Editor’s Choices

Mapping the Orientation of White Matter Fiber Bundles: A Comparative Study of Diffusion Tensor Imaging, Diffusional Kurtosis Imaging, and Diffusion Spectrum Imaging

Editor’s Choice

The authors evaluated fiber bundle orientations from DTI and diffusional kurtosis compared with diffusion spectrum imaging as a criterion standard to assess the performance of each technique. DTI, diffusional kurtosis imaging, and diffusion spectrum imaging datasets were acquired during 2 independent sessions in 3 volunteers. While orientation estimates from all 3 techniques had comparable angular reproducibility, diffusional kurtosis imaging decreased angular error throughout the white matter compared with DTI. Diffusion spectrum imaging and diffusional kurtosis imaging enabled the detection of crossing-fiber bundles. They conclude that fiber bundle orientation estimates from diffusional kurtosis imaging have less systematic error than those from DTI.

Abstract

BACKGROUND AND PURPOSE

White matter fiber tractography relies on fiber bundle orientation estimates from diffusion MR imaging. However, clinically feasible techniques such as DTI and diffusional kurtosis imaging use assumptions, which may introduce error into in vivo orientation estimates. In this study, fiber bundle orientations from DTI and diffusional kurtosis imaging are compared with diffusion spectrum imaging as a criterion standard to assess the performance of each technique.

MATERIALS AND METHODS

For each subject, full DTI, diffusional kurtosis imaging, and diffusion spectrum imaging datasets were acquired during 2 independent sessions, and fiber bundle orientations were estimated by using the specific theoretic assumptions of each technique. Angular variability and angular error measures were assessed by comparing the orientation estimates. Tractography generated with each of the 3 reconstructions was also examined and contrasted.

RESULTS

Orientation estimates from all 3 techniques had comparable angular reproducibility, but diffusional kurtosis imaging decreased angular error throughout the white matter compared with DTI. Diffusion spectrum imaging and diffusional kurtosis imaging enabled the detection of crossing-fiber bundles, which had pronounced effects on tractography relative to DTI. Diffusion spectrum imaging had the highest sensitivity for detecting crossing fibers; however, the diffusion spectrum imaging and diffusional

Differentiation of Speech Delay and Global Developmental Delay in Children Using DTI Tractography-Based Connectome

Editor’s Choice

This study investigated whether diffusion tensor imaging tractography-based connectome can differentiate global developmental delay from speech delay in young children. Twelve children with pure speech delay, 14 children with global developmental delay, and 10 children with typical development underwent 3T DTI. Whole-brain connectome analysis was performed by using 116 cortical ROIs. Network metrics were measured at individual regions: strength, efficiency, cluster coefficient, and betweeness. Compared with typical development, global and local efficiency were significantly reduced in both global developmental delay and speech delay. Nodal strength of the cognitive network was reduced in global developmental delay, whereas the nodal strength of the language network was reduced in speech delay. This finding resulted in a high accuracy of >83% to discriminate global developmental delay from speech delay.

Abstract

ROIs showing significantly altered network metrics in the group comparison of TD > GD. In the 2D connectogram, the color of anatomic label scales the P value of group difference in the AAL template. Similarly, the color of each circle represents the P value of individual metrics. The 3D connectogram shows individual pair-wise pathways having significant group differences in nodal strength (ie, the greater radius of the sphere, the greater the group difference). In both 2D and 3D connectograms, block arrows indicate the hippocampal network whose nodal properties are significantly reduced in GD compared with TD.
ROIs showing significantly altered network metrics in the group comparison of TD > GD. In the 2D connectogram, the color of anatomic label scales the P value of group difference in the AAL template. Similarly, the color of each circle represents the P value of individual metrics. The 3D connectogram shows individual pair-wise pathways having significant group differences in nodal strength (ie, the greater radius of the sphere, the greater the group difference). In both 2D and 3D connectograms, block arrows indicate the hippocampal network whose nodal properties are significantly reduced in GD compared with TD.

BACKGROUND AND PURPOSE

Pure speech delay is a common developmental disorder which, according to some estimates, affects 5%–8% of the population. Speech delay may not only be an isolated condition but also can be part of a broader condition such as global developmental delay. The present study investigated whether diffusion tensor imaging tractography-based connectome can differentiate global developmental delay from speech delay in young children.

MATERIALS AND METHODS

Twelve children with pure speech delay (39.1 ±

Interrogating the Functional Correlates of Collateralization in Patients with Intracranial Stenosis Using Multimodal Hemodynamic Imaging

Editor’s Choice

The authors assessed correlations among baseline perfusion and arterial transit time artifacts, cerebrovascular reactivity, and the presence of collateral vessels on digital subtraction angiography. Arterial spin-labeling MRI and DSA were compared with BOLD MR imaging measures of hypercapnic cerebrovascular reactivity in 18 patients with symptomatic intracranial stenosis. In regions with normal-to-high signal on ASL, collateral vessel presence on DSA strongly correlated with declines in cerebrovascular reactivity (as measured on BOLD MRI). These data support the use of ASL MR imaging rather than invasive DSA to assess the presence of collateralization, even for patients with internal carotid stenosis from nonatherosclerotic etiologies. Also, collaterals identified on ASL with arterial transit artifacts correlated with decreased CVR compared with regions not perfused via collaterals.

Abstract

A, Arterial transit artifacts (arrow) at the ganglionic level on ASL MR imaging in the M3 region (ASPECTS designation criteria) representing leptomeningeal collateralization. B, A similar distribution is shown in an early venous phase anteroposterior right ICA angiogram showing leptomeningeal collaterals (arrows) arriving at the periphery of the ischemic site.
A, Arterial transit artifacts (arrow) at the ganglionic level on ASL MR imaging in the M3 region (ASPECTS designation criteria) representing leptomeningeal collateralization. B, A similar distribution is shown in an early venous phase anteroposterior right ICA angiogram showing leptomeningeal collaterals (arrows) arriving at the periphery of the ischemic site.

BACKGROUND AND PURPOSE

The importance of collateralization for maintaining adequate cerebral perfusion is increasingly recognized. However, measuring collateral flow noninvasively has proved elusive. The aim of this study was to assess correlations among baseline perfusion and arterial transit time artifacts, cerebrovascular reactivity, and the presence of collateral vessels on digital subtraction angiography.

MATERIALS AND METHODS

The relationship between the presence of collateral vessels on arterial spin-labeling MR imaging and DSA was compared with blood oxygen level–dependent MR imaging measures of hypercapnic cerebrovascular reactivity in patients with symptomatic intracranial stenosis (n = 18). DSA maps were reviewed by a neuroradiologist and assigned the following scores: 1, collaterals to the periphery of the ischemic site; 2, complete irrigation of the ischemic bed via collateral flow; and 3, normal

Clinical Feasibility of Synthetic MRI in Multiple Sclerosis: A Diagnostic and Volumetric Validation Study

Editor’s Choice

SyMRI is a quantitative synthetic MR imaging method where a single saturation recovery TSE sequence is used to estimate the proton density, longitudinal relaxation rate, and transverse relaxation rate and allows for a free range of synthetic weightings. Twenty patients with MS and 20 healthy controls were enrolled and synthetic MR imaging was implemented on a Siemens 3T scanner. Diagnostic accuracy, lesion detection, and artifacts were assessed by blinded neuroradiologic evaluation, and CNR by manual tracing. Synthetic PD-, T1-, and T2-weighted images were of sufficient or good quality and were acquired in 7% less time than with conventional MRI. Synthetic FLAIR images suffered from artifacts. Also, synthetic MRI provided segmentations with the shortest processing time (16 seconds) and the lowest repeatability error for brain volume. Synthetic MRI can be an alternative to conventional MRI for generating diagnostic PD-, T1-, and T2-weighted images in patients with MS with fast and robust volumetric measurements.

Abstract

Conventional (top row) and synthetic (middle row) axial noncontrast MR imaging in a 49-year-old male patient with MS, from left to right: T1-, PD-, and T2-weighted, and FLAIR images. The bottom row shows brain tissue segmentations of the WM (cyan), GM (green), CSF (magenta), and other remaining brain tissues (yellow) from SyMRI.
Conventional (top row) and synthetic (middle row) axial noncontrast MR imaging in a 49-year-old male patient with MS, from left to right: T1-, PD-, and T2-weighted, and FLAIR images. The bottom row shows brain tissue segmentations of the WM (cyan), GM (green), CSF (magenta), and other remaining brain tissues (yellow) from SyMRI.

BACKGROUND AND PURPOSE

Quantitative MR imaging techniques are gaining interest as methods of reducing acquisition times while additionally providing robust measurements. This study aimed to implement a synthetic MR imaging method on a new scanner type and to compare its diagnostic accuracy and volumetry with conventional MR imaging in patients with MS and controls.

MATERIALS AND METHODS

Twenty patients with MS and 20 healthy controls were enrolled after ethics approval and written informed consent. Synthetic MR imaging was implemented on a Siemens 3T scanner. Comparable conventional and synthetic proton-density–, T1-, and T2-weighted, and

Brain Structural and Vascular Anatomy Is Altered in Offspring of Pre-Eclamptic Pregnancies: A Pilot Study

Editor’s Choice

The authors assessed the brain structural and vascular anatomy in 7- to 10-year-old offspring of pre-eclamptic pregnancies compared with matched controls (n=10 per group). TOF-MRA and a high-resolution anatomic T1-weighted MPRAGE sequence were acquired for each participant. Offspring of pre-eclamptic pregnancies exhibited enlarged brain regional volumes of the cerebellum, temporal lobe, brain stem, and right and left amygdalae. These offspring displayed reduced cerebral vessel radii in the occipital and parietal lobes. The authors conclude that these structural and vascular anomalies may underlie the cognitive deficits reported in the pre-eclamptic offspring population.

Abstract

Visual 3D representation of the vessel radii calculated for a segmented TOF-MRA dataset of a single female, 8-year-old PE-F1 participant who was born at 34 weeks of gestation.
Visual 3D representation of the vessel radii calculated for a segmented TOF-MRA dataset of a single female, 8-year-old PE-F1 participant who was born at 34 weeks of gestation.

BACKGROUND AND PURPOSE

Pre-eclampsia is a serious clinical gestational disorder occurring in 3%–5% of all human pregnancies and characterized by endothelial dysfunction and vascular complications. Offspring born of pre-eclamptic pregnancies are reported to exhibit deficits in cognitive function, higher incidence of depression, and increased susceptibility to stroke. However, no brain imaging reports exist on these offspring. We aimed to assess brain structural and vascular anatomy in 7- to 10-year-old offspring of pre-eclamptic pregnancies compared with matched controls.

MATERIALS AND METHODS

Offspring of pre-eclamptic pregnancies and matched controls (n = 10 per group) were recruited from an established longitudinal cohort examining the effects of pre-eclampsia. Children underwent MR imaging to identify brain structural and vascular anatomic differences. Maternal plasma samples collected at birth were assayed for angiogenic factors by enzyme-linked immunosorbent assay.

RESULTS

Offspring of pre-eclamptic pregnancies exhibited enlarged brain regional volumes of the cerebellum, temporal lobe, brain stem, and right and left amygdalae. These offspring displayed reduced cerebral vessel radii in the occipital and parietal lobes. Enzyme-linked immunosorbent assay analysis revealed underexpression of the placental growth factor

Mitotic Activity in Glioblastoma Correlates with Estimated Extravascular Extracellular Space Derived from Dynamic Contrast-Enhanced MR Imaging

Editor’s Choice

Twenty-eight patients with newly presenting glioblastoma multiforme underwent preoperative conventional imaging and T1 dynamic contrast-enhanced MRI. Parametric maps of the initial area under the contrast agent concentration curve, contrast transfer coefficient, estimate of volume of the extravascular extracellular space, and estimate of blood plasma volume were generated, and the enhancing fraction was calculated. High values of the estimate of volume of the extravascular extracellular space were associated with a fibrillary histologic pattern and increased mitotic activity. This finding is counterintuitive to the standard concept that more proliferative tumors would be more densely packed with cells and have less extracellular space. As the authors point out, this surprising finding requires more investigation to understand whether this relationship will hold, and what the underlying mechanism might be.

Abstract

Scatterplot of mitotic activity versus ve (P = .012, ρ = 0.470), marker shapes depict separate scores of cell density measures.
Scatterplot of mitotic activity versus ve (P = .012, ρ = 0.470), marker shapes depict separate scores of cell density measures.

BACKGROUND AND PURPOSE

A number of parameters derived from dynamic contrast-enhanced MR imaging and separate histologic features have been identified as potential prognosticators in high-grade glioma. This study evaluated the relationships between dynamic contrast-enhanced MRI–derived parameters and histologic features in glioblastoma multiforme.

MATERIALS AND METHODS

Twenty-eight patients with newly presenting glioblastoma multiforme underwent preoperative imaging (conventional imaging and T1 dynamic contrast-enhanced MRI). Parametric maps of the initial area under the contrast agent concentration curve, contrast transfer coefficient, estimate of volume of the extravascular extracellular space, and estimate of blood plasma volume were generated, and the enhancing fraction was calculated. Surgical specimens were used to assess subtype and were graded (World Health Organization classification system) and were assessed for necrosis, cell density, cellular atypia, mitotic activity, and overall vascularity scores. Quantitative assessment of endothelial surface area, vascular surface area, and a vascular profile count were made by using CD34 immunostaining. The relationships

Lateral Asymmetry and Spatial Difference of Iron Deposition in the Substantia Nigra of Patients with Parkinson Disease Measured with Quantitative Susceptibility Mapping

Editor’s Choice

The authors evaluated 24 patients with Parkinson disease and 24 age- and sex-matched healthy controls who underwent 3T MR imaging with a 3D multiecho gradient-echo sequence. On reconstructed quantitative susceptibility maps they measured the susceptibility values in the anterior, middle, and posterior parts of the substantia nigra, the whole substantia nigra, and other deep gray matter structures in both cerebral hemispheres. Susceptibility in the middle part, the posterior part, and the whole substantia nigra was significantly higher in the more and the less affected hemibrains of patients with Parkinson disease than in the healthy controls. Also, susceptibility was significantly higher in the posterior substantia nigra of the more affected hemibrain.

Abstract

A 59-year-old woman with Parkinson disease. A, QSM, axial section at the level of the basal ganglia. ROIs as large as possible were placed. Areas encircled in red, green, and blue are the caudate nucleus, putamen, and globus pallidus. B, QSM, axial section at the level of the midbrain. The encircled area identifies the red nucleus medial to the substantial nigra.
A 59-year-old woman with Parkinson disease. A, QSM, axial section at the level of the basal ganglia. ROIs as large as possible were placed. Areas encircled in red, green, and blue are the caudate nucleus, putamen, and globus pallidus. B, QSM, axial section at the level of the midbrain. The encircled area identifies the red nucleus medial to the substantial nigra.

BACKGROUND AND PURPOSE

Quantitative susceptibility mapping is useful for assessing iron deposition in the substantia nigra of patients with Parkinson disease. We aimed to determine whether quantitative susceptibility mapping is useful for assessing the lateral asymmetry and spatial difference in iron deposits in the substantia nigra of patients with Parkinson disease.

MATERIALS AND METHODS

Our study population comprised 24 patients with Parkinson disease and 24 age- and sex-matched healthy controls. They underwent 3T MR imaging by using a 3D multiecho gradient-echo sequence. On reconstructed quantitative susceptibility mapping, we measured the susceptibility values in the anterior, middle, and posterior parts of the substantia nigra, the whole substantia nigra, and other deep gray matter structures in both hemibrains. To identify the more and less affected hemibrains in patients

Cerebral Blood Flow Improvement after Indirect Revascularization for Pediatric Moyamoya Disease: A Statistical Analysis of Arterial Spin-Labeling MRI

Editor’s Choice

The authors evaluated 15 children treated by indirect cerebral revascularization with multiple burr-holes between 2011–2013. Arterial spin-labeling MR imaging and T1 sequences were analyzed under SPM8 before and after the operation (3 and 12 months). Group analysis showed statistically significant preoperative hypoperfusion in the MCA territory in the Moyamoya hemispheres and a significant increase of cerebral perfusion in the same territory after revascularization. The authors conclude that SPM analysis of arterial spin-labeling MR imaging offers a noninvasive evaluation of preoperative cerebral hemodynamic impairment and an objective assessment of postoperative improvement in children with Moyamoya disease.

Abstract

Click image to enlarge
Click image to enlarge

BACKGROUND AND PURPOSE

The severity of Moyamoya disease is generally scaled with conventional angiography and nuclear medicine. Arterial spin-labeling MR imaging is now acknowledged for the noninvasive quantification of cerebral blood flow. This study aimed to analyze CBF modifications with statistical parametric mapping of arterial spin-labeling MR imaging in children undergoing an operation for Moyamoya disease.

MATERIALS AND METHODS

We included 15 children treated by indirect cerebral revascularization with multiple burr-holes between 2011 and 2013. Arterial spin-labeling MR imaging and T1 sequences were then analyzed under SPM8, according to the general linear model, before and after the operation (3 and 12 months). Voxel-based analysis was performed at the group level, comparing all diseased hemispheres with all normal hemispheres and, at the individual level, comparing each patient with a control group.

RESULTS

Group analysis showed statistically significant preoperative hypoperfusion in the MCA territory in the Moyamoya hemispheres and a significant increase of cerebral perfusion in the same territory after revascularization (P < .05 family-wise error–corrected). Before the operation, individual analysis showed significant hypoperfusion for each patient co-localized with the angiographic defect on DSA. All except 1 patient had improvement of CBF after revascularization, correlated with their clinical status.

A Spiral Spin-Echo MR Imaging Technique for Improved Flow Artifact Suppression in T1-Weighted Postcontrast Brain Imaging: A Comparison with Cartesian Turbo Spin-Echo

Editor’s Choice

T1-weighted enhanced brain imaging was performed in 24 pediatric patients comparing the reference Cartesian TSE sequence (2 minutes 30 seconds) with a spiral spin-echo sequence (1 minutes 18 seconds) with similar spatial resolution and coverage. In 23/24 cases, spiral spin-echo was scored better than Cartesian TSE for flow artifact reduction and in 21 cases was superior in subjective preference. The authors demonstrate a relatively simple 2D spiral SE approach in T1-weighted postcontrast brain MR imaging that has minimal flow artifacts in comparison with its 2D Cartesian TSE counterpart.

Abstract

Figure 3, from Li et al. A Spiral Spin-Echo MR Imaging Technique for Improved Flow Artifact Suppression in T1-Weighted Postcontrast Brain Imaging: A Comparison with Cartesian Turbo Spin-Echo
Click image to enlarge

BACKGROUND AND PURPOSE

A challenge with the T1-weighted postcontrast Cartesian spin-echo and turbo spin-echo brain MR imaging is the presence of flow artifacts. Our aim was to develop a rapid 2D spiral spin-echo sequence for T1-weighted MR imaging with minimal flow artifacts and to compare it with a conventional Cartesian 2D turbo spin-echo sequence.

MATERIALS AND METHODS

T1-weighted brain imaging was performed in 24 pediatric patients. After the administration of intravenous gadolinium contrast agent, a reference Cartesian TSE sequence with a scanning time of 2 minutes 30 seconds was performed, followed by the proposed spiral spin-echo sequence with a scanning time of 1 minutes 18 seconds, with similar spatial resolution and volumetric coverage. The results were reviewed independently and blindly by 3 neuroradiologists. Scores from a 3-point scale were assigned in 3 categories: flow artifact reduction, subjective preference, and lesion conspicuity, if any. The Wilcoxon signed rank test was performed to evaluate the reviewer scores. The t test was used to evaluate the SNR. The Fleiss κ coefficient was calculated to examine interreader agreement.

RESULTS

In 23 cases, spiral spin-echo was scored over Cartesian TSE in flow artifact reduction (P < .001). In 21 cases, spiral spin-echo was rated superior in subjective preference (

Computational Identification of Tumor Anatomic Location Associated with Survival in 2 Large Cohorts of Human Primary Glioblastomas

Editor’s Choice

Preoperative T1 anatomic MR images of 384 patients with glioblastomas were evaluated by an automated computational image-analysis pipeline to determine the anatomic locations of tumor in each patient. Voxel-based differences in tumor location between good and poor survival groups identified in the training cohort were used to classify patients in The Cancer Genome Atlas cohort into 2 brain-location groups, for which clinical features, messenger RNA expression, and copy number changes were compared. Tumors in the right occipitotemporal periventricular white matter were significantly associated with poor survival in both training and test cohorts. Tumors in the right periatrial location were associated with hypoxia pathway enrichment and PDGFRA amplification. The authors conclude that voxel-based location in glioblastoma is associated with patient outcome and may have a potential role for guiding personalized treatment.

Abstract

Figure 1 from Liu et al, Computational Identification of Tumor Anatomic Location Associated with Survival in 2 Large Cohorts of Human Primary Glioblastomas, AJNR 2016
Click image to enlarge

BACKGROUND AND PURPOSE

Tumor location has been shown to be a significant prognostic factor in patients with glioblastoma. The purpose of this study was to characterize glioblastoma lesions by identifying MR imaging voxel-based tumor location features that are associated with tumor molecular profiles, patient characteristics, and clinical outcomes.

MATERIALS AND METHODS

Preoperative T1 anatomic MR images of 384 patients with glioblastomas were obtained from 2 independent cohorts (n = 253 from the Stanford University Medical Center for training and n = 131 from The Cancer Genome Atlas for validation). An automated computational image-analysis pipeline was developed to determine the anatomic locations of tumor in each patient. Voxel-based differences in tumor location between good (overall survival of >17 months) and poor (overall survival of <11 months) survival groups identified in the training cohort were used to classify patients in The Cancer Genome Atlas cohort into 2 brain-location groups, for which clinical features, messenger RNA expression, and copy number changes were compared to elucidate