MR Technology Research Articles

TU‐F‐BRB‐00: MRI‐Based Motion Management for RT

The current clinical standard of organ respiratory imaging, 4D‐CT, is fundamentally limited by poor soft‐tissue contrast and imaging dose. These limitations are potential barriers to beneficial “4D” radiotherapy methods which optimize the target and OAR dose‐volume considering breathing motion but rely on a robust motion characterization. Conversely, MRI imparts no known radiation risk and has excellent soft‐tissue contrast. MRI‐based motion management is therefore highly desirable and holds great promise to improve radiotherapy of moving cancers, particularly in the abdomen. Over the past decade, MRI techniques have improved significantly, making MR‐based motion management clinically feasible. For example, cine MRI has high temporal resolution up to 10 f/s and has been used to track and/or characterize tumor motion, study correlation between external and internal motions. New MR technologies, such as 4D‐MRI and MRI hybrid treatment machines (i.e. MR‐linac or MR‐Co60), have been recently developed. These technologies can lead to more accurate target volume determination and more precise radiation dose delivery via direct tumor gating or tracking. Despite all these promises, great challenges exist and the achievable clinical benefit of MRI‐based tumor motion management has yet to be fully explored, much less realized. In this proposal, we will review novel MR‐based motion management methods and technologies, the state‐of‐the‐art concerning MRI development and clinical application and the barriers to more widespread adoption.Learning Objectives: Discuss the need of MR‐based motion management for improving patient care in radiotherapy. Understand MR techniques for motion imaging and tumor motion characterization. Understand the current state of the art and future steps for clinical integration. Henry Ford Health System holds research agreements with Philips Healthcare. Research sponsored in part by a Henry Ford Health System Internal Mentored Grant.

TU‐PIS‐Exhibit Hall‐2: How to Move Beyond Dose Monitoring to Imaging Performance Utilization

The current clinical standard of organ respiratory imaging, 4D‐CT, is fundamentally limited by poor soft‐tissue contrast and imaging dose. These limitations are potential barriers to beneficial “4D” radiotherapy methods which optimize the target and OAR dose‐volume considering breathing motion but rely on a robust motion characterization. Conversely, MRI imparts no known radiation risk and has excellent soft‐tissue contrast. MRI‐based motion management is therefore highly desirable and holds great promise to improve radiotherapy of moving cancers, particularly in the abdomen. Over the past decade, MRI techniques have improved significantly, making MR‐based motion management clinically feasible. For example, cine MRI has high temporal resolution up to 10 f/s and has been used to track and/or characterize tumor motion, study correlation between external and internal motions. New MR technologies, such as 4D‐MRI and MRI hybrid treatment machines (i.e. MR‐linac or MR‐Co60), have been recently developed. These technologies can lead to more accurate target volume determination and more precise radiation dose delivery via direct tumor gating or tracking. Despite all these promises, great challenges exist and the achievable clinical benefit of MRI‐based tumor motion management has yet to be fully explored, much less realized. In this proposal, we will review novel MR‐based motion management methods and technologies, the state‐of‐the‐art concerning MRI development and clinical application and the barriers to more widespread adoption.Learning Objectives: Discuss the need of MR‐based motion management for improving patient care in radiotherapy. Understand MR techniques for motion imaging and tumor motion characterization. Understand the current state of the art and future steps for clinical integration. Henry Ford Health System holds research agreements with Philips Healthcare. Research sponsored in part by a Henry Ford Health System Internal Mentored Grant.

Hybrid PET/MR imaging: physics and technical considerations.

In just over a decade, hybrid imaging with FDG PET/CT has become a standard bearer in the management of cancer patients. An exquisitely sensitive whole-body imaging modality, it combines the ability to detect subtle biologic changes with FDG PET and the anatomic information offered by CT scans. With advances in MR technology and advent of novel targeted PET radiotracers, hybrid PET/MRI is an evolutionary technique that is poised to revolutionize hybrid imaging. It offers unparalleled spatial resolution and functional multi-parametric data combined with biologic information in the non-invasive detection and characterization of diseases, without the deleterious effects of ionizing radiation. This article reviews the basic principles of FDG PET and MR imaging, discusses the salient technical developments of hybrid PET/MR systems, and provides an introduction to FDG PET/MR image acquisition.

Visualization of synaptic domains in the Drosophila brain by magnetic resonance microscopy at 10 micron isotropic resolution.

Understanding the complex architecture, connectivity, and pathology of the human brain is a major application of magnetic resonance imaging (MRI). However, the cellular basis of MR signal is still poorly understood. The advent of MR microscopy (MRM) enables imaging biological samples at cellular resolution, helping to interpret the nature of MR signal at the cellular level. In this regard, the small Drosophila brain can reveal key aspects of MR signal through the visualization of complex, intact neuronal structures in their native spatial arrangement. Applying state-of-the-art MR technology, we imaged fixed Drosophila heads at 10 μm isotropic resolution by two endogenously contrasted MRM sequences. The improved MRM sensitivity described here delivered the highest 3D resolution of an intact animal head reported so far. 3D fast low angle shot (FLASH) revealed strong signal in most internal tissues, particularly in the brain cortex, which contains the cell bodies of neurons and glia. Remarkably, 3D diffusion weighted imaging (DWI) delivered unprecedented contrast within the modular brain neuropil, revealing hyperintense signal in synapse-rich microdomains. Thus, the complex Drosophila brain revealed unknown features of FLASH and DWI with potential applications in characterizing the structure and pathology of the mammalian brain.

MR image intensity inhomogeneity correction

MR technology is one of the best and most reliable ways of studying the brain. Its main drawback is the so-called intensity inhomogeneity or bias field which impairs the visual inspection and the medical proceedings for diagnosis and strongly affects the quantitative image analysis. Noise is yet another artifact in medical images. In order to accurately and effectively restore the original signal, reference is hereof made to filtering, bias correction and quantitative analysis of correction. In this report, two denoising algorithms are used; (i) Basis rotation fields of experts (BRFoE) and (ii) Anisotropic Diffusion (when Gaussian noise, the Perona-Malik and Tukey's biweight functions and the standard deviation of the noise of the input image are considered).

Advances in pediatric neuroimaging.

Conventional MRI protocols are an integral part of routine clinical imaging in pediatric patients. The advent of several newer MRI techniques provides crucial insight into the structural integrity and functional aspects of the developing brain, especially with the introduction of 3T MRI systems in clinical practice. The field of pediatric neuroimaging continues to evolve, with greater emphasis on high spatial resolution, faster scan time, as well as a quest for visualization of the functional aspects of the human brain. MR vendors are increasingly focusing on optimizing MR technology to make it suitable for children, in whom as compared to adults the head size is usually smaller and demonstrates inherent neuroanatomical differences relating to brain development. The eventual goal of these advances would be to evolve as potential biomarkers for predicting neurodevelopment outcomes and prognostication, in addition to their utility in routine diagnostic and therapeutic decision-making. Advanced MR techniques like diffusion tensor imaging, functional MRI, MR perfusion, spectroscopy, volumetric imaging and arterial spin labeling add to our understanding of normal brain development and pathophysiology of various neurological disease processes. This review is primarily focused on outlining advanced MR techniques and their current and potential pediatric neuroimaging applications as well as providing a brief overview of advances in hardware and machine design.

Imaging methodologies and applications for nutrition research: what can functional MRI offer?

Food intake is influenced by a complex regulatory system involving the integration of a wide variety of sensory inputs across multiple brain areas. Over the past decade, advances in neuroimaging using functional MRI (fMRI) have provided valuable insight into these pathways in the human brain. This review provides an outline of the methodology of fMRI, introducing the widely used blood oxygenation level-dependent contrast for fMRI and direct measures of cerebral blood flow using arterial spin labelling. A review of fMRI studies of the brain's response to taste, aroma and oral somatosensation, and how fat is sensed and mapped in the brain in relation to the pleasantness of food, and appetite control is given. The influence of phenotype on individual variability in cortical responses is addressed, and an overview of fMRI studies investigating hormonal influences (e.g. peptide YY, cholecystokinin and ghrelin) on appetite-related brain processes provided. Finally, recent developments in MR technology at ultra-high field (7T) are introduced, highlighting the advances this can provide for fMRI studies to investigate the neural underpinnings in nutrition research. In conclusion, neuroimaging methods provide valuable insight into the mechanisms of flavour perception and appetite behaviour.

Biceps and rotator interval: imaging update.

The rotator interval contains several important anatomical structures that contribute to the stability and normal function of the shoulder joint including the biceps tendon, coracohumeral ligament, superior glenohumeral ligament, rotator interval capsule, anterior fibers of the supraspinatus tendon, and superior fibers of the subscapularis tendon. Rotator interval pathology is associated with biceps instability, glenohumeral instability, and adhesive capsulitis, all of which can be challenging to clinically diagnose and treat. The complex anatomy and orientation of the rotator interval structures within a relatively small space can make it difficult to evaluate by imaging; however, improvements in MR technology have allowed better detection of disease in this region. Furthermore, the rotator interval is not routinely evaluated arthroscopically unless the clinical examination or imaging findings suggest pathology at this level. Imaging, therefore, can play a significant role in helping the clinician make the diagnosis and initiate appropriate treatment. This article discusses the normal anatomy and biomechanics of the rotator interval and its structures as well as the normal and pathologic appearances on imaging and the treatment options of abnormalities of structures in this region.

The Role of Cardiac MRI in Children’s Congenital and Acquired Heart Disease

: Cardiovascular magnetic resonance (CMR) is a valuable and accurate modality used in the evaluation of both structure and function of the heart. As a result of significant advances in MR technologies, it is increasingly considered to be a useful non-invasive modality which is instrumental in the management of cardiovascular conditions. Ongoing technological advancements in both data acquisition and data presentation have made integration of CMR into clinical practice possible. Evaluation of congenital heart disease is an important application of cardiac MRI as the morphological details of chambers, septum, defects, and anomalous connections are depicted accurately. Additionally, flow information across valves, chambers, outflow tracts, and shunts are also provided. The combination of exquisite 3D anatomy with physiological data enables CMR to provide a unique perspective for the management of many patients with congenital heart disease (CHD). Its utility is further increased after corrective surgery during the follow up period. Imaging small children with CHD is challenging, and in this manuscript, we will review the technical adjustments, imaging protocols, and application of CMR in the pediatric setting.

Typical and atypical brain development: a review of neuroimaging studies

In the course of development, the brain undergoes a remarkable process of restructuring as it adapts to the environment and becomes more efficient in processing information. A variety of brain imaging methods can be used to probe how anatomy, connectivity, and function change in the developing brain. Here we review recent discoveries regarding these brain changes in both typically developing individuals and individuals with neurodevelopmental disorders. We begin with typical development, summarizing research on changes in regional brain volume and tissue density, cortical thickness, white matter integrity, and functional connectivity. Space limits preclude the coverage of all neurodevelopmental disorders; instead, we cover a representative selection of studies examining neural correlates of autism, attention deficit/hyperactivity disorder, Fragile X, 22q11.2 deletion syndrome, Williams syndrome, Down syndrome, and Turner syndrome. Where possible, we focus on studies that identify an age by diagnosis interaction, suggesting an altered developmental trajectory. The studies we review generally cover the developmental period from infancy to early adulthood. Great progress has been made over the last 20 years in mapping how the brain matures with MR technology. With ever-improving technology, we expect this progress to accelerate, offering a deeper understanding of brain development, and more effective interventions for neurodevelopmental disorders.

Advances in MR imaging for cervical spondylotic myelopathy

To outline the pathogenesis of cervical spondylotic myelopathy (CSM), the correlative abnormalities observed on standard magnetic resonance imaging (MRI), the biological implications and current status of diffusion tensor imaging (DTI), and MR spectroscopy (MRS) as clinical tools, and future directions of MR technology in the management of CSM patients. A systematic review of the pathogenesis and current state-of-the-art in MR imaging technology for CSM was performed. CSM is caused by progressive, degenerative, vertebral column abnormalities that result in spinal cord damage related to both primary mechanical and secondary biological injuries. The T2 signal change on conventional MRI is most commonly associated with neurological deficits, but tends not to be a sensitive predictor of recovery of function. DTI and MRS show altered microstructure and biochemistry that reflect patient-specific pathogenesis. Advanced imaging techniques, including DTI and MRS, show higher sensitivity to microstructural and biochemical changes within the cord, and may aid in management of CSM patients.

Incidental pineal cysts in children who undergo 3-T MRI

Pineal cysts, both simple and complex, are commonly encountered in children. More cysts are being detected with MR technology; however, nearly all pineal cysts are benign and require no follow-up. To discover the prevalence of pineal cysts in children at our institution who have undergone high-resolution 3-T MRI. We retrospectively reviewed 100 consecutive 3-T brain MRIs in children ages 1month to 17years (mean 6.8 ± 5.1years). We evaluated 3-D volumetric T1-W imaging, axial T2-W imaging, axial T2-W FLAIR (fluid attenuated inversion recovery) and coronal STIR (short tau inversion recovery) sequences. Pineal parenchymal and cyst volumes were measured in three planes. Cysts were analyzed for the presence and degree of complexity. Pineal cysts were present in 57% of children, with a mean maximum linear dimension of 4.2mm (range 1.5-16mm). Of these cysts, 24.6% showed thin septations or fluid levels reflecting complexity. None of the cysts demonstrated complete T2/FLAIR signal suppression. No cyst wall thickening or nodularity was present. There was no significant difference between the ages of children with and without cysts. Cysts were more commonly encountered in girls than boys (67% vs. 52%; P = 0.043). There was a slight trend toward increasing pineal gland volume with age. Pineal cysts are often present in children and can be incidentally detected by 3-T MRI. Characteristic-appearing pineal cysts in children are benign, incidental findings, for which follow-up is not required if there are no referable symptoms or excessive size.

Screening for brain metastases in patients with stage III non-small cell lung cancer: Is there additive value of magnetic resonance imaging above a contrast-enhanced computed tomography of the brain?

IntroductionStage III NSCLC patients are candidates for treatment with curative intent. Current guidelines advise post contrast magnetic resonance imaging (MRI) or contrast enhanced computed tomography (CE-CT) of the brain in these patients to exclude brain metastases (BM). In previous small studies MRI was reported to be superior to CE-CT. However, CT and MR technology have evolved and 18F-deoxyglucose-positron-emission-tomography (18FDG-PET) has been implemented in staging of NSCLC. If CE-CT, performed together with 18FDG-PET-CT shows the same yield of BM detection as an additionally performed MRI, substantial gain in time and resources is expected. MethodsAll NSCLC patients who underwent a staging 18FDG-PET-CT between January 2008 and September 2011 were reviewed. Neurological asymptomatic patients with stage III NSCLC who were eligible for treatment with curative intent were selected, without taking into account the results of brain MRI. CT was compared to MRI to investigate whether additional BM were detected on MRI. Development of BM within a year after negative MRI was recorded. Results97/429 NSCLC patients who underwent a PET-CT had stage III disease. Three otherwise stage III patients already had occult BM on CE-CT. 77/97 (79%) patients underwent MRI, 45/77 (58%) CE-CT and 32/77 (42%) LD-CT. In none of the CE-CT, but in 5/32 (16%) LD-CT patients BM were detected on MRI. 9/72 patients (13%) without BM on MRI at diagnosis developed BM within a year. ConclusionsThis retrospective study suggests that there is no additive value of MRI to 18FDG-PET-CT with CE-CT in screening for BM in neurological asymptomatic patients with stage III NSCLC.

Diffusion tensor and susceptibility-weighted imaging in concussion assessment of national football league players

IntroductionStandard MRI is normal following the vast majority of concussions. Diffusion tensor imaging (DTI) and susceptibility-weighted imaging (SWI) are advanced MRI techniques hypothesized to be more sensitive in detecting subtle...

Temperature induced effects on the durability of MR fluids

Although commercial MR fluids exist for quite some time now and the feasibility as well as the advantages of the MR technology have been demonstrated for several applications by a variety of MR actuator prototypes, a sustainable market break-through of brake and clutch applications utilizing the shear mode is still missing. Essential impediments are the marginal knowledge about the durability of the MR technology. To overcome this situation, a long-term measurement system was developed for the durability analysis of MR fluid formulations within a technical relevant scale with respect to the volume of MR fluid and the transmitted torque. The focus of the presented series of measurements is given to the analysis of temperature induced effects on the durability. In this context four different failure indicators can be distinguished, namely an apparent negative viscosity, deviations in torque data obtained from different measurements as well as a pressure increase and a drop in the on-state torque. The measurement data of the present durability experiments indicate a significant dependency of the attainable energy intake density on the temperature. The aim of such durability tests is to establish a reliable data base for the industry to estimate the life-time of MR devices.

Progress and promises of human cardiac magnetic resonance at ultrahigh fields: A physics perspective

A growing number of reports eloquently speak about explorations into cardiac magnetic resonance (CMR) at ultrahigh magnetic fields (B0⩾7.0T). Realizing the progress, promises and challenges of ultrahigh field (UHF) CMR this perspective outlines current trends in enabling MR technology tailored for cardiac MR in the short wavelength regime. For this purpose many channel radiofrequency (RF) technology concepts are outlined. Basic principles of mapping and shimming of transmission fields including RF power deposition considerations are presented. Explorations motivated by the safe operation of UHF-CMR even in the presence of conductive implants are described together with the physics, numerical simulations and experiments, all of which detailing antenna effects and RF heating induced by intracoronary stents at 7.0T. Early applications of CMR at 7.0T and their clinical implications for explorations into cardiovascular diseases are explored including assessment of cardiac function, myocardial tissue characterization, MR angiography of large and small vessels as well as heteronuclear MR of the heart and the skin. A concluding section ventures a glance beyond the horizon and explores future directions. The goal here is not to be comprehensive but to inspire the biomedical and diagnostic imaging communities to throw further weight behind the solution of the many remaining unsolved problems and technical obstacles of UHF-CMR with the goal to transfer MR physics driven methodological advancements into extra clinical value.

Predictive and Diagnostic Capabilities of Noninvasive MR Technology in Non-Hodgkin Lymphoma Patients.

Abstract 2701Because of the wealth of information obtained using MR technology, this technique promises to be one of the best imaging methods in cancer. In addition, MR technology is fairly noninvasive and does not require ionizing radiation or radioactivity, making it one of the safest imaging modalities available. This study aims to evaluate the predictive and diagnostic capabilities of a multimodality MR exam to study non-Hodgkin lymphoma (NHL) patients. Experimental Design:Under ethical review board approval, a pretreatment MR exam was obtained in NHL patients, which included clinical MRI, diffusion weighted imaging (DWI), 1H MR spectroscopy (MRS) and/or 31P MRS. Using 3D-localized, 1H-irradiated 31P MRS the phosphomonoester (PME) levels normalized to nucleoside triphosphates (PME/NTP) were measured. Using single voxel 1H MRS the tumor total choline to water (tCho/H2O) ratio was determined. DWI was acquired using echo-planar imaging with fat suppression and b-values of 0 and 1000 s/mm2 to obtain the apparent diffusion constant (ADC) of water in the tumor. In regard to clinical information, treatment response was assessed six-months after treatment and the patients grouped as those with a complete response (CR) and those without a complete response (NCR). Time to treatment failure (TTF), was measured as the time between the end of one treatment and the start of a new one. Results:Pretreatment PME/NTP values were measured in 59 newly diagnosed NHL patients. Twenty-seven of these patients were diffuse large B-cell lymphoma (DLBCL) patients. From these patients, 20 were treated with CHOP or equivalent therapy. The significantly different mean pretreatment PME/NTP values (SD, n) for CR and NCR were 1.42 (0.41, 13) and 2.46 (0.40, 7), respectively (p<0.00001), with sensitivity and specificity of 0.85 in a Fisher test (p<0.01). PME/NTP correlated with TTF by Cox (p<0.02) and Kaplan-Meier tests (p<0.00001). The additional seven DLBCL patients were treated with added rituximab also showing significantly different mean pretreatment PME/NTP values: CR, 1.56 (0.61, 4) vs. NCR, 3.18 (0.41,3), (p<0.02), as well as Kaplan-Meier curves for TTF (p < 0.01). The remaining 32 patients with other forms of NHL were studied together. Again in this group of patients, the PME/NTP was significantly different in the response groups: CR, 1.41 (0.35, 5) vs. NCR, 2.11 (0.16, 27), p<0.04. In seven NHL patients the correlation of the PME/NTP values determined by 31P MRS vs. the tCho/H2O values determined by 1H MRS prior to receive treatment showed a statistically significant linear regression (y = 0.16× – 0.77, r2 = 0.7, p < 0.005). DWI was obtained in 15 NHL patients refractory to previous treatments demonstrating that the mean ADC value of refractory NHL patients is lower than the one in normal volunteers (0.91 [0.23, 15] vs. 1.13 [0.14, 10], p<0.01), but similar to those reported from newly diagnosed patients. Discussion:Our data validate the capabilities of a multimodality MR exam to study NHL patients by demonstrating that: 1) the pretreatment tumor PME/NTP levels predict both responses to treatment and TTF in different histological subtypes of NHL patients; 2) the correlation of PME/NTP with tCho/H2O that suggests that prediction of treatment outcome may also be possible using the ratio determined by 1H MRS, which will allow to use the increased sensitivity of 1H MRS; 3) the potential additional information provided by the simultaneous determination of 31P and 1H MRS; and 4) our preliminary DWI results suggesting that for newly diagnosed and refractory NHL patients, the quantitative ADC evaluation can aid assessing malignant masses and differentiate them from normal lymph nodes. Disclosures:No relevant conflicts of interest to declare.

Magnetic resonance imaging for diagnosis of acute pulmonary embolism: not yet a suitable alternative to CT‐PA

See also Revel MP, Sanchez O, Couchon S, Planquette B, Hernigou A, Niarra R, Meyer G, Chatellier G. Diagnostic accuracy of magnetic resonance imaging for acute pulmonary embolism: results of the ‘IRM-EP’ study. This issue, pp 743–50; and Sodhi KS, Saxena AK. Diagnostic accuracy of computed tomography pulmonary angiography and magnetic resonance imaging for an acute pulmonary embolism. This issue, pp 961.

Obrazowanie wentylacji i perfuzji płuc przy użyciu rezonansu magnetycznego

A close interaction between the respiratory pump, pulmonary parenchyma and blood circulation is essential for a normal lung function. Many pulmonary diseases present, especially in their initial phase, a variable regional impairment of ventilation and perfusion. In the last decades various techniques have been established to measure the lung function. Besides the global pulmonary function tests (PFTs) imaging techniques gained increasing importance to detect local variations in lung function, especially for ventilation and perfusion assessment. Imaging modalities allow for a deeper regional insight into pathophysiological processes and enable improved planning of invasive procedures. In contrast to computed tomography (CT) and the nuclear medicine techniques, magnetic resonance imaging (MRI), as a radiation free imaging modality gained increasing importance since the early 1990 for the assessment of pulmonary function. The major inherent problems of lung tissue, namely the low proton density and the pulmonary and cardiac motion, were overcome in the last years by a constant progress in MR technology. Some MR techniques are still under development, a process which is driven by scientific questions regarding the physiology and pathophysiology of pulmonary diseases, as well as by the need for fast and robust clinically applicable imaging techniques as safe therapy monitoring tools. MRI can be considered a promising ionizing-free alternative to techniques like CT or nuclear medicine techniques for the evaluation of lung function. The goal of this article is to provide an overview on selected MRI techniques for the assessment of pulmonary ventilation and perfusion.

Magnetic Resonance Imaging of Blood Brain/Nerve Barrier Dysfunction and Leukocyte Infiltration: Closely Related or Discordant?

Unlike other organs the nervous system is secluded from the rest of the organism by the blood brain barrier (BBB) or blood nerve barrier (BNB) preventing passive influx of fluids from the circulation. Similarly, leukocyte entry to the nervous system is tightly controlled. Breakdown of these barriers and cellular inflammation are hallmarks of inflammatory as well as ischemic neurological diseases and thus represent potential therapeutic targets. The spatiotemporal relationship between BBB/BNB disruption and leukocyte infiltration has been a matter of debate. We here review contrast-enhanced magnetic resonance imaging (MRI) as a non-invasive tool to depict barrier dysfunction and its relation to macrophage infiltration in the central and peripheral nervous system under pathological conditions. Novel experimental contrast agents like Gadofluorine M (Gf) allow more sensitive assessment of BBB dysfunction than conventional Gadolinium (Gd)-DTPA enhanced MRI. In addition, Gf facilitates visualization of functional and transient alterations of the BBB remote from lesions. Cellular contrast agents such as superparamagnetic iron oxide particles (SPIO) and perfluorocarbons enable assessment of leukocyte (mainly macrophage) infiltration by MR technology. Combined use of these MR contrast agents disclosed that leukocytes can enter the nervous system independent from a disturbance of the BBB, and vice versa, a dysfunctional BBB/BNB by itself is not sufficient to attract inflammatory cells from the circulation. We will illustrate these basic imaging findings in animal models of multiple sclerosis, cerebral ischemia, and traumatic nerve injury and review corresponding findings in patients.