PARALLEL IMAGING PERFORMANCE AS A FUNCTION OF FIELD STRENGTH AN EXPERIMENTAL IN

并行成像性能作为场强函数的实验

• 批准号: 7721343
• 负责人: FLORIAN WIESINGER
• 金额: $ 3.57万
• 依托单位: UNIVERSITY OF MINNESOTA
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-06-01 至 2009-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7721343
• 关键词: Agreement; Behavior; Computer Retrieval of Information on Scientific Projects Database; Condition; Dependence; Ethanol; Funding; Grant; Image; Institution; Magnetic Resonance Imaging; Maps; N-methylformamide; Noise; Performance; Range; Research; Research Personnel; Resources; Sodium Chloride; Source; United States National Institutes of Health; Water; Work; base; decane; image reconstruction; magnetic field; radiofrequency

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. In this work, the dependence of parallel MRI performance on main magnetic field strength is experimentally investigated. Using the general framework of electrodynamic scaling, the B0-dependent behavior of the relevant radiofrequency fields at a single physical field strength of 7 T is studied. In the chosen implementation this is accomplished by adjusting the permittivity and conductivity of a homogeneous spherical phantom. With different mixing ratios of decane, ethanol, purified water, N-methylformamide, and sodium chloride, field strengths in the range of 1.5 to 11.5 T are mimicked. Based on sensitivity maps of an eight-coil receiver array, the field-dependent performance of parallel imaging is assessed in terms of the geometry factor g, which reflects noise enhancement in parallel imaging reconstruction. At low field strengths the SNR penalty was nearly independent of B0 and favorably low for 1D reduction factors up to between 3 and 4. At higher field strengths the transition between favorable and prohibitive parallel imaging conditions was found to shift toward higher feasible reduction factors. These findings are in good agreement with previous theoretical predictions. From this agreement it is concluded that parallel MRI at high B0 benefits specifically from onsetting far-field behavior of the involved radiofrequency fields.

该子项目是利用该技术的众多研究子项目之一 资源由 NIH/NCRR 资助的中心拨款提供。子项目及 研究者 (PI) 可能已从 NIH 的另一个来源获得主要资金， 因此可以在其他 CRISP 条目中表示。列出的机构是 对于中心来说，它不一定是研究者的机构。 在这项工作中，通过实验研究了并行 MRI 性能对主磁场强度的依赖性。使用电动力学标度的一般框架，研究了相关射频场在 7 T 的单一物理场强度下的 B0 相关行为。在所选的实现中，这是通过调整均匀球形模型的介电常数和电导率来实现的。通过癸烷、乙醇、纯净水、N-甲基甲酰胺和氯化钠的不同混合比例，模拟了 1.5 至 11.5 T 范围内的场强。基于八线圈接收器阵列的灵敏度图，根据几何因子 g 评估并行成像的场相关性能，该几何因子反映了并行成像重建中的噪声增强。在低场强下，SNR 损失几乎与 B0 无关，并且对于高达 3 到 4 之间的 1D 缩减因子来说，SNR 损失非常低。在较高场强下，有利和禁止的并行成像条件之间的过渡被发现会转向更高的可行缩减因子。这些发现与之前的理论预测非常吻合。从该协议可以得出结论，高 B0 的并行 MRI 特别受益于所涉及射频场的远场行为。