QUANTITATIVE SODIUM MRI AT 7T WITH 12 CHANNEL PHASED-ARRAY COIL

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 为了最大化信噪比(SNR)并最小化松弛加权，超短回波(UTE) 一般情况下，钠核磁共振的读数更受青睐。UTE方法也被用于 测量组织中的总钠浓度(TSC)，尽管这通常需要准确 B1字段的映射。B1测量通常有噪声且容易出错，因此具有良好的TSC 除非B1高度均匀，否则很难进行测量。多通道相位线圈 在钠核磁共振研究中是首选的，因为信噪比的增加比 鸟笼线圈，使良好的B1测量在大多数钠核磁共振应用中非常重要。UTE 方法还在读出方向上遭受非共振和T2*相关的模糊， 进一步使使用这些技术进行定量测量变得困难。一个更可靠的 钠核磁共振的定量参数是测量脑组织的长成分 横向弛豫时间，T2L*。通过收集短横波后的几个回波 松弛分量已经衰减，则所得到的衰减曲线可以准确地拟合到 单指数曲线。UTE方法通常使用径向或螺旋读数，分两个或三个- 维度，然后在傅里叶变换为图像之前在笛卡尔k空间上进行网格划分 太空。我们发现，使用收购加权可以获得非常相似的结果 直接在笛卡尔网格上的半回波读数。然后我们在这个半回声读数之后添加了 五个全回声标准笛卡尔读数。该成像序列的好处是产生 具有最高可能SNR和最低可能松弛权重的图像，同时还 提供了一个稳健的量化参数。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. To maximize signal-to-noise ratio (SNR) and minimize relaxation weighting, ultra-short echo (UTE) readouts have been generally been favored for sodium MRI. UTE methods have also been used to measure total sodium concentration (TSC) in tissues, although this typically requires accurate mapping of the B1 field. B1 measurements are typically noisy and error prone, making good TSC measurements difficult unless the B1 is highly homogeneous. The multi-channel phase coils that are preferred in sodium MRI studies because of the increase SNR are more inhomogeneous that birdcage coils, making good B1 measurement important in most sodium MRI applications. UTE methods also suffer from off-resonance and T2*-associated blurring in the readout direction, further making quantitative measurements with these techniques difficult. A more reliable quantitative parameter for sodium MRI is the measurement of the long component of the transverse relaxation time, T2L*. By collecting several echoes after the short transverse relaxation component has decayed, the resulting decay curve can be accurately fitted to a monoexponential curve. UTE methods typically use a radial or spiral readout in two or three- dimensions, followed by gridding onto Cartesian k-space before Fourier transforming to image space. We have found that we can obtain very similar results using an acquisition weighted half-echo readout directly on a Cartesian grid. We then followed this half-echo readout with five full-echo standard Cartesian readouts. This imaging sequence has the benefit of producing an image with the highest possible SNR and lowest possible relaxation weighting while also providing a robust quantitative parameter.