Ratio-images calculated from interictal positron emission tomography and single-photon emission computed tomography for quantification of the uncoupling of brain metabolism and perfusion in epilepsy.
OBJECTIVE
Image processing techniques were applied to interictal positron emission tomography (PET) and single-photon emission computed tomography (SPECT) brain images to aid in the localization of epileptogenic foci by calculating a functional image that represents the degree of coupling between perfusion and metabolism. Uncoupling of these two functions has been demonstrated to be a characteristic of epileptogenic tissue in temporal lobe epilepsy and has the potential to serve as a diagnostic measure for localization in other areas as well.


METHODS
Interictal PET ((18)F-FDG) and interictal SPECT ((99m)Tc-HMPAO) scans were acquired from 11 epilepsy patients. The metabolism and perfusion images were three-dimensionally spatially registered, and a functional ratio-image was computed. These functional maps are overlaid onto a three-dimensional rendering of the same patient's magnetic resonance imaging anatomy.


RESULTS
In all patients, an average uniform perfusion-to-metabolism ratio showed approximately constant values throughout most of the whole brain. However, the epileptogenic area (confirmed on surgery) demonstrated an area of elevated perfusion/metabolism in the grey matter.


CONCLUSIONS
Although hypometabolism in the PET image was observed in most of these patients, the calculation of a functional ratio-image demonstrated localized foci that in some cases could not be observed on the PET image alone. The ratio-image also yields a quantitative measure of the uncoupling phenomenon.
Zubal
I G
IG
Department of Diagnostic Imaging, Yale University School of Medicine, New Haven, Connecticut, USA. George.Zubal@Yale.edu
Avery
R A
RA
Stokking
R
R
Studholme
C
C
Corsi
M
M
Dey
H
H
Seibyl
J P
JP
Spencer
S S
SS
D000293:Adolescent; D000328:Adult; D001921:Brain / Q000098:blood supply* / Q000000981:diagnostic imaging / Q000378:metabolism*; D001931:Brain Mapping; D003627:Data Interpretation, Statistical; D004827:Epilepsy / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000378:metabolism; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000378:metabolism; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D012039:Regional Blood Flow; D019690:Technetium Tc 99m Exametazime; D014055:Tomography, Emission-Computed / Q000706:statistics & numerical data*; D015899:Tomography, Emission-Computed, Single-Photon / Q000706:statistics & numerical data*
D019788:Fluorodeoxyglucose F18; D019690:Technetium Tc 99m Exametazime