Post-Acquisition Processing Confounds in Brain Volumetric Quantification of White Matter Hyperintensities

BACKGROUND: Disparate research sites using identical or near-identical magnetic resonance imaging (MRI) acquisition techniques often produce results that demonstrate significant variability regarding volumetric quantification of white matter hyperintensities (WMH) in the aging population. The sources of such variability have not previously been fully explored. NEW METHOD: 3D FLAIR sequences from a group of randomly selected aged subjects were analyzed to identify sources-of-variability in post-acquisition processing that can be problematic when comparing WMH volumetric data across disparate sites. The methods developed focused on standardizing post-acquisition protocol processing methods to develop a protocol with less than 0.5% inter-rater variance. RESULTS: A series of experiments using standard MRI acquisition sequences explored post-acquisition sources-of-variability in the quantification of WMH volumetric data. Sources-of-variability included: the choice of image center, software suite and version, thresholding selection, and manual editing procedures (when used). Controlling for the identified sources-of-variability led to a protocol with less than 0.5% variability between independent raters in post-acquisition WMH volumetric quantification. COMPARISON WITH EXISTING METHOD(S): Post-acquisition processing techniques can introduce an average variance approaching 15% in WMH volume quantification despite identical scan acquisitions. Understanding and controlling for such sources-of-variability can reduce post-acquisition quantitative image processing variance to less than 0.5%. DISCUSSION: Considerations of potential sources-of-variability in MRI volume quantification techniques and reduction in such variability is imperative to allow for reliable cross-site and cross-study comparisons

Supplementary Material for: Microalbuminuria and the Combination of MRI Markers of Cerebral Small Vessel Disease

<b><i>Background:</i></b> Kidney function has been related to the presence of individual markers of cerebral small vessel disease (CSVD), as lacunes, white matter hyperintensities (WMH) or microbleeds. We aimed at studying the relationship of kidney dysfunction with the combination of several markers of CSVD. <b><i>Methods:</i></b> Subjects are those included in the ISSYS cohort (Investigating Silent Strokes in hypertensives: a magnetic resonance imaging study). A scale ranging from 0 to 4 points was applied based on the presence (one point each) of lacunes, deep microbleeds, moderate to extensive basal ganglia enlarged perivascular spaces (EPVS), and periventricular or deep WMH. We determined the creatinine-based glomerular filtration rate and the urinary albumin-to-creatinine ratio (UACR) as markers of kidney function and studied their association with the scale of CSVD in univariate and ordinal logistic regression analyses. <b><i>Results:</i></b> Among the 975 patients included, 28.2% presented one or more CSVD markers, being the most prevalent marker (either alone or in combination) basal ganglia EPVS. The UACR was elevated at increasing the scores of the CSVD scale and remained as independent predictor of the combination of markers (common OR per natural log unit increase in UACR: 1.23, 1.07-1.41) after controlling per age, gender, cardiovascular risk, antihypertensive treatment and hypertension duration. In contrast, no associations were found between the CSVD scores and the creatinine-based estimated glomerular filtration rate. <b><i>Conclusions:</i></b> A significant proportion of stroke-free hypertensives present at least one imaging marker of CSVD. UACR but not creatinine-based glomerular filtration rate is associated with the combination of markers of CSVD

Biochemical markers in vascular cognitive impairment associated with subcortical small vessel disease - A consensus report.

BACKGROUND: Vascular cognitive impairment (VCI) is a heterogeneous entity with multiple aetiologies, all linked to underlying vascular disease. Among these, VCI related to subcortical small vessel disease (SSVD) is emerging as a major homogeneous subtype. Its progressive course raises the need for biomarker identification and/or development for adequate therapeutic interventions to be tested. In order to shed light in the current status on biochemical markers for VCI-SSVD, experts in field reviewed the recent evidence and literature data. METHOD: The group conducted a comprehensive search on Medline, PubMed and Embase databases for studies published until 15.01.2017. The proposal on current status of biochemical markers in VCI-SSVD was reviewed by all co-authors and the draft was repeatedly circulated and discussed before it was finalized. RESULTS: This review identifies a large number of biochemical markers derived from CSF and blood. There is a considerable overlap of VCI-SSVD clinical symptoms with those of Alzheimer's disease (AD). Although most of the published studies are small and their findings remain to be replicated in larger cohorts, several biomarkers have shown promise in separating VCI-SSVD from AD. These promising biomarkers are closely linked to underlying SSVD pathophysiology, namely disruption of blood-CSF and blood-brain barriers (BCB-BBB) and breakdown of white matter myelinated fibres and extracellular matrix, as well as blood and brain inflammation. The leading biomarker candidates are: elevated CSF/blood albumin ratio, which reflects BCB/BBB disruption; altered CSF matrix metalloproteinases, reflecting extracellular matrix breakdown; CSF neurofilment as a marker of axonal damage, and possibly blood inflammatory cytokines and adhesion molecules. The suggested SSVD biomarker deviations contrasts the characteristic CSF profile in AD, i.e. depletion of amyloid beta peptide and increased phosphorylated and total tau. CONCLUSIONS: Combining SSVD and AD biomarkers may provide a powerful tool to identify with greater precision appropriate patients for clinical trials of more homogeneous dementia populations. Thereby, biomarkers might promote therapeutic progress not only in VCI-SSVD, but also in AD