Metabolite Phantom Correction of the Nonuniform Volume-Selection Profiles in MR Spectroscopic Imaging: Application to Temporal Lobe Epilepsy

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Fig 1.
Axial/coronal T1-weighted image at the level of the hippocampi with the MRSI voxels 1, 2, and 3 chosen to represent the hippocampus. The 100- and 80-mm-wide VOIs are shown (white rectangles).
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Fig 2.
Phantom profile for water signal intensity with the 180° Hamming-weighted sinc pulse of the PRESS CSI sequence (solid line with black boxes) obtained by selecting the right-left dimension of the 100-mm VOI (vertical lines). Profile shifted by 10 mm (dashed line with white boxes). This displacement approximately corresponds to the chemical-shift difference between water and NAA with the typical excitation bandwidth of 1500 Hz for the section-selective 180° pulse. Images shows the difference between the original profile and the shifted profile spanning the VOI (dotted line with gray circles). The water intensity on the y axis is expressed in institutional units (i.u.), and the x axis corresponds to the 10-mm voxels in the 160-mm FOV.

TABLE 1:

Clinical, MR imaging, and MRSI findings in patients with TLE

Patient/Age (y)/Sex	Epilepsy Clinical Lateralization and Type	MR Imaging	MRSI Lateralization		Comment^*
Patient/Age (y)/Sex	Epilepsy Clinical Lateralization and Type	MR Imaging	No Correction	Pulse Correction	Comment^*
1/9/M	L TLE	L T dysmyelination	None	R	Seizure-free without operation
2/10/F	L TLE	L hippocampal dysgenesis (possible)	None	None	Seizure-free without operation
3/16/F	L TLE, possible R FLE	Normal	L	L	No resection, VNS
4/16/F	L TLE	L MTS	L	L	L TL resection, seizure-free
5/13/F	R/L TLE	Normal	L	L	No operation, monthly seizures
6/17/F	R/L TLE	R/L hamartomas (tuberous sclerosis)	None	R	Daily seizures from R TL, rare from L TL, VNS
7/9/M	R TLE	R hippocampal edema	None	R	No operation, rare seizures
8/12/F	R TLE	R MTS	L	L	R TL resection, seizure-free
9/15/F	R TLE	R hippocampus, small	L	L	R TL resection, seizure-free
10/15/M	R TLE	Sturge-Weber syndrome R TO	R	R	Seizure-free without operation
11/34/F	R TLE	Normal	None	R	R TL resection, seizure-free for 6 mo, postoperative seizures from L TL
12/9/F	Multifocal	R hippocampus, small	None	None	Seizures not from TL
13/14/M	L TOE	Dysgenesis L TO	None	None	None
14/15/M	Undetermined	L hippocampus, abnormal	None	None	Not operation, rare seizures
15/50/F	R TLE or R FLE	Normal	None	None	Not operation, monthly seizures

Note.—FLE = frontal lobe epilepsy, TOE = temporo-occipital epilepsy, MTS = mesial temporal sclerosis, TL = temporal lobe, VNS = vagal nerve stimulation.
* Rare seizures were fewer than one per 6 months.