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

该子项目是利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH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 中心，不一定是研究者的机构。 为了最大化信噪比（SNR）和最小化弛豫加权， 钠MRI通常倾向于读出。 UTE方法也被用于 测量组织中的总钠浓度（TSC），尽管这通常需要精确的 B1场的映射。 B1测量通常有噪音且容易出错，因此可以进行良好的TSC 测量困难，除非B1是高度均匀的。 该多通道相位线圈 在钠MRI研究中是优选的，因为SNR的增加更不均匀， 鸟笼线圈，使良好的B1测量在大多数钠MRI应用中非常重要。 UTE 这些方法还遭受在读出方向上的非共振和T2* 相关模糊， 进一步使得用这些技术进行定量测量变得困难。 更可靠的 钠MRI的定量参数是测量钠的长成分， 横向弛豫时间T2 L *。 通过收集短横截后的几个回声 如果松弛分量已经衰减，则所得到的衰减曲线可以精确地拟合到 单指数曲线 UTE方法通常使用径向或螺旋读数，在两个或三个- 维度，然后在笛卡尔k空间上网格化，然后傅立叶变换为图像 空间 我们发现，我们可以获得非常相似的结果，使用收购加权 直接在笛卡尔网格上进行半回波读出。 然后，我们跟随这个半回声读数， 五个全回波标准笛卡尔读数 这个成像序列的好处是 具有最高可能SNR和最低可能松弛加权的图像，同时还 从而提供稳健的定量参数。

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. 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.