Faculty Bibliography

Background: Atrophy of the hippocampus is a key pathological hallmark of Alzheimer's disease (AD). An interest of subfields of hippocampal imaging has emerged in recent years due to the advent of ultra-high field MR. This work was to evaluate the imaging parameters on human postmortem brain at 7T MR using 3D susceptibility-sensitivity imaging (SWI) with enhanced tissue susceptibility contrast to better identify these layers and hippocampal subfields that are not available on conventional MR in order to better understand the transition of the hippocampus in AD as disease progresses. Methods: Imaging was performed on a 7.0T Siemens MAGNETOM using a 24-element phased array head coil. Post-mortem brain specimens of the hippocampus were obtained from 3 patients (mean: 72.2+4.3 years) with clinically diagnosed AD and 4 age-matched healthy controls (71.4+5.2 years). Coronal brain slices were preserved and fixed in 2% agar for this study. High resolution 3D SWI was obtained with isotropic voxel size 150~320mum. For imaging optimization to better visualize amyloid plaques, we varied TR, TE, BWand flip angle from 30-100ms, 12-36ms, 60-140Hz/ pixel and 10-40degree; respectively. The SWI filtered phase images were used (multiplication factor of 4 ~ 8) to enhance susceptibility contrast in the SWI images. Results: With optimal SWI parameters TR/TE/FA of 80ms/ 20ms/30IS at 7T, Figure 1 exemplifies the excellent image contrast for visualization of hippocampal layers (Fig A) and subfields (Fig B) in an elderly post-mortem brain without AD, specifically for cell types/layers: (1) Alveus; (2) Stratum Oriens; (3) Stratum Pyramidale; (4) Stratum Radiatum; (5) Stratum Lacunosum; (6) Stratum Moleculare; and for Hippocampal Formation subfields: (1) Hippocampal Head; (2, 2') Dentate Gyrus, (3, 3') Cornu Ammonis (CA1), (4) CA2, (5) CA3, (6) Pre-Subiculum/ Subiculum, (7) Para-Subiculum, (8) Entorhinal Cortex. There was significant atrophy of the whole hippocampal formation and subfields inADsamples with lessening of the!

Purpose: To investigate longitudinal changes in global and regional brain volume in patients 1 year after mild traumatic brain injury (MTBI) and to correlate such changes with clinical and neurocognitive metrics. Materials and Methods: This institutional review board-approved study was HIPAA compliant. Twenty-eight patients with MTBI (with 19 followed up at 1 year) with posttraumatic symptoms after injury and 22 matched control subjects (with 12 followed up at 1 year) were enrolled. Automated segmentation of brain regions to compute regional gray matter (GM) and white matter (WM) volumes was performed by using three-dimensional T1-weighted 3.0-T magnetic resonance imaging, and results were correlated with clinical metrics. Pearson and Spearman rank correlation coefficients were computed between longitudinal brain volume and neurocognitive scores, as well as clinical metrics, over the course of the follow-up period. Results: One year after MTBI, there was measurable global brain atrophy, larger than that in control subjects. The anterior cingulate WM bilaterally and the left cingulate gyrus isthmus WM, as well as the right precuneal GM, showed significant decreases in regional volume in patients with MTBI over the 1st year after injury (corrected P < .05); this was confirmed by means of cross-sectional comparison with data in control subjects (corrected P < .05). Left and right rostral anterior cingulum WM volume loss correlated with changes in neurocognitive measures of memory (r = 0.65, P = .005) and attention (r = 0.60, P = .01). At 1-year follow-up, WM volume in the left cingulate gyrus isthmus correlated with clinical scores of anxiety (Spearman rank correlation r = -0.68, P = .007) and postconcussive symptoms (Spearman rank correlation r = -0.65, P = .01). Conclusion: These observations demonstrate structural changes to the brain 1 year after injury after a single concussive episode. Regional brain atrophy is not exclusive to moderate and severe traumatic brain injury but may be seen after mild injury. In particular, the anterior part of the cingulum and the cingulate gyrus isthmus, as well as the precuneal GM, may be distinctively vulnerable 1 year after MTBI. (c) RSNA, 2013.

BACKGROUND AND PURPOSE: CC is extensively involved in MS with interhemispheric dysfunction. The purpose of this study was to determine whether interhemispheric correlation is altered in MS by use of a recently developed RS-fMRI homotopy technique and whether these homotopic changes correlate with CC pathology. MATERIALS AND METHODS: Twenty-four patients with relapsing-remitting MS and 24 age-matched healthy volunteers were studied with RS-fMRI and DTI acquired at 3T. The Pearson correlation of each pair of symmetric interhemispheric voxels of RS-fMRI time-series data was performed to compute VMHC, and z-transformed for subsequent group-level analysis. In addition, 5 CC segments in the midsagittal area and DTI-derived FA were measured to quantify interhemispheric microstructural changes and correlate with global and regional VMHC in MS. RESULTS: Relative to control participants, patients with MS exhibited an abnormal homotopic pattern with decreased VMHC in the primary visual, somatosensory, and motor cortices and increased VMHC in several regions associated with sensory processing and motor control including the insula, thalamus, pallidum, and cerebellum. The global VMHC correlates moderately with the average FA of the entire CC for all participants in both groups (r = 0.3; P = .03). CONCLUSIONS: Our data provide preliminary evidence of the potential usefulness of VMHC analyses for the detection of abnormalities of interhemispheric coordination in MS. We demonstrated that the whole-brain homotopic RS-fMRI pattern was altered in patients with MS, which was partially associated with the underlying structural degenerative changes of CC measured with FA.

Background. Brain lesions are common in neuromyelitis optica spectrum disorder (NMOsd) and may resemble lesions of multiple sclerosis (MS). Objectives. To describe the imaging characteristics of supratentorial lesions in NMOsd on ultrahigh-field (7 T) MRI with special attention to vessel-lesion relationship. Methods. Ten NMOsd patients, all women and all seropositive for NMO IgG, with mean age of 51.3 +/- 15.4 years and disease duration of 9.2 +/- 6.4 years, were scanned at a 7 T whole-body human MR system with high-resolution 2D gradient echo sequence optimized to best visualize lesions and venous structures, T2- and T1-weighted imaging. Results. In 10 patients with NMOsd, a total of 92 lesions were observed (mean: 9.2 +/- 8.8; range: 2-30), but only 8 lesions (9%) were traversed by a central venule. All lesions were <5 mm in diameter, and 83% were located in subcortical white matter. There were no lesions in the cortex or basal ganglia. Two patients exhibited diffuse periependymal abnormalities on FLAIR. Conclusions. Small, subcortical lesions without a central venule are the most consistent finding of NMOsd on 7 T MRI of the brain. Ultrahigh-field imaging may be useful for differentiating between NMOsd and MS.

Purpose: To investigate the integrity of the default-mode network (DMN) by using independent component analysis (ICA) methods in patients shortly after mild traumatic brain injury (MTBI) and healthy control subjects, and to correlate DMN connectivity changes with neurocognitive tests and clinical symptoms. Materials and Methods: This study was approved by the institutional review board and complied with HIPAA regulations. Twenty-three patients with MTBI who had posttraumatic symptoms shortly after injury (<2 months) and 18 age-matched healthy control subjects were included in this study. Resting-state functional magnetic resonance imaging was performed at 3 T to characterize the DMN by using ICA methods, including a single-participant ICA on the basis of a comprehensive template from core seeds in the posterior cingulate cortex (PCC) and medial prefrontal cortex (MPFC) nodes. ICA z images of DMN components were compared between the two groups and correlated with neurocognitive tests and clinical performance in patients by using Pearson and Spearman rank correlation. Results: When compared with the control subjects, there was significantly reduced connectivity in the PCC and parietal regions and increased frontal connectivity around the MPFC in patients with MTBI (P < .01). These frontoposterior opposing changes within the DMN were significantly correlated (r = -0.44, P = .03). The reduced posterior connectivity correlated positively with neurocognitive dysfunction (eg, cognitive flexibility), while the increased frontal connectivity correlated negatively with posttraumatic symptoms (ie, depression, anxiety, fatigue, and postconcussion syndrome). Conclusion: These results showed abnormal DMN connectivity patterns in patients with MTBI, which may provide insight into how neuronal communication and information integration are disrupted among DMN key structures after mild head injury. (c) RSNA, 2012.

Objectives: To compare supratentorial lesions in patients with neuromyelitis optica spectrum disorders (NMOsd) and multiple sclerosis (MS) on ultra-high-field (7-Tesla) MRI. 508Background: Brain lesions are common in NMOsd. The distinction between NMOsd and MS is not always possible with conventional brain MRI. The aim of this study is to compare supratentorial lesions in NMOsd and MS on ultra-high-field (7-Tesla) MRI, and to attempt to develop criteria for differentiating the two conditions on neuro-radiologic basis. Design/methods: NMOsd and MS patients matched by age and disease duration were recruited from the NYU-MS Center. Imaging data were acquired on a 7T whole-body human MR system (MAGNETOM, Siemens). NMO and MS patients were scanned using identical imaging protocol that included a high-resolution 2D gradient echo sequence optimized to best visualize venous structures (TR/TE/flip angle = 500ms/25ms/35degree, voxel size = 0.23x0.23x2 mm³). This sequence is highly sensitive to venous vasculature and is used to visually examine for presence of central venule in supratentorial brain lesions. Results: 10 patients with NMOsd and 5 patients with MS underwent 7T brain MRI. NMOsd patients were all women, all NMO IgG-seropositive, with average age of 47.8+9.0 years and disease duration of 11.4+6.5 years. MS patients were 80% women, with mean age of 43.6+10.0 years, and disease duration of 15.5+10.1 years. NMOsd patients had a total of 74 supratentorial lesions (7.4 per patient), versus 152 in MS patients (30.4 per patient). There were striking differences in lesion distribution: in NMOsd, 93% of lesions were subcortical versus 30% in MS group; by contrast, only 1% of NMOsd lesions were periventricular v. 53% for MS. MS patients also exhibited more lesions in juxtocortical white matter (9% v. 3 % in NMOsd) and in corpus callosum (11% v. 3% in NMOsd). Importantly, we did not detect any cortical lesions in NMOsd, while 3 out of 5 MS patients had detectable cortical lesions. Central venul!

Purpose: Normal neuronal activity is tightly linked to and depends on the increase of blood flow for instantaneous supply of oxygen and glucose. This study is to evaluate whether there are cerebral blood flow (CBF) regulation abnormalities in MS with measurement of cerebrovascular reactivity (CVR) using hypercapnia perfusion MRI. Materials and Methods: Sixteen patients with MS (14 relapsing remitting and 2 secondary progressive) (mean age: 45.1+14.2 years, mean EDSS: 2.9+1.6) and age-matched 13 healthy controls (mean age: 44.5+12.2 years) were recruited for this study. CO2 is a potent vasodilator, and an increase of CO2 tension in blood (referred to as hypercapnia) is known to cause CBF increase. Such CBF changes were measured with a standard pseudo-continuous arterial spin labeling (pCASL) MRI at 3T, with quantitative CBF (ml/min/100g) maps generated during both room air and hypercapnia (mixed 5%CO2, 21%O2, and 74%N2) exposure. The imaging parameters of pCASL include TR/TE=3950/17ms, 52 repetitions, FOV=22cm, in-plane matrix=64x64, slice thickness=5mm, labeling duration=1500ms, postlabeling delay=1230ms, and label location = 84mm below AC-PC line. End-tidal CO2 (EtCO2) was recorded continuously during the scan with a capnograph device and was used as an input function in the analysis. The CVR was calculated as (% change in CBF comparing CO2 inhalation to room-air breathing) divided by (EtCO2 during CO2 inhalation - EtCO2 during room-air breathing). Segmented whole brain grey matter (GM), white matter (WM), and brain parenchymal CVR were calculated for the group analysis. Results: The averaged CVR (%CBF/mmHg EtCO2) showed significant difference for whole brain parenchymal (P=0.009), GM (P=0.008), and WM (P=0.03) between patients (4.74+0.88%, 4.89+1.08%, and 4.73+1.02%) and healthy controls (3.46+1.51%, 3.51+1.47%, and 3.53+1.83%, respectively). There was a significant correlation between brain parenchymal CVR and EDSS (r=-0.69, P=0.007). Whole brain CVR changes correlate with fractional brain p!

Conventional imaging is unable to detect damage that accounts for permanent cognitive impairment in patients with mild traumatic brain injury (MTBI). While diffusion tensor imaging (DTI) can help to detect diffuse axonal injury (DAI), it is a limited indicator of tissue complexity. It has also been suggested that the thalamus may play an important role in the development of clinical sequelae in MTBI. The purpose of this study was to determine if diffusional kurtosis imaging (DKI), a novel quantitative magnetic resonance imaging (MRI) technique, can provide early detection of damage in the thalamus and white matter (WM) of MTBI patients and if thalamic injury is associated with cognitive impairment. Twenty-two MTBI patients and 14 controls underwent MRI and neuropsychological testing. Mean kurtosis (MK), fractional anisotropy (FA), and mean diffusivity (MD) were measured in the thalamus and several WM regions classically identified with DAI. Compared to controls, patients examined within one year after injury exhibited variously altered DTI and DKI derived measures in the thalamus and the internal capsule while, in addition to these regions, patients examined more than one year after injury also showed similar differences in the splenium of the corpus callosum and the centrum semiovale. Cognitive impairment was correlated to MK in the thalamus and the internal capsule. These findings suggest that combined use of DTI and DKI provides a more sensitive tool for identifying brain injury. In addition, MK in the thalamus might be useful for early prediction of permanent brain damage and cognitive outcome