Posture and regional cerebrovascular reactivity; technological advancements with positional MRI

随着磁共振成像（MRI）技术的发展，大脑解剖学和生理学领域的研究出现了令人兴奋的时刻。这项提议的基础是采用一种独特的成像技术来推动我们对人脑局部血流调节的基本理解。脑血流的循环受到当地主要pH值（酸碱平衡）的深刻影响。脑血管外组织的pH值增加（酸度降低）会减少血流量，而pH值降低（酸度增加）会增加脑血流量。脑血管外pH值的变化每天都会发生，这在很大程度上取决于呼吸频率的变化（进而取决于动脉CO2分压的变化）。脑血管对pH值变化的自然“反应性”似乎是大脑健康的替代品。也就是说，对于给定的pH值变化，血流变化越多，他们就越“健康”。事实上，那些反应性较低的人患脑血管疾病的风险较高。目前，跨不同脑区域的脑反应性的区域变化仍然研究得很差（需要昂贵的成像技术），而在姿势变化期间对pH变化的区域反应性仍然完全不确定。了解这些基本的脑血管反应对于确定可能增加缺血性卒中风险的脑区域特别重要。人类的大部分时间都是直立的;因此，描述仰卧和直立时对pH值变化的“自然”（健康）脑血管反应是谨慎的。在获得这些数据之前，无法量化在直立位置可能恶化的脑血管疾病病理。不列颠哥伦比亚省坎卢普斯的欢迎回来MRI和疼痛管理中心目前拥有加拿大唯一的直立MRI，具有脑血管成像的潜在能力。这项合作研究提案的目标是利用这种独特的测量工具，量化健康人体仰卧和直立姿势下自然局部脑血流对pH值变化的反应。

With the advancement of magnetic resonance imaging (MRI) techniques, an exciting time has emerged for research in the field of cerebral anatomy and physiology. The basis of this proposal is to employ a one of a kind imaging technique to drive forward our basic understanding of regional blood flow regulation in the human brain. The circulation of brain blood flow is profoundly influenced by the local prevailing pH (acid-base balance). An increased pH (reduced acidity) of cerebral extra-vascular tissue reduces blood flow, while a decreased pH (increased acidity) increases the cerebral blood flow. Changes in cerebral extra-vascular pH occur daily - determined in large part from variations in breathing frequency (and in turn changes in arterial partial pressure of CO2). The natural 'reactivity' of the cerebral vessels to changes in pH appear to be a surrogate for cerebral health. That is, the more the blood flow changes for a given change in pH, the 'healthier' they are. Indeed, those with lower reactivity are at higher risk of cerebrovascular disease. Currently, the regional variations in cerebral reactivity across separate brain regions remains poorly studied (requiring expensive imaging techniques), while the regional reactivity to changes in pH during changes in posture remain completely undetermined. Understanding these basic cerebrovascular responses is particularly important for determining brain regions that may have an increased risk for ischemic stroke. Humans spend the majority of life in the upright position; it is therefore prudent to describe the 'natural' (healthy) cerebrovascular response to changes in pH while both supine and upright. Before these data are acquired, cerebrovascular disease pathology potentially exacerbated in the upright position cannot be quantified. The Welcome Back MRI and Pain Management Centre in Kamloops, BC, currently possess the only upright MRI in Canada with the potential capacity to image the cerebral vessels. The goal of this collaborative research proposal is to take advantage of this unique measurement tool and quantify the natural regional cerebral blood flow response to changes in pH while in the supine AND upright posture in healthy humans.