Abstract
ObjectivesTo assess the feasibility of using an optimised ultra-high-field high-spatial-resolution low-distortion arterial spin labelling (ASL) MRI acquisition to measure focal haemodynamic pathology in cortical lesions (CLs) in multiple sclerosis (MS).MethodsTwelve MS patients (eight female, mean age 50 years; range 35–64 years) gave informed consent and were scanned on a 7 Tesla Philips Achieva scanner. Perfusion data were collected at multiple post-labelling delay times using a single-slice flow-sensitive alternating inversion recovery ASL protocol with a balanced steady-state free precession readout scheme. CLs were identified using a high-resolution Phase-Sensitive Inversion Recovery (PSIR) scan. Significant differences in perfusion within CLs compared to immediately surrounding normal appearing grey matter (NAGMlocal) and total cortical normal appearing grey matter (NAGMcortical) were assessed using paired t-tests.ResultsForty CLs were identified in PSIR scans that overlapped with the ASL acquisition coverage. After excluding lesions due to small size or intravascular contamination, 27 lesions were eligible for analysis. Mean perfusion was 40 ± 25 ml/100 g/min in CLs, 53 ± 12 ml/100 g/min in NAGMlocal, and 53 ± 8 ml/100 g/min in NAGMcortical. CL perfusion was significantly reduced by 23 ± 9% (mean ± SE, p = 0.013) and 26 ± 9% (p = 0.006) relative to NAGMlocal and NAGMcortical perfusion, respectively.ConclusionThis is the first ASL MRI study quantifying CL perfusion in MS at 7 Tesla, demonstrating that an optimised ASL acquisition is sensitive to focal haemodynamic pathology previously observed using dynamic susceptibility contrast MRI. ASL requires no exogenous contrast agent, making it a more appropriate tool to monitor longitudinal perfusion changes in MS, providing a new window to study lesion development.Key Points• Perfusion can be quantified within cortical lesions in multiple sclerosis using an optimised high spatial resolution arterial spin Labelling MRI acquisition at ultra-high-field.• The majority of cortical lesions assessed using arterial spin labelling are hypo-perfused compared to normal appearing grey matter, in agreement with dynamic susceptibility contrast MRI literature.• Arterial spin labelling MRI, which does not involve the injection of a contrast agent, is a safe and appropriate technique for repeat scanning of an individual patient.
Highlights
Cortical lesions (CLs) in patients with multiple sclerosis (MS) are associated with physical disability [1] and cognitive impairment [2]; little is known about the formation and development of cortical lesions (CLs) due to their typically small size [3] and the insufficient sensitivity and spatial resolution offered by conventional imaging modalities
Arterial spin labelling magnetic resonance imaging (MRI), which does not involve the injection of a contrast agent, is a safe and appropriate technique for repeat scanning of an individual patient
Cortical lesions (CLs) in patients with multiple sclerosis (MS) are associated with physical disability [1] and cognitive impairment [2]; little is known about the formation and development of CLs due to their typically small size [3] and the insufficient sensitivity and spatial resolution offered by conventional imaging modalities
Summary
Cortical lesions (CLs) in patients with multiple sclerosis (MS) are associated with physical disability [1] and cognitive impairment [2]; little is known about the formation and development of CLs due to their typically small size [3] and the insufficient sensitivity and spatial resolution offered by conventional imaging modalities. Techniques including phase-sensitive inversion recovery (PSIR) [6] and double inversion recovery (DIR) [7] can identify CLs and track their structural development. The haemodynamic changes within CLs have been characterised using dynamic susceptibility contrast (DSC) MRI, revealing that local haemodynamics change with the status of the lesion: chronic CLs in grey matter exhibit reduced perfusion and cerebral blood volume [8,9,10], whereas in acute lesions elevated cerebral blood volume has been reported [8]. Reports of changes in perfusion prior to lesion formation and contrast enhancement [11] suggest that studies of local haemodynamics may predict such tissue damage, identifying a critical window for intervention
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