Stratifying differences on ictal/interictal subtraction SPECT images.
ABSTRACT Subtraction of interictal from ictal single-photon emission computed tomography (SPECT) yields numerous foci that encompass a range of pixel values scattered in the brain. This preliminary study evaluated the significance of this range of values.
Subtraction images were obtained by registering, normalizing, and subtracting interictal from ictal SPECT for 13 patients. Pixel values of the resulting foci were divided into two groups: group I with 75-100% and group II with 50-75% of the maximal pixel value. Locations of these foci were determined, and concordance with surgical outcomes and scalp and invasive EEG findings was evaluated.
In 10 of 13 cases, group I foci showed good concordance with ictal scalp EEG. In addition, group I foci corresponded well to invasive EEG findings in nine of 10 cases. Group I foci had bilateral distributions in seven of 13 cases. In 10 of 13 cases, group I foci corresponded well to regions of surgical resection. Of these 10 patients, nine showed good concordance with scalp EEG, eight showed good invasive EEG concordance, and eight were seizure free after resection. Conversely, group II foci had good concordance with ictal scalp EEG in only five of 13 cases, and invasive EEG findings, in only five of 10 cases. Group II foci had bilateral distributions in 10 of 13 cases. All 10 cases underwent unilateral surgical resections, and all had good surgical outcomes. In six of 13 cases, group II foci showed concordance with surgical sites. Of these six foci, four had poor concordance with scalp EEG, one had poor concordance with invasive EEG, and five had good surgical outcomes. Sensitivity and specificity for seizure localization of Group I foci were 40% and 88% respectively while sensitivity and specificity of Group II foci were 20% and 79% respectively.
Our data demonstrate that foci with 75-100% of maximal pixel values show good concordance with seizure foci, whereas foci of 50-75% may not. Therefore stratifying ictal/interictal differences may improve the specificity and localizing value of subtraction SPECT.
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ABSTRACT: In pharmacoresistant partial epilepsy (PRPE) in children, functional cerebral imaging helps localizing the epileptogenic zone using SPECT (Single Photon Emission Computed Tomography) and PET (Positron Emission Tomography) and the functional motor and language cortex using functional MRI. Regarding SPECT, only ictal SPECT exhibits an acceptable sensitivity (80 p. 100), together with interictal SPECT and subtraction image processing. Regarding PET, sensitivity has not been validated yet compared with intracranial EEG, neither using 18FDG, nor using more recent tracers such as 11C-flumazénil or 11C-alpha-méthyl-tryptophane. However, both techniques are useful to decide the placement of the intracranial electrodes, particularly in cryptogenic cases or when preoperative data are discordant. Functional MRI for language is going to be validated compared with WADA test and to provide a very useful and non invasive alternative method to lateralize the language networks in children able to cooperate. FMRI also provides a unique opportunity to follow the post-lesional or post-surgery plasticity of these networks using repeated examinations in a same patient. Functional imaging techniques therefore provide a useful additional contribution in the presurgery work-up of PRPE in children.Revue Neurologique 06/2004; 160:131-137. · 0.60 Impact Factor
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ABSTRACT: The most challenging technical problem in ictal brain SPECT for localization of an epileptogenic focus is obtaining a timely injection of a radiopharmaceutical. In our institution, the first dedicated commercially available, remotely controlled automatic injector has been used in the pediatric epilepsy unit in conjunction with 24-h video and electroencephalogram monitoring. The goal of this study was to demonstrate the improved success rate of ictal injection by use of the automatic injector in the pediatric population. METHODS: Eighty-four pediatric patients and eighty-four (99m)Tc-ethylcysteinate dimer ((99m)Tc-ECD) ictal brain SPECT studies were retrospectively analyzed in a masked manner. The group with manual injection consisted of 45 studies performed from 2004 to 2010 before the introduction of the automatic injector. The group with automatic injection consisted of 39 studies performed from 2010 to 2011 after the introduction of the automatic injector. The 2 groups were comparable in the total duration of seizure, injected dose, and time from the injection to the image acquisition. The latency time from the seizure onset to the initiation time of injection, the ratio of latency time to total duration of seizure (L/T), the number of patients with repeated studies, the number of days of additional hospitalization for each study, and the localization rate for identifying a single focus in each study were compared between the groups. RESULTS: The median latency time in the group with automatic injection (8 s) was significantly lower than that of the group with manual injection (18 s) (P < 0.05). Also there was a statistically significant decrease in the number of patients with repeated studies in the group with automatic injection (2/39 [5%]), compared with the group with manual injection (14/45 [31%]) (P < 0.05). The median number of days of additional hospitalization in the group with manual injection (range, 0-7) was statistically significantly different, compared with the group with automatic injection (range, 0-1) (P < 0.05). In the group with automatic injection, 31 of 39 scans demonstrated a single localizing focus, compared to 22 of 45 scans from the manual-injection group, a significant difference (P < 0.05). The radiation exposure rate to nursing staff during the periods with automatic injection was lower than during the periods with manual injection. CONCLUSION: The automatic injector combined with 24-h video and electroencephalogram monitoring demonstrated significant clinical value by decreasing latency time, the number of patients with repeated studies, and the number of days of additional hospitalization while increasing the number of studies with a single localizing focus.Journal of Nuclear Medicine 03/2013; · 5.56 Impact Factor
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ABSTRACT: Surgery of partial epilepsies in childhood has largely benefited from the recent advances of imaging techniques, which carry a triple goal: (1) to contribute to the localization of the epilepsy onset zone, (2) to detect and delineate an underlying lesion, and (3) to study the spatial relationship between the epileptogenic zone and the neighboring functional cortex, in order to select patients and plan the resection. This noninvasive presurgical imaging workup must be compared to clinical and electrical data to estimate the postoperative prognosis, while invasive techniques such as SEEG, cortical stimulations, and IAT often remain indispensable in difficult cases, i.e., in cryptogenic epilepsies. As in adults, advances in MRI allow us to detect more and more subtle underlying lesions, but this requires repeating MR studies during early childhood and using adapted sequence parameters to account for ongoing myelination. Ictal SPECT and PET imaging prove especially useful in planning depth electrode placement when video-EEG is not contributive, when MRI looks normal or shows multiple abnormalities, or in cases of discrepant findings. Multimodal imaging greatly enhances the sensitivity of all of these techniques. Finally, functional MRI of motor and language functions provide noninvasive cortical mapping of essential functions, using age-adapted paradigms, in cooperating children from age five to six and from IQs around 60.Neurochirurgie 05/2008; 54(3):212-218. · 0.47 Impact Factor