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All figures (11)
Figure 30.9. Reconstruction of the 4D EP-COSI/EP-JRESI datasets
Figure 30.2. Comparison of exponential and sine-bell filters for processing the 2D L-COSY sequence; even though the raw data matrix (t2, t1) contained 100 t1 signals, only 4 t1 signals are shown on the left
Figure 30.5. (a) Partial 2D L-COSY sequence showing the t1 increments and 90 ∘ RF pulse followed by detection along t2. (b) Conversion of the 2D L-COSY sequence into a 2D L-SECSY is depicted
Figure 30.8. A schematic diagram of a 4D EP-COSI sequence
Figure 30.3. Eddy current (EC) correction scheme. Re and Im represent the real and imaginary parts of the complex time-domain signal; 𝜙WS and 𝜙NWS represent the phase angles calculated from the water-suppressed and water-unsuppressed data sets
Figure 30.1. A schematic diagram of the 2D L-COSY sequence containing three slice-selective RF pulses (90∘, 180∘, 90∘) for volume localization. The B0-crusher gradient pulses were played around the 180∘ refocusing and the second 90∘ coherence transfer RF pulses. After the evolution during 2𝜏, there is a formation of the Hahn spin echo. Direct acquisition along t2 and indirect detection along t1 enable encoding of two spectral dimensions
Figure 30.13. (a) Multivoxel spatial distribution of 2D diagonal peaks of Cr and Cho (3.0 and 3.2 ppm) overlaid on a T1-weighted axial MRI. The white box indicates PRESS inner-volume localization, with voxels in the mid-occipital and left temporal lobes highlighted in blue and yellow, respectively. (b) Selected 2D J-resolved spectra extracted from the mid-occipital and (c) left temporal voxels
Figure 30.11. Different steps for postprocessing the MEEP-COSI/MEEP-JRESI datasets
Figure 30.7. (a) A schematic for a JPRESS sequence utilizing maximum-echo sampling for acquisition (highlighted in gold; FID; ADC, analog-to-digital converter). Half-echo sampling is started exactly at the echo time (green), whereas maximum-echo sampling starts immediately after the last crusher gradient (blue). The number of t2 points sampled using each method is the same. (b) The effects of adding a linear phase correction to refocus the chemical shift information. The linear phase acts as if a second t1 increment is added after the last 180 ∘ pulse. The linear phase correction effectively halves the spectral bandwidth in the indirect dimension
Figure 30.14. Comparison of the performance of the (a) MEEP-COSI and the (b) EP-COSI sequences in the calf of a healthy 28-year-old male volunteer. Spatial projections of the creatine diagonal peak at 3.9 ppm are overlaid on top of T1-weighted axial MRI. (Reproduced with permission from Ref. 96. © John Wiley & Sons, Ltd., 2014)
Figure 30.10. (a) The MEEP-COSI Pulse sequence diagram. (b) Diagram showing the effect of both T2 (dashed line) and T2* (solid line) on the overall shape of the signal envelope
Reference Entry
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DOI
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2‐D MR Spectroscopy Combined with 2‐D/3‐D Spatial Encoding
[...]
M. Albert Thomas
1
,
Zohaib Iqbal
1
,
Manoj K. Sarma
1
,
Rajakumar Nagarajan
1
,
Paul M. Macey
1
,
Amir Huda
1
,
Amir Huda
2
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+3 more
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Institutions (2)
University of California, Los Angeles
1
,
California State University, Fresno
2
15 Mar 2016
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