Multinuclear localized spectroscopy at ultra-high field wholebody MRI

我们在4.7T核磁共振谱仪上实现了三通道发射器和四通道接收器。为了实现对^1H、^ P和^ C三重核的测量<31><13>，我们构造了三调谐射频线圈。首先，我们制作了一个直径为8 cm的双环线圈，<31>然后添加了一个直径为12 cm的单环线圈。这些表面线圈与用于头部的^1H TEM线圈（内径30 cm）集成。该集成探头被仔细调谐为200.43、81.14和50的三个频率。40兆赫。三个频率之间的耦合保持足够小。为了使软件能够在三重核中进行测量，我们制作了一个脉冲序列，该脉冲序列结合了用于^1H的超短回波时间STEAM序列和用于^ P的ISIS序列<31>。该序列使我们能够<31>以交错方式测量来自同一局部区域的^1H和^ P光谱。对于^ C的定域谱<13>，我们<13>在H定域谱中加入了^ C编辑的特征。为了实现编辑，我们<13>在交替扫描的STEAM序列的TM周期期间为^ C核添加了反转脉冲。STEAM的TE也被调整为7.7ms，这对应于<CH>sp_3-boded CH自旋的1/J_。使用三重调谐线圈和用于^1H、^ P和^ C的交错测量的序列<31><13>，我们测试了我们的方法的性能。在<13><31>含有50 mM乙酸盐、50 mM谷氨酸盐和100 mM ATP的体模样品中，在局部2 × 2 × 2 cm ^3区域成功观察到^1H、^1H检测到的^1C和^1P光谱。然后，我们将该方法应用于人类大脑。在人脑枕叶3 × 3 × 3立方厘米的区域内，我们可以在10分钟内测量^1H和<31>^1P的光谱。我们将这种方法命名为Trinity，以三通道光谱学中的三重核命名。

We implemented three channels of transmitter and four channels of receiver to the 4.7T MRI spectrometer To enable triple nuclei measurements for ^1H, ^<31>P and ^<13>C, we constructed triple-tuned rf coils. First, we made a dual loop coil (8cm in diameter) for ^<31>P. Then, a single loop coil (12cm in diameter) was added up. These surface coils were integrated with a ^1H TEM coil for head (inner diameter of 30cm). This integrated probe was carefully tuned for three frequencies at 200.43, 81.14, and 50. 40MHz. Couplings among three frequencies were kept small enough. For the software to enable measurements in triple nuclei, we made a pulse sequence combining a ultra-short-echo time STEAM sequence for ^1H and an ISIS sequence for^<31>P This sequence enables us to measure ^1H and ^<31>P spectra from the same localized area in an interleave manner. For the localized spectroscopy for ^<13>C we added up a feature of ^<13>C editing to H localized spectrum. To attain the editing we added an inversion pulse for ^<13>C nucleus during the TM period of the STEAM sequence in alternative scans. TE for the STEAM was also adjusted to 7.7ms, which corresponds to 1/J_<CH> for sp_3-boded CH spins. With a triple tuned coil and a sequence for interleave measurements for ^1H, ^<31>P, and ^<13>C we tested performances of our method. ^1H, ^1H-detected ^<13>C, and ^<31>P spectra were successfully observed in the localized 2x2x2cm^3 area in the phantom sample containing 50 mM acetate, 50mM glutamate, and 100mM ATP. Then we applied the method to human brains. In the 3x3x3cm^3 area in the occipital lobe of human brain we could measure ^1H and ^<31>P spectra in ten minutes. We named this method as TRINITY after TRIple Nuclei In Triple channel spectroscopY.