Multinuclear localized spectroscopy at ultra-high field wholebody MRI

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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.