Radiology - Research Publications
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ItemGlutamate weighted imaging contrast in gliomas with 7 Tesla magnetic resonance imaging(ELSEVIER SCI LTD, 2019)INTRODUCTION: Diffuse gliomas are incurable malignancies, which undergo inevitable progression and are associated with seizure in 50-90% of cases. Glutamate has the potential to be an important glioma biomarker of survival and local epileptogenicity if it can be accurately quantified noninvasively. METHODS: We applied the glutamate-weighted imaging method GluCEST (glutamate chemical exchange saturation transfer) and single voxel MRS (magnetic resonance spectroscopy) at 7 Telsa (7 T) to patients with gliomas. GluCEST contrast and MRS metabolite concentrations were quantified within the tumour region and peritumoural rim. Clinical variables of tumour aggressiveness (prior adjuvant therapy and previous radiological progression) and epilepsy (any prior seizures, seizure in last month and drug refractory epilepsy) were correlated with respective glutamate concentrations. Images were separated into post-hoc determined patterns and clinical variables were compared across patterns. RESULTS: Ten adult patients with a histo-molecular (n = 9) or radiological (n = 1) diagnosis of grade II-III diffuse glioma were recruited, 40.3 +/- 12.3 years. Increased tumour GluCEST contrast was associated with prior adjuvant therapy (p = .001), and increased peritumoural GluCEST contrast was associated with both recent seizures (p = .038) and drug refractory epilepsy (p = .029). We distinguished two unique GluCEST contrast patterns with distinct clinical and radiological features. MRS glutamate correlated with GluCEST contrast within the peritumoural voxel (R = 0.89, p = .003) and a positive trend existed in the tumour voxel (R = 0.65, p = .113). CONCLUSION: This study supports the role of glutamate in diffuse glioma biology. It further implicates elevated peritumoural glutamate in epileptogenesis and altered tumour glutamate homeostasis in glioma aggressiveness. Given the ability to non-invasively visualise and quantify glutamate, our findings raise the prospect of 7 T GluCEST selecting patients for individualised therapies directed at the glutamate pathway. Larger studies with prospective follow-up are required.
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ItemAlterations in dorsal and ventral posterior cingulate connectivity in APOE ε4 carriers at risk of Alzheimer's disease(ROYAL COLL PSYCHIATRISTS, 2015-10)
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ItemTremor in multiple sclerosis is associated with cerebello-thalamic pathology(SPRINGER WIEN, 2017-12)Tremor in people with multiple sclerosis (MS) is a frequent and debilitating symptom with a relatively poorly understood pathophysiology. To determine the relationship between clinical tremor severity and structural magnetic resonance imaging parameters. Eleven patients with clinically definite MS and right-sided upper limb tremor were studied. Tremor severity was assessed using the Bain score (overall severity, writing, and Archimedes spiral drawing). Cerebellar dysfunction was assessed using the Scale for the Assessment and Rating of Ataxia. Dystonia was assessed using the Global Dystonia Scale adapted for upper limb. For all subjects, volume was calculated for the thalamus from T1-weighted volumetric scans using Freesurfer. Superior cerebellar peduncle (SCP) cross-sectional areas were measured manually. The presence of lesions was visually determined and the lesion volumes were calculated by the lesion growth algorithm as implemented in the Lesion Segmentation Toolbox. Right thalamic volume negatively correlated with Bain tremor severity score (ρ = - 0.65, p = 0.03). Left thalamic volume negatively correlated with general Bain tremor severity score (ρ = - 0.65, p = 0.03) and the Bain writing score (ρ = - 0.65, p = 0.03). Right SCP area negatively correlated with Bain writing score (ρ = - 0.69, p = 0.02). Finally, Bain Archimedes score was significantly higher in patients with lesions in the contralateral thalamus. Whole brain lesion load showed no relationship with tremor severity. These results implicate degeneration of key structures within the cerebello-thalamic pathway as pathological substrates for tremor in MS patients.
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ItemAssessment of Optic Pathway Structure and Function in Patients With Compression of the Optic Chiasm: A Correlation With Optical Coherence Tomography(ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 2016-07)PURPOSE: The purpose of this study was to investigate correlations between retinal fiber thickness measured by optical coherence tomography (OCT) and anterograde functional and structural differences in the optic pathway of patients with compression of the optic chiasm. Our hypothesis was that loss of visual acuity caused by chronic compressive pathologies may lead to an irreversible decline in vision because of permanent neurodegeneration of the optic radiations and visual cortex. METHODS: Quantitative OCT, functional magnetic resonance imaging (MRI) and diffusion tensor MRI measurements were made in 17 patients being surgically treated for chiasmal compression. RESULTS: In our study we found that surgically irreversible visual field defects and reduced retinal nerve fiber layer thickness were significantly associated with lower fractional diffusion anisotropy and higher diffusivities in optic radiations and less functional MRI activation in the visual cortex. CONCLUSIONS: Damage to the retinal nerve fiber layer is associated with downstream structural and functional degradation of the optic pathway. This may be related to trans-synaptic degeneration and the fact that these factors are important potential imaging biomarkers for predicting visual recovery after surgical decompression.