Disparity of perfusion and glucose metabolism of epileptogenic zones in temporal lobe epilepsy demonstrated by SPM/SPAM analysis on 15O water PET, [18F]FDG-PET, and [99mTc]-HMPAO SPECT.
OBJECTIVE
To elucidate uncoupling of perfusion and metabolism and its significance in epilepsy, 15O water and 18F fluorodeoxyglucose (FDG) positron emission tomography (PET) and Tc-99m hexamethyl-propyleneamine-oxime (HMPAO) single-photon emission computed tomography (SPECT) were examined by SPM (statistical parametric mapping) and quantitation by using SPAM (statistical probabilistic anatomic map).


METHODS
[15O]water and [18F]FDG-PET, and [99mTc]-HMPAO SPECT were performed in 25 patients (SPECT in 17 of 25) with medial temporal lobe epilepsy. For volume of interest (VOI) count analysis, the normalized counts using VOI based on SPAM templates of PET and SPECT were compared with those of the normal controls. Perfusion or metabolism was found abnormal if the Z score was >2 for each VOI. For SPM analysis, the differences between each patient's image and a group of normal control images (t statistic for p < 0.01) on a voxel-by-voxel basis were examined to find significant decreases in perfusion or metabolism.


RESULTS
With SPAM VOI count analysis, areas of hypoperfusion were found in 13 patients in the epileptogenic temporal lobes by [15O]water PET and areas of hypometabolism in 21 patients by [18F]FDG-PET. With voxel-based SPM analysis, the epileptogenic zones were localized in 15 by [15O]water PET and in 23 patients by [18F]FDG-PET. The localization by [15O]water PET was concordant with that of [18F]FDG-PET. The areas of hypoperfusion on [15O]water PET were absent or smaller than the areas of hypometabolism on [18F]FDG-PET. Interictal [99mTc]-HMPAO SPECT revealed the hypoperfused zones in seven of 17 patients on visual assessment.


CONCLUSIONS
SPAM VOI count and SPM analysis of [15O]water and [18F]FDG-PET and [99mTc]-HMPAO SPECT revealed that in the same patients, the areas of hypoperfusion were concordant with but smaller than the areas of hypometabolism. Discordance of perfusion and metabolic abnormalities represents an uncoupling of perfusion and metabolism in the epileptogenic zones, and this might explain the lower diagnostic accuracy of perfusion imaging in temporal lobe epilepsy.
Lee
D S
DS
Seoul National University Medical Research Center, Institute of Radiation Medicine, Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul, Korea.
Lee
J S
JS
Kang
K W
KW
Jang
M J
MJ
Lee
S K
SK
Chung
J K
JK
Lee
M C
MC
D000293:Adolescent; D000328:Adult; D003627:Data Interpretation, Statistical; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000378:metabolism; D005260:Female; D019788:Fluorodeoxyglucose F18; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D010104:Oxygen Radioisotopes; D012039:Regional Blood Flow; D019690:Technetium Tc 99m Exametazime; D013702:Temporal Lobe / Q000098:blood supply* / Q000000981:diagnostic imaging / Q000378:metabolism*; D014055:Tomography, Emission-Computed / Q000706:statistics & numerical data; D015899:Tomography, Emission-Computed, Single-Photon / Q000706:statistics & numerical data; D014867:Water
D010104:Oxygen Radioisotopes; D014867:Water; D019788:Fluorodeoxyglucose F18; D019690:Technetium Tc 99m Exametazime; D005947:Glucose