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AJNR - American Journal of Neuroradiology

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American Journal of Neuroradiology 26:1072-1077, May 2005
© 2005 American Society of Neuroradiology

BRAIN

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

J. O. Jesper Lundbom^a, Kim E. Vuori^a, Eija K. Gaily^b, R. I. Marja-Liisa Granström^b, Göran C. Blomstedt^c, Anna-Maija Häkkinen^d, Sami M. Heikkinen^a and Nina M. I. Lundbom^a

^a Helsinki Medical Imaging Center, Helsinki University Central Hospital, Finland
^b Department of Pediatric Neurology, Hospital for Children and Adolescents, Helsinki University Central Hospital, Finland
^c Department of Neurosurgery, Helsinki University Central Hospital, Finland
^d Department of Oncology, Helsinki University Central Hospital, Finland

Address correspondence to Sami Heikkinen, Helsinki Medical Imaging Center, Helsinki University Central Hospital, Helsinki, Finland, FIN-00029 HUS, Finland, PB 340

BACKGROUND AND PURPOSE: 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.

CONCLUSION: 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.