Anthony R. Whittemore

Diffusion tensor tractography of traumatic diffuse axonal injury.

BACKGROUND Diffuse axonal injury is a common consequence of traumatic brain injury that frequently involves the parasagittal white matter, corpus callosum, and brainstem. OBJECTIVE To examine the potential of diffusion tensor tractography in detecting diffuse axonal injury at the acute stage of injury and predicting long-term functional outcome. DESIGN Tract-derived fiber variables were analyzed to distinguish patients from control subjects and to determine their relationship to outcome. SETTING Inpatient traumatic brain injury unit. PATIENTS From 2005 to 2006, magnetic resonance images were acquired in 12 patients approximately 7 days after injury and in 12 age- and sex-matched controls. MAIN OUTCOME MEASURES Six fiber variables of the corpus callosum, fornix, and peduncular projections were obtained. Glasgow Outcome Scale-Extended scores were assessed approximately 9 months after injury in 11 of the 12 patients. RESULTS At least 1 fiber variable of each region showed diffuse axonal injury-associated alterations. At least 1 fiber variable of the anterior body and splenium of the corpus callosum correlated significantly with the Glasgow Outcome Scale-Extended scores. The predicted outcome scores correlated significantly with actual scores in a mixed-effects model. CONCLUSION Diffusion tensor tractography-based quantitative analysis at the acute stage of injury has the potential to serve as a valuable biomarker of diffuse axonal injury and predict long-term outcome.

Cerebral Atrophy after Traumatic White Matter Injury: Correlation with Acute Neuroimaging and Outcome

Traumatic brain injury (TBI) is a pathologically heterogeneous disease, including injury to both neuronal cell bodies and axonal processes. Global atrophy of both gray and white matter is common after TBI. This study was designed to determine the relationship between neuroimaging markers of acute diffuse axonal injury (DAI) and cerebral atrophy months later. We performed high-resolution magnetic resonance imaging (MRI) at 3 Tesla (T) in 20 patients who suffered non-penetrating TBI, during the acute (within 1 month after the injury) and chronic stage (at least 6 months after the injury). Volume of abnormal fluid-attenuated inversion-recovery (FLAIR) signal seen in white matter in both acute and follow-up scans was quantified. White and gray matter volumes were also quantified. Functional outcome was measured using the Functional Status Examination (FSE) at the time of the chronic scan. Change in brain volumes, including whole brain volume (WBV), white matter volume (WMV), and gray matter volume (GMV), correlates significantly with acute DAI volume (r = -0.69, -0.59, -0.58, respectively; p <0.01 for all). Volume of acute FLAIR hyperintensities correlates with volume of decreased FLAIR signal in the follow-up scans (r = -0.86, p < 0.001). FSE performance correlates with acute hyperintensity volume and chronic cerebral atrophy (r = 0.53, p = 0.02; r = -0.45, p = 0.03, respectively). Acute axonal lesions measured by FLAIR imaging are strongly predictive of post-traumatic cerebral atrophy. Our findings suggest that axonal pathology measured as white matter lesions following TBI can be identified using MRI, and may be a useful measure for DAI-directed therapies.

Magnetic resonance methods for measurement of disease progression in rheumatoid arthritis

Magnetic resonance imaging methods are described for measurement of disease activity in knee in rheumatoid arthritis patients. Measurements of cartilage thickness, joint effusion volume, and pannus volume have been made. The latter measurement relies on synthetic fractional enhancement images of the response to gadopentetate dimeglumine.

MR Imaging of Hippocampal Asymmetry at 3T in a Multiethnic, Population-Based Sample: Results from the Dallas Heart Study

BACKGROUND AND PURPOSE: Asymmetry of the hippocampus is regarded as an important clinical finding, but limited data on hippocampal asymmetry are available for the general population. Here we present hippocampal asymmetry data from the Dallas Heart Study determined by automated methods and its relationship to age, sex, and ethnicity. MATERIALS AND METHODS: 3D magnetization-prepared rapid acquisition of gradient echo MR imaging was performed in 2082 DHS-2 participants. The MR images were analyzed by using 2 standard automated brain-segmentation programs, FSL-FIRST and FreeSurfer. Individuals with imaging errors, self-reported stroke, or major structural abnormalities were excluded. Statistical analyses were performed to determine the significance of the findings across age, sex, and ethnicity. RESULTS: At the 90th percentile, FSL-FIRST demonstrated hippocampal asymmetry of 9.8% (95% CI, 9.3%–10.5%). The 90th percentile of hippocampal asymmetry, measured by the difference in right and left hippocampi volume and the larger hippocampus, was 17.9% (95% CI, 17.0%–19.1%). Hippocampal asymmetry increases with age (P = .0216), men have greater asymmetry than women as shown by FSL-FIRST (P = .0036), but ethnicity is not significantly correlated with asymmetry. To confirm these findings, we used FreeSurfer. FreeSurfer showed asymmetry of 4.4% (95% CI, 4.3%–4.7%) normalized to total volume and 8.5% (95% CI, 8.3%–9.0%) normalized by difference/larger hippocampus. FreeSurfer also showed that hippocampal asymmetry increases with age (P = .0024) and that men had greater asymmetry than women (P = .03). CONCLUSIONS: There is a significant degree of hippocampal asymmetry in the population. The data provided will aid in the research, diagnosis, and treatment of temporal lobe epilepsy and other neurologic disease.

Validation of Non-Rigid Registration Between Functional and Anatomical Magnetic Resonance Brain Images

This paper presents a set of validation procedures for nonrigid registration of functional EPI to anatomical MRI brain images. Although various registration techniques have been developed and validated for high-resolution anatomical MRI images, due to a lack of quantitative and qualitative validation procedures, the use of nonrigid registration between functional EPI and anatomical MRI images has not yet been deployed in neuroimaging studies. In this paper, the performance of a robust formulation of a nonrigid registration technique is evaluated in a quantitative manner based on simulated data and is further evaluated in a quantitative and qualitative manner based on in vivo data as compared to the commonly used rigid and affine registration techniques in the neuroimaging software packages. The nonrigid registration technique is formulated as a second-order constrained optimization problem using a free-form deformation model and mutual information similarity measure. Bound constraints, resolution level and cross-validation issues have been discussed to show the degree of accuracy and effectiveness of the nonrigid registration technique. The analyses performed reveal that the nonrigid approach provides a more accurate registration, in particular when the functional regions of interest lie in regions distorted by susceptibility artifacts.

The utility of preoperative diffusion tensor imaging in the surgical management of brainstem cavernous malformations

OBJECT Resection of brainstem cavernous malformations (BSCMs) may reduce the risk of stepwise neurological deterioration secondary to hemorrhage, but the morbidity of surgery remains high. Diffusion tensor imaging (DTI) and diffusion tensor tractography (DTT) are neuroimaging techniques that may assist in the complex surgical planning necessary for these lesions. The authors evaluate the utility of preoperative DTI and DTT in the surgical management of BSCMs and their correlation with functional outcome. METHODS A retrospective review was conducted to identify patients who underwent resection of a BSCM between 2007 and 2012. All patients had preoperative DTI/DTT studies and a minimum of 6 months of clinical and radiographic follow-up. Five major fiber tracts were evaluated preoperatively using the DTI/DTT protocol: 1) corticospinal tract, 2) medial lemniscus and medial longitudinal fasciculus, 3) inferior cerebellar peduncle, 4) middle cerebellar peduncle, and 5) superior cerebellar peduncle. Scores were applied according to the degree of distortion seen, and the sum of scores was used for analysis. Functional outcomes were measured at hospital admission, discharge, and last clinic visit using modified Rankin Scale (mRS) scores. RESULTS Eleven patients who underwent resection of a BSCM and preoperative DTI were identified. The mean age at presentation was 49 years, with a male-to-female ratio of 1.75:1. Cranial nerve deficit was the most common presenting symptom (81.8%), followed by cerebellar signs or gait/balance difficulties (54.5%) and hemibody anesthesia (27.2%). The majority of the lesions were located within the pons (54.5%). The mean diameter and estimated volume of lesions were 1.21 cm and 1.93 cm(3), respectively. Using DTI and DTT, 9 patients (82%) were found to have involvement of 2 or more major fiber tracts; the corticospinal tract and medial lemniscus/medial longitudinal fasciculus were the most commonly affected. In 2 patients with BSCMs without pial presentation, DTI/DTT findings were important in the selection of the surgical approach. In 2 other patients, the results from preoperative DTI/DTT were important for selection of brainstem entry zones. All 11 patients underwent gross-total resection of their BSCMs. After a mean postoperative follow-up duration of 32.04 months, all 11 patients had excellent or good outcome (mRS Score 0-3) at the time of last outpatient clinic evaluation. DTI score did not correlate with long-term outcome. CONCLUSIONS Preoperative DTI and DTT should be considered in the resection of symptomatic BSCMs. These imaging studies may influence the selection of surgical approach or brainstem entry zones, especially in deep-seated lesions without pial or ependymal presentation. DTI/DTT findings may allow for more aggressive management of lesions previously considered surgically inaccessible. Preoperative DTI/DTT changes do not appear to correlate with functional postoperative outcome in long-term follow-up.

Automated quantification of white matter disease extent at 3 T: Comparison with volumetric readings

To develop and validate an algorithm to automatically quantify white matter hyperintensity (WMH) volume.

Evaluation of a practical visual MRI rating scale of brain white matter hyperintensities for clinicians based on largest lesion size regardless of location

BACKGROUND AND PURPOSE: Age-related white matter hyperintensities have prognostic implications, but no accepted clinical standard exists for their assessment. We propose a simple objective visual rating system by using 3T brain MR imaging. MATERIALS AND METHODS: MR imaging from 559 participants was processed by using an automated method to determine WMH volumes and evaluated with a new visual rating scale based on the single largest WMH lesion diameter regardless of location. The reproducibility of the visual system was assessed. The association of WMH visual scores and automated volumes was then compared with cognitive scores from the Montreal Cognitive Assessment, which was available for 510 participants. RESULTS: Inter-reader reproducibility was good for subsamples with both high (n = 52) and low (n = 40) prevalence of large automated WMH volumes (agreement of 67% and 87.5%, κ = 0.71 and 0.76, respectively). Correlation between increased WMH and cognitive deficit measurements was equal for our visual ratings and automated volumes (Spearman ρ = 0.118 and 0.109; P values = 0.008 and 0.014, respectively). The visual scale retained a significant association with MoCA score after adjusting for age, sex, and education (standardized β = −0.087, P = .042). CONCLUSIONS: We propose a simple visual WMH scoring system suitable for use as a baseline evaluation in clinical practice.

The Anatomic Basis of Vertebrogenic Pain in Lumbar Disc Extrusion: A Retrospective MR Study

Extruded lumbar intervertebral discs have traditionally been categorized as posterior or postero-lateral in location (PDE), although occasional reports have addressed extrusions extending anteriorly (ADE) and centrally (CDE). the clinical state of neurogenic radiating pain accompanying posterior extrusions with somatic nerve root compression is well defined, however the uncomplicated ADE and CDE may also be associated with a definite clinical syndrome, which includes both local and referred symptoms with much the same somatic distribution as that observed in true sciatica.