Name: diffusion tensor magnetic resonance imaging in chronic spinal cord compression
Uploaded: 2019-05-07T13:00:00.000+00:00
Duration: 7 min
Description: Watch this Scientific Journal Video about Diffusion Tensor Magnetic Resonance Imaging in Chronic Spinal Cord Compression at JoVE.com

This study was supported by Guangzhou Science and Technology Project of China (No. 201607010021) and the Nature Science Foundation of JiangXi (No. 20142BAB205065)

The study was approved by the local Medical Ethics Committee in Guangzhou First People&#8217;s Hospital in China. Signed informed consent forms were received from healthy volunteers and participants prior to participation. All of the studies were conducted in accordance with the World Medical Association Declaration of Helsinki.
1. Subject Preparation
<ol>
	<li>Ensure that each participant meets the following criteria for chronic spinal cord compression: a) a history of loss of significant neurological function, b) a positive myelopathy physical examination, and c) MRI evidence of cervical cord compression.&#160; 
	NOTE: The exclusion criteria are a) incapability of providing written consent and b) inability to obtain DTI parameters of artifacts. For controls, inclusion criteria are a) no history of significant back or neck injuries, neurological disorders, or spine surgeries; b) no MRI evidence of cervical cord compression.</li>
	<li>sk each participant to complete and sign a consent form that lists MRI safety guidelines and the imaging protocol. Specifically, patients with chronic spinal cord compression are examined by MRI preoperatively and 1 year postoperatively.</li>
	<li>rovide earplugs for each participant. Place them in a supine position with a head/neck coil enclosing the cervical region, and a landmark at the thyroid cartilage level. Ensure that each participant is in a comfortable position that effectively reduces movement.</li>
</ol>
2. Structural MRI Parameters&#160;
NOTE: Anatomical T1-weighted (T1 W) images, T2-weighted (T2 W) images, and DTI acquired on a 3 Tesla MRI scanner with a 16-channel head coil.
<ol>
	<li>Use fast perturbation gradient echo (FPGR) for localization scanning to obtain axial, sagittal, and coronal position maps.</li>
	<li>Position the sagittal positioning line with the coronal position maps to ensure that the positioning baseline is parallel to the spinal canal (spinal cord); first locate the sagittal plane T2 W, then copy and paste the sagittal T1 W positioning line to the T2 W positioning line.
	<ol>
		<li>Use the following imaging parameters for T1 W and T2 W sagittal imaging: field of view (FOV) = 240 mm x 240 mm, voxel size = 1.0 mm x 0.8 mm x 3.0 mm, slice gap = 0.3 mm, slice thickness = 3 mm, number of excitation (NEX) = 2, fold-over direction = feet/head (FH), and time of echo (TE)/time of repetition (TR) = 10/700 ms (T1 W) and 101/2,500 ms (T2 W). Obtain nine sagittal images covering the entire cervical spinal cord.&#160;</li>
	</ol>
	</li>
	<li>Position the axial positioning line on the sagittal T2 W image and cover the intervertebral disc from C2/3 to C6/7, centering on the anteroposterior diameter of the intervertebral space. Use the following imaging parameters: FOV = 180 mm x 180 mm, voxel size = 0.7 mm x 0.6 mm x 3.0 mm, slice thickness = 3 mm, fold-over direction = anterior/posterior (AP), NEX = 2, and TE/TR = 120/3,000 ms.</li>
	<li>Position the axial positioning line on the sagittal T2 W image, centering on the anteroposterior diameter of the intervertebral space, with 45 slices covering the cervical spinal cord from C1 to C7.
	<ol>
		<li>Obtain DTI via the following sequence: single-shot spin-echo echo-planar imaging (SE-EPI) with 20 orthogonal directions. Non-coplanar diffusion directions with b-value = 800 s/mm2.&#160;</li>
		<li>Use the following imaging parameters: FOV = 230 mm x 230 mm, acquisition matrix = 98 x 98, reconstructed resolution = 1.17 x 1.17, slice thickness = 3 mm, fold-over direction = AP, NEX = 2, EPI factor = 98, and TE/TR = 74/8,300 ms. Provide a time course summarizing the steps in the MRI protocol, as shown in Figure 1.&#160; 
		NOTE: The time course summarizing the MRI and DTI protocol is shown in Figure 1.</li>
	</ol>
	</li>
</ol>
3. Image Postprocessing and Data Measurement Indexes
<ol>
	<li>Automatically convey all scanning images to the Syngo MR B17. Load the T2 W sagittal and axial imaging of the intervertebral space in the filming interface and find the most compressed portion of the cervical spinal cord.</li>
	<li>In the 2:1 viewing interface, load the FA image and click the Position Display: Series tab. Count and record the level of highest compression from the top to the bottom of the location map.</li>
	<li>Click the File tab to select the tensor image, then use the applications toolbar at the top left of the screen to select Neuro 3D(MR) to automatically create ADC and FA colormaps.</li>
	<li>Turn to the level of the highest compression site, and create spherical regions of interest (ROIs) of identical volumes (with a size of 6 mm3) using the Start Evaluation Mode tab. The ROIs must be selected, including the inner spinal cord to exclude the partial volume effects of cerebrospinal fluid (CSF).</li>
	<li>Calculate and display the FA and ADC values at the bottom right of the screen automatically. Display the E1, E2, and E3 values by clicking the Diffusion toolbar and choosing them. 
	NOTE: All measurements were performed by two radiologists blinded to the patients&#8217; clinical details. The final results were determined as the average of the two.</li>
	<li>Perform image processing of the DTI datasets using a Syngo MR B17 Advantage Workstation, following the steps in Figure 2.</li>
</ol>

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The authors have nothing to disclose.

Conventional MRI is usually utilized to assess the prognosis of patients with various spine conditions. However, this imaging modality provides macroscopic anatomic detail rather than microstructure evaluation14, which limits the prediction of neurological function. Furthermore, traditional MRI may underestimate the severity and extent of spinal cord damage. The emergence of DTI can help surgeons to evaluate spinal cord function more accurately by providing quantitative information on water molecule diffusion.&#160;
In the present study, a methodological framework was described to demonstrate the application of DTI parameters in patients with chronic spinal cord compression. DTI is a sensitive technique to measure the direction and diffusion magnitude of water molecules in tissues15. Surgeons can quantitatively assess neural damage in various pathologies of the spinal cord by evaluating DTI parameters. In this protocol, we manually drew ROIs on axial slices because existing dedicated software for the automatic segmentation of CSF and myelin is not adequate for the spinal cord. The small spinal cord cross-sectional area is a major limitation to effectively apply automatic segmentation. We selected ROIs at the most serious compression site. ROIs must include the inner spinal cord to eliminate the partial volume effects of CSF. In addition, DTI processing should reduce the effects of artifactual factors such as EPI-related geometric distortion artifacts and eddy current artifacts. The available options of the software package could help operators obtain useful information depending on the orientation of the diffusion-weighting gradient and separate eddy current correction. Conventional MRI scanning in the present study applied a fast spin-echo sequence to provide more image information. The longer echo chain and smaller echo interval were specifically designed to minimize artifacts created by spinal instrumentation. We selected a short echo time, wide readout frequency band, and small voxels to reduce artifacts. FA and ADC are commonly used DTI parameters in the measurements of the spinal cord. FA represents the degree of anisotropy in a range of 0 to 1. FA values closer to 1 indicate high tissue anisotropy13. The ADC is related to the average value of diffusivities in the three principal axes, and its change is consistent with the process of histopathological tissue injury6. The present work confirmed that chronic spinal cord compression might result in decreased FA and increased ADC values, as previously reported12. Chronic spinal cord compression can cause recurrent ischemic damage to the spinal cord and produce histopathological changes in downstream nerve fibers, such as angioedema, gliosis, neuron function loss, and eventually necrosis16. In the present work, these above-mentioned changes were clearly visualized on DTI.&#160;
DTI can serve as a tool to assess functional improvement and provide valuable prognostic information. Previous studies showed that high preoperative FA might be related to better neural functional recovery after surgery17. Kerkovsky et al. reported that patients with symptomatic cervical spondylotic myelopathy had higher ADC values and lower FA values compared with those who had no relevant symptoms but had radiological evidence of cord compression18. In a previous study of a chronic spinal cord compression rat model, DTI parameters were associated with pathological spinal cord conditions. Importantly, DTI can quantitatively assess the functional status of the spinal cord16. An analysis of 66 patients with chronic spinal cord compression also showed that DTI parameters were related to the Japanese Orthopedic Association recovery rate of patients with chronic spinal cord compression, and ADC, mean diffusivity, radial diffusivity, and axial diffusivity values might reflect neurologic impairment and be useful for evaluating postoperative prognosis19. Compared with conventional MRI, DTI is a useful quantitative tool to measure the recuperative potential of the spinal cord.
There were some limitations to this study. First, adequate spatial resolution is still difficult to achieve. Motion artifacts, arising from respiratory and cardiac motion and CSF pulsation, can produce bad effects on DTI, especially in the lower cervical cord and thoracic cord20. The longer echo chain and smaller echo interval were specifically designed to minimize artifacts created by spinal instrumentation. In this protocol, we selected a short echo time, wide readout frequency band, and small voxels to reduce artifacts. In addition, it was difficult to distinguish between white and gray matter on DTI with a 3 Tesla MR system21, which meant that both gray and white matter might be included in the ROIs. That could significantly influence DTI parameter measurements. ROI-based quantification might lead to a biased identification of the tract caused by user experience and anatomical knowledge. This manual delineation approach can be tedious and time-consuming, especially if there are several spinal cord slices, tracts, and subjects. ROIs should be selected at the inner spinal cord to exclude partial volume effects because of CSF. Useful methods to segment gray and white matter regions and discern available and effective ROIs are required in future studies.
In summary, this methodological framework demonstrates the application of DTI parameters in chronic spinal cord compression. DTI provides a measure of water molecular direction and diffusion magnitude in tissues. Surgeons can use this sensitive technique to quantitatively assess neural damage in various spinal cord pathologies.

Chronic spinal cord compression is the most common cause of spinal cord impairment1. This condition can be due to posterior longitudinal ligament ossification, hematoma, cervical disc herniation, vertebral degeneration, or intraspinal tumors2,3. Chronic spinal cord compression can lead to various degrees of functional deficits; however, there are clinical cases with serious spinal cord compression without any neurological symptoms and signs, as well as patients with mild spinal cord compression but serious neurological deficits4. Under these circumstances, sensitive imaging is essential to evaluate compression severity and identify the range of damage.
Conventional MRI plays a significant role in elucidating spinal cord anatomy. This technique is usually utilized to evaluate the compression degree because of its sensitivity to soft tissues5. Many parameters can be measured from MRI, such as MR signal intensity, cord morphology, and spinal canal area. However, MRI has some limitations and only provides qualitative information rather than quantitative results6. Patients with chronic spinal cord compression often have abnormal signal changes of MRI intensity. However, discrepancies between clinical symptoms and MRI intensity changes make it hard to diagnose a functional condition based solely on MRI characteristics7. Previous studies highlight this controversy in terms of the prognostic value of MRI T2 hyperintensity in the spinal cord8. Two groups reported that T2 hyperintensity of the spinal cord is a poor prognostic parameter after surgery for chronic spinal cord compression8,9. In contrast, some authors found no significant association between T2 signal changes and prognosis8,9. Chen et al. and Vedantam et al. divided MRI T2 hyperintensities into two categories corresponding to different prognostic outcomes10,11. Type 1 showed faint, fuzzy, indistinct borders, and this category demonstrated reversible histologic changes. Type 2 images presented intense, well-defined borders, which corresponded to irreversible pathologic damage. Conventional T1/T2 MRI techniques do not provide adequate information to identify these two categories and evaluate patient prognosis. By contrast, DTI, a more sophisticated imaging technique, may help obtain more specific prognostic information by quantitatively detecting microstructural changes in tissues via water molecule diffusion.
In recent years, DTI has garnered increasing attention due to its ability to describe spinal cord microarchitecture. DTI can measure the direction and magnitude of water molecule diffusion in tissues. DTI parameters can quantitatively evaluate neural damage in patients with chronic spinal cord compression. FA and the ADC are the most commonly applied parameters during spinal cord evaluation. The FA value reveals the degree of anisotropy to orientate surrounding axonal fibers and describe anatomic boundaries12,13. The ADC value provides information on the characteristics of molecular motion in many directions in a three-dimensional space and reveals the mean of diffusivities along the three principal axes6,12. Changes in these parameters are associated with microstructural alterations that influence water molecule diffusion. Therefore, surgeons can utilize/measure DTI parameters to identify spinal cord pathology. The present study provides DTI methods and processes that provide more detailed prognostic information to treat patients with chronic spinal cord compression.

<table><tbody><tr><td>3-Tesla MRI scanner</td><td>Siemens</td><td>40708</td><td>Software: NUMARIS/4</td></tr><tr><td>Syngo MR B17</td><td>Siemens</td><td>40708</td><td>Software: NUMARIS/4</td></tr></tbody></table>

diffusion tensor magnetic resonance imaging in chronic spinal cord compression

Chronic spinal cord compression is the most common cause of spinal cord impairment in patients with nontraumatic spinal cord damage. Conventional magnetic resonance imaging (MRI) plays an important role in both confirming the diagnosis and evaluating the degree of compression. However, the anatomical detail provided by conventional MRI is not sufficient to accurately estimate neuronal damage and/or assess the possibility of neuronal recovery in chronic spinal cord compression patients. In contrast, diffusion tensor imaging (DTI) can provide quantitative results according to the detection of water molecule diffusion in tissues. In the present study, we develop a methodological framework to illustrate the application of DTI in chronic spinal cord compression disease. DTI fractional anisotropy (FA), apparent diffusion coefficients (ADCs), and eigenvector values are useful for visualizing microstructural pathological changes in the spinal cord. Decreased FA and increases in ADCs and eigenvector values were observed in chronic spinal cord compression patients compared to healthy controls. DTI could help surgeons understand spinal cord injury severity and provide important information regarding prognosis and neural functional recovery. In conclusion, this protocol provides a sensitive, detailed, and noninvasive tool to evaluate spinal cord compression.

This is a summary of results obtained from healthy volunteers and patients with cervical spondylotic myelopathy. The protocol enabled the physician to view DTI maps. This technology could serve as an objective measure to measure functional status in myelopathic conditions. DTI maps of healthy volunteers are shown in Figure 3. The DTI parameters of healthy volunteers were as follows: FA = 0.661; ADC = 1.006 x 10-3 mm2/s; E1 = 1.893 x 10-3 mm2/s; E2 = 0.746 x 10-3 mm2/s; E3 = 0.377 x 10-3 mm2/s (Figure 3). DTI maps of chronic spinal cord compression patients are displayed in Figure 4 and have the following parameters: FA = 0.605; ADC = 1.522 x 10-3 mm2/s; E1 = 2.731 x 10-3 mm2/s; E2 = 1.058 x 10-3 mm2/s; E3 = 0.776 x 10-3 mm2/s (Figure 4). Postoperative imaging was also performed. Figure 5 shows DTI maps of patients with chronic spinal cord compression who underwent surgery. The DTI parameters are as follows: FA = 0.616; ADC = 1.210 x 10-3 mm2/s; E1 = 2.190 x 10-3 mm2/s; E2 = 0.858 x 10-3 mm2/s; E3 = 0.582 x 10-3 mm2/s (Figure 5).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/59069/59069fig1.jpg" /> 
Figure 1: Time course of the clinical MRI protocol. First, the FSPGR sequence was selected for localization scanning, and then the rapid recovery of fast spin echo was performed to acquire the sagittal T2 W and T1 W images and axial T2 W images. Finally, DTI was performed using single-shot SE-EPI with 20 orthogonal directions. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/59069/59069fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/59069/59069fig2.jpg" /> 
Figure 2: Flowchart of the steps involved in DTI processing. Flowchart showing four DTI postprocessing steps with a workstation. First, acquire conventional MRI and DTI in the workstation. Then, find the site of the highest compression based on conventional MRI images. Finally, perform the tensor calculation. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/59069/59069fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/59069/59069fig3.jpg" /> 
Figure 3: Sagittal and axial MRI and DTI in a healthy volunteer. (A) Sagittal MRI T1 W. (B) Sagittal MRI T2 W. (C) Axial MRI T2 W. (D) FA. (E) ADC. (F) E1. (G) E2. (H) E3. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/59069/59069fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/59069/59069fig4.jpg" /> 
Figure 4: Sagittal and axial MRI and DTI in a patient with chronic spinal cord compression. (A) Sagittal MRI T1 W. (B) Sagittal MRI T2 W. (C) Axial MRI T2 W. (D) FA. (E) ADC. (F) E1. (G) E2. (H) E3. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/59069/59069fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/59069/59069fig5.jpg" /> 
Figure 5: Sagittal and axial MRI and DTI in a patient with chronic spinal cord compression after surgery. (A) Sagittal MRI T1 W. (B) Sagittal MRI T2 W. (C) Axial MRI T2 W. (D) FA. (E) ADC. (F) E1. (G) E2. (H) E3. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/59069/59069fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

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Diffusion Tensor Magnetic Resonance Imaging in Chronic Spinal Cord Compression

Here, we present a protocol for the application of diffusion tensor imaging parameters to evaluate spinal cord compression.

Chronic spinal cord compression is the most common cause of spinal cord impairment in patients with nontraumatic spinal cord damage. Conventional magnetic ...

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8.8K Views.  Guangzhou Medical University. Here, we present a protocol for the application of diffusion tensor imaging parameters to evaluate spinal cord compression.

Video: Diffusion Tensor Magnetic Resonance Imaging in Chronic Spinal Cord Compression

Dissection and Culture of Commissural Neurons from Embryonic Spinal Cord

Commissural neurons have been widely used to investigate the mechanisms underlying axon guidance during embryonic spinal cord development. The cell bodies of these neurons are located in the dorsal spinal cord and their axons follow stereotyped trajectories during embryonic development. Commissural axons initially project ventrally towards the floorplate. After crossing the midline, these axons turn anteriorly and project towards the brain. Each of these steps is regulated by the action of several guidance cues. Cultures highly enriched in commissural neurons are ideally suited for many experiments addressing the mechanisms of axon pathfinding, including turning assays, immunochemistry and biochemistry. Here, we describe a method to dissect and culture commissural neurons from E13 rat dorsal spinal cord. First, the spinal cord is isolated and dorsal strips are dissected out. The dorsal tissue is then dissociated into a cell suspension by trypsinization and mechanical disruption. Neurons are plated onto poly-L-lysine-coated glass coverslips or tissue-culture dishes. After 30 hours in vitro, most neurons have extended an axon. The purity of the culture (Yam et al. 2009), typically over 90%, can be assessed by immunolabeling with the commissural neuron markers DCC, LH2 and TAG1 (Helms and Johnson, 1998). This neuronal preparation is a useful tool for in vitro studies of the cellular and molecular mechanisms of commissural axon growth and guidance during spinal cord development.

This video demonstrates a method to dissect and culture commissural neurons from E13 rat dorsal spinal cord. Dissociated commissural neurons are useful to study the cellular and molecular mechanisms of axon growth and guidance.

Commissural neurons have been widely used to investigate the mechanisms underlying axon guidance during embryonic spinal cord development. The cell bodies ...

Multiple-mouse Neuroanatomical Magnetic Resonance Imaging

The field of mouse phenotyping with magnetic resonance imaging (MRI) is rapidly growing, motivated by the need for improved tools for characterizing and evaluating mouse models of human disease. MRI is an excellent modality for investigating genetically altered animals. It is capable of whole brain coverage, can be used in vivo, and provides multiple contrast mechanisms for investigating different aspects of neuranatomy and physiology. The advent of high-field scanners along with the ability to scan multiple mice simultaneously allows for rapid phenotyping of novel mutations.
Effective mouse MRI studies require attention to many aspects of experiment design. In this article, we will describe general methods to acquire quality images for mouse phenotyping using a system that images mice concurrently in shielded transmit/receive radio frequency (RF) coils in a common magnet (Bock et al., 2003). We focus particularly on anatomical phenotyping, an important and accessible application that has shown a high potential for impact in many mouse models at our imaging centre. Before we can provide the detailed steps to acquire such images, there are important practical considerations for both in vivo brain imaging (Dazai et al., 2004) and ex vivo brain imaging (Spring et al., 2007) that should be noted. These are discussed below.

Magnetic resonance imaging (MRI) has become an increasingly popular tool for examining the phenotype of genetically altered mice. This article illustrates the methods necessary to achieve high-throughput phenotyping of genetically altered mice using multiple-mouse MRI.

The field of mouse phenotyping with magnetic resonance imaging (MRI) is rapidly growing, motivated by the need for improved tools for characterizing and ...

Diffusion Tensor Magnetic Resonance Imaging in the Analysis of Neurodegenerative Diseases

Diffusion tensor imaging (DTI) techniques provide information on the microstructural processes of the cerebral white matter (WM) in vivo. The present applications are designed to investigate differences of WM involvement patterns in different brain diseases, especially neurodegenerative disorders, by use of different DTI analyses in comparison with matched controls. 	
DTI data analysis is performed in a variate fashion, i.e. voxelwise comparison of regional diffusion direction-based metrics such as fractional anisotropy (FA), together with fiber tracking (FT) accompanied by tractwise fractional anisotropy statistics (TFAS) at the group level in order to identify differences in FA along WM structures, aiming at the definition of regional patterns of WM alterations at the group level. Transformation into a stereotaxic standard space is a prerequisite for group studies and requires thorough data processing to preserve directional inter-dependencies. The present applications show optimized technical approaches for this preservation of quantitative and directional information during spatial normalization in data analyses at the group level. On this basis, FT techniques can be applied to group averaged data in order to quantify metrics information as defined by FT. Additionally, application of DTI methods, i.e. differences in FA-maps after stereotaxic alignment, in a longitudinal analysis at an individual subject basis reveal information about the progression of neurological disorders. Further quality improvement of DTI based results can be obtained during preprocessing by application of a controlled elimination of gradient directions with high noise levels.	
In summary, DTI is used to define a distinct WM pathoanatomy of different brain diseases by the combination of whole brain-based and tract-based DTI analysis.

Diffusion tensor imaging (DTI) basically serves as an MRI-based tool to identify in vivo the microstructure of the brain and pathological processes due to neurological disorders within the cerebral white matter. DTI-based analyses allow for application to brain diseases both at the group level and in single subject data.

Diffusion tensor imaging (DTI) techniques provide information on the microstructural processes of the cerebral white matter (WM) in vivo. The present ...

Medicine

Quantitative Magnetic Resonance Imaging of Skeletal Muscle Disease

Quantitative magnetic resonance imaging (qMRI) describes the development and use of MRI to quantify physical, chemical, and/or biological properties of living systems. Neuromuscular diseases often exhibit a temporally varying, spatially heterogeneous, and multi-faceted pathology. The goal of this protocol is to characterize this pathology using qMRI methods. The MRI acquisition protocol begins with localizer images (used to locate the position of the body and tissue of interest within the MRI system), quality control measurements of relevant magnetic field distributions, and structural imaging for general anatomical characterization. The qMRI portion of the protocol includes measurements of the longitudinal and transverse relaxation time constants (T1 and T2, respectively). Also acquired are diffusion-tensor MRI data, in which water diffusivity is measured and used to infer pathological processes such as edema. Quantitative magnetization transfer imaging is used to characterize the relative tissue content of macromolecular and free water protons. Lastly, fat-water MRI methods are used to characterize fibro-adipose tissue replacement of muscle. In addition to describing the data acquisition and analysis procedures, this paper also discusses the potential problems associated with these methods, the analysis and interpretation of the data, MRI safety, and strategies for artifact reduction and protocol optimization.

Neuromuscular diseases often exhibit a temporally varying, spatially heterogeneous, and multi-faceted pathology. The goal of this protocol is to characterize this pathology using non-invasive magnetic resonance imaging methods.

Quantitative magnetic resonance imaging (qMRI) describes the development and use of MRI to quantify physical, chemical, and/or biological properties of ...

Diffusion Imaging in the Rat Cervical Spinal Cord

Magnetic resonance imaging (MRI) is the state of the art approach for assessing the status of the spinal cord noninvasively, and can be used as a diagnostic and prognostic tool in cases of disease or injury. Diffusion weighted imaging (DWI), is sensitive to the thermal motion of water molecules and allows for inferences of tissue microstructure. This report describes a protocol to acquire and analyze DWI of the rat cervical spinal cord on a small-bore animal system. It demonstrates an imaging setup for the live anesthetized animal and recommends a DWI acquisition protocol for high-quality imaging, which includes stabilization of the cord and control of respiratory motion. Measurements with diffusion weighting along different directions and magnitudes (b-values) are used. Finally, several mathematical models of the resulting signal are used to derive maps of the diffusion processes within the spinal cord tissue that provide insight into the normal cord and can be used to monitor injury or disease processes noninvasively.

The goal of this protocol is to obtain high-quality diffusion weighted magnetic resonance imaging (DWI) of the rat spinal cord for noninvasive characterization of tissue microstructure. This protocol describes optimizations of the MRI sequence, radiofrequency coil, and analysis methods to enable DWI images free from artifacts.

Magnetic resonance imaging (MRI) is the state of the art approach for assessing the status of the spinal cord noninvasively, and can be used as a ...

Contrast Enhanced Ultrasound Imaging for Assessment of Spinal Cord Blood Flow in Experimental Spinal Cord Injury

Reduced spinal cord blood flow (SCBF) (i.e., ischemia) plays a key role in traumatic spinal cord injury (SCI) pathophysiology and is accordingly an important target for neuroprotective therapies. Although several techniques have been described to assess SCBF, they all have significant limitations. To overcome the latter, we propose the use of real-time contrast enhanced ultrasound imaging (CEU). Here we describe the application of this technique in a rat contusion model of SCI. A jugular catheter is first implanted for the repeated injection of contrast agent, a sodium chloride solution of sulphur hexafluoride encapsulated microbubbles. The spine is then stabilized with a custom-made 3D-frame and the spinal cord dura mater is exposed by a laminectomy at ThIX-ThXII. The ultrasound probe is then positioned at the posterior aspect of the dura mater (coated with ultrasound gel). To assess baseline SCBF, a single intravenous injection (400 &#181;l) of contrast agent is applied to record its passage through the intact spinal cord microvasculature. A weight-drop device is subsequently used to generate a reproducible experimental contusion model of SCI. Contrast agent is re-injected 15 min following the injury to assess post-SCI SCBF changes. CEU allows for real time and in-vivo assessment of SCBF changes following SCI. In the uninjured animal, ultrasound imaging showed uneven blood flow along the intact spinal cord. Furthermore, 15 min post-SCI, there was critical ischemia at the level of the epicenter while SCBF remained preserved in the more remote intact areas. In the regions adjacent to the epicenter (both rostral and caudal), SCBF was significantly reduced. This corresponds to the previously described &#8220;ischemic penumbra zone&#8221;. This tool is of major interest for assessing the effects of therapies aimed at limiting ischemia and the resulting tissue necrosis subsequent to SCI.

Contrast Enhanced Ultrasound imaging is a reliable in-vivo tool for quantifying spinal cord blood flow in an experimental rat spinal cord injury model. This paper contains a comprehensive protocol for application of this technique in association with a contusion model of thoracic spinal cord injury.

Reduced spinal cord blood flow (SCBF) (i.e., ischemia) plays a key role in traumatic spinal cord injury (SCI) pathophysiology and is accordingly an ...

An In Vivo Duo-color Method for Imaging Vascular Dynamics Following Contusive Spinal Cord Injury

Spinal cord injury (SCI) causes significant vascular disruption at the site of injury. Vascular pathology occurs immediately after SCI and continues throughout the acute injury phase. In fact, endothelial cells appear to be the first to die after a contusive SCI. The early vascular events, including increased permeability of the blood-spinal cord barrier (BSCB), induce vasogenic edema and contribute to detrimental secondary injury events caused by complex injury mechanisms. Targeting the vascular disruption, therefore, could be a key strategy to reduce secondary injury cascades that contribute to histological and functional impairments after SCI. Previous studies were mostly performed on postmortem samples and were unable to capture the dynamic changes of the vascular network. In this study, we have developed an in vivo duo-color two-photon imaging method to monitor acute vascular dynamic changes following contusive SCI. This approach allows detecting blood flow, vessel diameter, and other vascular pathologies at various sites of the same rat pre- and post-injury. Overall, this method provides an excellent venue for investigating vascular dynamics.

An In Vivo Duo-color Method for Imaging Vascular Dynamics Following Contusive Spinal Cord Injury

We introduce an in vivo imaging method using two different fluorescent dyes to track dynamic spinal vascular changes following a contusive spinal cord injury in adult Sprague-Dawley rats.

Spinal cord injury (SCI) causes significant vascular disruption at the site of injury. Vascular pathology occurs immediately after SCI and continues ...

Advanced Diffusion Imaging in The Hippocampus of Rats with Mild Traumatic Brain Injury

Mild traumatic brain injury (mTBI) is the most common type of acquired brain injury. Since patients with traumatic brain injury show a tremendous variability and heterogeneity (age, gender, type of trauma, other possible pathologies, etc.), animal models play a key role in unraveling factors that are limitations in clinical research. They provide a standardized and controlled setting to investigate the biological mechanisms of injury and repair following TBI. However, not all animal models mimic the diffuse and subtle nature of mTBI effectively. For example, the commonly used controlled cortical impact (CCI) and lateral fluid percussion injury (LFPI) models make use of a craniotomy to expose the brain and induce widespread focal trauma, which are not commonly seen in mTBI. Therefore, these experimental models are not valid to mimic mTBI. Thus, an appropriate model should be used to investigate mTBI. The Marmarou weight drop model for rats induces similar microstructural alterations and cognitive impairments as seen in patients who sustain mild trauma; therefore, this model was selected for this protocol. Conventional computed tomography and magnetic resonance imaging (MRI) scans commonly show no damage following a mild injury, because mTBI induces often only subtle and diffuse injuries. With diffusion weighted MRI, it is possible to investigate microstructural properties of brain tissue, which can provide more insight into the microscopic alterations following mild trauma. Therefore, the goal of this study is to obtain quantitative information of a selected region-of-interest (i.e., hippocampus) to follow up disease progression after obtaining a mild and diffuse brain injury.

The overall goal of this procedure is to obtain quantitative microstructural information of the hippocampus in a rat with mild traumatic brain injury. This is done using an advanced diffusion-weighted magnetic resonance imaging protocol and region-of-interest based analysis of parametric diffusion maps.

Mild traumatic brain injury (mTBI) is the most common type of acquired brain injury. Since patients with traumatic brain injury show a tremendous ...

Magnetic Resonance Imaging of Multiple Sclerosis at 7.0 Tesla

The overall goal of this article is to demonstrate a state-of-the-art ultrahigh field (UHF) magnetic resonance (MR) protocol of the brain at 7.0 Tesla in multiple sclerosis (MS) patients. MS is a chronic inflammatory, demyelinating, neurodegenerative disease that is characterized by white and gray matter lesions. Detection of spatially and temporally disseminated T2-hyperintense lesions by the use of MRI at 1.5 T and 3 T represents a crucial diagnostic tool in clinical practice to establish accurate diagnosis of MS based on the current version of the 2017 McDonald criteria. However, the differentiation of MS lesions from brain white matter lesions of other origins can sometimes be challenging due to their resembling morphology at lower magnetic field strengths (typically 3 T). Ultrahigh field MR (UHF-MR) benefits from increased signal-to-noise ratio and enhanced spatial resolution, both key to superior imaging for more accurate and definitive diagnoses of subtle lesions. Hence, MRI at 7.0 T has shown encouraging results to overcome the challenges of MS differential diagnosis by providing MS-specific neuroimaging markers (e.g., central vein sign, hypointense rim structures and differentiation of MS grey matter lesions). These markers and others can be identified by other MR contrasts other than T1 and T2 (T2*, phase, diffusion) and substantially improve the differentiation of MS lesions from those occurring in other neuroinflammatory conditions such as neuromyelitis optica and Susac syndrome. In this article, we describe our current technical approach to study cerebral white and grey matter lesions in MS patients at 7.0 T using different MR acquisition methods. The up-to-date protocol includes the preparation of the MR setup including the radio-frequency coils customized for UHF-MR, standardized screening, safety and interview procedures with MS patients, patient positioning in the MR scanner and acquisition of dedicated brain scans tailored for examining MS.

Here, we present a protocol to acquire magnetic resonance (MR) images of multiple sclerosis (MS) patient brains at 7.0 Tesla. The protocol includes preparation of the setup including the radio-frequency coils, standardized interview procedures with MS patients, subject positioning in the MR scanner and MR data acquisition.

The overall goal of this article is to demonstrate a state-of-the-art ultrahigh field (UHF) magnetic resonance (MR) protocol of the brain at 7.0 Tesla in ...

Using Diffusion Tensor Imaging in Traumatic Brain Injury

Source: Laboratories of Jonas T. Kaplan and Sarah I. Gimbel&#8212;University of Southern California
Traditional brain imaging techniques using MRI are very good at visualizing the gross structures of the brain. A structural brain image made with MRI provides high contrast of the borders between gray and white matter, and information about the size and shape of brain structures. However, these images do not detail the underlying structure and integrity of white matter networks in the brain, which consist of axon bundles that interconnect local and distant brain regions.
Diffusion MRI uses pulse sequences that are sensitive to the diffusion of water molecules. By measuring the direction of diffusion, it is possible to make inferences about the structure of white matter networks in the brain. Water molecules within an axon are constrained in their movements by the cell membrane; instead of randomly moving in every direction with equal probability (isotropic movement), they are more likely to move in certain directions, in parallel with the axon (anisotropic movement; Figure 1). Therefore, measures of diffusion anisotropy are thought to reflect properties of the white matter such as fiber density, axon thickness, and degree of myelination. One common measure is fractional anisotropy (FA). FA values range from 0, which represents completely isotropic movement, to 1, reflecting maximum anisotropy.
<img alt="Figure 1" src="/files/ftp_upload/10276/10276fig1.jpg" /> 
Figure 1: Diffusion anisotropy. When the direction of diffusion is unconstrained and random, movement is measured in all directions equally. This is isotropic diffusion (A). When water molecules are contained within the axon of a neuron, diffusion is anisotropic, tending to occur more frequently along the direction of the axon (B). <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/10276/10276fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
In this experiment we will use diffusion tensor imaging (DTI) to measure white matter integrity in traumatic brain injury (TBI). TBI occurs when an external force injures the brain, such as a blow to the head or a sudden movement like the kind that might occur in a car accident. This type of brain injury from mechanical forces is associated with diffuse axonal injury-damage to white matter throughout the brain. Because it is an injury affecting white matter integrity, standard neuroimaging techniques may not reveal the damage. However, measures of diffusion are especially sensitive to these anatomical changes. Following a study by Kraus et al.1, we compare a group of healthy controls to a group of people with TBI and use diffusion imaging to measure the effect of TBI on cerebral white matter. Furthermore, we will test the relationship between white matter integrity and cognitive function using an attention task.2 This study uses a region of interest (ROI) approach focusing on three white matter tracts: the splenium of the corpus callosum, the anterior corona radiata, and the superior longitudinal fasciculus (Figure 2).
<img alt="Figure 2" src="/files/ftp_upload/10276/10276fig2.jpg" /> 
Figure 2: Regions of interest. The three ROIs, defined from the ICBM DTI-81 atlas, are shown here in horizontal slices through the brain. In green is the splenium of the corpus callosum. The splenium is the most posterior part of the corpus callosum. In blue is the anterior corona radiata. The superior longitudinal fasciculus is shown in red. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/10276/10276fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Diffusion Tensor Imaging in Traumatic Brain Injury

Source: Laboratories of Jonas T. Kaplan and Sarah I. Gimbel&#8212;University of Southern California
Traditional brain imaging techniques using MRI are ...

Diffusion Tensor Magnetic Resonance Imaging in Chronic Spinal Cord Compression

Summary

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Chapters in this video

Dissection and Culture of Commissural Neurons from Embryonic Spinal Cord

Multiple-mouse Neuroanatomical Magnetic Resonance Imaging

Diffusion Tensor Magnetic Resonance Imaging in the Analysis of Neurodegenerative Diseases

Quantitative Magnetic Resonance Imaging of Skeletal Muscle Disease

Diffusion Imaging in the Rat Cervical Spinal Cord

Contrast Enhanced Ultrasound Imaging for Assessment of Spinal Cord Blood Flow in Experimental Spinal Cord Injury

An In Vivo Duo-color Method for Imaging Vascular Dynamics Following Contusive Spinal Cord Injury

Advanced Diffusion Imaging in The Hippocampus of Rats with Mild Traumatic Brain Injury

Magnetic Resonance Imaging of Multiple Sclerosis at 7.0 Tesla

Using Diffusion Tensor Imaging in Traumatic Brain Injury