚未在患者中进行全球或区域OEF验证。在这项研究中，一个集成的PET/MR系统，允许真正同时进行PET和MR图像采集，将用于直接比较MR和PET OEF，而没有与顺序成像相关的潜在混淆因素。该项目的总体目标是：(1)开发一种快速、可靠的新型MR OEF测量方法，以满足临床研究的需要；(2)在局灶性病理患者中同时使用O15 PET测量来验证MR OEF测量。由于MR已广泛应用，该项目的成功将允许在许多患者中获得PET可比的OEF测量结果，并为将来将该方法整合到时间敏感的患者管理决策中铺平道路。此外，该提案的技术发展-最大限度地减少MR成像伪影，提高测量效率，协同PET和MR扫描-可以推广到许多其他神经成像研究。

DESCRIPTION (provided by applicant): Oxygen extraction fraction (OEF) is an important cerebral oxygen metabolic parameter that provides critical information for understanding the pathophysiology of cerebrovascular disease, predicting tissue infarction and patient outcome, and may identify patients who will benefit from therapeutic intervention. It has been demonstrated that elevation of oxygen extraction fraction (OEF) in brain tissue portends a 6-7 fold increased risk of subsequent stroke in patients with chronic atherosclerotic carotid artery occlusion. Moreover, during acute ischemic stroke, "misery perfusion", marked by an elevation of OEF and decreased blood flow, has been used as an indicator of "at-risk" tissue that is a target of therapeutic treatments. On the other hand, indiscriminate treatment without screening for "at-risk" tissue may lead to serious treatment- related complications. Therefore, a reliable and non-invasive measure of OEF that can be obtained with a routine clinical setup will have a great impact on appropriate patient diagnosis and treatment. Despite its importance, cerebral oxygenation can only be quantified using 15O positron emission tomography (PET). However, the requirement of an onsite cyclotron has limited 15O PET measurements to only a few medical centers around the world. In the past decade, significant technical progress has been made towards non-invasive quantitative OEF measurements using magnetic resonance imaging (MRI). Though absolute OEF measurements have been successfully obtained in healthy human subjects, the clinical utility of these methods remains minor due to a host of unaddressed issues that are particularly challenging in patient studies. Moreover, neither global nor regional OEF validation has yet been performed in patients. In this study, an integrated PET/MR system which allows truly simultaneous PET and MR image acquisition will be utilized for a direct comparison between MR and PET OEF without potential confounding factors associated with sequential imaging. The overall objectives of this project are (1) to develop a novel MR OEF measurement that is rapid and robust to meet the need of clinical studies; and (2) to validate the MR OEF measurements using simultaneous O15 PET measurements in patients with focal pathology. Since MR is widely available, the success of this project will permit the acquisition of PET comparable OEF measurements in many patients, and pave the way for future integration of this method into time-sensitive patient management decisions. Furthermore, the technical developments from this proposal-- minimizing MR imaging artifacts, improving measurement efficiency, and synergizing PET and MR scans--can be generalized to many other neuroimaging studies.