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Wu Q, Gong P, Liu S, Li Y, Liang D, Zheng H, Wu Y. B 1 inhomogeneity corrected CEST MRI based on direct saturation removed omega plot model at 5T. Magn Reson Med 2024; 92:532-542. [PMID: 38650080 DOI: 10.1002/mrm.30112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 02/23/2024] [Accepted: 03/25/2024] [Indexed: 04/25/2024]
Abstract
PURPOSE CEST can image macromolecules/compounds via detecting chemical exchange between labile protons and bulk water. B1 field inhomogeneity impairs CEST quantification. Conventional B1 inhomogeneity correction methods depend on interpolation algorithms, B1 choices, acquisition number or calibration curves, making reliable correction challenging. This study proposed a novel B1 inhomogeneity correction method based on a direct saturation (DS) removed omega plot model. METHODS Four healthy volunteers underwent B1 field mapping and CEST imaging under four nominal B1 levels of 0.75, 1.0, 1.5, and 2.0 μT at 5T. DS was resolved using a multi-pool Lorentzian model and removed from respective Z spectrum. Residual spectral signals were used to construct the omega plot as a linear function of 1/B 1 2 $$ {B}_1^2 $$ , from which corrected signals at nominal B1 levels were calculated. Routine asymmetry analysis was conducted to quantify amide proton transfer (APT) effect. Its distribution across white matter was compared before and after B1 inhomogeneity correction and also with the conventional interpolation approach. RESULTS B1 inhomogeneity yielded conspicuous artifact on APT images. Such artifact was mitigated by the proposed method. Homogeneous APT maps were shown with SD consistently smaller than that before B1 inhomogeneity correction and the interpolation method. Moreover, B1 inhomogeneity correction from two and four CEST acquisitions yielded similar results, superior over the interpolation method that derived inconsistent APT contrasts among different B1 choices. CONCLUSION The proposed method enables reliable B1 inhomogeneity correction from at least two CEST acquisitions, providing an effective way to improve quantitative CEST MRI.
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Affiliation(s)
- Qiting Wu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Pengcheng Gong
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
- Department of Biomedical Engineering, Chongqing University of Technology, Chongqing, China
| | - Shengping Liu
- Department of Biomedical Engineering, Chongqing University of Technology, Chongqing, China
| | - Ye Li
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Dong Liang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Hairong Zheng
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Yin Wu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
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Schmitz-Abecassis B, Najac C, Plugge J, van Osch MJP, Ercan E. Investigation of metabolite correlates of CEST in the human brain at 7 T. NMR IN BIOMEDICINE 2024; 37:e5104. [PMID: 38258649 DOI: 10.1002/nbm.5104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Revised: 12/05/2023] [Accepted: 12/23/2023] [Indexed: 01/24/2024]
Abstract
Metabolite-weighted chemical exchange saturation transfer MRI can be used to indirectly image metabolites such as creatine and glutamate. This study aims to further explore the contrast of CEST at 2 ppm in the human brain at 7T and investigate the metabolite correlates of CEST at 2 ppm via correlations with magnetic resonance spectroscopy (MRS). Simulations were performed to establish the optimal acquisition parameters, such as total saturation time (tsat) and B1 root mean squared (B1rms) for CEST at 2 ppm in the human brain. Parameters were validated via in vitro phantom studies at 7T using concentrations, pH and temperature comparable to what is found in the human brain. Finally, 10 healthy volunteers were scanned at 7T for comparison with MRS. Our results show that the optimal parameters to acquire CEST at 2 ppm images are: B1rms = 2.14 μT & tsat = 1500 ms, respectively. Comparison with MRS showed no significant correlation between CEST at 2 ppm and total Creatine measured by MRS (R = 0.19; p-value = 0.273). However, a significant correlation was found between CEST at 2 ppm and Glu (R = 0.39; p-value = 0.033), indicating the broad Glutamate-weighted CEST as the main measurable contributor to CEST at 2 ppm. We identified and confirmed optimal CEST at 2 ppm sequence parameters and validated CEST at 2 ppm measurements in a controlled in vitro environment. Our findings suggest that glutamate is a substantial contributor to the CEST at 2 ppm contrast observed in the human brain, whereas the creatine contribution to CEST at 2 ppm in the brain did not show a measurable contribution.
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Affiliation(s)
- Bárbara Schmitz-Abecassis
- C.J. Gorter MRI Center, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
- Medical Delta, Delft, The Netherlands
| | - Chloé Najac
- C.J. Gorter MRI Center, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Jaimy Plugge
- C.J. Gorter MRI Center, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
- Leiden Institute of Physics, Leiden University, Leiden, The Netherlands
| | - Matthias J P van Osch
- C.J. Gorter MRI Center, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
- Medical Delta, Delft, The Netherlands
| | - Ece Ercan
- C.J. Gorter MRI Center, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
- MR R&D, Clinical Science, Philips, Best, The Netherlands
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Fabian MS, Rajput JR, Schüre JR, Weinmüller S, Mennecke A, Möhle TA, Rampp S, Schmidt M, Dörfler A, Zaiss M. Comprehensive 7 T CEST: A clinical MRI protocol covering multiple exchange rate regimes. NMR IN BIOMEDICINE 2024; 37:e5096. [PMID: 38343093 DOI: 10.1002/nbm.5096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 11/27/2023] [Accepted: 12/05/2023] [Indexed: 04/04/2024]
Abstract
Chemical exchange saturation transfer (CEST) is a magnetic resonance (MR) imaging method providing molecular image contrasts based on indirect detection of low concentrated solutes. Previous CEST studies focused predominantly on the imaging of single CEST exchange regimes (e.g., slow, intermediate or fast exchanging groups). In this work, we aim to establish a so-called comprehensive CEST protocol for 7 T, covering the different exchange regimes by three saturation B1 amplitude regimes: low, intermediate and high. We used the results of previous publications and our own simulations in pulseq-CEST to produce a 7 T CEST protocol that has sensitivity to these three B1 regimes. With postprocessing optimization (simultaneous mapping of water shift and B1, B0-fitting, multiple interleaved mode saturation B1 correction, neural network employment (deepCEST) and analytical input feature reduction), we are able to shorten our initially 40 min protocol to 15 min and generate six CEST contrast maps simultaneously. With this protocol, we measured four healthy subjects and one patient with a brain tumor. We established a comprehensive CEST protocol for clinical 7 T MRI, covering three different B1 amplitude regimes. We were able to reduce the acquisition time significantly by more than 50%, while still maintaining decent image quality and contrast in healthy subjects and one patient with a tumor. Our protocol paves the way to perform comprehensive CEST studies in clinical scan times for hypothesis generation regarding molecular properties of certain pathologies, for example, ischemic stroke or high-grade brain tumours.
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Affiliation(s)
- Moritz Simon Fabian
- Institute of Neuroradiology, University Hospital Erlangen, Friedrich Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Junaid Rasool Rajput
- Institute of Neuroradiology, University Hospital Erlangen, Friedrich Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Jan-Rüdiger Schüre
- Institute of Neuroradiology, University Hospital Erlangen, Friedrich Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Simon Weinmüller
- Institute of Neuroradiology, University Hospital Erlangen, Friedrich Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Angelika Mennecke
- Institute of Neuroradiology, University Hospital Erlangen, Friedrich Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Tim Alexius Möhle
- Institute of Neuroradiology, University Hospital Erlangen, Friedrich Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Stefan Rampp
- Institute of Neuroradiology, University Hospital Erlangen, Friedrich Alexander University Erlangen-Nürnberg, Erlangen, Germany
- Department of Neurosurgery, University Hospital Erlangen, Friedrich Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Manuel Schmidt
- Institute of Neuroradiology, University Hospital Erlangen, Friedrich Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Arnd Dörfler
- Institute of Neuroradiology, University Hospital Erlangen, Friedrich Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Moritz Zaiss
- Institute of Neuroradiology, University Hospital Erlangen, Friedrich Alexander University Erlangen-Nürnberg, Erlangen, Germany
- High-field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
- Department Artificial Intelligence in Biomedical Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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Lucas A, Mouchtaris S, Tranquille A, Sinha N, Gallagher R, Mojena M, Stein JM, Das S, Davis KA. Mapping hippocampal and thalamic atrophy in epilepsy: A 7-T magnetic resonance imaging study. Epilepsia 2024; 65:1092-1106. [PMID: 38345348 DOI: 10.1111/epi.17908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 01/22/2024] [Accepted: 01/22/2024] [Indexed: 04/16/2024]
Abstract
OBJECTIVE Epilepsy patients are often grouped together by clinical variables. Quantitative neuroimaging metrics can provide a data-driven alternative for grouping of patients. In this work, we leverage ultra-high-field 7-T structural magnetic resonance imaging (MRI) to characterize volumetric atrophy patterns across hippocampal subfields and thalamic nuclei in drug-resistant focal epilepsy. METHODS Forty-two drug-resistant epilepsy patients and 13 controls with 7-T structural neuroimaging were included in this study. We measured hippocampal subfield and thalamic nuclei volumetry, and applied an unsupervised machine learning algorithm, Latent Dirichlet Allocation (LDA), to estimate atrophy patterns across the hippocampal subfields and thalamic nuclei of patients. We studied the association between predefined clinical groups and the estimated atrophy patterns. Additionally, we used hierarchical clustering on the LDA factors to group patients in a data-driven approach. RESULTS In patients with mesial temporal sclerosis (MTS), we found a significant decrease in volume across all ipsilateral hippocampal subfields (false discovery rate-corrected p [pFDR] < .01) as well as in some ipsilateral (pFDR < .05) and contralateral (pFDR < .01) thalamic nuclei. In left temporal lobe epilepsy (L-TLE) we saw ipsilateral hippocampal and some bilateral thalamic atrophy (pFDR < .05), whereas in right temporal lobe epilepsy (R-TLE) extensive bilateral hippocampal and thalamic atrophy was observed (pFDR < .05). Atrophy factors demonstrated that our MTS cohort had two atrophy phenotypes: one that affected the ipsilateral hippocampus and one that affected the ipsilateral hippocampus and bilateral anterior thalamus. Atrophy factors demonstrated posterior thalamic atrophy in R-TLE, whereas an anterior thalamic atrophy pattern was more common in L-TLE. Finally, hierarchical clustering of atrophy patterns recapitulated clusters with homogeneous clinical properties. SIGNIFICANCE Leveraging 7-T MRI, we demonstrate widespread hippocampal and thalamic atrophy in epilepsy. Through unsupervised machine learning, we demonstrate patterns of volumetric atrophy that vary depending on disease subtype. Incorporating these atrophy patterns into clinical practice could help better stratify patients to surgical treatments and specific device implantation strategies.
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Affiliation(s)
- Alfredo Lucas
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Sofia Mouchtaris
- Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Ashley Tranquille
- Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Nishant Sinha
- Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Ryan Gallagher
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Marissa Mojena
- Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Joel M Stein
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Sandhitsu Das
- Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Kathryn A Davis
- Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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Wu Q, Qi Y, Gong P, Huang B, Cheng G, Liang D, Zheng H, Sun PZ, Wu Y. Fast and robust pulsed chemical exchange saturation transfer (CEST) MRI using a quasi-steady-state (QUASS) algorithm at 3 T. Magn Reson Imaging 2024; 105:29-36. [PMID: 37898416 DOI: 10.1016/j.mri.2023.10.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 10/21/2023] [Accepted: 10/22/2023] [Indexed: 10/30/2023]
Abstract
Chemical exchange saturation transfer (CEST) has emerged as a powerful technique to image dilute labile protons. However, its measurement depends on the RF saturation duration (Tsat) and relaxation delay (Trec). Although the recently developed quasi-steady-state (QUASS) solution can reconstruct equilibrium CEST effects under continuous-wave RF saturation, it does not apply to pulsed-CEST MRI on clinical scanners with restricted hardware or specific absorption rate limits. This study proposed a QUASS algorithm for pulsed-CEST MRI and evaluated its performance in muscle CEST measurement. An approximated expression of a steady-state pulsed-CEST signal was incorporated in the off-resonance spin-lock model, from which the QUASS pulsed-CEST effect was derived. Numerical simulation, creatine phantom, and healthy volunteer scans were conducted at 3 T. The CEST effect was quantified with asymmetry analysis in the simulation and phantom experiments. CEST effects of creatine, amide proton transfer, phosphocreatine, and combined magnetization transfer and nuclear Overhauser effects were isolated from a multi-pool Lorentzian model in muscles. Apparent and QUASS CEST measurements were compared under different Tsat/Trec and duty cycles. Paired Student's t-test was employed with P < 0.05 as statistically significant. The simulation, phantom, and human studies showed the strong impact of Tsat/Trec on apparent CEST measurements, which were significantly smaller than the corresponding QUASS CEST measures, especially under short Tsat/Trec times. In comparison, the QUASS algorithm mitigates such impact and enables accurate CEST measurements under short Tsat/Trec times. In conclusion, the QUASS algorithm can accelerate robust pulsed-CEST MRI, promising the efficient detection and evaluation of muscle diseases in clinical settings.
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Affiliation(s)
- Qiting Wu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China; Medical AI Lab, School of Biomedical Engineering, Medical School, Shenzhen University, Shenzhen, Guangdong, China
| | - Yulong Qi
- Department of Medical Imaging, Peking University Shenzhen Hospital, Shenzhen, Guangdong, China
| | - Pengcheng Gong
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Bingsheng Huang
- Medical AI Lab, School of Biomedical Engineering, Medical School, Shenzhen University, Shenzhen, Guangdong, China
| | - Guanxun Cheng
- Department of Medical Imaging, Peking University Shenzhen Hospital, Shenzhen, Guangdong, China
| | - Dong Liang
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Hairong Zheng
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Phillip Zhe Sun
- Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, USA
| | - Yin Wu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China.
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Li Y, Liu P, Lin Q, Zhou D, An D. Postoperative seizure and memory outcome of temporal lobe epilepsy with hippocampal sclerosis: A systematic review. Epilepsia 2023; 64:2845-2860. [PMID: 37611927 DOI: 10.1111/epi.17757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Revised: 08/21/2023] [Accepted: 08/21/2023] [Indexed: 08/25/2023]
Abstract
We conducted a systematic review and meta-analysis to evaluate postoperative seizure and memory outcomes of temporal lobe epilepsy with different hippocampal sclerosis (HS) subtypes classified by International League Against Epilepsy (ILAE) Consensus Guidelines in 2013. Following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) and MOOSE (Meta-Analysis of Observational Studies in Epidemiology) guidelines, we searched PubMed, Embase, Web of Science, and Cochrane Library from January 1, 2013 to August 6, 2023. Observational studies reporting seizure and memory outcomes among different HS subtypes were included. We used the Newcastle-Ottawa scale to assess the risk of bias and the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach to grade the quality of evidence. Seizure freedom and improved outcome (Engel 1 or ILAE class 1-2) ≥1 year after surgery were defined as the primary and secondary seizure outcome. A random-effects meta-analysis by DerSimonian and Laird method was performed to obtain pooled risk ratio (RRs) with 95% confidence interval (CIs). The memory impairment was narratively reviewed because of various evaluation tools. Fifteen cohort studies with 2485 patients were eligible for the meta-analysis of seizure outcome. Six cohorts with detailed information on postoperative memory outcome were included. The pooled RRs of seizure freedom, with moderate to substantial heterogeneity, were .98 (95% CI = .84-1.15) between HS type 2 and type 1, 1.11 (95% CI = .82-1.52) between type 3 and type 1, and .80 (95% CI = .62-1.03) between the no-HS and HS groups. No significant difference of improved outcome was found between different subtypes (p > .05). The quality of evidence was deemed to be low to very low according to GRADE. The long-term seizure outcome (≥5 years after surgery) and memory impairment remained controversial.
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Affiliation(s)
- Yuming Li
- Department of Neurology, West China Hospital, Sichuan University, Chengdu, China
| | - Peiwen Liu
- Department of Neurology, West China Hospital, Sichuan University, Chengdu, China
| | - Qiuxing Lin
- Department of Neurology, West China Hospital, Sichuan University, Chengdu, China
| | - Dong Zhou
- Department of Neurology, West China Hospital, Sichuan University, Chengdu, China
| | - Dongmei An
- Department of Neurology, West China Hospital, Sichuan University, Chengdu, China
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Nemati SS, Sadeghi L, Dehghan G, Sheibani N. Lateralization of the hippocampus: A review of molecular, functional, and physiological properties in health and disease. Behav Brain Res 2023; 454:114657. [PMID: 37683813 DOI: 10.1016/j.bbr.2023.114657] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 09/04/2023] [Accepted: 09/05/2023] [Indexed: 09/10/2023]
Abstract
The hippocampus is a part of the brain's medial temporal lobe that is located under the cortex. It belongs to the limbic system and helps to collect and transfer information from short-term to long-term memory, as well as spatial orientation in each mammalian brain hemisphere. After more than two centuries of research in brain asymmetry, the hippocampus has attracted much attention in the study of brain lateralization. The hippocampus is very important in cognitive disorders, related to seizures and dementia, such as epilepsy and Alzheimer's disease. In addition, the motivation to study the hippocampus has increased significantly due to the asymmetry in the activity of the left and right hippocampi in healthy people, and its disruption during some neurological diseases. After a general review of the hippocampal structure and its importance in related diseases, the asymmetry in the brain with a focus on the hippocampus during the growth and maturation of healthy people, as well as the differences created in patients at the molecular, functional, and physiological levels are discussed. Most previous work indicates that the hippocampus is lateralized in healthy people. Also, lateralization at different levels remarkably changes in patients, and it appears that the most complex cognitive disorder is caused by a new dominant asymmetric system.
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Affiliation(s)
- Seyed Saman Nemati
- Department of Biology, Faculty of Natural Sciences, University of Tabriz, 51666-16471 Tabriz, Iran
| | - Leila Sadeghi
- Department of Biology, Faculty of Natural Sciences, University of Tabriz, 51666-16471 Tabriz, Iran.
| | - Gholamreza Dehghan
- Department of Biology, Faculty of Natural Sciences, University of Tabriz, 51666-16471 Tabriz, Iran.
| | - Nader Sheibani
- Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA
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Yoganathan K, Malek N, Torzillo E, Paranathala M, Greene J. Neurological update: structural and functional imaging in epilepsy surgery. J Neurol 2023; 270:2798-2808. [PMID: 36792721 PMCID: PMC10130132 DOI: 10.1007/s00415-023-11619-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 02/05/2023] [Accepted: 02/08/2023] [Indexed: 02/17/2023]
Abstract
Structural and functional imaging prior to surgery in drug-resistant focal epilepsy, has an important role to play alongside electroencephalography (EEG) techniques, in planning the surgical approach and predicting post-operative outcome. This paper reviews the role of structural and functional imaging of the brain, namely computed tomography (CT), magnetic resonance imaging (MRI), functional MRI (fMRI), single photon emission computed tomography (SPECT) and positron emission tomography (PET) imaging in the preoperative work-up of people with medically refractory epilepsy. In MRI-negative patients, the precise localisation of the epileptogenic zone may be established by demonstrating hypometabolism on PET imaging or hyperperfusion on SPECT imaging in the area surrounding the seizure focus. These imaging modalities are far less invasive than intracranial EEG, which is the gold standard but requires surgical placement of electrodes or recording grids. Even when intracranial EEG is needed, PET or SPECT imaging can assist in the planning of EEG electrode placement, due to its' limited spatial sampling. Multimodal imaging techniques now allow the multidisciplinary epilepsy surgery team to identify and better characterise focal pathology, determine its' relationship to eloquent areas of the brain and the degree of interconnectedness within both physiological and pathological networks, as well as improve planning and surgical outcomes for patients. This paper will update the reader on this whole field and provide them with a practical guide, to aid them in the selection of appropriate investigations, interpretation of the findings and facilitating patient discussions in individuals with drug-resistant focal epilepsy.
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Affiliation(s)
- Katie Yoganathan
- University of Oxford and Oxford University Hospitals, Oxford, UK. .,Department of Neurology, National Hospital for Neurology and Neurosurgery, London, UK.
| | - Naveed Malek
- Department of Neurology, Queen's Hospital, Romford, UK
| | - Emma Torzillo
- Department of Neurology, National Hospital for Neurology and Neurosurgery, London, UK
| | | | - John Greene
- Department of Neurology, Institute of Neurological Sciences, Queen Elizabeth University Hospital, Glasgow, UK
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