Dynamic Contrast-Enhanced Magnetic Resonance Imaging Suggests Normal Perfusion in Normal-Appearing White Matter in Multiple Sclerosis

Dynamic contrast-enhanced MRI shows altered blood-brain barrier function of deep gray matter structures in neuroborreliosis: a case-control study

BACKGROUND

Main aim was assessment of regional blood-brain barrier (BBB) function by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in patients with neuroborreliosis. Secondary aim was to study the correlation of BBB function with biochemical, clinical, and cognitive parameters.

METHODS

Regional ethical committee approved this prospective single-center case-control study. Within 1 month after diagnosis of neuroborreliosis, 55 patients underwent DCE-MRI. The patient group consisted of 25 males and 30 females with mean age 58 years, and the controls were 8 males and 7 females with mean age 57 years. Pharmacokinetic compartment modelling with Patlak fit was applied, providing estimates for capillary leakage rate and blood volume fraction. Nine anatomical brain regions were sampled with auto-generated binary masks. Fatigue, severity of clinical symptoms and findings, and cognitive function were assessed in the acute phase and 6 months after treatment.

RESULTS

Leakage rates and blood volume fractions were lower in patients compared to controls in the thalamus (p = 0.027 and p = 0.018, respectively), caudate nucleus (p = 0.009 for both), and hippocampus (p = 0.054 and p = 0.009). No correlation of leakage rates with fatigue, clinical disease severity or cognitive function was found.

CONCLUSIONS

In neuroborreliosis, leakage rate and blood volume fraction in the thalamus, caudate nucleus, and hippocampus were lower in patients compared to controls. DCE-MRI provided new insight to pathophysiology of neuroborreliosis, and can serve as biomarker of BBB function and regulatory mechanisms of the neurovascular unit in infection and inflammation.

RELEVANCE STATEMENT

DCE-MRI provided new insight to pathophysiology of neuroborreliosis, and can serve as biomarker of blood-brain barrier function and regulatory mechanisms of the neurovascular unit in infection and inflammation.

KEY POINTS

• Neuroborreliosis is an infection with disturbed BBB function. • Microvessel leakage can be studied with DCE-MRI. • Prospective case-control study showed altered microvessel properties in thalamus, caudate, and hippocampus.

Reproducibility and Optimal Arterial Input Function Selection in Dynamic Contrast-Enhanced Perfusion MRI in the Healthy Brain

BACKGROUND

Dynamic contrast-enhanced MRI (DCE-MRI) has seen increasing use for quantification of low level of blood-brain barrier (BBB) leakage in various pathological disease states and correlations with clinical outcomes. However, currently there exists limited studies on reproducibility in healthy controls, which is important for the establishment of a normality threshold for future research.

PURPOSE

To investigate the reproducibility of DCE-MRI and to evaluate the effect of arterial input function (AIF) selection and manual region of interests (ROI) delineation vs. automated global segmentation.

STUDY TYPE

Prospective.

POPULATION

A total of 16 healthy controls; 11 females; mean age 28.7 years (SD 10.1).

FIELD STRENGTH/SEQUENCE

A 3T; GE DCE; 3D TFE T1WI. 2D TSE T2.

ASSESSMENT

The influx constant K_i , a measure of BBB permeability, and V_p , the blood plasma volume, was calculated using the Patlak model. Cerebral blood flow (CBF) was calculated using Tikhonov model free deconvolution. Manual tissue ROIs, drawn by H.J.S. (30+ years of experience), were compared to automatic tissue segmentation.

STATISTICAL TESTS

Intraclass correlation coefficient (ICC) and repeatability coefficient (RC) was used to assess reproducibility. Bland-Altman plots were used to evaluate agreement between measurements day 1 vs. day 2, and manual vs. segmentation method.

RESULTS

K_i showed excellent reproducibility in both white and gray matter with an ICC between 0.79 and 0.82 and excellent agreement between manual ROI and automatic segmentation, with an ICC of 0.89 for K_i in WM. Furthermore, K_i values in gray and white matter conforms with histological tissue characteristics, where gray matter generally has a 2-fold higher vessel density. The highest reproducibility measures of K_i (ICC = 0.83), CBF (ICC = 0.77) and V_d (ICC = 0.83) was obtained with the AIF sampled in the internal carotid artery (ICA).

DATA CONCLUSION

DCE-MRI shows excellent reproducibility of pharmacokinetic variables derived from healthy controls.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 2.

Dynamic contrast-enhanced (DCE) imaging: state of the art and applications in whole-body imaging

Dynamic contrast-enhanced (DCE) imaging is a non-invasive technique used for the evaluation of tissue vascularity features through imaging series acquisition after contrast medium administration. Over the years, the study technique and protocols have evolved, seeing a growing application of this method across different imaging modalities for the study of almost all body districts. The main and most consolidated current applications concern MRI imaging for the study of tumors, but an increasing number of studies are evaluating the use of this technique also for inflammatory pathologies and functional studies. Furthermore, the recent advent of artificial intelligence techniques is opening up a vast scenario for the analysis of quantitative information deriving from DCE. The purpose of this article is to provide a comprehensive update on the techniques, protocols, and clinical applications - both established and emerging - of DCE in whole-body imaging.

Extended perfusion protocol for MS lesion quantification

This study aims to examine a time-extended dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) protocol and report a comparative study with three different pharmacokinetic (PK) models, for accurate determination of subtle blood-brain barrier (BBB) disruption in patients with multiple sclerosis (MS). This time-extended DCE-MRI perfusion protocol, called Snaps, was applied on 24 active demyelinating lesions of 12 MS patients. Statistical analysis was performed for both protocols through three different PK models. The Snaps protocol achieved triple the window time of perfusion observation by extending the magnetic resonance acquisition time by less than 2 min on average for all patients. In addition, the statistical analysis in terms of adj-R ² goodness of fit demonstrated that the Snaps protocol outperformed the conventional DCE-MRI protocol by detecting 49% more pixels on average. The exclusive pixels identified from the Snaps protocol lie in the low k ^trans range, potentially reflecting areas with subtle BBB disruption. Finally, the extended Tofts model was found to have the highest fitting accuracy for both analyzed protocols. The previously proposed time-extended DCE protocol, called Snaps, provides additional temporal perfusion information at the expense of a minimal extension of the conventional DCE acquisition time.

Assessment of the Characteristics of Different Kinds of MS Lesions Using Multi-Parametric MRI

Background: Studying different pathological aspects of lesions in multiple sclerosis (MS) patients could be useful to modify the diagnosis and treatment of this neurological disorder. Magnetic resonance imaging (MRI) modalities have the potential to investigate variations in brain tissue because of inflammatory and neurodegenerative processes in various types of MS-related lesions. Objectives: This study was done to investigate the quantitative changes in MRI-based parameters, like perfusion and magnetization transfer ratio (MTR) of different types of brain lesions, to demonstrate the ability of MRI to detect structural and pathological differences in MS lesions. Methods: Quantitative MRI modalities were performed on 18 patients with five different kinds of lesions (T1 holes, acute and chronic white matter (WM), and acute and chronic gray matter (GM) lesions) using a 3 T MRI scanner. The following protocols were used to characterize the pathology of lesions: (I) fluid-attenuated inversion recovery (FLAIR); (II) pre- and post-contrast T1-weighted; (III) dynamic contrast-enhanced (DCE); and (IV) MTR imaging. Quantitative comparison of Ktrans, cerebral blood volume (CBV), cerebral blood flow (CBF), and MTR was done to find the best parameter to distinguish different lesions. Finally, a multivariate classifier was applied to introduce the best parameter to indicate differences in lesions. Results: Five lesions were characterized by perfusion and MTR parameters. The pathological changes were measured, including: (I) the highest value of parameters in both acute WM and GM lesions; (II) the lowest value of four parameters in both chronic WM and GM lesions; (III) MTR had the highest rank among parameters using the classifier. Conclusions: The degree of pathological alterations due to inflammatory and neurodegenerative processes in MS-related lesions was indicated through the used parameters in different kinds of lesions. Inflammation was the dominant process in acute lesions, while neurodegeneration and tissue loss were observed mostly in chronic lesions. Both inflammation and neurodegeneration were detected in T1 holes. Perfusion parameters and MTR were reasonable parameters to describe differences in brain lesions. Thus, it could be confirmed that magnetization transfer imaging (MTI) and DCE-MRI are high-sensitivity methods to detect microstructural changes in the brain and subtle changes in the blood-brain-barrier. Classification of the parameters indicated that MTR was the best biomarker than others to show variations in lesions pathology.

Cortical and Deep Gray Matter Perfusion Associations With Physical and Cognitive Performance in Multiple Sclerosis Patients

Background: Reports suggest presence of cerebral hypoperfusion in multiple sclerosis (MS). Currently there are no studies that examine if the cerebral MS perfusion is affected by presence of cardiovascular comorbidities. Objective: To investigate associations between cerebral perfusion and disease outcomes in MS patients with and without comorbid cardiovascular diseases (CVD). Materials: One hundred three MS patients (75.7% female) with average age of 54.4 years and 21.1 years of disease duration underwent 3T MRI dynamic susceptibility contrast (DSC) imaging and were tested with Expanded Disability Status Scale, Multiple Sclerosis Severity Score (MSSS), Timed 25-Foot Walk (T25FW), 9-Hole Peg Test (9HPT) and Symbol Digit Modalities Test (SDMT). Structural and perfusion-based normalized measures of cerebral blood flow (nCBF), cerebral blood volume (nCBV) and mean transit time (MTT) of global, tissue-specific and deep gray matter (DGM) areas were derived. CBV and CBF were normalized by the normal-appearing white matter counterpart. Results: In linear step-wise regression analysis, age- and sex-adjusted, MSSS (R ² = 0.186) was associated with whole brain volume (WBV) (β = -0.244, p = 0.046) and gray matter (GM) nCBF (β = -0.22, p = 0.035). T25FW (R ² = 0.278) was associated with WBV (β = -0.289, p = 0.012) and hippocampus nCBV (β = -0.225, p = 0.03). 9HPT (R ² = 0.401) was associated with WBV (β = 0.195, p = 0.049) and thalamus MTT (β = -0.198, p=0.032). After adjustment for years of education, SDMT (R ² = 0.412) was explained by T2-lesion volume (β = -0.305, p = 0.001), and GM nCBV (β = 0.236, p = 0.013). No differences in MTT, nCBF nor nCBV measures between patients with (n = 42) and without CVD (n = 61) were found. Perfusion-measures were also not able to distinguish CVD status in a logistic regression model. Conclusion: Decreased GM and deep GM perfusion is associated with poorer MS outcomes, but not with presence of CVD.

Early perfusion changes in multiple sclerosis patients as assessed by MRI using arterial spin labeling

Background

Gadolinium-perfusion magnetic resonance (MR) identifies gray matter abnormalities in early multiple sclerosis (MS), even in the absence of structural differences. These perfusion changes could be related to the cognitive disability of these patients, especially in the working memory. Arterial spin labeling (ASL) is a relatively recent perfusion technique that does not require intravenous contrast, making the technique especially attractive for clinical research.

Purpose

To verify the perfusion alterations in early MS, even in the absence of cerebral volume changes. To introduce the ASL sequence as a suitable non-invasive method in the monitoring of these patients.

Material and Methods

Nineteen healthy controls and 28 patients were included. The neuropsychological test EDSS and SDMT were evaluated. Cerebral blood flow and bolus arrival time were collected from the ASL study. Cerebral volume and cortical thickness were obtained from the volumetric T1 sequence. Spearman's correlation analyzed the correlation between EDSS and SDMT tests and perfusion data. Differences were considered significant at a level of P < 0.05.

Results

Reduction of the cerebral blood flow and an increase in the bolus arrival time were found in patients compared to controls. A negative correlation between EDSS and thalamus transit time, and between EDSS and cerebral blood flow in the frontal cortex, was found.

Conclusion

ASL perfusion might detect changes in MS patients even in absent structural volumetric changes. More longitudinal studies are needed, but perfusion parameters could be biomarkers for monitoring these patients.

Vascular aspects of multiple sclerosis: emphasis on perfusion and cardiovascular comorbidities

INTRODUCTION

Multiple sclerosis (MS) is a chronic inflammatory, demyelinating, and neurodegenerative disease of the central nervous system. Over the last two decades, more favorable MS long-term outcomes have contributed toward increase in prevalence of the aged MS population. Emergence of age-associated pathology, such as cardiovascular diseases, may interact with the MS pathophysiology and further contribute to disease progression. Areas covered: This review summarizes the cardiovascular involvement in MS pathology, its disease activity, and progression. The cardiovascular health, the presence of various cardiovascular diseases, and their effect on MS cognitive performance are further explored. In similar fashion, the emerging evidence of a higher incidence of extracranial arterial pathology and its association with brain MS pathology are discussed. Finally, the authors outline the methodologies behind specific perfusion magnetic resonance imaging (MRI) and ultrasound Doppler techniques, which allow measurement of disease-specific and age-specific vascular changes in the aging population and MS patients. Expert opinion: Cardiovascular pathology significantly contributes to worse clinical and MRI-derived disease outcomes in MS. Global and regional cerebral hypoperfusion may be associated with poorer physical and cognitive performance. Prevention, improved detection, and treatment of the cardiovascular-based pathology may improve the overall long-term health of MS patients.

Comparison of Unenhanced T1-Weighted Signal Intensities Within the Dentate Nucleus and the Globus Pallidus After Serial Applications of Gadopentetate Dimeglumine Versus Gadobutrol in a Pediatric Population

OBJECTIVE

The aim of this study was to evaluate and compare changes in T1-weighted signal intensity (SI) within the dentate nucleus (DN) and globus pallidus (GP) in a pediatric population after serial applications of the linear gadolinium-based magnetic resonance contrast medium gadopentetate dimeglumine and the more stable macrocyclic agent gadobutrol.

MATERIALS AND METHODS

Institutional review board approval was obtained. Two similar pediatric patient cohorts who underwent at least 3 serial contrast-enhanced magnetic resonance imaging (MRI) examinations with sole application of gadopentetate dimeglumine or gadobutrol were analyzed. All MRI examinations were performed on a 1.5 T system acquiring unenhanced T1-weighted spin echo sequences, which were evaluated on the baseline MRI and after the contrast medium administrations. For analysis of SI changes in the DN, the ratios of the DN to the pons (P) and to the middle cerebellar peduncle (MCP) were assessed. The GP was compared with the thalamus (TH) by dividing the SIs between GP and TH (GP-to-TH ratio).

RESULTS

Twenty-eight patients (13 boys, 15 girls; mean age, 8.4 ± 6.8 years) who received at least 3 applications of gadopentetate dimeglumine and 25 patients (13 boys, 12 girls; mean age, 9.7 ± 5.4 years) with 3 or more gadobutrol injections were included. After 3 administrations of gadopentetate dimeglumine, the T1-weighted SI ratios significantly increased: mean difference value of 0.036 ± 0.031 (DN-to-P; P < 0.001), 0.034 ± 0.032 (DN-to-MCP; P < 0.001), and 0.025 ± 0.025 (GP-to-TH; P = 0.001). In a subanalysis of 12 patients with more than 3 injections of gadopentetate dimeglumine, the mean differences of the SI ratios were slightly higher: 0.043 ± 0.032 (DN-to-P; P = 0.001), 0.041 ± 0.035 (DN-to-MCP; P = 0.002), and 0.028 ± 0.025 (GP-to-TH; P = 0.003). In contrast, gadobutrol did not show a significant influence on the SI ratios, neither after 3 nor after more than 3 applications.

CONCLUSIONS

The T1-weighted SI increase within the DN and GP after serial administrations of the linear contrast medium gadopentetate dimeglumine, but not after serial applications of the macrocyclic agent gadobutrol, found in a pediatric population, is consistent with results published for adult patients. The clinical impact of the intracranial T1-hyperintensities is currently unclear. However, in accordance with the recent decision of the Pharmacovigilance and Risk Assessment Committee of the European Medicines Agency, intravenous macrocyclic agents should be preferred and MR contrast media should be used with caution and awareness of the pediatric brain development in children and adolescents.

What Have We Learned from Perfusion MRI in Multiple Sclerosis?

Using MR imaging, perfusion can be assessed either by dynamic susceptibility contrast MR imaging or arterial spin-labeling. Alterations of cerebral perfusion have repeatedly been described in multiple sclerosis compared with healthy controls. Acute lesions exhibit relative hyperperfusion in comparison with normal-appearing white matter, a finding mostly attributed to inflammation in this stage of lesion development. In contrast, normal-appearing white and gray matter of patients with MS has been mostly found to be hypoperfused compared with controls, and correlations with cognitive impairment as well as fatigue in multiple sclerosis have been described. Mitochondrial failure, axonal degeneration, and vascular dysfunction have been hypothesized to underlie the perfusion MR imaging findings. Clinically, perfusion MR imaging could allow earlier detection of the acute focal inflammatory changes underlying relapses and new lesions, and could constitute a marker for cognitive dysfunction in MS. Nevertheless, the clinical relevance and pathogenesis of the brain perfusion changes in MS remain to be clarified.

Understanding a role for hypoxia in lesion formation and location in the deep and periventricular white matter in small vessel disease and multiple sclerosis

The deep and periventricular white matter is preferentially affected in several neurological disorders, including cerebral small vessel disease (SVD) and multiple sclerosis (MS), suggesting that common pathogenic mechanisms may be involved in this injury. Here we consider the potential pathogenic role of tissue hypoxia in lesion development, arising partly from the vascular anatomy of the affected white matter. Specifically, these regions are supplied by a sparse vasculature fed by long, narrow end arteries/arterioles that are vulnerable to oxygen desaturation if perfusion is reduced (as in SVD, MS and diabetes) or if the surrounding tissue is hypoxic (as in MS, at least). The oxygen crisis is exacerbated by a local preponderance of veins, as these can become highly desaturated 'sinks' for oxygen that deplete it from surrounding tissues. Additional haemodynamic deficiencies, including sluggish flow and impaired vasomotor reactivity and vessel compliance, further exacerbate oxygen insufficiency. The cells most vulnerable to hypoxic damage, including oligodendrocytes, die first, resulting in demyelination. Indeed, in preclinical models, demyelination is prevented if adequate oxygenation is maintained by raising inspired oxygen concentrations. In agreement with this interpretation, there is a predilection of lesions for the anterior and occipital horns of the lateral ventricles, namely regions located at arterial watersheds, or border zones, known to be especially susceptible to hypoperfusion and hypoxia. Finally, mitochondrial dysfunction due to genetic causes, as occurs in leucodystrophies or due to free radical damage, as occurs in MS, will compound any energy insufficiency resulting from hypoxia. Viewing lesion formation from the standpoint of tissue oxygenation not only reveals that lesion distribution is partly predictable, but may also inform new therapeutic strategies.

Magnetic resonance imaging perfusion is associated with disease severity and activity in multiple sclerosis

PURPOSE

The utility of perfusion-weighted imaging in multiple sclerosis (MS) is not well investigated. The purpose of this study was to compare baseline normalized perfusion measures in subgroups of newly diagnosed MS patients. We wanted to test the hypothesis that this method can differentiate between groups defined according to disease severity and disease activity at 1 year follow-up.

METHODS

Baseline magnetic resonance imaging (MRI) including a dynamic susceptibility contrast perfusion sequence was performed on a 1.5-T scanner in 66 patients newly diagnosed with relapsing-remitting MS. From the baseline MRI, cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) maps were generated. Normalized (n) perfusion values were calculated by dividing each perfusion parameter obtained in white matter lesions by the same parameter obtained in normal-appearing white matter. Neurological examination was performed at baseline and at follow-up approximately 1 year later to establish the multiple sclerosis severity score (MSSS) and evidence of disease activity (EDA).

RESULTS

Baseline normalized mean transit time (nMTT) was lower in patients with MSSS >3.79 (p = 0.016), in patients with EDA (p = 0.041), and in patients with both MSSS >3.79 and EDA (p = 0.032) at 1-year follow-up. Baseline normalized cerebral blood flow and normalized cerebral blood volume did not differ between these groups.

CONCLUSION

Lower baseline nMTT was associated with higher disease severity and with presence of disease activity 1 year later in newly diagnosed MS patients. Further longitudinal studies are needed to confirm whether baseline-normalized perfusion measures can differentiate between disease severity and disease activity subgroups over time.