John Grinstead

Multimodal Magnetic Resonance Imaging Assessment of White Matter Aging Trajectories Over the Lifespan of Healthy Individuals

BACKGROUND Postmortem and volumetric imaging data suggest that brain myelination is a dynamic lifelong process that, in vulnerable late-myelinating regions, peaks in middle age. We examined whether known regional differences in axon size and age at myelination influence the timing and rates of development and degeneration/repair trajectories of white matter (WM) microstructure biomarkers. METHODS Healthy subjects (n = 171) 14-93 years of age were examined with transverse relaxation rate (R(2)) and four diffusion tensor imaging measures (fractional anisotropy [FA] and radial, axial, and mean diffusivity [RD, AxD, MD, respectively]) of frontal lobe, genu, and splenium of the corpus callosum WM (FWM, GWM, and SWM, respectively). RESULTS Only R(2) reflected known levels of myelin content with high values in late-myelinating FWM and GWM regions and low ones in early-myelinating SWM. In FWM and GWM, all metrics except FA had significant quadratic components that peaked at different ages (R(2) < RD < MD < AxD), with FWM peaking later than GWM. Factor analysis revealed that, although they defined different factors, R(2) and RD were the metrics most closely associated with each other and differed from AxD, which entered into a third factor. CONCLUSIONS The R(2) and RD trajectories were most dynamic in late-myelinating regions and reflect age-related differences in myelination, whereas AxD reflects axonal size and extra-axonal space. The FA and MD had limited specificity. The data suggest that the healthy adult brain undergoes continual change driven by development and repair processes devoted to creating and maintaining synchronous function among neural networks on which optimal cognition and behavior depend.

Combined intravoxel incoherent motion and diffusion tensor imaging of renal diffusion and flow anisotropy.

We used a combined intravoxel incoherent motion–diffusion tensor imaging (IVIM‐DTI) methodology to distinguish structural from flow effects on renal diffusion anisotropy.

Diffusion tensor imaging predicts functional impairment in mild-to-moderate cervical spondylotic myelopathy

BACKGROUND CONTEXT Magnetic resonance imaging (MRI) is the standard imaging modality for the assessment of cervical spinal cord; however, MRI assessment of the spinal cord in cervical spondylotic myelopathy patients has not demonstrated a consistent association with neurologic function or outcome after surgical or medical intervention. Thus, there is a need for sensitive imaging biomarkers that can predict functional impairment in patients with advanced cervical spondylosis. PURPOSE To implement diffusion tensor imaging (DTI) as an imaging biomarker for microstructural integrity and functional impairment in patients with cervical spondylosis. STUDY DESIGN Nonrandomized, single institution study. PATIENT SAMPLE Forty-eight cervical spondylosis patients with or without spinal cord signal change underwent DTI of the spinal cord along with functional assessment. OUTCOME MEASURES Functional measures of neurologic function via modified Japanese Orthopedic Association (mJOA) score. METHODS A zoomed-echoplanar imaging technique and two-dimensional spatially selective radiofrequency excitation pulse were used for DTI measurement. Fractional anisotropy (FA), mean diffusivity (MD), radial and axial diffusion (AD) coefficient, AD anisotropy, ψ, defined as AD-MD, and the standard deviation (SD) of primary eigenvector orientation were evaluated at the site of compression. RESULTS Results suggest average FA, transverse apparent diffusion coefficient, ψ, and SD of primary eigenvector orientation at the spinal level of highest compression were linearly correlated with mJOA score. Receiver-operator characteristic analysis suggested FA and ψ could identify stenosis patients with mild-to-moderate symptoms with a relatively high sensitivity and specificity. CONCLUSIONS The results of this study support the potential use of DTI as a biomarker for predicting functional impairment in patients with cervical spondylosis.

Visualization and Quantification of Flow and Velocity Fields in Intracranial Arteriovenous Malformations Using Phase-Contrast MR Angiography

OBJECTIVE The objective of this study was to describe postprocessing tools for MR phase-contrast flow quantification images and apply those tools to cerebral arteriovenous malformations (AVMs) to visualize blood flow dynamics noninvasively. CONCLUSION Inflow and outflow zones were clearly depicted at different regions in the AVM. The processed images showed flow patterns including vortical flow and variations in velocity over the cardiac cycle. Particle tracking gave an impression of the overall flow state and of the venous drainage system in particular.

In-plane velocity encoding with coherent steady-state imaging.

Standard phase‐contrast flow quantification (PC‐FQ) using radiofrequency (RF) spoiled steady‐state (SS) incoherent gradient‐echo sequences have a relatively low signal‐to‐noise ratio (SNR). Unspoiled SS coherent (SSC) gradient‐echo sequences have a higher intrinsic SNR and are T2/T1 weighted so that blood has a relatively large signal compared to other tissues. An SSC sequence that was modified to allow in‐plane velocity encoding is presented. Velocity encoding was achieved by inverting the readout gradients. This offers the benefit that there is no resultant increase in repetition time (TR), which avoids increased sensitivity to off‐resonance artifacts when conventional velocity‐encoding methods using separate velocity‐encoding gradients are extended to SSC sequences. The results of standard PC‐FQ and the new method from in vitro experiments of constant and sinusoidal flow, and in vivo imaging of the carotid artery were compared. Vector field maps and paths obtained from particle‐tracking calculations based on the velocity‐encoded images were used to visualize the velocity data. The technique has the potential to increase the precision of PC‐FQ measurements. Magn Reson Med 54:138–145, 2005.

Nigrosome 1 absence in de novo Parkinson disease

A 63-year-old man with 6 months of mild left hand rest tremor and bradykinesia and subtle left wrist cogwheel rigidity was diagnosed with idiopathic Parkinson disease (PD). The most profound neuronal degeneration in PD occurs in nigrosome 1, a lens-shaped substructure of the substantia nigra containing approximately 22,000 cell bodies in each hemi-midbrain, measuring 6 × 6 × 1 mm.1,2 A 7T MRI at the caudal level of red nucleus (figure, A) shows nigrosome 1 signal present in the left nigra and absent in the right, consistent with the clinically affected side. 7T MRI of a healthy 63-year-old with normal bilateral nigrosome 1 signal is shown for comparison (figure, B).

POSTMORTEM 7T MRI FOR GUIDED HISTOLOGY AND TISSUE SEGMENTATION

MK6240 SUVRw [F]AZD4694 SUVR + age + gender + APOE + education. Results:The unique association between amyloidosis and NFTs was present in entorhinal cortex and PCC in CN; precuneus, PCC, and parahippocampal gyrus in MCI; ACC, entorhinal cortex, parahippocampal gyrus, and orbitofrontal cortex in AD. All groups showed the association in lateral temporal and middle frontal gyrus. Conclusions: Our results revealed both similar and different association patterns between amyloidosis andNFTs across AD stage. Most common association pattern was present at left lateral temporal cortex across all stages while the different association pattern moved from PCC, precuneus, to orbitofrontal cortex in CN, MCI, and AD, respectively. This corroborates the two pathologies spread from the posterior to anterior regions of the brain.

Ruptured intranidal aneurysm of an arteriovenous malformation diagnosed by delay alternating with nutation for tailored excitation (DANTE)–prepared contrast-enhanced magnetic resonance imaging

This case report describes the usefulness of delay alternating with nutation for tailored excitation (DANTE)–prepared, contrast-enhanced magnetic resonance imaging (CE-MRI) for detecting the rupture site of an arteriovenous malformation (AVM). A ruptured intranidal aneurysm was confirmed histopathologically. Accurate non-invasive information about the possible rupture site of an AVM is critical for optimal treatment and evaluation. Vessel wall enhancement visualized by DANTE-prepared CE-MRI may be a useful tool for providing information about changes in inflammatory status and vulnerability to further developments.