Novel Imaging Acquisition Methods

Neuroinflammation is implicated in various brain pathologies and is proposed as a mechanism underlying Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS), a condition with largely unknown pathophysiology. The neuroinflammatory response is difficult to image non-invasively. However, magnetic resonance spectroscopy (MRS) offers a suitable approach to address this gap by enabling the measurement of metabolites that can serve as markers of neuroinflammation. Specifically, glutamine and glutamate (combined as Glx) are relevant due to their role in excitotoxicity and neuroinflammatory activation (Velu et al., 2024), while total N-acetylaspartate (tNAA) serves as a marker of neuronal integrity and a mitigating factor regarding inflammatory responses (Felice et al., 2024). Myo-inositol (mI), a recognized glial marker, reflects astrocytic activation and proliferation, central to the neuroinflammatory process (Harris et al., 2015). Total choline (tCho) indicates membrane turnover and is associated with neuroinflammation (Mueller et al., 2024). Additionally, lactate (Lac) may modulate immune responses, potentially affecting the hypothesised neuroinflammatory response in ME/CFS (Manosalva et al., 2022). This study investigated whether neurochemical concentrations of these metabolites are associated with a ME/CFS diagnosis. We hypothesise Glx, tCho, mI and lactate to be elevated, and tNAA to be downregulated in individuals with ME/CFS. 

Hyperspectral imaging (HSI) is vital in biomedical fields like brain imaging, distinguishing tissues via spectral differences for diagnostics and surgical tools (Fabelo, 2018; Yoon, 2022). Mass Spectrometry Imaging (MSI), a prominent HSI technique, maps thousands of chemicals but faces "3S triangle" trade-offs between spectral resolution, spatial resolution, and speed, limiting spatial resolution to 10–100 µm.
HyReS, a deep learning-based restoration and super-resolution method, overcomes these challenges. By integrating physics-informed Fourier constraints, it ensures spectral and spatial fidelity without large datasets. HyReS restores resolution beyond hardware limits, preserving data integrity and enabling precise downstream analyses, advancing HSI applications. 

Diffusion tensor image analysis along the perivascular space (DTI-ALPS) has emerged to evaluate glymphatic function in Alzheimer's disease (Taoka, 2020). However, the underlying mechanism for ALPS change remains controversial(Wright et al., 2023; Taoka et al., 2024). With the post-mortem brains DTI with autopsy-confirmed AD change, we aim to explore and correct the structural bias on the ALPS index. 

High-resolution diffusion imaging can help depict small structures and complex fiber architectures. The resolution of 2D acquisitions is limited by SNR, particularly when using diffusion encoding. Additionally, the long TR required for full brain coverage, due to the large number of slices, results in low SNR efficiency. Simultaneous multislice imaging (SMS) (Setsompop, 2012) is widely used in 2D diffusion imaging to improve acquisition efficiency. As an alternative, 3D multislab (Engström, 2013; Frost, 2014; Wu, 2016) acquisition divides FOV into multiple slabs and achieve Fourier encoding along slice direction within each slab. Simultaneous multi-slab imaging (SMSlab) (Dai, 2021; Liu, 2023; Zhang, 2023) integrates SMS and 3D multislab techniques, exciting multiple 3D slabs simultaneously to increase the spatial coverage along the slice direction without extending the TR.

SMSlab has shown significant potential for achieving optimal SNR efficiency (TR=1-2s) in high resolution DWI (Liu, 2023; Zhang, 2023). However, the acquisition of an external navigator to correct for the inter-shot phase variations accounts for approximately 30% of the total acquisition time, which may compromise SNR efficiency due to prolonged TR. Inspired by a recently proposed self-navigated 3D multislab DWI (Li, 2024), we incorporated the kz-blip sampling technique into our SMSlab framework and proposed self-navigated 3D SMSlab DWI using blipped-CAIPI in the multiband dimension. 

Optically-pumped magnetometers (OPMs) have been identified as a possible candidate for use in evaluations of patients with epilepsy. OPMs combine high spatial and temporal resolution with the ability to track brain activity even when a subject is moving, making them ideal for long-term monitoring - especially for children who have difficulty staying still. OPMs offer the advantage of being cryogen-free, potentially lowering operational costs and simplifying the setup compared to traditional MEG systems. Although several research sites have begun using wearable OPM-based MEG systems in children and adults with epilepsy (Feys et al., 2022; Hillebrand et al., 2023; Pedersen et al., 2022; Sequeiros & Hamandi, 2024; Vivekananda et al., 2020), the technology has not yet been systematically tested in larger groups. We present first results of an ongoing cross-validation study performed in 12 adult patients with drug-resistant focal epilepsy to date. To assess the OPM data quality, subjects underwent simultaneously EEG and MEG recordings on a cryogenic MEG system and an on-scalp MEG system. Interictal activity was localized from resting-state recordings and the locations were compared between the recordings with different modalities. In addition, somatosensory-evoked activity was recorded and localized. The goal of the study is to compare the data quality between OPM-based MEG and conventional cryogenic MEG, using simultaneous EEG and MEG recordings. 

Conventional, high-field (3 Tesla) magnetic resonance imaging can provide crucial insights into brain structure and function but remains limited to high-resource settings. Novel, low-field (<0.1T) imaging techniques offer a more cost-effective, accessible alternative (1). However, to harness their potential, including in low- and middle-income countries (LMIC), we first need to establish the validity of low-field data at spatial resolutions relevant to research and clinic (including at the vertex-level); and this was the aim of the present study.