Better localisation for epilepsy surgery by optimising simultaneous EEG and functional MRI recordings at 7T

对于患有局灶性癫痫的成人和儿童，手术切除导致癫痫发作的大脑区域是唯一可能的彻底治愈方法。这可以消除对药物的依赖，并显著提高生活质量。外科手术的成功依赖于通过MRI和脑电(EEG)等成像技术准确定位癫痫活动的发生器。这两种关键模式可以结合在一起；在脑电中测量的癫痫活动被用作功能磁共振时间序列预期变化的模型。这提供了一张高空间分辨率的地图，显示了与癫痫活动相关的信号变化的区域，这已被证明是一种有用的定位方法[1]。然而，EEG-fMRI受到fMRI灵敏度的限制，通常测量1-2%的信号变化。超高场7T磁共振成像提供了一种解决方案，因为fMRI信号变化显著增加到5-10%，这可以显著提高该技术的敏感度和空间特异性。然而，在7T时同时进行EEG-fMRI是一个重大的技术挑战[2]。该项目将设计和测试在7T下使用的脑电配置，以便可以在患者群体中使用。这将包括研究组织加热和脑电系统设计解决方案，以减轻这种风险。此外，将描述每种模式在数据质量方面对另一种模式的影响，并重新设计EEG系统硬件配置以优化信号质量。这也可能包括改进图像质量的潜在算法开发，包括改进当前去噪方法的人工智能方法。在优化了7T EEG-fMRI后，可以设想对其在癫痫中的作用进行初步的试点调查。调查的目的(最多150字)：该项目将设计和测试7T时使用的EEG配置，以便它可以用于患者群体。这将包括研究组织加热和脑电系统设计解决方案，以减轻这种风险。此外，将描述每种模式在数据质量方面对另一种模式的影响，并重新设计EEG系统硬件配置以优化信号质量。这也可能包括改进图像质量的潜在算法开发，包括改进当前去噪方法的人工智能方法。在优化了7T EEG-fMRI后，可以设想对其在癫痫中的应用进行初步的试点研究。目标1：确定新的7T兼容EEG系统的操作安全界限我们将与项目合作伙伴Brain Products一起测试和优化定制配置的EEG系统设计。这将包括在幻影和人体受试者身上进行体温测量和热成像测试。使用电磁场(EM)仿真软件包Sim4life使用硅内模型进行的仿真也可能涉及到初始实验测试的结果。将测试不同的电缆布线以及导线内阻抗的大小和分布。新型高场7T扫描仪的主要局限性之一是射频发射场(B1+)的高空间变异性，这是由于所需的较短波长增加了组织相互作用。通过图b中相关成像伪影的初始测试，可以在下面的图c中看到B1+场的降低。缓解这一问题的一个重要方法是发射RF线圈，该线圈从多个线圈元件提供不同的场，当最佳组合时，降低了B1场的变异性，并可用于减少与EEG帽的相互作用。因此，将对单个和并行传输的MRI线圈以及探索的限制EEG相互作用的操作模式进行此测试。1-6个月，加热风险评估和减少。4-12个月探索使用并行传输操作模式降低风险。目标2：描述和减轻7T下新的7T兼容脑电系统的伪影。&目标3：磁共振成像方案开发和数据评估

For adults and children with focal epilepsy, surgical removal of the brain region responsible for seizure generation is the only possible complete cure. This can remove dependence on medication, and dramatically improve quality of life. Surgical success relies on accurate localisation of the generators of epileptic activity via imaging techniques such as MRI and electroencephalography (EEG). These two key modalities can be combined; epileptic activity measured in EEG is used as a model of expected changes in functional MRI timeseries. This provides a high spatial resolution map showing the areas with signalchanges associated with the epileptic activity that has been shown to be a useful localisation method [1].However, EEG-fMRI is limited by fMRI sensitivity that typically measures signal changes of 1-2%. Ultra-high field 7T MRI offers a solution because fMRI signal changes are substantially increased to 5-10% and this could dramatically improve the technique's sensitivity and spatial specificity. However, simultaneous EEG-fMRI at 7T is a significant technical challenge [2]. This project will design and test EEG configurations for use at 7T so it can be used in patient populations. This will include investigating tissue heating and EEG system design solutions to mitigate this risk. Further, the impact of each modality on the other in terms of data quality will be characterised and the EEG system hardware configuration redesigned to optimise signal quality. This may also encompass potential algorithmic development to improve image quality, including AI methods to improve upon current denoising approaches. Having optimised 7T EEG-fMRI an initial pilot investigation of its utility in epilepsy is envisaged.Aim of the investigation (up to 150 words): This project will design and test EEG configurations for use at 7T so it can be used in patient populations. This will include investigating tissue heating and EEG system design solutions to mitigate this risk. Further, the impact of each modality on the other in terms of data quality will be characterised and the EEG system hardware configuration redesigned to optimise signal quality. This may also encompass potential algorithmic development to improve image quality, including AI methods to improve upon current denoising approaches. Having optimised 7T EEG-fMRI an initial pilot investigation of its utility in epilepsy isenvisaged.Objective 1: Determine safety limits for operation of new 7T compatible EEG systemWe will test and optimise custom configured EEG system designs with the project partner Brain Products. This will involve thermometry and thermal imaging testing in phantoms and human subjects. Simulation using in-silico models using the electromagnetic field (EM) simulation software package Sim4life may also be involved informed by the results of initial experimental testing. Different cable routings and the size and distribution of impedance within the wires will be tested. One of the main limitations of new high field 7T scanners is the high spatial variability in the RF transmit field (B1+) owing to the shorterwavelength required that increases tissue interactions. Reductions to the B1+ field can be seen in the figure c below from initial testing with associated imaging artefacts in figure b. One important method for mitigating this is transmit RF coils that provide different fields from multiple coil elements that, when optimally combined, reduce B1 field variability and could be used to reduce interactions with the EEG cap. This testing will therefore be performed for both single and parallel transmit MRI coils, and modes of operation that limit EEG interactions explored.Months 1-6, heating risk assessment and reduction. Months 4-12 exploration of risk reduction using parallel transmit modes of operation.Objective 2: Characterise and mitigate artefacts for new 7T compatible EEG systems at 7T. & Objective 3: MRI Protocol development and data assessme