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To improve image quality and resolution of dynamic susceptibility contrast perfusion weighted imaging (DSC-PWI) by developing acquisition and reconstruction methods exploiting the temporal regularity property of DSC-PWI signal.A novel regularized reconstruction is proposed that recovers DSC-PWI series from interleaved segmented spiral k-space acquisition using higher order temporal smoothness (HOTS) properties of the DSC-PWI signal. The HOTS regularization is designed to tackle representational insufficiency of the standard first-order temporal regularizations for supporting higher accelerations. The higher accelerations allow for k-space coverage with shorter spiral interleaves resulting in improved acquisition point spread function, and acquisition of images at multiple TEs for more accurate DSC-PWI analysis.The methods were evaluated in simulated and in-vivo studies. HOTS regularization provided increasingly more accurate models for DSC-PWI than the standard first-order methods with either quadratic or robust norms at the expense of increased noise. HOTS DSC-PWI optimized for noise and accuracy demonstrated significant advantages over both spiral DSC-PWI without temporal regularization and traditional echo-planar DSC-PWI, improving resolution and mitigating image artifacts associated with long readout, including blurring and geometric distortions. In context of multi-echo DSC-PWI, the novel methods allowed ∼4.3× decrease of voxel volume, providing 2× number of TEs compared to the previously published results.Proposed HOTS reconstruction combined with dynamic spiral sampling represents a valid mechanism for improving image quality and resolution of DSC-PWI significantly beyond those available with established fast imaging techniques.

PURPOSE: T1- and T2-weighted (T1w, and T2w) imaging are essential sequences in routine clinical practice to detect and characterize a wide variety of pathologies. Many approaches have been proposed to obtain T1w and T2w contrast although many challenges still remain, including long acquisition time, and limitations that favor 2D imaging, etc. In this study, we propose a novel method for simultaneous T1w and T2w imaging using RF phase-modulated 3D gradient echo (GRE) imaging. THEORY: Configuration theory is used to derive closed form equations for the steady-state of RF phase-modulated GRE signal. These equations suggest the use of small RF phase increments to provide orthogonal signal contrast with T2w and T1w in the real and imaginary components, respectively. Background phase can be removed using a two-pass acquisition with opposite RF phase increments. METHODS: Simulation and phantom experiments were performed to validate our proposed method. Volunteer images of the brain and knee were acquired to demonstrate the clinical feasibility. The proposed method was compared with T1w and T2w fast spin-echo (FSE) imaging. RESULTS: The relative signal intensity of images acquired using the proposed method agreed closely with simulations and FSE imaging in phantoms. Images from volunteer imaging showed very similar contrast compared to conventional FSE imaging. CONCLUSION: RF phase-modulated GRE with small RF phase increments is an alternative method that provides simultaneous T1w and T2w contrast in short scan times with 3D volumetric coverage.

A comprehensive mapping of the structural and functional circuitry of the brain is a major unresolved problem in contemporary neuroimaging research. Diffusion-weighted and functional MRI have provided investigators with the capability to assess structural and functional connectivity in-vivo, driven primarily by methods of white matter tractography and resting-state fMRI, respectively. These techniques have paved the way for the construction of the functional and structural connectomes, which are quantitative representations of brain architecture as neural networks, comprised of nodes and edges. The connectomes, typically depicted as matrices or graphs, possess topological properties that inherently characterize the strength, efficiency, and organization of the connections between distinct brain regions. Graph theory, a general mathematical framework for analyzing networks, can be implemented to derive metrics from the connectomes that are sensitive to changes in brain connectivity associated with age, sex, cognitive function, and disease. These quantities can be assessed at either the global (whole brain) or local levels, allowing for the identification of distinct regional connectivity hubs and associated localized brain networks, which together serve crucial roles in establishing the structural and functional architecture of the brain. As a result, structural and functional connectomes have each been employed to study the brain circuitry underlying early brain development, neuroplasticity, developmental disorders, psychopathology, epilepsy, aging, neurodegenerative disorders, and traumatic brain injury. While these studies have yielded important insights into brain structure, function, and pathology, a precise description of the innate relationship between functional and structural networks across the brain remains unachieved. To date, connectome research has merely scratched the surface of potential clinical applications and related characterizations of brain-wide connectivity. Continued advances in diffusion and functional MRI acquisition, the delineation of functional and structural networks, and the quantification of neural network properties in specific brain regions, will be invaluable to future progress in neuroimaging science.

Purpose To characterize the visual pathway integrity of five glaucoma animal models using diffusion tensor imaging (DTI). Methods Two experimentally induced and three genetically determined models of glaucoma were evaluated. For inducible models, chronic IOP elevation was achieved via intracameral injection of microbeads or laser photocoagulation of the trabecular meshwork in adult rodent eyes. For genetic models, the DBA/2J mouse model of pigmentary glaucoma, the LTBP2 mutant feline model of congenital glaucoma, and the transgenic TBK1 mouse model of normotensive glaucoma were compared with their respective genetically matched healthy controls. DTI parameters, including fractional anisotropy, axial diffusivity, and radial diffusivity, were evaluated along the optic nerve and optic tract. Results Significantly elevated IOP relative to controls was observed in each animal model except for the transgenic TBK1 mice. Significantly lower fractional anisotropy and higher radial diffusivity were observed along the visual pathways of the microbead- and laser-induced rodent models, the DBA/2J mice, and the LTBP2-mutant cats compared with their respective healthy controls. The DBA/2J mice also exhibited lower axial diffusivity, which was not observed in the other models examined. No apparent DTI change was observed in the transgenic TBK1 mice compared with controls. Conclusions Chronic IOP elevation was accompanied by decreased fractional anisotropy and increased radial diffusivity along the optic nerve or optic tract, suggestive of disrupted microstructural integrity in both inducible and genetic glaucoma animal models. The effects on axial diffusivity differed between models, indicating that this DTI metric may represent different aspects of pathological changes over time and with severity.

Background The feeding of irradiated food to healthy adult cats results in widespread, noninflammatory demyelination of the central nervous system (CNS); a return to a normal diet results in endogenous remyelination with functional recovery. This recently discovered, reversible disease might provide a compelling clinical neuroimaging model system for the development and testing of myelin-directed MRI methods as well as future remyelination therapies. Purpose Identify the noninvasive imaging characteristics of this new disease model and determine whether it features measurable changes on conventional and quantitative MRI. Study type Pilot study. Animal model Ten adult cats at various stages of demyelinating disease induced by an irradiated diet (35-55 kGy), and during recovery following a return to a normal diet. Field strength/sequence Conventional (T2 -weighted) and quantitative (diffusion tensor, magnetization transfer) at 3T. Assessment MRI of the brain, optic nerves, and cervical spinal cord; a subset of diseased cats was euthanized for comparative histopathology. Statistical tests Descriptive statistics. Results Disease produced T2 prolongation, progressing from patchy to diffuse throughout most of the cerebral white matter (eventually involving U-fibers) and spinal cord (primarily dorsal columns, reminiscent of subacute combined degeneration but without evidence of B12 deficiency). Magnetization transfer parameters decreased by 50-53% in cerebral white matter and by 25-30% in optic nerves and spinal cord dorsal columns. Fractional diffusion anisotropy decreased by up to 20% in pyramidal tracts, primarily driven by increased radial diffusivity consistent with axon preservation. Histopathology showed scattered myelin vacuolation of major white matter tracts as well as many thin myelin sheaths consistent with remyelination in the recovery phase, which was detectable on magnetization transfer imaging. Data conclusion Feline irradiated diet-induced demyelination features noninvasively imageable and quantifiable demyelination and remyelination of the CNS. It is therefore a compelling clinical neuroimaging model system. Level of evidence 4 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:1304-1311.

Background: Functional Magnetic Resonance Imaging (fMRI) is a presurgical planning technique used to localize functional cortex so as to maximize resection of diseased tissue and avoid viable tissue. In this retrospective study, we examined differences in morbidity and mortality of brain tumor patients who received preoperative fMRI in comparison to those who did not. Methods: Brain tumor patients (n = 206) were selected from a retrospective review of neurosurgical case logs from 2001 to 2009 at the University of Wisconsin-Madison. Results: Univariate analysis showed improved mortality in the fMRI group and the fMRI + Electrical Cortical Stimulation Mapping (ECM) group compared to the No-fMRI group. Multivariate analyses showed improved mortality of the fMRI group and the fMRI + ECM group compared to the No-fMRI group, with age and tumor grade being the most significant influencers. Overall, the fMRI group showed survival benefits at 3 years; twice that of the No-fMRI group. Furthermore, patients with high-grade tumors showed significant survival benefits in the fMRI group, while patients with low-grade tumors did not (controlling for age and ECM). There was also a significant difference in the two groups with respect to morbidity, with patients receiving fMRI showing improved outcomes in the motor and language domains. Conclusions: This study analyzing a large retrospective series of brain tumor patients with and without the use of fMRI in the preoperative planning has resulted in improved mortality and morbidity outcomes with the use of fMRI. These results point to the importance of incorporating fMRI in presurgical planning in the clinical management of patients with brain tumors. Keywords: Brain mapping, Brain tumors, Functional neuroimaging

Multiple sclerosis (MS) is a common cause of neurologic disease in young adults that is primarily treated with disease-modifying therapies which target the immune and inflammatory responses. Promotion of remyelination has opened a new therapeutic avenue, but how best to determine efficacy of remyelinating drugs remains unresolved. Although prolongation and then shortening of visual evoked potential (VEP) latencies in optic neuritis in MS may identify demyelination and remyelination, this has not been directly confirmed. We recorded VEPs in a model in which there is complete demyelination of the optic nerve, with subsequent remyelination. We examined the optic nerves microscopically during active disease and recovery, and quantitated both demyelination and remyelination along the length of the nerves. Latencies of the main positive component of the control VEP demonstrated around 2-fold prolongation during active disease. VEP waveforms were nonrecordable in a few subjects or exhibited a broadened profile which precluded peak identification. As animals recovered neurologically, the VEP latencies decreased in association with complete remyelination of the optic nerve but remained prolonged relative to controls. Thus, it has been directly confirmed that VEP latencies reflect the myelin status of the optic nerve and will provide a surrogate marker in future remyelination clinical trials.

Background Hypertrophic olivary degeneration (HOD) occurs because of posterior fossa or brainstem lesions that disrupt the dentato-rubro-olivary tract, well known as the Guillain-Mollaret triangle. Clinical and radiologic hallmarks of this condition are palatal myoclonus and T2 hyperintensity of the inferior olivary complex on magnetic resonance imaging (MRI), respectively. Because symptomatic HOD can complicate the recovery of patients with posterior fossa or brainstem lesions, the purpose of this study is to evaluate clinical and imaging findings of patients with HOD. Methods Sixteen patients (8 female and 8 male) with a mean age of 40.7 years, (range, 5–83 years) years were included in this study based on clinical symptoms and MRI findings. Results We reviewed the clinical and imaging findings in 16 cases of HOD at our institution. Seven patients (43.7%) had posterior fossa tumors, 6 patients (37.5%) had cavernoma, 2 patients (12.5%) sustained traumatic brain injury, and only 1 patient (6.2%) had cerebellar infarction. Posterior fossa surgery was performed in 13 (81.2%) of these patients. HOD was detected a mean of 7.2 months (range, 0.5–18 months) after surgery or primary neurologic insult. Unilateral HOD was observed in 10 patients (62.5%), while bilateral HOD was observed in only 6 patients (37.5%). Seven patients (43.7%) were asymptomatic for HOD, whereas 5 patients (31.2%) had symptoms attributable to HOD. Two patients died because of primary tumors, although mean follow-up after detection of HOD on MRI was 52.2 months (range, 1–120 months) in the remaining 14 patients. In these cases, no change in clinical symptoms or imaging findings was detected during follow-up. Conclusions In this series, posterior fossa tumors and cavernomas were the most common causes of HOD. Although most of the patients with HOD remained asymptomatic, HOD complicated the course of recovery in almost one quarter of the patients included in this study. Neurosurgeons should be aware of HOD, which has characteristic clinical and imaging findings. In addition, HOD can complicate the recovery of patients with disruption to the dentato-rubro-olivary tract.

Many facets of an image acquisition workflow leave a digital footprint, making workflow analysis amenable to an informatics-based solution. This paper describes a detailed framework for analyzing workflow and uses acute stroke response timeliness in CT as a practical demonstration. We review methods for accessing the digital footprints resulting from common technologist/device interactions. This overview lays a foundation for obtaining data for workflow analysis. We demonstrate the method by analyzing CT imaging efficiency in the setting of acute stroke. We successfully used digital footprints of CT technologists to analyze their workflow. We presented an overview of other digital footprints including but not limited to contrast administration, patient positioning, billing, reformat creation, and scheduling. A framework for analyzing image acquisition workflow was presented. This framework is transferable to any modality, as the key steps of image acquisition, image reconstruction, image post processing, and image transfer to PACS are common to any imaging modality in diagnostic radiology.

Background: The hygiene hypothesis suggests that microbial replacement may be therapeutic in allergic and autoimmune diseases. Nevertheless, the results of helminth treatment, including in multiple sclerosis (MS), have been inconclusive. Objective: To assess safety and brain magnetic resonance imaging (MRI) activity in subjects with relapsing-remitting multiple sclerosis (RRMS) during oral administration of ova from the porcine whipworm, Trichuris suis (TSO). Methods: A total of 16 disease-modifying treatment (DMT) naive RRMS subjects were studied in a baseline versus treatment (BVT) controlled prospective study. MRI scans were performed during 5 months of screening-observation, 10 months of treatment, and 4 months of post-treatment surveillance. Results: No serious symptoms or adverse events occurred during treatment. For the cohort, there was a trend consistent with a 35% diminution in active lesions when observation MRIs were compared to treatment MRIs ( p = 0.08), and at the level of individuals, 12 of 16 subjects improved during TSO treatment. T regulatory lymphocytes were increased during TSO treatment. Conclusion: TSO is safe in RRMS subjects. Potentially favorable MRI outcomes and immunoregulatory changes were observed during TSO treatment; however, the magnitude of these effects was modest, and there was considerable variation among the responses of individual subjects.

Rationale and Objectives The study aimed to assess perceptions of reading room workflow and the impact separating image-interpretive and nonimage-interpretive task workflows can have on radiologist perceptions of workplace disruptions, workload, and overall satisfaction. Materials and Methods A 14-question survey instrument was developed to measure radiologist perceptions of workplace interruptions, satisfaction, and workload prior to and following implementation of separate image-interpretive and nonimage-interpretive reading room workflows. The results were collected over 2 weeks preceding the intervention and 2 weeks following the end of the intervention. The results were anonymized and analyzed using univariate analysis. Results A total of 18 people responded to the preintervention survey: 6 neuroradiology fellows and 12 attending neuroradiologists. Fifteen people who were then present for the 1-month intervention period responded to the postintervention survey. Perceptions of workplace disruptions, image interpretation, quality of trainee education, ability to perform nonimage-interpretive tasks, and quality of consultations ( P Conclusion Implementation of parallel dedicated image-interpretive and nonimage-interpretive workflows may improve markers of radiologist perceptions of workplace satisfaction.

PURPOSE: To develop and evaluate a retrospective method to minimize motion artifacts in structural MRI. MATERIALS AND METHODS: The motion-correction strategy was developed for three-dimensional radial data collection and demonstrated with MPnRAGE, a technique that acquires high-resolution volumetric magnetization-prepared rapid gradient-echo, or MPRAGE, images with multiple tissue contrasts. Forty-four pediatric participants (32 with autism spectrum disorder [mean age ± standard deviation, 13 years ± 3] and 12 age-matched control participants [mean age, 12 years ± 3]) were imaged without sedation. Images with and images without retrospective motion correction were scored by using a Likert scale (0–4 for unusable to excellent) by two experienced neuroradiologists. The Tenengrad metric (a reference-free measure of image sharpness) and statistical analyses were performed to determine the effects of performing retrospective motion correction. RESULTS: MPnRAGE T1-weighted images with retrospective motion correction were all judged to have good or excellent quality. In some cases, retrospective motion correction improved the image quality from unusable (Likert score of 0) to good (Likert score of 3). Overall, motion correction improved mean Likert scores from 3.0 to 3.8 and reduced standard deviations from 1.1 to 0.4. Image quality was significantly improved with motion correction (Mann-Whitney U test; P < .001). Intraclass correlation coefficients for absolute agreement of Tenengrad scores with reviewers 1 and 2 were 0.92 and 0.88 (P < .0005 for both), respectively. In no cases did the retrospective motion correction induce severe image degradation. CONCLUSION: Retrospective motion correction of MPnRAGE data were shown to be highly effective for consistently improving image quality of T1-weighted MRI in unsedated pediatric participants, while also enabling multiple tissue contrasts to be reconstructed for structural analysis. © RSNA, 2018 Online supplemental material is available for this article.

Background The feeding of irradiated food to healthy adult cats results in widespread, noninflammatory demyelination of the central nervous system (CNS); a return to a normal diet results in endogenous remyelination with functional recovery. This recently discovered, reversible disease might provide a compelling clinical neuroimaging model system for the development and testing of myelin‐directed MRI methods as well as future remyelination therapies. Purpose Identify the noninvasive imaging characteristics of this new disease model and determine whether it features measurable changes on conventional and quantitative MRI. Study Type Pilot study. Animal Model Ten adult cats at various stages of demyelinating disease induced by an irradiated diet (35–55 kGy), and during recovery following a return to a normal diet. Field Strength/Sequence Conventional (T2‐weighted) and quantitative (diffusion tensor, magnetization transfer) at 3T. Assessment MRI of the brain, optic nerves, and cervical spinal cord; a subset of diseased cats was euthanized for comparative histopathology. Statistical Tests Descriptive statistics. Results Disease produced T2 prolongation, progressing from patchy to diffuse throughout most of the cerebral white matter (eventually involving U‐fibers) and spinal cord (primarily dorsal columns, reminiscent of subacute combined degeneration but without evidence of B12 deficiency). Magnetization transfer parameters decreased by 50–53% in cerebral white matter and by 25–30% in optic nerves and spinal cord dorsal columns. Fractional diffusion anisotropy decreased by up to 20% in pyramidal tracts, primarily driven by increased radial diffusivity consistent with axon preservation. Histopathology showed scattered myelin vacuolation of major white matter tracts as well as many thin myelin sheaths consistent with remyelination in the recovery phase, which was detectable on magnetization transfer imaging. Data Conclusion Feline irradiated diet‐induced demyelination features noninvasively imageable and quantifiable demyelination and remyelination of the CNS. It is therefore a compelling clinical neuroimaging model system. Level of Evidence: 4 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:1304–1311.

Operative management of intrinsic brainstem lesions remains challenging despite advances in electrophysiological monitoring, neuroimaging, and neuroanatomical knowledge. Surgical intervention in this region requires detailed knowledge of adjacent critical white matter tracts, brainstem nuclei, brainstem vessels, and risks associated with each surgical approach. Our aim was to systematically verify internal anatomy associated with each brainstem safety entry zone (BSEZ) via neuroimaging modalities commonly used in pre-operative planning, namely high-resolution magnetic resonance imaging (MRI) and diffusion tensor tractography (DTT). Twelve BSEZs were simulated in eight, formalin-fixed, cadaveric brains. Specimens then underwent radiological investigation including T2-weighted imaging and DTT using 4.7 T MRI to verify internal anatomic relationships between simulated BSEZs and adjacent critical white matter tracts and nuclei. The distance between simulated BSEZs and pre-defined, adjacent critical structures was systemically recorded. Entry points and anatomic limits on the surface of the brainstem are described for each BSEZ, along with description of potential neurological sequelae if such limits are violated. With high-resolution imaging, we verified a maximal depth for each BSEZ. The relationship between proposed safe entry corridors and adjacent critical structures within the brainstem is quantified. In combination with tissue dissection, high-resolution MR diffusion tensor imaging allows the surgeon to develop a better understanding of the internal architecture of the brainstem, particularly as related to BSEZs, prior to surgical intervention. Through a careful study of such imaging and use of optimal surgical corridors, a more accurate and safe surgery of brainstem lesions may be achieved.

SUMMARY: The past decade has seen impressive advances in the types of neuroimaging information that can be acquired in patients with traumatic brain injury. However, despite this increase in information, understanding of the contribution of this information to prognostic accuracy and treatment pathways for patients is limited. Available techniques often allow us to infer the presence of microscopic changes indicative of alterations in physiology and function in brain tissue. However, because histologic confirmation is typically lacking, conclusions reached by using these techniques remain solely inferential in almost all cases. Hence, a need exists for validation of these techniques by using data from large population samples that are obtained in a uniform manner, analyzed according to well-accepted procedures, and correlated with closely monitored clinical outcomes. At present, many of these approaches remain confined to population-based research rather than diagnosis at an individual level, particularly with regard to traumatic brain injury that is mild or moderate in degree. A need and a priority exist for patient-centered tools that will allow advanced neuroimaging tools to be brought into clinical settings. One barrier to developing these tools is a lack of an age-, sex-, and comorbidities-stratified, sequence-specific, reference imaging data base that could provide a clear understanding of normal variations across populations. Such a data base would provide researchers and clinicians with the information necessary to develop computational tools for the patient-based interpretation of advanced neuroimaging studies in the clinical setting. The recent “Joint ASNR-ACR HII-ASFNR TBI Workshop: Bringing Advanced Neuroimaging for Traumatic Brain Injury into the Clinic” on May 23, 2014, in Montreal, Quebec, Canada, brought together neuroradiologists, neurologists, psychiatrists, neuropsychologists, neuroimaging scientists, members of the National Institute of Neurologic Disorders and Stroke, industry representatives, and other traumatic brain injury stakeholders to attempt to reach consensus on issues related to and develop consensus recommendations in terms of creating both a well-characterized normative data base of comprehensive imaging and ancillary data to serve as a reference for tools that will allow interpretation of advanced neuroimaging tests at an individual level of a patient with traumatic brain injury. The workshop involved discussions concerning the following: 1) designation of the policies and infrastructure needed for a normative data base, 2) principles for characterizing normal control subjects, and 3) standardizing research neuroimaging protocols for traumatic brain injury. The present article summarizes these recommendations and examines practical steps to achieve them.

BACKGROUND AND PURPOSE: Synthetic MR imaging enables reconstruction of various image contrasts from 1 scan, reducing scan times and potentially providing novel information. This study is the first large, prospective comparison of synthetic-versus-conventional MR imaging for routine neuroimaging. MATERIALS AND METHODS: A prospective multireader, multicase noninferiority trial of 1526 images read by 7 blinded neuroradiologists was performed with prospectively acquired synthetic and conventional brain MR imaging case-control pairs from 109 subjects (mean, 53.0 ± 18.5 years of age; range, 19–89 years of age) with neuroimaging indications. Each case included conventional T1- and T2-weighted, T1 and T2 FLAIR, and STIR and/or proton density and synthetic reconstructions from multiple-dynamic multiple-echo imaging. Images were randomized and independently assessed for diagnostic quality, morphologic legibility, radiologic findings indicative of diagnosis, and artifacts. RESULTS: Clinical MR imaging studies revealed 46 healthy and 63 pathologic cases. Overall diagnostic quality of synthetic MR images was noninferior to conventional imaging on a 5-level Likert scale (P < .001; mean synthetic-conventional, −0.335 ± 0.352; Δ = 0.5; lower limit of the 95% CI, −0.402). Legibility of synthetic and conventional morphology agreed in >95%, except in the posterior limb of the internal capsule for T1, T1 FLAIR, and proton-density views (all, >80%). Synthetic T2 FLAIR had more pronounced artifacts, including +24.1% of cases with flow artifacts and +17.6% cases with white noise artifacts. CONCLUSIONS: Overall synthetic MR imaging quality was similar to that of conventional proton-density, STIR, and T1- and T2-weighted contrast views across neurologic conditions. While artifacts were more common in synthetic T2 FLAIR, these were readily recognizable and did not mimic pathology but could necessitate additional conventional T2 FLAIR to confirm the diagnosis.

The potential utility of diffusion tensor (DT) imaging in clinical practice is broad, and new applications continue to evolve as technology advances. Clinical applications of DT imaging and tractography include tissue characterization, lesion localization, and mapping of white matter tracts. DT imaging metrics are sensitive to microstructural changes associated with central nervous system disease; however, further research is needed to enhance specificity so as to facilitate more widespread clinical application. Preoperative tract mapping, with either directionally encoded color maps or tractography, provides useful information to the neurosurgeon and has been shown to improve clinical outcomes.

Purpose To assess the impact of separate non-image interpretive task and image-interpretive task workflows in an academic neuroradiology practice. Materials and Methods A prospective, randomized, observational investigation of a centralized academic neuroradiology reading room was performed. The primary reading room fellow was observed over a one-month period using a time-and-motion methodology, recording frequency and duration of tasks performed. Tasks were categorized into separate image interpretive and non-image interpretive workflows. Post-intervention observation of the primary fellow was repeated following the implementation of a consult assistant responsible for non-image interpretive tasks. Pre- and post-intervention data were compared. Results Following separation of image-interpretive and non-image interpretive workflows, time spent on image-interpretive tasks by the primary fellow increased from 53.8% to 73.2% while non-image interpretive tasks decreased from 20.4% to 4.4%. Mean time duration of image interpretation nearly doubled, from 05:44 to 11:01 ( p = 0.002). Decreases in specific non-image interpretive tasks, including phone calls/paging (2.86/hr versus 0.80/hr), in-room consultations (1.36/hr versus 0.80/hr), and protocoling (0.99/hr versus 0.10/hr), were observed. The consult assistant experienced 29.4 task switching events per hour. Rates of specific non-image interpretive tasks for the CA were 6.41/hr for phone calls/paging, 3.60/hr for in-room consultations, and 3.83/hr for protocoling. Conclusion Separating responsibilities into NIT and IIT workflows substantially increased image interpretation time and decreased TSEs for the primary fellow. Consolidation of NITs into a separate workflow may allow for more efficient task completion.

A possibly causal relationship between multiple sclerosis and chronic cerebrospinal venous insufficiency has recently been hypothesized. Studies investigating chronic cerebrospinal venous insufficiency have reported conflicting results and few have employed multiple diagnostic imaging modalities across a large patient and control population. In this study, three complementary imaging modalities were used to investigate the chronic cerebrospinal venous insufficiency hypothesis in patients with multiple sclerosis and two age- and sex-matched control groups: healthy volunteers and patients with other neurological diseases. Strictly blinded Doppler ultrasound according to the original chronic cerebrospinal venous insufficiency hypothesis; four-dimensional flow magnetic resonance imaging of venous flow in the head, neck, and chest; and contrast-enhanced magnetic resonance venography for neck and chest venous luminography were acquired. An internal jugular vein stenosis evaluation was also performed across modalities. Percentage of subjects meeting ultrasound-based chronic cerebrospinal venous insufficiency criteria was small and similar between groups. In group-wise and pairwise testing, no four-dimensional flow magnetic resonance imaging variables were statistically significantly different, for any measurement location. In contrast-enhanced magnetic resonance venography of the internal jugular and azygos veins, no statistically significant differences were observed in stenosis scores between groups. These results represent compelling evidence against the chronic cerebrospinal venous insufficiency hypothesis in multiple sclerosis.

Neurodegenerative diseases comprise a broad swath of different neurologic diseases characterized by loss of neurons in the central nervous system. The most common neurodegenerative disease is Alzheimer disease, a dementing disease. Dementia is commonly understood as loss of function in at least two cognitive domains that is severe enough to affect daily activities in the social or occupational spheres. Elderly adults represent a significant and rapidly expanding proportion of the population. Some estimates state that by 2030 there will be 72 million individuals over the age of 65 years in the United States, constituting 19% of the population. The World Health Organization estimated in 2010 that there were 36.5 million people worldwide living with dementia, with the global cost for care being $604 billion per year. A new case of dementia is diagnosed approximately every 4 seconds. As the prevalence of many neurologic diseases increases with age, it can be difficult to differentiate between the effects of aging and those of prodromal age-related disease. Advances in neuroimaging have afforded significant insight into progressive neurodegenerative disorders and their mimics. Besides the improvements in structural imaging that have come about through thinner slices, 3-dimensional volumes, and higher spatial resolution, molecular and cellular imaging have made a big impact on how we look at the brain and its function. MR spectroscopy, diffusion tensor imaging, perfusion imaging, functional MRI, and PET scans have further increased our understanding of the pathophysiology of neurodegenerative disorders. Distinguishing between preventable diseases, potentially reversible diseases, and progressive, irreversible diseases is important in planning for a patient’s future medical, social, and economic spheres. Imaging of Neurodegenerative Disorders is a comprehensive, updated reference covering the latest techniques used in neuroimaging as well as the basic structural imaging that facilitates diagnosis of various neurodegenerative disorders. Because there never has been a dedicated textbook on the imaging of neurodegenerative diseases, the aim of this book is to cover each disease as it is currently understood and to show what it might look like using various imaging techniques. Imaging helps enormously in affirming suspicions, differentiating entities that have a clinical overlap, and charting the progression of neurodegenerative diseases. The book is organized into 16 parts with 41 chapters written by 83 contributors who have brought fresh insights and expertise that encompass many disease entities. They attempt to fill the gap of knowledge that exists in the imaging and understanding of neurodegenerative diseases. Chapters are arranged by specific diseases and cover their clinical features, pathologic characteristics, and imaging. Along with a brief discussion of each disease are the images themselves—superb in quality and quite illustrative—in addition to what tests to order, what to look for, what one expects to see for each disorder, and what new clinical and research modalities are available. This book is useful for radiologists, neuroradiologists, neurologists, neurosurgeons, and other internal or family medical physicians, as well as anyone seeking to understand neurodegenerative disorders through the lens of imaging techniques that are becoming increasingly sophisticated.

Magnetization transfer (MT) imaging quantitatively assesses cerebral white matter disease through its sensitivity to macromolecule-bound protons including those associated with myelin proteins and lipid bilayers. However, traditional MT contrast measured by the MT ratio (MTR) lacks pathologic specificity as demyelination, axon loss, inflammation and edema all impact MTR, directly and/or indirectly through multiple covariances among imaging parameters (particularly MTR with T(1)) and tissue features (e.g. axon loss with demyelination). In this study, more complex modeling of MT phenomena ("quantitative" MT or qMT) was applied to a less complex disease model (the myelin mutant shaking [sh] pup, featuring hypomyelination but neither inflammation nor axon loss) in order to eliminate the covariances on both sides of the MR-pathology "equation" and characterize these important relationships free from the usual confounds. qMT measurements were acquired longitudinally in 6 sh pups and 4 age-matched controls ranging from 3 to 21 months of age and compared with histology. The qMT parameter, bound pool fraction (f), was the most distinctive between diseased and control animals; both f and longitudinal relaxation rate R(1) tracked myelination with normal aging, whereas MTR did not--presumably owing to counterbalancing MT and R(1) effects. qMT imaging provides a more accurate and potentially more specific non-invasive tissue characterization.

Higher serum homocysteine (Hcy) levels in humans are associated with vascular pathology and greater risk for dementia, as well as lower global and regional volumes in frontal lobe and hippocampus. Calorie restriction (CR) in rhesus monkeys (Macaca mulatta) may confer neural protection against age- or Hcy-related vascular pathology. Hcy was collected proximal to a magnetic resonance imaging (MRI) acquisition in aged rhesus monkeys and regressed against volumetric and diffusion tensor imaging indexes using voxel-wise analyses. Higher Hcy was associated with lower white matter volume in pons and corpus callosum. Hcy was correlated with lower gray matter volume and density in prefrontal cortices and striatum. CR did not influence Hcy levels. However, control monkeys exhibited a strong negative correlation between Hcy and global gray matter, whereas no relationship was evident for the CR monkeys. Similar group differences were also seen across modalities in the splenium of the corpus callosum, prefrontal cortices, hippocampus, and somatosensory areas. The data suggest that CR may ameliorate the influence of Hcy on several important age-related parameters of parenchymal health.

A new time-efficient and accurate technique for simultaneous mapping of T(1) and B(1) is proposed based on a combination of the actual flip angle (FA) imaging and variable FA methods. Variable FA-actual FA imaging utilizes a single actual FA imaging and one or more spoiled gradient-echo acquisitions with a simultaneous nonlinear fitting procedure to yield accurate T(1)/B(1) maps. The advantage of variable FA-actual FA imaging is high accuracy at either short T(1) times or long repetition times in the actual FA imaging sequence. Simulations show this method is accurate to 0.03% in FA and 0.07% in T(1) for ratios of repetition time to T1 time over the range of 0.01-0.45. We show for the case of brain imaging that it is sufficient to use only one small FA spoiled gradient-echo acquisition, which results in reduced spoiling requirements and a significant scan time reduction compared to the original variable FA method. In vivo validation yielded high-quality 3D T(1) maps and T(1) measurements within 10% of previously published values and within a clinically acceptable scan time. The variable FA-actual FA imaging method will increase the accuracy and clinical feasibility of many quantitative MRI methods requiring T(1)/B(1) mapping such as dynamic contrast enhanced perfusion and quantitative magnetization transfer imaging.

The image contrast in magnetic resonance imaging (MRI) is highly sensitive to several mechanisms that are modulated by the properties of the tissue environment. The degree and type of contrast weighting may be viewed as image filters that accentuate specific tissue properties. Maps of quantitative measures of these mechanisms, akin to microstructural/environmental-specific tissue stains, may be generated to characterize the MRI and physiological properties of biological tissues. In this article, three quantitative MRI (qMRI) methods for characterizing white matter (WM) microstructural properties are reviewed. All of these measures measure complementary aspects of how water interacts with the tissue environment. Diffusion MRI, including diffusion tensor imaging, characterizes the diffusion of water in the tissues and is sensitive to the microstructural density, spacing, and orientational organization of tissue membranes, including myelin. Magnetization transfer imaging characterizes the amount and degree of magnetization exchange between free water and macromolecules like proteins found in the myelin bilayers. Relaxometry measures the MRI relaxation constants T1 and T2, which in WM have a component associated with the water trapped in the myelin bilayers. The conduction of signals between distant brain regions occurs primarily through myelinated WM tracts; thus, these methods are potential indicators of pathology and structural connectivity in the brain. This article provides an overview of the qMRI stain mechanisms, acquisition and analysis strategies, and applications for these qMRI stains.

Systemic levels of proinflammatory cytokines such as interleukin-6 (IL-6) increase in old age and may contribute to neural atrophy in humans. We investigated IL-6 associations with age in T1-weighted segments and microstructural diffusion indices using MRI in aged rhesus monkeys (Macaca mulatta). Further, we determined if long-term 30% calorie restriction (CR) reduced IL-6 and attenuated its association with lower tissue volume and density. Voxel-based morphometry (VBM) and diffusion-weighted voxelwise analyses were conducted. IL-6 was associated with less global gray and white matter (GM and WM), as well as smaller parietal and temporal GM volumes. Lower fractional anisotropy (FA) was associated with higher IL-6 levels along the corpus callosum and various cortical and subcortical tracts. Higher IL-6 concentrations across subjects were also associated with increased mean diffusivity (MD) throughout many brain regions, particularly in corpus callosum, cingulum, and parietal, frontal, and prefrontal areas. CR monkeys had significantly lower IL-6 and less associated atrophy. An IL-6xCR interaction across modalities also indicated that CR mitigated IL-6 related changes in several brain regions compared to controls. Peripheral IL-6 levels were correlated with atrophy in regions sensitive to aging, and this relationship was decreased by CR.

Caloric restriction (CR) reduces the pathological effects of aging and extends the lifespan in many species, including nonhuman primates, although the effect on the brain is less well characterized. We used two common indicators of aging, motor performance speed and brain iron deposition measuredin vivousing magnetic resonance imaging, to determine the potential effect of CR on elderly rhesus macaques eating restricted (n= 24, 13 males, 11 females) and standard (n= 17, 8 males, 9 females) diets. Both the CR and control monkeys showed age-related increases in iron concentrations in globus pallidus (GP) and substantia nigra (SN), although the CR group had significantly less iron deposition in the GP, SN, red nucleus, and temporal cortex. A Diet × Age interaction revealed that CR modified age-related brain changes, evidenced as attenuation in the rate of iron accumulation in basal ganglia and parietal, temporal, and perirhinal cortex. Additionally, control monkeys had significantly slower fine motor performance on the Movement Assessment Panel, which was negatively correlated with iron accumulation in left SN and parietal lobe, although CR animals did not show this relationship. Our observations suggest that the CR-induced benefit of reduced iron deposition and preserved motor function may indicate neural protection similar to effects described previously in aging rodent and primate species.

BACKGROUND: Using diffusion tensor imaging (DTI) in neurosurgical planning allows identification of white matter tracts and has been associated with a reduction in postoperative functional deficits. OBJECTIVE: This study explores the relationship between the lesion-to-tract distance (LTD) and postoperative morbidity and mortality in patients with brain tumors in order to evaluate the role of DTI in predicting postoperative outcomes. METHODS: Adult patients with brain tumors (n = 60) underwent preoperative DTI. Three major white matter pathways (superior longitudinal fasciculi [SLF], cingulum, and corticospinal tract) were identified using DTI images, and the shortest LTD was measured for each tract. Postoperative morbidity and mortality information was collected from electronic medical records. RESULTS: The ipsilesional corticospinal tract LTD and left SLF LTD were significantly associated with the occurrence rate of total postoperative motor (P = .018) and language (P

The diffusion properties of biological tissues are independent of magnetic field strength. Field strength, however, does affect the signal-to-noise ratio (SNR) and artifacts of diffusion-weighted (DW) images, which ultimately will influence the quantitative and spatial accuracy of diffusion tensor imaging (DTI). In this article, the effects of field strength on DTI are reviewed. The effects of parallel imaging also are discussed. A small study comparing DTI measurements both as a function of field strength (1.5 T and 3.0 T) and parallel imaging was performed. Overall, the SNR of the DW images roughly doubled going from 1.5 T to 3.0 T, and there was a relatively small decrease in SNR (15% to 30%) when parallel imaging was used. The increased SNR at 3.0 T resulted in smaller variances in the estimated mean diffusivities and fractional anisotropies. As expected, the amount of echo-planar image distortion roughly doubled going from 1.5 T to 3.0 T, but was reduced by 50% when using parallel imaging. In summary, DTI studies at 3.0 T using parallel imaging will provide significantly improved DTI measurements relative to studies at 1.5 T.

Background and purpose Functional magnetic resonance imaging (fMRI) is a non-invasive pre-surgical tool used to assess localization and lateralization of language function in brain tumor and vascular lesion patients in order to guide neurosurgeons as they devise a surgical approach to treat these lesions. We investigated the effect of varying the statistical thresholds as well as the type of language tasks on functional activation patterns and language lateralization. We hypothesized that language lateralization indices (LIs) would be threshold- and task-dependent. Materials and methods Imaging data were collected from brain tumor patients (n = 67, average age 48 years) and vascular lesion patients (n = 25, average age 43 years) who received pre-operative fMRI scanning. Both patient groups performed expressive (antonym and/or letter-word generation) and receptive (tumor patients performed text-reading; vascular lesion patients performed text-listening) language tasks. A control group (n = 25, average age 45 years) performed the letter-word generation task. Results Brain tumor patients showed left-lateralization during the antonym-word generation and text-reading tasks at high threshold values and bilateral activation during the letter-word generation task, irrespective of the threshold values. Vascular lesion patients showed left-lateralization during the antonym and letter-word generation, and text-listening tasks at high threshold values. Conclusion Our results suggest that the type of task and the applied statistical threshold influence LI and that the threshold effects on LI may be task-specific. Thus identifying critical functional regions and computing LIs should be conducted on an individual subject basis, using a continuum of threshold values with different tasks to provide the most accurate information for surgical planning to minimize post-operative language deficits., Highlights • FMRI calculation of language lateralization is valuable for pre-surgical planning. • Both applied statistical thresholds and task specificity affect lateralization index. • A continuum of threshold values provides a dynamic range for presurgical planning. • Reorganization of language function is dependent on brain pathology. • Identification of critical language areas will optimize lesion resection (e.g. tumor).

Caffeine is the most widely used stimulant in the world. The stimulant effects of caffeine are mediated through its antagonistic properties on neuronal adenosine receptors. In addition, caffeine blocks neurovascular adenosine receptors and decreases cerebral perfusion. Although the effects of caffeine on blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging measures are extremely important, there are few studies addressing this issue in the literature. Because chronic caffeine use causes an upregulation of adenosine receptors, the differential effects of caffeine in low and high users is of particular interest. The present study was designed to test the hypothesis that caffeine has differential effects on the BOLD signal in high and low caffeine users. We demonstrated that the BOLD signal change in visual cortex was significantly greater in high users than in low users in the presence of caffeine. In addition, the magnitude of the BOLD signal was significantly correlated with caffeine consumption. We propose that the outcome observed here was due to an upregulation of adenosine receptors in high users, resulting in differential contributions of the neural and vascular effects of adenosine in the two study populations.

The reproducibility of quantitative cerebral blood flow (CBF) measurements using MRI with arterial spin labeling and acetazolamide challenge was assessed in 12 normal subjects, each undergoing the identical experimental procedure on two separate days. CBF was measured on a 1.5T scanner using a flow-sensitive alternating inversion recovery (FAIR) pulse sequence, performed both at baseline and 12 min after intravenous administration of acetazolamide. T(1) was measured in conjunction with the FAIR scan in order to calculate quantitative CBF. The CBF maps were segmented to separate gray matter (GM) from white matter (WM) for region-of-interest (ROI) analyses. Post- acetazolamide CBF values (ml/100 g/min, mean +/- SD) of 87.5 +/- 12.5 (GM) and 46.1 +/- 10.8 (WM) represented percent increases of 37.7% +/- 24.4% (GM) and 40.1% +/- 24.4% (WM). Day-to-day differences in baseline CBF were -1.7 +/- 6.9 (GM) and -1.4 +/- 4.7 (WM) or, relative to the mean CBF over both days for each subject, -2.5% +/- 11.7% (GM) and -3.8% +/- 13.6% (WM) Day- to-day differences in absolute post-ACZ CBF increase were -2.5 +/- 6.8 (GM) and 2.7 +/- 9.4 (WM) or, relative to the mean CBF increase over both days for each subject, -4.7% +/- 13.3% (GM) and 9.1% +/- 26.2% (WM). Thus, FAIR- based CBF measurements show satisfactory reproducibility from day to day, but with sufficient variation to warrant caution in interpreting longitudinal data. The hemispheric asymmetry of baseline CBF and post-acetazolamide CBF increases varied within a narrower range and should be sensitive to small changes related to disease or treatment.