ADC histograms from routine DWI for longitudinal studies in cerebral small vessel disease: a field study in CADASIL

Contrast agent-free state-of-the-art magnetic resonance imaging on cerebral small vessel disease - Part 2: Diffusion tensor imaging and functional magnetic resonance imaging

Cerebral small vessel disease (cSVD) has been widely studied using conventional magnetic resonance imaging (MRI) methods, although the association between MRI findings and clinical features of cSVD is not always concordant. We assessed the additional contribution of contrast agent-free, state-of-the-art MRI techniques, particularly diffusion tensor imaging (DTI) and functional magnetic resonance imaging (fMRI), to understand brain damage and structural and functional connectivity impairment related to cSVD. We performed a review following the PICOS worksheet and Search Strategy, including 152 original papers in English, published from 2000 to 2022. For each MRI method, we extracted information about their contributions regarding the origins, pathology, markers, and clinical outcomes in cSVD. In general, DTI studies have shown that changes in mean, radial, and axial diffusivity measures are related to the presence of cSVD. In addition to the classical deficit in executive functions and processing speed, fMRI studies indicate connectivity dysfunctions in other domains, such as sensorimotor, memory, and attention. Neuroimaging metrics have been correlated with the diagnosis, prognosis, and rehabilitation of patients with cSVD. In short, the application of contrast agent-free, state-of-the-art MRI techniques has provided a complete picture of cSVD markers and tools to explore questions that have not yet been clarified about this clinical condition. Longitudinal studies are desirable to look for causal relationships between image biomarkers and clinical outcomes.

MRI whole-lesion texture analysis on ADC maps for the prognostic assessment of ischemic stroke

Background

This study aims is to explore whether it is feasible to use magnetic resonance texture analysis (MRTA) in order to distinguish favorable from unfavorable function outcomes and determine the prognostic factors associated with favorable outcomes of stroke.

Methods

The retrospective study included 103 consecutive patients who confirmed unilateral anterior circulation subacute ischemic stroke by computed tomography angiography between January 2018 and September 2019. Patients were divided into favorable outcome (modified Rankin scale, mRS ≤ 2) and unfavorable outcome (mRS > 2) groups according to mRS scores at day 90. Two radiologists manually segmented the infarction lesions based on diffusion-weighted imaging and transferred the images to corresponding apparent diffusion coefficient (ADC) maps in order to extract texture features. The prediction models including clinical characteristics and texture features were built using multiple logistic regression. A univariate analysis was conducted to assess the performance of the mean ADC value of the infarction lesion. A Delong’s test was used to compare the predictive performance of models through the receiver operating characteristic curve.

Results

The mean ADC performance was moderate [AUC = 0.60, 95% confidence interval (CI) 0.49–0.71]. The texture feature model of the ADC map (tADC), contained seven texture features, and presented good prediction performance (AUC = 0.83, 95%CI 0.75–0.91). The energy obtained after wavelet transform, and the kurtosis and skewness obtained after Laplacian of Gaussian transformation were identified as independent prognostic factors for the favorable stroke outcomes. In addition, the combination of the tADC model and clinical characteristics (hypertension, diabetes mellitus, smoking, and atrial fibrillation) exhibited a subtly better performance (AUC = 0.86, 95%CI 0.79–0.93; P > 0.05, Delong’s).

Conclusion

The models based on MRTA on ADC maps are useful to evaluate the clinical function outcomes in patients with unilateral anterior circulation ischemic stroke. Energy obtained after wavelet transform, kurtosis obtained after Laplacian of Gaussian transform, and skewness obtained after Laplacian of Gaussian transform were identified as independent prognostic factors for favorable stroke outcomes.

The Value of First-Order Features Based on the Apparent Diffusion Coefficient Map in Evaluating the Therapeutic Effect of Low-Intensity Pulsed Ultrasound for Acute Traumatic Brain Injury With a Rat Model

Purpose

In order to evaluate the neuroprotective effect of low-intensity pulsed ultrasound (LIPUS) for acute traumatic brain injury (TBI), we studied the potential of apparent diffusion coefficient (ADC) values and ADC-derived first-order features regarding this problem.

Methods

Forty-five male Sprague Dawley rats (sham group: 15, TBI group: 15, LIPUS treated: 15) were enrolled and underwent magnetic resonance imaging. Scanning layers were acquired using a multi-shot readout segmentation of long variable echo trains (RESOLVE) to decrease distortion. The ultrasound transducer was applied to the designated region in the injured cortical areas using a conical collimator and was filled with an ultrasound coupling gel. Regions of interest were manually delineated in the center of the damaged cortex on the diffusion weighted images (b = 800 s/mm²) layer by layer for the TBI and LIPUS treated groups using the open-source software ITK-SNAP. Before analysis and modeling, the features were normalized using a z-score method, and a logistic regression model with a backward filtering method was employed to perform the modeling. The entire process was completed using the R language.

Results

During the observation time, the ADC values ipsilateral to the trauma in the TBI and LIPUS groups increased rapidly up to 24 h. After statistical analysis, the 10th percentile, 90th percentile, mean, skewness, and uniformity demonstrated a significant difference among three groups. The receiver operating characteristic curve (ROC) analysis shows that the combined LR model exhibited the highest area under the curve value (AUC: 0.96).

Conclusion

The combined LR model of first-order features based on the ADC map can acquire a higher diagnostic performance than each feature only in evaluating the neuroprotective effect of LIPUS for TBI. Models based on first-order features may have potential value in predicting the therapeutic effect of LIPUS in clinical practice in the future.

Conformance of a 3T Radiotherapy MRI Scanner to the QIBA Diffusion Profile

Purpose

To assess the technical performance of the apparent diffusion coefficient (ADC) on a dedicated 3T radiotherapy scanner, using a standardized phantom and sequences. Investigations into factors that could impact the technical performance of ADC in the clinic were also completed, including changing the slice‐encoded imaging direction and the reference sample ADC value.

Methods

ADC acquisitions were performed monthly on an isotropic diffusion phantom over 1 year. Measurements of ADC %bias, coefficients of variation for short‐/long‐term repeatability and precision (CV_ST/CV_LT and CV_P), and b‐value dependency (Dep_b) were calculated. The measurements were then assessed according to the Quantitative Imaging Biomarker Alliance (QIBA) Diffusion Profile specifications.

Results

The average of all measurements over the year was within Profile recommended ranges. This included when testing was performed in different imaging directions, and on samples that had different ADC reference values (0.4–1.1 μm²/ms). Results in the axial plane for the central water vial included a bias of +0.05%, CV_ST /CV_LT/CV_P = 0.1%/ 0.9%/0.4% and Dep_b = 0.4%.

Conclusions

The technical performance of ADC on a radiotherapy dedicated MRI scanner over the course of 12 months was considered conformant to the QIBA Profile. Quantifying these metrics and factors that may affect the performance is essential in progressing the use of ADC clinically: ensuring that the observed change of ADC in a tissue is due to a physiological response and not measurement variability.

Diffuse Tract Damage Correlates With Global Cognitive Impairment in Cerebral Autosomal Dominant Arteriopathy With Subcortical Infarcts and Leukoencephalopathy: A Tract-Based Spatial Statistics Study

PURPOSE

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common familial arteriopathy characterized by recurrent lacunar stroke, migraine, and depression. The mechanism of cognitive dysfunction in CADASIL is still uncertain. The aim of this study was to use tract-based spatial statistics (TBSS) to map voxelwise the spatial distribution of brain microstructural change revealed by DTI-derived indices in patients with CADASIL to further study the underlying neuropsychopathological mechanism of CADASIL.

METHOD

Twelve patients with CADASIL and 11 age-, sex-matched healthy controls underwent magnetic resonance imaging at 3 T. Then we evaluated DTI-derived indices (fractional anisotropy [FA], mode of anisotropy [MO], mean diffusivity [MD], axial diffusivity [AD] and radial diffusivity [RD]) of brain white matter (WM) between CADASIL patients and healthy subjects through TBSS.

RESULTS

Compared with healthy controls, patients with CADASIL showed extensive decreased FA, MO and increased RD, AD, and MD throughout the entire brain (mainly the WM of the temporal poles, inferior and superior longitudinal fasciculus, inferior fronto-occipital fasciculus, corpus callosum, uncinate fasciculus, internal capsule, external capsule, corona radiata, thalamic radiation, and cingulum). Furthermore, these WM microstructural alterations were significantly correlated with cognitive scores and Scheltens scores. Decreased FA values and MO values were positively correlated with Montreal Cognitive Assessment scores in CADASIL patients. Increased AD, RD, and MD values were significantly negatively correlated with Montreal Cognitive Assessment scores.

CONCLUSIONS

Widespread WM abnormalities were clearly shown in CADASIL by using TBSS. Severity of microstructural changes correlates significantly with extension of T2 hyperintensity. Moreover, WM microstructural damage and cognitive impairment were significantly correlated. This study indicated that WM tract damage plays an important role in cognitive impairment in CADASIL.

[CADASIL syndrome: differential diagnosis with multiple sclerosis]

Two cases of clinical and MRI manifestations of genetically verified CADASIL syndrome in female patients under 40 years of age are presented. The primary misinterpretation of clinical data and the neuroimaging results within multiple sclerosis indicates a lack of awareness of radiologists and neurologists about this disease. The article reviewed the current literature on the problems of diagnosis and treatment of CADASIL. The clinical and neuroimaging pattern of the syndrome, the approaches to genetic testing and the basic principles of patient management are considered in detail.

Why Are Only Some Subcortical Ischemic Lesions on Diffusion Magnetic Resonance Imaging Associated With Stroke Symptoms in Small Vessel Disease?

Background and Purpose- In cerebral small vessel diseases, small subcortical ischemic lesions (SSIL) on diffusion imaging are responsible for stroke manifestations but can also be occasionally observed in the absence of overt neurological symptoms. We aimed to determine, in a large cohort of young patients with CADASIL (Cerebral Autosomal-Dominant Arteriopathy With Subcortical Infarcts and Leukoencephalopathy), a severe monogenic condition leading to SSIL in young patients, the characteristics of SSIL and of surrounding cerebral tissue associated with the presence of stroke symptoms. Methods- Among a cohort of 323 genetically confirmed CADASIL patients who were systematically evaluated every 18 months clinically and with magnetic resonance imaging, we studied all visible SSIL and documented ischemic stroke events with available magnetic resonance imaging data. We used mixed-effect logistic regression models to determine whether the presence of stroke symptoms was associated with age, sex, the volume of SSIL, their location with respect to preexisting white matter hyperintensities and with the load of the different magnetic resonance imaging markers of small vessel disease. Results- We identified 73 SSIL (30 with stroke symptoms and 43 without) in 55 patients. In multivariable models, stroke symptoms were more frequent in male patients (estimate=1.94; SE=0.82; P=0.03) and less frequent when SSIL appeared in contact to preexisting white matter hyperintensities (estimate=-2.12; SE=0.83; P=0.01). Within pyramidal tracts, stroke symptoms were more frequent in patients with extensive white matter hyperintensities (estimate=3.8×10^-5; SE=9.3×10^-6; P<10^-4). Conclusions- Altogether, our results suggest that when SSIL occur, the presence of stroke symptoms may depend on sex and alterations of the surrounding brain tissue rather than on the characteristics of the SSIL itself.

Using DTI to assess white matter microstructure in cerebral small vessel disease (SVD) in multicentre studies

Diffusion tensor imaging (DTI) metrics such as fractional anisotropy (FA) and mean diffusivity (MD) have been proposed as clinical trial markers of cerebral small vessel disease (SVD) due to their associations with outcomes such as cognition. However, studies investigating this have been predominantly single-centre. As clinical trials are likely to be multisite, further studies are required to determine whether associations with cognition of similar strengths can be detected in a multicentre setting. One hundred and nine patients (mean age =68 years) with symptomatic lacunar infarction and confluent white matter hyperintensities (WMH) on MRI was recruited across six sites as part of the PRESERVE DTI substudy. After handling missing data, 3T-MRI scanning was available from five sites on five scanner models (Siemens and Philips), alongside neuropsychological and quality of life (QoL) assessments. FA median and MD peak height were extracted from DTI histogram analysis. Multiple linear regressions were performed, including normalized brain volume, WMH lesion load, and n° lacunes as covariates, to investigate the association of FA and MD with cognition and QoL. DTI metrics from all white matter were significantly associated with global cognition (standardized β =0.268), mental flexibility (β =0.306), verbal fluency (β =0.376), and Montreal Cognitive Assessment (MoCA) (β =0.273). The magnitudes of these associations were comparable with those previously reported from single-centre studies found in a systematic literature review. In this multicentre study, we confirmed associations between DTI parameters and cognition, which were similar in strength to those found in previous single-centre studies. The present study supports the use of DTI metrics as biomarkers of disease progression in multicentre studies.

Diffusion magnetic resonance imaging in cerebral small vessel disease

Cerebral small vessel disease (SVD) is frequent in the elderly, and accounts for a wide spectrum of clinical and radiological manifestations. This report summarizes the most important findings obtained using diffusion MRI (DWI) in SVD. With DWI and apparent diffusion coefficient (ADC) maps, recent ischemic lesions can easily be detected after acute stroke in SVD, while even multiple simultaneous lesions may be observed. Microstructural changes are frequent in SVD, with increases in diffusivity and decreases in anisotropy being the most reliable findings observed, mainly in white matter. These tissue changes are associated with clinical severity and especially executive dysfunction. They can also precede the usual MRI markers of SVD, such as white matter hyperintensities, microbleeds and lacunes. Thus, DWI may reveal surrogate markers of SVD progression and offer a better understanding of their underlying mechanisms.

Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL) as a model of small vessel disease: update on clinical, diagnostic, and management aspects

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common and best known monogenic small vessel disease. Here, we review the clinical, neuroimaging, neuropathological, genetic, and therapeutic aspects based on the most relevant articles published between 1994 and 2016 and on the personal experience of the authors, all directly involved in CADASIL research and care. We conclude with some suggestions that may help in the clinical practice and management of these patients.

A Novel Imaging Marker for Small Vessel Disease Based on Skeletonization of White Matter Tracts and Diffusion Histograms

OBJECTIVE

To establish a fully automated, robust imaging marker for cerebral small vessel disease (SVD) and related cognitive impairment that is easy to implement, reflects disease burden, and is strongly associated with processing speed, the predominantly affected cognitive domain in SVD.

METHODS

We developed a novel magnetic resonance imaging marker based on diffusion tensor imaging, skeletonization of white matter tracts, and histogram analysis. The marker (peak width of skeletonized mean diffusivity [PSMD]) was assessed along with conventional SVD imaging markers. We first evaluated associations with processing speed in patients with genetically defined SVD (n = 113). Next, we validated our findings in independent samples of inherited SVD (n = 57), sporadic SVD (n = 444), and memory clinic patients with SVD (n = 105). The new marker was further applied to healthy controls (n = 241) and to patients with Alzheimer's disease (n = 153). We further conducted a longitudinal analysis and interscanner reproducibility study.

RESULTS

PSMD was associated with processing speed in all study samples with SVD (p-values between 2.8 × 10(-3) and 1.8 × 10(-10) ). PSMD explained most of the variance in processing speed (R(2) ranging from 8.8% to 46%) and consistently outperformed conventional imaging markers (white matter hyperintensity volume, lacune volume, and brain volume) in multiple regression analyses. Increases in PSMD were linked to vascular but not to neurodegenerative disease. In longitudinal analysis, PSMD captured SVD progression better than other imaging markers.

INTERPRETATION

PSMD is a new, fully automated, and robust imaging marker for SVD. PSMD can easily be applied to large samples and may be of great utility for both research studies and clinical use. Ann Neurol 2016;80:581-592.

Diffusion Tensor Imaging to Map Brain Microstructural Changes in CADASIL

BACKGROUND AND PURPOSE

Diffusion tensor imaging (DTI) is sensitive to brain microstructural changes. The aims of this DTI study were to map voxelwise the spatial distribution of brain microstructural changes in patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) and to investigate any correlation between DTI-derived indices and extension of T2 hyperintensity.

METHODS

Eighteen patients with CADASIL and 18 age-, sex-, and education-level-matched healthy controls underwent magnetic resonance imaging at 3 T. Differences in DTI-derived indices (mean diffusivity [MD], fractional anisotropy [FA], axial [AD] and radial [RD] diffusivities, and mode of anisotropy [MO]) of brain white matter (WM) between CADASIL patients and healthy subjects were assessed through tract-based spatial statistics. Then, DTI-derived indices were correlated with the patient's score on the extended Fazekas visual scale of the T2 hyperintensity.

RESULTS

When compared to healthy controls, CADASIL patients showed extensive symmetric areas of increased MD/RD and decreased AD/FA/MO that involved almost the entire hemispheric cerebral WM (internal and external capsule, WM of the temporal poles, superior and inferior longitudinal fasciculus, inferior frontal-occipital fasciculus, uncinate fasciculus, cingulum, forceps major and minor, corticospinal tracts, and thalamic radiations), thalami, and corpus callosum. Additional areas of increased RD were observed in pons, midbrain, cerebellar peduncles, and cerebellar WM. Only FA was negatively correlated with extended Fazekas visual score.

CONCLUSIONS

Our results indicate that brain damage in CADASIL is associated with extensive microstructural changes implying impairment of intra- and inter-hemispheric cerebral, thalamocortical, and cerebrocerebellar connections. Severity of microstructural changes correlates with extension of T2 hyperintensity.

Application of Diffusion Tensor Imaging Parameters to Detect Change in Longitudinal Studies in Cerebral Small Vessel Disease

Cerebral small vessel disease (SVD) is the major cause of vascular cognitive impairment, resulting in significant disability and reduced quality of life. Cognitive tests have been shown to be insensitive to change in longitudinal studies and, therefore, sensitive surrogate markers are needed to monitor disease progression and assess treatment effects in clinical trials. Diffusion tensor imaging (DTI) is thought to offer great potential in this regard. Sensitivity of the various parameters that can be derived from DTI is however unknown. We aimed to evaluate the differential sensitivity of DTI markers to detect SVD progression, and to estimate sample sizes required to assess therapeutic interventions aimed at halting decline based on DTI data. We investigated 99 patients with symptomatic SVD, defined as clinical lacunar syndrome with MRI confirmation of a corresponding infarct as well as confluent white matter hyperintensities over a 3 year follow-up period. We evaluated change in DTI histogram parameters using linear mixed effect models and calculated sample size estimates. Over a three-year follow-up period we observed a decline in fractional anisotropy and increase in diffusivity in white matter tissue and most parameters changed significantly. Mean diffusivity peak height was the most sensitive marker for SVD progression as it had the smallest sample size estimate. This suggests disease progression can be monitored sensitively using DTI histogram analysis and confirms DTI’s potential as surrogate marker for SVD.

Injuries of neural tracts in a patient with CADASIL: a diffusion tensor imaging study

Background

We report a patient with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), who showed injuries of the neural tracts, which was demonstrated by diffusion tensor tractography (DTT).

Case presentation

A 64-year-old male patient and seven age-matched control volunteers were recruited. Since approximately 1.5 years ago, he had felt mild weakness of the right arm and was diagnosed as CADASIL by the finding of the exon 11 mutation of the NOTCH3 gene approximately 10 months ago. T2-weighted and FLAIR brain MRI images obtained at admission showed high signal intensity lesions in the subcortical gray matter and periventricular white matter. He showed mild quadriparesis, mild dysarthria, mild cognitive impairment, and emotional problems. Diffusion tensor imaging was performed and nine neural tracts (corticospinal tract, corticobulbar tract, corticofugal tract from the supplementary motor area, corticofugal tract from the premotor cortex, thalmoprefrontal tract [TPT] to the dorsolateral prefrontal cortex, TPT to the ventrolateral prefrontal cortex, TPT to the orbitoprefrontal cortex, fornix, and cingulum) were reconstructed. Fractional anisotropy (FA), mean diffusivity (MD), and tract volume of each neural tract were measured. All neural tracts except for the left fornix showed at least one more abnormality in terms of DTT parameters (decrement of FA, increment of MD, or decrement of tract volume).

Conclusion

We demonstrated injuries of the neural tracts in a patient with CADASIL. It appears that clinical manifestations in this patient were related to injuries of the neural tracts.

Imaging characteristics of cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL)

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL) is an autosomal dominant vascular disorder. Diagnosis and follow-up in patients with CADASIL are based mainly on magnetic resonance imaging (MRI). MRI shows white matter hyperintensities (WMHs), lacunar infarcts and cerebral microbleeds (CMBs). WMHs lesions tend to be symmetrical and bilateral, distributed in the periventricular and deep white matter. The anterior temporal lobe and external capsules are predilection sites for WMHs, with higher specificity and sensitivity of anterior temporal lobe involvement compared to an external capsule involvement. Lacunar infarcts are presented by an imaging signal that has intensity of cerebrospinal fluid in all MRI sequences. They are localized within the semioval center, thalamus, basal ganglia and pons. CMBs are depicted as focal areas of signal loss on T2 images which increases in size on the T2*-weighted gradient echo planar images ("blooming effect").