Controlling sensitivity bias in functional MRI studies due to field inhomogeneity

控制功能 MRI 研究中由于场不均匀性导致的灵敏度偏差

• 批准号: 7989950
• 负责人: Bradley P Sutton
• 金额: $ 21.85万
• 依托单位: UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2012-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7989950
• 关键词: Adoption; Affect; Aging; Air; Amygdaloid structure; Anatomy; Area; Brain; Brain region; Clinical; Data; Data Quality; Data Set; Dependence; Dependency; Development; Evaluation; Feedback; Financial compensation; Functional Imaging; Functional Magnetic Resonance Imaging; Future; Goals; Hippocampus (Brain); Image; Impaired cognition; Individual; Literature; Location; Magnetic Resonance Imaging; Magnetism; Maps; Measures; Mental Depression; Methods; Motivation; Participant; Pathway interactions; Population; Positioning Attribute; Predisposition; Procedures; Protocols documentation; Relative (related person); Research Personnel; Sampling; Signal Transduction; Site; Source; Specific qualifier value; Structure of inferior temporal gyrus; Subject Headings; Time; Tissues; Validation; Variant; Weight; Work; addiction; blood oxygen level dependent; blood oxygenation level dependent response; design; healthy aging; magnetic field; neuroimaging; public health relevance; relating to nervous system; research study; tool; volunteer

DESCRIPTION (provided by applicant): During a magnetic resonance imaging (MRI) study, local variations of the magnetic field in the brain exist around air/tissue interfaces. These local variations in the magnetic field behave similarly to apply imaging gradients and can affect both the quality of the acquisition and the functional weighting of the signal in a functional MRI (fMRI) acquisition. The main hypothesis of this proposal is that the sensitivity of fMRI in regions near air/tissue interfaces in the brain will have a strong dependence on: acquisition trajectory, acquisition timing, magnetic field shim, subject positioning, and magnetic field strength. These protocol choices and anatomical changes can be significant both individually and together, resulting in a wide range of sensitivity to functional signals throughout the brain. Because investigators are currently ignoring the effect of magnetic field distribution on echo time and fMRI sensitivity, the literature is creating results that are incomplete and, at times, misleading. This proposal will examine changes in magnetic field induced fMRI sensitivity as a function of: 1) acquisition sequence and timing, 2) subject positioning, and 3) magnetic field strength. Three-dimensional magnetic field maps will be measured on volunteer participants in multiple, specified orientations to examine the impact of variations in the pitch of a subjects head in an fMRI study. fMRI sensitivity changes due to position will be examined along with an analysis of the impact of anatomical variability among individuals. Additionally, changes in fMRI sensitivity will be validated by using a robust breath hold task that produces a signal similar to functional brain activations. The estimated fMRI sensitivity changes from susceptibility gradients will be examined to see if they explain significant variance in the breath hold data. Regions of the brain will be identified that have high variability in predicted fMRI sensitivity between subjects. Additionally, an fMRI sensitivity assessment tool will be developed and widely distributed that will allow neuroimaging researchers and clinicians to assess the quality of the functional data in various brain regions given their acquisition trajectory and a field map of a subject. This tool will enable the evaluation of protocol choices as they relate to magnetic field gradients. Further, the tool will provide motivation for future imaging protocols designed to study regions of the brain with high magnetic susceptibility. PUBLIC HEALTH RELEVANCE: Magnetic field variations due to air spaces next to the brain can have a dramatic effect on the sensitivity of functional magnetic resonance imaging in certain regions of the brain. Although this information is critical in interpreting functional imaging results, the effect is ignored in current neuroimaging studies. We propose a framework for evaluating the effect of magnetic field gradients around these airspaces and determine how protocol settings can influence their impact on functional imaging studies.

描述（由申请人提供）：在磁共振成像（MRI）研究中，空气/组织界面周围存在脑中磁场的局部变化。磁场中的这些局部变化对应用成像梯度的行为类似，并且可以影响采集的质量和功能性MRI（fMRI）采集中信号的功能权重。该提议的主要假设是，大脑中空气/组织界面附近区域中fMRI的敏感性将有很强的依赖性：采集轨迹，采集时机，磁场垫片，受试者定位和磁场强度。这些协议选择和解剖学变化都可以单独和共同重大，从而对整个大脑的功能信号产生广泛的敏感性。由于研究人员目前正在忽略磁场分布对回声时间和fMRI敏感性的影响，因此文献创造的结果是不完整的，有时会引起误导。该建议将检查磁场引起的fMRI灵敏度的变化，其功能：1）采集序列和时机，2）受试者定位，以及3）磁场强度。在fMRI研究中，将对多个指定方向的志愿者参与者进行三维磁场图的影响，以检查受试者头部螺距中的变化的影响。将检查由于位置而引起的fMRI敏感性变化，并分析个体解剖变异性的影响。此外，通过使用强大的呼吸固定任务来验证fMRI敏感性的变化将得到验证，该任务可产生类似于功能性大脑激活的信号。将检查估计的fMRI敏感性变化，以查看它们是否解释了呼气数据中的显着差异。将确定大脑的区域在受试者之间的fMRI敏感性方面具有很高的变化。此外，将开发FMRI敏感性评估工具并广泛分布，这将使研究人员和临床医生能够评估各个大脑区域的功能数据质量，因为它们的获取轨迹和受试者的现场图。该工具将在与磁场梯度相关的协议选择中评估。此外，该工具将为未来的成像协议提供动力，该方案旨在研究具有高磁化率的大脑区域。 公共卫生相关性：由于大脑旁边的空气空间引起的磁场变化可能会对大脑某些区域的功能磁共振成像的灵敏度产生巨大影响。尽管此信息对于解释功能成像结果至关重要，但在当前的神经影像研究中忽略了效果。我们提出了一个框架，用于评估这些空间周围磁场梯度的影响，并确定协议设置如何影响其对功能成像研究的影响。