Analysis of magnetic resonance spectroscopy relative metabolite ratios in mild traumatic brain injury and normative controls.

INTRODUCTION: We evaluated magnetic resonance spectroscopy (MRS) in United States military personnel with persistent symptoms after mild traumatic brain injury (mTBI), comparing over time two groups randomized to receive hyperbaric oxygen or sham chamber sessions and a third group of normative controls. METHODS: Active-duty or veteran military personnel and normative controls underwent MRS outcome measures at baseline, 13 weeks (mTBI group only), and six months. Participants received 3.0 Tesla brain MRS for analysis of water-suppressed two-dimensional (2D) multivoxel 1H-MRS of the brain using point resolved spectroscopy (PRESS) with volume selection localized above the lateral ventricles and within the brain parenchyma, of which one voxel was chosen in each hemisphere without artifact. Script-based automatic data processing was used to assess N-acetylaspartate (NAA), creatine (Cr), and choline (Cho). Metabolite ratios for white matter were then calculated for NAA/Cr (Area), Cho/Cr (Area), and Cho/NAA (Area). These ratios were compared using standard analysis methodology. RESULTS: There were no observable differences between participants with mTBI and normative controls nor any observable changes over time in the NAA/Cr (area), Cho/Cr (area), and Cho/NAA (area) ratios. Similarly, the control and injured participants were indistinguishable. DISCUSSION: While participants with mild TBI showed no difference in MRS compared to normative controls, our results are limited by the few voxels chosen and potentially by less sensitive MRS markers.

Quantitative analysis tool for clinical functional MRI in mild traumatic brain injury.

Functional magnetic resonance imaging (fMRI) has been available commercially for clinical diagnostic use for many years. However, both clinical interpretation of fMRI by a neuroradiologist and quantitative analysis of fMRI data can require significant personnel resources that exceed reimbursement. In this report, a fully automated computer-based quantification methodology (Enumerated Auditory Response, EAR) has been developed to provide an auditory fMRI assessment of patients who have suffered a mild traumatic brain injury. Fifty-five study participants with interpretable auditory fMRI sequence data were assessed by EAR analysis, as well as both clinical radiologist fMRI interpretation and voxelwise general linear model (GLM) analysis. Comparison between the clinical interpretation and the two computer analysis methods resulted in 67% concordance (identical), 32% nearconcordance (one level difference), and 1% discordant. Comparison between the clinical computer-based quantification (EAR) and GLM analysis yielded significant correlations in right and left ear responses (p⟨0.05) for the full subject group. Automated fMRI quantification analysis equivalent to EAR might be appropriate for both future research projects with constrained resources, as well as possible routine clinical use.

Validation of volumetric and single-slice MRI adipose analysis using a novel fully automated segmentation method.

PURPOSE: To validate a fully automated adipose segmentation method with magnetic resonance imaging (MRI) fat fraction abdominal imaging. We hypothesized that this method is suitable for segmentation of subcutaneous adipose tissue (SAT) and intra-abdominal adipose tissue (IAAT) in a wide population range, easy to use, works with a variety of hardware setups, and is highly repeatable. MATERIALS AND METHODS: Analysis was performed comparing precision and analysis time of manual and automated segmentation of single-slice imaging, and volumetric imaging (78-88 slices). Volumetric and single-slice data were acquired in a variety of cohorts (body mass index [BMI] 15.6-41.76) including healthy adult volunteers, adolescent volunteers, and subjects with nonalcoholic fatty liver disease and lipodystrophies. A subset of healthy volunteers was analyzed for repeatability in the measurements. RESULTS: The fully automated segmentation was found to have excellent agreement with manual segmentation with no substantial bias across all study cohorts. Repeatability tests showed a mean coefficient of variation of 1.2 ± 0.6% for SAT, and 2.7 ± 2.2% for IAAT. Analysis with automated segmentation was rapid, requiring 2 seconds per slice compared with 8 minutes per slice with manual segmentation. CONCLUSION: We demonstrate the ability to accurately and rapidly segment regional adipose tissue using fat fraction maps across a wide population range, with varying hardware setups and acquisition methods.

Comparison of brown and white adipose tissues in infants and children with chemical-shift-encoded water-fat MRI.

PURPOSE: To compare fat-signal fractions (FFs) and T2* values between brown (BAT) and white (WAT) adipose tissue located within the supraclavicular fossa and subcutaneous depots, respectively. MATERIALS AND METHODS: Twelve infants and 39 children were studied. Children were divided into lean and overweight/obese subgroups. Chemical-shift-encoded water-fat magnetic resonance imaging (MRI) was used to quantify FFs and T2* metrics in the supraclavicular and adjacent subcutaneous adipose tissue depots. Linear regression and t-tests were performed. RESULTS: Infants had lower supraclavicular FFs than children (P < 0.01) but T2* values were similar (P = 0.5). Lean children exhibited lower supraclavicular FFs and T2* values than overweight children (P < 0.01). In each individual infant and child, supraclavicular FFs were consistently lower than adjacent subcutaneous FFs. Supraclavicular T2* values were consistently lower than subcutaneous T2* values in children, but not in infants. FFs in both depots were positively correlated with age and weight in infants (P < 0.01). In children, they were correlated with weight and body mass index (BMI) (P < 0.01), but not age. Correlations between T2* and anthropometric variables existed in children (P < 0.01), but were absent in infants. CONCLUSION: Cross-sectional comparisons suggest variations in FF and T2* values in the supraclavicular and subcutaneous depots of infants and children, which are potentially indicative of physiological differences in adipose tissue fat content, amount, and metabolic activity.

Characterization of human brown adipose tissue by chemical-shift water-fat MRI.

OBJECTIVE: The purpose of this study was to characterize human brown adipose tissue (BAT) with chemical-shift water-fat MRI and to determine whether trends and differences in fat-signal fractions and T2(*) relaxation times between BAT and white adipose tissue (WAT) are consistently observed postmortem and in vivo in infants, adolescents, and adults. MATERIALS AND METHODS: A postmortem body and eight patients were studied. A six-echo spoiled gradient-echo chemical-shift water-fat MRI sequence was performed at 3 T to jointly quantify fat-signal fraction and T2(*) in interscapular-supraclavicular BAT and subcutaneous WAT. To confirm BAT identity, biopsy and histology served as the reference in the postmortem study and PET/CT was used in five of the eight patients who required examination for medical care. RESULTS: Fat-signal fractions and T2(*) times were lower in BAT than in WAT in the postmortem example and in seven of eight patients. With the exception of one case, nominal comparisons between brown and white adipose tissues were statistically significant (p < 0.05). Between subjects, a large range of fat-signal fraction values was observed in BAT but not in WAT. CONCLUSION: We have shown that fat-signal fractions and T2(*) values jointly derived from chemical-shift water-fat MRI are lower in BAT than in WAT likely because of differences in cellular structures, triglyceride content, and vascularization. The two metrics can serve as complementary biomarkers in the detection of BAT.

Magnetic resonance venography and genetics of a female patient with pelvic venous thrombosis.

A femoral vein thrombosis, originally diagnosed with conventional ultrasound, was fully elucidated and monitored utilizing serial high-resolution magnetic resonance venography in a 19-year-old female with a family history of venous thromboembolism. Genetic testing revealed she was heterozygous for a F5 gene mutation, an abnormality that predisposes carriers to factor V Leiden thrombophilia. An additional risk factor included use of oral contraceptive pills. Subsequent testing of her family uncovered other carriers of the mutation, allowing for the implementation of preventive measures for the entire family. Although magnetic resonance venography has not yet proven to be a cost-effective method for monitoring clot resolution, the case presented here encourages further research on the clinical utility and cost-benefit of utilizing this technology for monitoring venous thrombosis and for clinical management purposes.

Whole-spine dynamic magnetic resonance study of contortionists: anatomy and pathology.

OBJECT: Whole-spine magnetic resonance (MR) images were obtained using a cylindrical 3-T MR imaging system in 5 contortionists to assess the pathological changes possibly associated with the practice of contortion. Whole-spine dynamic MR images were obtained using a 1-T open MR imaging system in 2 of these contortionists with the purpose of defining the range of motion (ROM) achieved during extreme contortion. The range of spinal motion in this unique population was then quantified. METHODS: The study included 5 female contortionists 20-49 years of age. Imaging was performed using open 1-T and cylindrical 3-T high-field MR imaging systems. Data were viewed and analyzed with DICOM-compliant tools. Real-time, dynamic, and standard MR imaging allowed for quantification of the contortionists' ROM. RESULTS: There was a difference of 238 degrees between full spinal extension and full flexion. Three of the 5 contortionists had 4 anterosuperior limbus vertebrae at T-11 and the upper lumbar levels. CONCLUSIONS: Whole-spine dynamic MR imaging is a valuable tool for the evaluation of the extreme ROM in contortionists, allowing for the quantification of extreme mobility. The limbus fractures present in 3 of the 5 contortionists is postulated to be due to avulsion on hyperextension. Future research may open the use of whole-spine dynamic MR imaging into such areas as pain management and traumatic spinal injuries.

MRI detection of brown adipose tissue with low fat content in newborns with hypothermia.

PURPOSE: To report the observation of brown adipose tissue (BAT) with low fat content in neonates with hypoxic-ischemic encephalopathy (HIE) after they have undergone hypothermia therapy. MATERIALS AND METHODS: The local ethics committee approved the imaging study. Ten HIE neonates (3 males, 7 females, age range: 2-3days) were studied on a 3-T MRI system using a low-flip-angle (3°) six-echo proton-density-weighted chemical-shift-encoded water-fat pulse sequence. Fat-signal fraction (FF) measurements of supraclavicular and interscapular (nape) BAT and adjacent subcutaneous white adipose tissues (WAT) were compared to those from five non-HIE neonates, two recruited for the present investigation and three from a previous study. RESULTS: In HIE neonates, the FF range for the supraclavicular, interscapular, and subcutaneous regions was 10.3%-29.9%, 28.0%-57.9%, and 62.6%-88.0%, respectively. In non-HIE neonates, the values were 23.7%-42.2% (p=0.01), 45.4%-59.5% (p=0.06), and 67.8%-86.3% (p=0.38), respectively. On an individual basis, supraclavicular BAT FF was consistently the lowest, interscapular BAT values were higher, and subcutaneous WAT values were the highest (p<0.01). CONCLUSION: We speculate that hypothermia therapy in HIE neonates likely promotes BAT-mediated non-shivering thermogenesis, which subsequently leads to a depletion of the tissue's intracellular fat stores. We believe that this is consequently reflected in lower FF values, particularly in the supraclavicular BAT depot, in contrast to non-HIE neonates.

Sagittal whole-spine magnetic resonance imaging in 750 consecutive outpatients: accurate determination of the number of lumbar vertebral bodies.

OBJECT: When the number of lumbar and sacral vertebrae is being assessed, variations from typical lumbosacral anatomy may confuse the practitioner, potentially leading to significant clinical errors. In this study, the authors describe the statistical variation in lumbar spine anatomy in an outpatient imaging setting, evaluate the potential implications for clinical practice based on the variation in the number of lumbar-type vertebrae identified, and recommend a method for rapidly determining the number of lumbar spine vertebral bodies (VBs) in outpatients referred for lumbar spine MR imaging. METHODS: A total of 762 patients (male and female) who presented with low back-related medical conditions underwent whole-spine MR imaging in an outpatient setting. RESULTS: The high-speed whole-spine evaluation was successful for determining the number of lumbar-type VBs in 750 (98%) of 762 consecutive patients. The sagittal whole-spine 3-T MR imaging system images obtained between the beginning of January 2005 and the end of February 2007 were reviewed. The VBs were counted successively from the level of C-2 inferiorly to the intervertebral disc below the most inferior lumbar-type VB. Numbers of disc herniations were also evaluated in the context of the number of VBs. CONCLUSIONS: One in 5 of these outpatients did not have 5 lumbar-type vertebrae: 14.5% had 6; 5.3% had 4; and 1 (0.13%) had the rare finding of 3 lumbar-type vertebrae. Two-thirds of the individuals with 6 lumbar-type vertebrae were male and two-thirds of the individuals with 4 lumbar-type vertebrae were female. Sagittal whole-spine MR imaging can be performed rapidly and efficiently in the majority of patients (98%), and provides improved accuracy for the determination of the number of lumbar-type VBs. A supplementary coronal MR, Ferguson view radiograph or intraoperative fluoroscopic determination for the presence of lumbosacral transitional vertebrae may add additional information when indicated for clinical treatment or surgical planning.

Traumatic brain injury: a review and high-field MRI findings in 100 unarmed combatants using a literature-based checklist approach.

This study reviewed the literature for the extent of neuroimaging findings in boxers, indicative of traumatic brain injury (TBI) as identified in magnetic resonance imaging (MRI). The study then utilized a systematic checklist approach to assess 100 unselected consecutive 1.5- and 3.0-Tesla MRI examinations of professional unarmed combatants to determine the extent of identifiable TBI findings. The percentage of positive findings and the localization of lesions were quantified using the checklist that included the MRI findings previously reported in the medical literature. Seventy-six percent of the unarmed combatants had at least one finding that may be associated with TBI: 59% hippocampal atrophy, 43% cavum septum pellucidum, 32% dilated perivascular spaces, 29% diffuse axonal injury, 24% cerebral atrophy, 19% increased lateral ventricular size, 14% pituitary gland atrophy, 5% arachnoid cysts, and 2% had contusions. Statistical relationships were found between number of bouts and lateral ventricular size (tau-b = 0.149, p = 0.0489), with years of fighting correlating with the presence of dilated perivascular spaces (tau-b = 0.167, p = 0.0388) and diffuse axonal injury (tau-b = 0.287, p = 0.0013) findings. The improved resolution and increased signal-to-noise ratio on 1.5- and 3.0-Tesla high-field MRI systems defines the range of pathological variations that may occur in professional unarmed combatants. Additionally, the use of a systematic checklist approach insures evaluation for all possible TBI-related abnormalities. This knowledge can be used to anticipate the regions of potential brain pathology for radiologists and emergency medicine physicians, and provides important information for evaluating unarmed combatants relative to their safety and long-term neurocognitive outcome.