The Value Of The Hybrid PET/MR In The Diagnosis Of Refractory Epileptic Foci

Background and objectiveEpilepsy is one of the most common chronic diseases of the nervous system,with a prevalence of about 7.6‰,of which about 20%to 40%are refractory epilepsy.Drug therapy often cannot effectively control the epileptic seizures,surgical resection of epileptic foci is a common treatment method for refractory epilepsy,which can achieve postoperative remission in about 60 to 70%of epileptic patients.Accurate localization of epileptic foci before surgery is the key to successful operation.MRI has the advantages of high soft tissue resolution,no additional radiation damage,multi-directional and multi-sequence imaging,and repeatability,etc.It has become the preferred examination for epilepsy patients.However,due to no structural changes or slight changes in some patients,no abnormal findings are often found in structural MR.ASL is a form of functional magnetic resonance imaging,utilizes endogenous water molecules as imaging agent to indicate changes in cerebral blood perfusion.It has high sensitivity in the lateral and localization of epileptic foci in epilepsy patients.PET is a functional imaging that shows changes in brain glucose metabolism and can be used to early diagnosis disease at the cellular or molecular before have no structural changes.But,PET has the disadvantages of low resolution and unclear anatomical structure display,which makes it difficult to accurately locate epileptic foci,and the abnormal lesions shown by PET are often lager than epileptic foci.Previous studies have reported that PET has a high sensitivity and specificity in refractory epilepsy,and there is good consistency between PET and ASL.However,some studies believe that the overall positive diagnostic rate of PET in patients with refractory epilepsy is not very ideal.PET/MR is the most advanced imaging equipment at present,which can simultaneously acquisition anatomical,metabolic and blood flow information in the same physiologic or pathophysiologic states.It combines the advantages of PET and MR,and can improves the detection sensitivity and positioning accuracy of diagnosis.The purpose of this study was to investigate the value of integrated PET/MR multimodal imaging in the detection and localization epileptic foci in refractory epilepsy patients.And the value of PET/MR multimodal imaging in the sensitivity and accuracy of preoperative localization of epileptic foci in patients with refractory epilepsy was studied using the postoperative pathology and follow-up results of patients who had been operated as the gold standard.Methods1.Patients with refractory epilepsy diagnosed in the Department of Neurology of Henan Provincial People’s Hospital from October 2019 to December 2020 were prospectively collected and underwent 18F-FDG PET/MR examination.Included criteria:according to 2010 the ILAE of antiepileptic guide diagnosis for patients with refractory epilepsy,no PET/MR contraindications,no seizure for at least two day before PET/MR imaging.All patients had undergone MRI more than once before.2.All patients was instructed to fast for at least 6h,and had a confirmed serum glucose level below 11.1 mmol/L.Brain images were acquired with the patient in the supine position 60 min after an intravenous injection of ¹⁸F-FDG.And then the simultaneous PET and MR were performed.All patients signed informed consent before the examination.The images of PET,structural MR,fusion PET/MR and ASL were respectively double-blind reviewed by 2 experienced nuclear medicine physicians.Positive criteria:Abnormal manifestations of structural MR include:local cerebral cortex thickening or thinning;The boundary between gray and white matter is blurred;cortical or subcortical abnormal signals;lobe atrophy or sulci widening;The hippocampus or temporal lobe volume decreased,T2 signal increased,etc.Visual analysis was used in both PET and ASL,abnormality was defined as high or lower metabolism or perfusion in two or more consecutive levels in peripheral brain regions or corresponding brain regions in the contralateral hemisphere Clinical surgeons performed epileptogenic foci resection for some refractory epilepsy patients with clear localization of epileptogenic foci combined with MRI,PET,EEG and clinical manifestations,no serious neurological damage would be caused after surgical resection of epileptogenic foci,and the patients themselves or their family members had a strong desire for surgery.The surgical data and postoperative pathological results were collected and compared with the results of PET/MR examination.The seizure control of patients was followed up by telephone or inquiry in returned at 1month,3months 6 months and 1year after surgery.3.SPSS 21.0 software was used for Statistical analysis.Measurement data conforming to normal distribution were as mean standard deviation（（?）±s）,t-test or rank-sum test were used for comparision between groups as number of case and percentage,andχ² test was used for comparision between groups.When P was less than 0.05,the difference was considered statistically significant.Results1.Study group inclusion results.A total of 38 patients with RE who completed the 18F-FDG PET/MR multimodal examination.In the later data analysis,it was found that 3 patients were excluded from the group due to the poor quality of ASL perfusion image.A total of 35 patients were included in the final statistical analysis,including 21 males and 14 females,age ranged from 5 to 58 years,with an average age of（22.49±14.13）years.At present,10 of the 35 patients have received surgical treatment,including 5 males and 5 females,age ranged from 5 to 51 years,with an average age of（22.20±15.23）years.2.The positive of 35 pitients in PET/MR multimodal imaging.All patients had interictal PET/MR examination.Among the 35 cases,32 case had metabolic abnormalities as shown in the PET image,and all of them showed hypometabolism,the positive rate of PET was 91.43%（32/35）.19 case of brain structure and/or signal abnormalities were found on MRI images,with a positive rate of 54.29%（19/35）.Among the 19 cases,there was no structural or signal abnormality in 4 case,suspected abnormality in 2 cases,definite abnormality in 13 cases,PET/MR increased the positive rate of MRI by 17.14%（6/35）.PET/MR modal MRI detection rate is higher than pure MRI detection rate,and the difference was statistically significant between them（χ²=4.167,Ρ=0.031<0.05）.24 patients with ASL showed single or multiple abnormal perfusion,and all of them were in the area of hypoperfusion.The positive detection rate of ASL was 68.57%（24/35）.3.Comparison of positive detection rates of PET,structural MRI,ASL and PET/MR multimodal imaging in 35 patients.Using matchingχ² test,PET positive rate was higher than that of MRI and ASL positive rate,difference was statistically significant（χ²=11.077、4.900,Ρ<0.05）.ASL positive rate was higher than that of MRI positive rate,but there was no statistically significant difference between them（χ²=1.455,Ρ>0.05）.In total,33 of the 35 patients with refractory epilepsy had more than one positive finding in PET/MR multimodal examination,and the total positive rate was 94.29%（33/35）,which was higher than MRI（54.29%）and ASL（68.57%）,respectively,the difference was statistically significant（χ²=12.071,7.111,P values<0.05）,but with PET（91.43%）,there were no statistical difference between them（χ²=0.000,P>0.05）.4.Comparison of consistency between PET,structural MRI and ASL in 35patients.4.1 Consistency between PET and MRI:There were 19 patients with positive MRI,of which 13 cases were completely consistent with MRI and PET positioning,4cases had metabolic abnormalities in other brain regions except for MRI abnormal sites,and the remaining 2 cases were completely different with PET and MRI.Among the 16 patients with negative MRI,PET showed single or multiple hypometabolic in13 patients,and both PET and structural MRI were negative in the remaining 3patients.The coincidence rate of PET and MRI positioning was 37.14%（13/35）.4.2 Consistency between PET and ASL:Among the 24 patients with positive ASL,18 cases had PET consistent with ASL positioning,3 cases PET had metabolic abnormalities in other brain regions except for abnormal ASL sites,2 cases ASL had abnormal perfusion except for abnormal PET sites,and the remaining 1 case was negative for PET.Among the 11 ASL negative patients,9 showed abnormal hypometabolic foci on PET,and the remaining 2 showed no abnormal findings on PET.The coincidence rate of PET and ASL positioning was 51.4%（18/35）.4.3Consistency between MRI and ASL:Among the 16 with dual positive structural MRI and ASL,9 had complete agreement between structural MRI and ASL,3 had abnormal blood perfusion in other brain regions except for the abnormal MRI site,2 had structural abnormal in other brain regions except for the abnormal ASL site,and the remaining 2 had completely different localization.The ASL of 8 patients showed hypoperfusion,and no abnormal findings were found on MRI.Structural MRI was positive in 3 patients,and ASL showed no abnormal.No abnormality was found in structural MRI and ASL in 8 patients.The coincidence rate of structural MRI and ASL localization was 25.71%（9/35）.4.4Consistency of PET,MRI and ASL in positive lesions:Of the 35 patients,9cases were completely consistent with PET,MRI and ASL positive lesions,and the overall location coincidence rate of the multimodal examinations was 25.71%（9/35）.5.Analysis of refractory epilepsy patients undergoing surgical resection of epileptic foci.A total of 10 refractory patients underwent surgery during the study,there were 6 cases of temporal lobe,2 cases of frontal lobe,1 case of occipital lobe,and 1 case of temporo-parietal occipital junction.There were 8 cases of focal cortical dysplasia（FCDIa 2,FCDIb 2,FCDII 4）and 2 cases of tumor（1 case of diffuse astrocytoma and 1 case of low-grade glioma）.The control of postoperative epilepsy of 10 patients:Follow-up period was 1 month to 1 years,8 of them did not have seizures during the follow-up period;During the follow-up period,2 patients had 2 to3 small attacks,and the frequency of attacks and symptoms were significantly reduced.Preoperative PET/MR results of 10 patients were reviewed.Hypometabolism were found in all the 10 patients undergoing surgery on PET images,among which 8patients showed single focal hypometabolism,and the PET localization results were completely consistent with the surgical pathological site;2 patients showed multifocal hypometabolism,and one of the hypometabolic lesions was consistent with the postoperative pathological results.Hypoperfusion areas could be observed on ASL in8 patients,of which 7 cases were consistent with the surgical pathological site,and 1case showed multifocal hypoperfusion,among which one cerebral lobe with hypoperfusion was consistent with the surgical pathological site.7 patients were found to have structural or signal abnormalities on MRI,of which 6 cases were consistent with the site of postoperative resection and 1 case was different from the site of postoperative resection.The sensitivity and accuracy of PET、MRI and ASL was 100%and 80%,80%and 70%,70%and 60%,respectively.Using PET/MR combined with anatomical,metabolic and perfusion information,10 patients with refractory epilepsy were accurately identified with a sensitivity and accuracy of100%.Conclusion1.The hybrid PET/MR multimode can simultaneously obtain the information of brain tissue anatomy,metabolism and perfusion of epilepsy patients under the same physiological or pathological state.And is significantly better than PET and MRI alone in the sensitivity of epileptic focal detection and localization accuracy.2.PET/MR multimodal imaging can not only detect epileptigenic lesions without structural abnormalities in MRI more sensitively by improving the image quality of PET metabolism imaging,but also significantly improve the detection rate of structural abnormalities in brain on MRI alone by PET metabolism abnormality.3 The combination PET and MRI perfusion can improve the detection of epileptic foci without structural abnormalities and increase the diagnostic confidence.4.The epileptogenic foci with strong consistency of PET/MR multimodal information judgment and localization are highly consistent with postoperative pathology.It is suggested that hybrid PET/MR has important application value in the diagnosis and treatment of refractory epilepsy patients.