Zhu X H, Merkle H, Kwag J H, Ugurbil K, Chen W
Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota School of Medicine, Minneapolis, Minnesota 55455, USA.
Magn Reson Med. 2001 Apr;45(4):543-9. doi: 10.1002/mrm.1073.
17O spin relaxation times and sensitivity of detection were measured for natural abundance H(2)(17)O in the rat brain at 4.7 and 9.4 Tesla. The relaxation times were found to be magnetic field independent (T(2) = 3.03 +/- 0.08 ms, T()(2) = 1.79 +/- 0.04 ms, and T(1) = 4.47 +/- 0.14 ms at 4.7T (N = 5); T(2) = 3.03 +/- 0.09 ms, T()(2) = 1.80 +/- 0.06 ms, and T(1) = 4.84 +/- 0.18 ms at 9.4T (N = 5)), consistent with the concept that the dominant relaxation mechanism is the quadrupolar interaction for this nucleus. The (17)O NMR sensitivity was more than fourfold higher at 9.4T than at 4.7T, for both the rat brain and a sodium chloride solution. With this sensitivity gain, it was possible to obtain localized (17)O spectra with an excellent signal-to-noise ratio (SNR) within 15 s of data acquisition despite the relatively low gyromagnetic ratio of this nucleus. Such a 15-s 2D (17)O-MRS imaging data set obtained for natural abundance H(2)(17)O in the rat brain yielded an SNR greater than 40:1 for a approximately 16 microl voxel. This approach was employed to measure cerebral blood flow using a bolus injection of H(2)(17)O via one internal carotid artery. These results demonstrate the ability of (17)O-MRS imaging to reliably map the H(2)(17)O dynamics in the brain tissue, and its potential for determining tissue blood flow and oxygen consumption rate changes in vivo. Magn Reson Med 45:543-549, 2001.
在4.7和9.4特斯拉的磁场强度下，对大鼠脑中天然丰度的H₂¹⁷O测量了¹⁷O自旋弛豫时间和检测灵敏度。发现弛豫时间与磁场无关（在4.7T时，T₂ = 3.03±0.08毫秒，T₂* = 1.79±0.04毫秒，T₁ = 4.47±0.14毫秒（N = 5）；在9.4T时，T₂ = 3.03±0.09毫秒，T₂* = 1.80±0.06毫秒，T₁ = 4.84±0.18毫秒（N = 5）），这与该原子核的主要弛豫机制是四极相互作用的概念一致。对于大鼠脑和氯化钠溶液，¹⁷O NMR灵敏度在9.4T时比在4.7T时高出四倍多。有了这种灵敏度提升，尽管该原子核的旋磁比相对较低，但在15秒的数据采集时间内仍有可能获得具有出色信噪比（SNR）的局部¹⁷O谱。从大鼠脑中天然丰度的H₂¹⁷O获得的这样一个15秒的二维¹⁷O - MRS成像数据集，对于大约16微升的体素，SNR大于40:1。该方法用于通过向一条颈内动脉推注H₂¹⁷O来测量脑血流量。这些结果证明了¹⁷O - MRS成像能够可靠地描绘脑组织中H₂¹⁷O的动态变化，以及其在体内确定组织血流量和氧消耗率变化的潜力。《磁共振医学》45:543 - 549，2001年。
