Jonathan C. Lau

In vivo MRI signatures of hippocampal subfield pathology in intractable epilepsy

Our aim is to assess the subfield‐specific histopathological correlates of hippocampal volume and intensity changes (T1, T2) as well as diff!usion MRI markers in TLE, and investigate the efficacy of quantitative MRI measures in predicting histopathology in vivo.

Investigation of hippocampal substructures in focal temporal lobe epilepsy with and without hippocampal sclerosis at 7T

To provide a more detailed investigation of hippocampal subfields using 7T magnetic resonance imaging (MRI) for the identification of hippocampal sclerosis in temporal lobe epilepsy (TLE).

Functional Magnetic Resonance Imaging for Preoperative Planning in Brain Tumour Surgery.

BACKGROUND Functional magnetic resonance imaging (fMRI) is being increasingly used for the preoperative evaluation of patients with brain tumours. METHODS The study is a retrospective chart review investigating the use of clinical fMRI from 2002 through 2013 in the preoperative evaluation of brain tumour patients. Baseline demographic and clinical data were collected. The specific fMRI protocols used for each patient were recorded. RESULTS Sixty patients were identified over the 12-year period. The tumour types most commonly investigated were high-grade glioma (World Health Organization grade III or IV), low-grade glioma (World Health Organization grade II), and meningioma. Most common presenting symptoms were seizures (69.6%), language deficits (23.2%), and headache (19.6%). There was a predominance of left hemispheric lesions investigated with fMRI (76.8% vs 23.2% for right). The most commonly involved lobes were frontal (64.3%), temporal (33.9%), parietal (21.4%), and insular (7.1%). The most common fMRI paradigms were language (83.9%), motor (75.0%), sensory (16.1%), and memory (10.7%). The majority of patients ultimately underwent a craniotomy (75.0%), whereas smaller groups underwent stereotactic biopsy (8.9%) and nonsurgical management (16.1%). Time from request for fMRI to actual fMRI acquisition was 3.1±2.3 weeks. Time from fMRI acquisition to intervention was 4.9±5.5 weeks. CONCLUSIONS We have characterized patient demographics in a retrospective single-surgeon cohort undergoing preoperative clinical fMRI at a Canadian centre. Our experience suggests an acceptable wait time from scan request to scan completion/analysis and from scan to intervention.

Impact of Functional Magnetic Resonance Imaging on Clinical Outcomes in a Propensity-Matched Low Grade Glioma Cohort

BACKGROUND This study aims to evaluate the impact of preoperative functional magnetic resonance imaging (fMRI) on clinical outcomes in patients with low grade glioma (LGG). METHODS In a retrospective propensity-matched cohort study, we compared patients with LGG based on whether they underwent fMRI as part of preoperative assessment. Twelve patients with LGG who underwent preoperative fMRI were selected, and a contemporaneous group of 12 control patients with LGG who did not undergo fMRI were matched to the fMRI group based on age, sex, and 1p/19q status. RESULTS fMRI group subjects tended to have more aggressive surgeries (67% resection, 33% biopsy) than the control group (33% resection, 67% biopsy). There were no significant differences in outcomes between the 2 groups. Time between clinical assessment and surgery tended to be longer in the fMRI group (6.3 ± 4.2 weeks) than in the control group (2.7 ± 2.2 weeks). Extent of resection was similar between the 2 cohorts. fMRI group subjects had lower preoperative functional status and tended to have a greater postoperative functional status improvement than control group subjects. Mean survival was not significantly different (fMRI group 5-year survival: 88.9%, control group 5-year survival: 61.1%). CONCLUSIONS We evaluated the impact of preoperative fMRI in patients with LGG in this propensity-matched cohort study. This study has not demonstrated any significant difference in outcomes between the fMRI and control groups; however, there were nonsignificant trends for patients who underwent fMRI to undergo more aggressive surgical interventions and have a greater postoperative functional status improvement.

Unfolding the hippocampus: An intrinsic coordinate system for subfield segmentations and quantitative mapping

&NA; The hippocampus, like the neocortex, has a morphological structure that is complex and variable in its folding pattern, especially in the hippocampal head. The current study presents a computational method to unfold hippocampal grey matter, with a particular focus on the hippocampal head where complexity is highest due to medial curving of the structure and the variable presence of digitations. This unfolding was performed on segmentations from high‐resolution, T2‐weighted 7T MRI data from 12 healthy participants and one surgical patient with epilepsy whose resected hippocampal tissue was used for histological validation. We traced a critical image feature composed of the hippocampal sulcus and stratum radiatum lacunosum‐moleculare, (SRLM) in these images, then employed user‐guided semi‐automated techniques to detect and subsequently unfold the surrounding hippocampal grey matter. This unfolding was performed by solving Laplaces equation in three dimensions of interest (long‐axis, proximal‐distal, and laminar). The resulting ‘unfolded coordinate space’ provides an intuitive way of mapping the hippocampal subfields in 2D space (long‐axis and proximal‐distal), such that similar borders can be applied in the head, body, and tail of the hippocampus independently of variability in folding. This unfolded coordinate space was employed to map intracortical myelin and thickness in relation to subfield borders, which revealed intracortical myelin differences that closely follow the subfield borders used here. Examination of a histological resected tissue sample from a patient with epilepsy reveals that our unfolded coordinate system has biological validity, and that subfield segmentations applied in this space are able to capture features not seen in manual tracing protocols. HighlightsSRLM in hippocampal head consistently detected with 7T, T2 isotropic MRI.Hippocampal grey matter unfolded using Laplaces equation in 3D.Intracortical myelin and thickness mapped in unfolded coordinate space.Unfolded subfields capture critical structural regularities and agree with histology.

Novel Connectivity Map Normalization Procedure for Improved Quantitative Investigation of Structural Thalamic Connectivity in Temporal Lobe Epilepsy Patients: Structural Parcellation of the Thalamus

Connectivity studies targeting the thalamus have revealed patterns of atrophy and deafferentiation in temporal lobe epilepsy (TLE). The thalamus can be parcellated using probabilistic tractography to demonstrate regions of cortical connectivity; however, sensitivity to smaller or less connected regions is low.

Individual feature maps: a patient-specific analysis tool with applications in temporal lobe epilepsy

PurposeMRI-based diagnosis of temporal lobe epilepsy (TLE) can be challenging when pathology is not visually evident due to low image contrast or small lesion size. Computer-assisted analyses are able to detect lesions common in a specific patient population, but most techniques do not address clinically relevant individual pathologies resulting from the heterogeneous etiology of the disease. We propose a novel method to supplement the radiological inspection of TLE patients (

Ultra-High Field Template-Assisted Target Selection for Deep Brain Stimulation Surgery

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