Validation of FDG-PET/MRI coregistration in nonlesional refractory childhood epilepsy

Abstract

SUMMARYPurpose: To validate the use of 18F-fluorodeoxyglucosepositron emission tomography/magnetic resonance imaging (FDG-PET/MRI) coregistration for epileptogenic zone detection in children with MRI nonlesional refractory epilepsy and to assess its ability to guide a second interpretation of the MRI studies. Methods: Thirty-one children with refractory epilepsy whose MRI results were nonlesional were included prospectively. All patients underwent presurgical evaluation following the standard protocol of our epilepsy unit, which included FDG-PET and FDG-PET/MRI coregistration. Cerebral areas of decreased uptake in PET and PET/MRI fusion images were compared visually and then contrasted with presumed epileptogenic zone localization, which had been obtained from other clinical data. A second interpretation of MRI studies was carried out, focusing on the exact anatomic region in which hypometabolism was located in FDG-PET/MRI fusion images.Key Findings: Both FDG-PET and FDG-PET/MRI detected hypometabolism in 67.8% of patients, with good concordance on a subject basis and on the cerebral region involved (j statistic = 0.83 and 0.79, respectively). Hypometabolism detected by single PET, as well as by PET/MRI fusion images, was located in the same hemisphere, as indicated by electroclinical data in 58% of patients, and at the same place in 39% of cases. Of the patients who showed hypometabolism on PET/MRI, 43% also experienced changes in the guided second MRI interpretation, from nonlesional to subtlelesional. Significance: PET/MRI coregistration is an imaging variant that is at least as accurate as PET alone in detecting epileptogenic zone in pediatric nonlesional patients, and can guide a second look at MRI studies previously reported as nonlesional, turning a meaningful percentage into subtle-lesional.

The Utility of Positron Emission Tomography in Epilepsy

“…However, 37 retrospective studies 44 and three prospective studies [45][46][47] were identified to be relevant to this systematic review (Figure 1). Six of these studies were reported solely in abstract form, 17,24,25,34,38,41 whereas two studies 30,33 had both the full publication and the abstract. Because of the heterogeneity of the studies in the patient population, study design, outcome measurements, and methods of PET interpretation, the results of the studies included in the systematic review could not be pooled.…”

“…In this same cohort, surgical resection guided by PET/MRI coregistration and electrocorticography resulted in 82% of the patients achieving seizure freedom. In another retrospective study involving children with refractory epilepsy, 30 PET/MRI coregistration guided the second MRI interpretation from nonlesional to subtle lesional in 42% of the cases. Similarly, PET/ MRI coregistration was able to detect Taylor-type focal cortical dysplasia in patients with negative MRI and where a PET scan alone does not allow a conclusive diagnosis.…”

Potential Pediatric Applications of PET/MR

“…Because somatostatin receptors (especially subtype 2) are expressed on the surface of some neuroblastomas, radiolabeled somatostatin analogs such as 68 Ga-and 177 Lu-octreotide may be beneficial for imaging and targeted radiotherapy, especially for primary refractory or relapsed high-risk neuroblastomas (52). Given the higher sensitivity and better spatial resolution of somatostatin receptor PET than of somatostatin receptor scintigraphy for detecting somatostatin receptor-positive tumor lesions, combined PET/MR may be advantageous, especially for small liver lesions.…”

Review of Epilepsy - Etiology, Diagnostic Evaluation and Treatment

“…This may reflect the difficulty in localizing and resecting the epileptogenic zone [60]. In order to improve the radiographic detection of epileptogenic lesions, more advanced imaging techniques have been used such as 7T MRI, volumetric analysis, Diffusion Tensor Imaging (DTI), arterial spin labeling and PET [38,[66][67][68][69][70][71][72][73][74]. However, it is currently unknown if such techniques willimprove outcomes.…”

“…Anti-NMDA antibody, Anti-GABAB antibody, Anti-AMPA antibody, Anti-LGI1 antibody, Anti-CASPR2 antibody, Anti-contactin-2 antibody, Anti-GAD antibody, Anti-VGKC antibody [32][33][34][35][36][37][38].…”