Metabolite phantom correction of the nonuniform volume-selection profiles in MR spectroscopic imaging: application to temporal lobe epilepsy.
OBJECTIVE
In MR spectroscopic imaging (MRSI), the volume-selection profiles of metabolites differ from each other. These differences cause variations in metabolite intensities, which are particularly prominent when the hippocampi are evaluated. We hypothesize that the errors arising from these effects cause notable artifact when temporal lobe epilepsy (TLE) is lateralized with MRSI.


METHODS
We examined a metabolite phantom, control subjects, and patients with TLE by using MRSI. We calculated the error arising from the different volume-selection profiles of metabolites in vitro and evaluated this correction in the examination of the control subjects and in the lateralization of epilepsy in the patients.


RESULTS
Without a correction, a considerable error in the metabolite content existed, even deep inside the spectroscopic volume of interest. The result was false asymmetry (P < .008) in the hippocampi of control subjects. Among the 11 patients, TLE was correctly lateralized in three only after the correction was made, and in one, TLE was incorrectly lateralized.


CONCLUSIONS
The volume-selection profiles of N-acetylaspartate, choline, and creatine differ enough to cause a significant error, even in the metabolite ratios, when patients with TLE are examined with MRSI. We propose a simple phantom method to correct for this error without a need to modify the pulse sequence.
Lundbom
J O Jesper
JO
Helsinki Medical Imaging Center, Helsinki University Central Hospital, Finland.
Vuori
Kim E
KE
Gaily
Eija K
EK
Granström
R I Marja-Liisa
RI
Blomstedt
Göran C
GC
Häkkinen
Anna-Maija
AM
Heikkinen
Sami M
SM
Lundbom
Nina M I
NM
D000293:Adolescent; D000328:Adult; D002648:Child; D004833:Epilepsy, Temporal Lobe / Q000378:metabolism*; D005260:Female; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged