Trading Spectral Separation at 3T for Acquisition Speed in Multi Spin-Echo Spectroscopic Imaging
U. Dydaka,
D. Meiera,
R. Lamerichsb and
P. Boesigera
a Institute of Biomedical Engineering, University of Zurich and Swiss Federal Institute of Technology Zurich, Zurich, Switzerland
b Philips Medical Systems, Best, The Netherlands
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Fig 1. Comparison between 3T and 1.5T: multiple spin-echo MRSI data with ETL = 6 and an echo spacing of 144 ms acquired in the same healthy volunteer. Shown are the T2-weighted images, the creatine maps, and the spectra from the outlined voxel.
A, 3T data: The spectral sampling resolution of 8.9 Hz is sufficient to clearly resolve the creatine resonance at 3.0 ppm and the choline resonance at 3.2 ppm.
B, 1.5T data: Although the creatine map still shows some structure, the spectrum shows that an 8-Hz sampling resolution cannot distinguish the 2 resonances anymore.
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Fig 2. Example of multiple spin-echo MRSI data (ETL = 6) in a patient with a meningioma, acquired with a 32 x 32 matrix in 5:12 (minutes:seconds). Post-gadolinium T1-weighted image (A), choline map (B), and NAA map showing the region (C) from which the spectra are depicted in D. The spatial resolution allows visualization of the change of metabolism from the tumorous region (high choline, no creatine, no NAA) to healthy metabolism outside the meningioma.
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Fig 3. Multisection multiple spin-echo MRSI with ETL = 6 at 3T: Inversion recovery images of the 6 sections covering a large part of the brain, including both cerebellum and cerebrum (A), choline maps (B), creatine maps (C), and NAA maps of the 6 sections (D).
E, Spectra from the outlined voxels (isotropic nominal voxel size = 1.33 cm3) from section 2 of a 20 x 20 x 6 MRSI measurement acquired in 11:23 (minutes:seconds).
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Fig 4. Combination of SENSE and multiple spin-echo MRSI with ETL = 6 at 3T: creatine maps (A) and spectra (B) from the outlined voxel of a 24 x 24 MRSI measurement. From left to right, the MRSI scans were acquired with ETL = 1 in 11:04 (minutes:seconds), with ETL = 2 in 5:37, with ETL = 6 in 2:30, with SENSE and ETL = 2 in 1:37, and finally with SENSE and ETL = 6 in only 0:54.
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