Scott Tschuppert, Christophe Valmaggia, Margarita G. Todorova
Acute zonal occult outer retinopathy (AZOOR) is a rare outer retinal disorder that may mimic inherited retinal dystrophy. This study revises a retrospective AZOOR case series by integrating retinal oximetry as a metabolic imaging biomarker and comparing the oximetry findings with retinitis pigmentosa (RP) and healthy control data. Seven consecutive patients diagnosed with AZOOR at HOCH Health Ostschweiz in St. Gallen, Switzerland were retrospectively reviewed. Multimodal assessment included best-corrected visual acuity, fundus examination, spectral-domain optical coherence tomography (SD-OCT), fundus autofluorescence (FAF), near-infrared reflectance (NIR-R), fluorescein angiography, visual field testing, multifocal electroretinography (mfERG), full-field electroretinography (ffERG), laboratory work-up, and magnetic resonance imaging. Retinal vessel oxygen saturation data (arteriolar: A-SO 2, venular: V-SO 2 and their difference: A-V SO 2) were available in four AZOOR patients and compared with an existing institutional retinal oximetry dataset containing RP patients and healthy controls. Retinal oxygen saturation and vessel diameter were assessed using Oxymap T1 dual-wavelength retinal oximetry in a predefined peripapillary measurement area. Because of the limited AZOOR sample, all comparative analyses were exploratory. The AZOOR cohort comprised seven patients (5 female, 2 male; median age 28 years, range 20–53). Six patients presented unilaterally; one patient had congenital aniridia bilaterally but AZOOR was clinically assigned to one presenting eye. Ellipsoid-zone disruption on SD-OCT was present in all affected eyes. MfERG demonstrated macular dysfunction in six of seven patients, whereas ffERG was abnormal in five of seven patients or showed normal full-field responses. Complete retinal oximetry data were available for eight eye/image measurements from four patients. Kruskal–Wallis testing across controls, RP, and AZOOR showed significant intergroup differences for A-SO 2 (H = 10.406, df = 2, p = 0.005) and A-V SO 2 (H = 9.538, df = 2, p = 0.008), but not for V-SO 2 (H = 1.002, df = 2, p = 0.606). Exploratory pairwise Mann–Whitney U tests showed lower A-SO 2 and lower A-V SO 2 in AZOOR compared with controls and RP, whereas V-SO 2 did not differ significantly. Retinal oximetry added a metabolic dimension to multimodal AZOOR assessment. In this small exploratory cohort, AZOOR showed reduced arterial saturation and reduced arteriovenous oxygen difference compared with controls and RP, whereas venous saturation was not altered. This distinct metabolic AZOOR profile indicates reduced oxygen delivery resulting in altered oxygen use contrary to the known RP pattern of increased oxygen saturation and reduced oxygen use associated with photoreceptor degeneration. These findings should be interpreted cautiously but support further prospective evaluation of retinal oximetry as a complementary imaging biomarker in AZOOR and other outer retinal disorders.
Nawab Azizi, Zier Zhou, Alexander Ibrahim, Omar Islam
Patients in remote communities often lack access to magnetic resonance imaging (MRI), necessitating long-distance transfers to tertiary centres for neuroimaging. Portable MRI (pMRI) addresses this gap by enabling bedside imaging without conventional scanner infrastructure. Its environmental profile, including energy consumption, patient transportation, and waste generation, compared with fixed MRI systems has not been comprehensively quantified in the literature. We conducted a mixed-methods analysis of an ultra-low-field pMRI scanner, focusing on three domains: (i) energy consumption, (ii) transportation-related greenhouse gas (GHG) emissions, and (iii) waste generation. Published data on energy use and emissions from 1.5 Tesla (T) and 3 T scanners were compared with modelled estimates for pMRI. Transportation emissions were calculated for patient travel between Weeneebayko General Hospital (Moose Factory, Ontario) and Kingston Health Sciences Centre (Kingston, Ontario) using commercial, charter, and air ambulance flights. Waste-related emissions were assessed based on shielding materials, helium consumption, and gadolinium-based contrast agent use. pMRI consumed 11.8–17.4-fold less energy per scan than fixed 1.5 T and 3 T systems, corresponding to approximately 0.065 tons (t) CO₂ annually in a modelled 100–scan/year scenario. Based on published estimates, 56% of patients could avoid inter-facility transfer, which is estimated to reduce 14.3 t CO₂ emissions per year, equivalent to emissions from ~1.9 single-family homes. Waste analyses demonstrated that pMRI eliminated helium use, reduced shielding requirements, and minimized contrast-related waste, together preventing an additional ~5.4–9.8 t CO₂ per scanner over its lifecycle, which was equivalent to emissions produced by ~0.73–1.3 homes annually. This conservatively equates to a total carbon emissions reduction of 19.7–24.3 t per year or 2.6–3.1 home equivalents per year with pMRI implementation. In a remote Canadian setting, pMRI provided local neuroimaging access to a predominantly Indigenous population, with 56% of patients avoiding inter-facility transfer while maintaining diagnostic quality. These clinical benefits were accompanied by a markedly reduced carbon footprint, supporting pMRI as both a health-equity intervention and a sustainable imaging strategy for underserved, remote regions.
William Royer, James Gholam, Mara Cercignani, Derek K. Jones, Emre Kopanoglu
Diffusion MRI underpins much of modern population neuroscience, yet scanner access remains concentrated in high-income settings, excluding the genetic, developmental, and disease diversity needed for generalizable discovery. Portable low-field MRI systems (field strengths below 0.1 T) offer a cheaper, infrastructure-light alternative that could extend diffusion imaging to under-represented populations, but only if the measurements are sufficiently repeatable. Here we provide the first systematic test-retest evaluation of tract-based diffusion tensor MRI (DT-MRI) metrics at 64 mT. Ten healthy participants were scanned at two time-points (median interval 13 days) with an 18-direction (b = 900s/mm 2) diffusion protocol and a T 2 -weighted structural sequence on a portable 64 mT scanner. After correction for distortions and gradient imperfections, diffusion tensors were estimated and constrained spherical deconvolution was performed to enable bundle-specific tractography. Tract averaged fractional anisotropy, mean diffusivity, and radial diffusivity were extracted from a selection of white-matter tracts spanning projection, association, and commissural fiber categories. Bland-Altman analysis and within-subject coefficients of variation indicated strong scan-rescan agreement, while intraclass correlation coefficients were variable across tracts and metrics. Compared with high-field data, coefficients of variation were 3–10 times larger and standard deviations in the means were approximately an order of magnitude higher. Despite this, statistical power calculations yielded feasible sample-size estimates for detecting group differences in a two-tailed t -test: for a 4% difference in means, approximately 25 participants per group were sufficient for the majority of tracts in MD and RD, and around 65 for FA. Although absolute DT-MRI metric values diverge from high-field references due to partial volume effects and noise-floor bias, continued advances in acquisition, reconstruction, and processing are expected to further narrow this gap. The results demonstrate that portable 64 mT MRI can deliver repeatable DT-MRI metrics, establishing a foundation for democratizing advanced neuroimaging and enabling population-scale studies in regions that have historically been excluded from brain research.
Omar Rutledge, Richard B. Goyette, Kimberly L. Wang, Madelynn S. Park, John D. E. Gabrieli
Cannabidiol (CBD) is a non-intoxicating phytocannabinoid primarily derived from hemp (cannabis sativa L.) that has been investigated for its potential anxiolytic effects. Prior functional neuroimaging studies suggest that CBD may affect brain regions associated with stress and anxiety. However, it remains unclear if there is a consistent pattern of modulation within these regions and if there is a correlation with behavioral or physiological measures. We conducted a systematic review examining adult human neuroimaging investigations comparing CBD with placebo under conditions related to stress or anxiety. We searched PubMed, Web of Science, EBSCO, and ProQuest for studies published before June 30, 2025. The quality of the evidence was assessed with the revised Cochrane Risk of Bias Tool for Randomized Trials (RoB 2), findings were summarized using a Synthesis Without Meta-analysis (SWiM) approach, and certainty of evidence was rated using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) framework. A total of 12 studies with 146 participants in 7 cohorts met the eligibility criteria and were included in the synthesis. Results indicated a wide distribution of reported peaks across many cortical and subcortical regions with mixed directions of activation or perfusion, demonstrating substantial heterogeneity in the reported findings. Risk of bias assessments generally indicated either some concerns or high risk of bias, and the certainty of evidence was judged to be low to very low. Overall, there is a lack of consistent evidence showing the acute effects of CBD on the brain across various study designs. The current literature on the putative anxiolytic effects of CBD is constrained by methodological variability and limited statistical power. Future studies should employ standardized paradigms, improve reporting practices, and include more diverse and adequately powered samples to clarify the neural correlates of CBD-related effects on stress and anxiety. PROSPERO, CRD420251063369.
Dana Kanel, Fiona Young, Kiran K. Seunarine, Chris A. Clark, Kristian Aquilina, Jonathan D. Clayden
Accurate delineation of white matter tracts is critical in the pre-operative assessment of paediatric brain tumour patients, where preservation of eloquent pathways directly influences surgical planning and functional outcomes. Tractfinder is a recently introduced automated method for white matter tract segmentation in tumour patients, but its voxel-based (mask) outputs limit compatibility with streamline-based tractography tools, visualisation workflows, and downstream analytical frameworks. Here we introduce Tractfinder-constrained Tractography (TcT), a streamline-based extension that constrains probabilistic tractography to the probability maps produced by Tractfinder, generating streamline representations while preserving the speed and automation that make Tractfinder clinically appealing. We evaluated TcT in ten pre-operative paediatric patients with supratentorial tumours, targeting three clinically relevant tracts – the corticospinal tract, arcuate fasciculus, and optic radiation. Spatial agreement between TcT and conventional tractography was assessed using Bundle Adjacency (BA). Mean BA scores across all three tracts ranged from 2.1 to 2.6 mm, comparing favourably against published inter-protocol benchmarks for conventional probabilistic tractography (4.3 mm), and approaching within-protocol variability. The TcT pipeline was fully automated, required no manual region-of-interest placement, and completed in approximately 5–15 min per subject compared to 1–2 h for conventional tractography. These results demonstrate that TcT produces streamline-based tract segmentations with good spatial agreement to conventional tractography, while offering substantially reduced processing time and operator burden.
