Matter Contrast Research Articles

Possibilities and limitations for high resolution small animal MRI on a clinical whole-body 3T scanner

To investigate the potential of a clinical 3 T scanner to perform MRI of small rodents. Different dedicated small animal coils and several imaging sequences were evaluated to optimize image quality with respect to SNR, contrast and spatial resolution. As an application, optimal grey-white-matter contrast and resolution were investigated for rats. Furthermore, manganese-enhanced MRI was applied in mice with unilateral crush injury of the optic nerve to investigate coil performance on topographic mapping of the visual projection. Differences in SNR and CNR up to factor 3 and more were observed between the investigated coils. The best grey-white matter contrast was achieved with a high resolution 3D T (2)-weighted TSE (SPACE) sequence. Delineation of the retino-tectal projection and detection of defined visual pathway damage on the level of the optic nerve could be achieved by using a T (1)-weighted, 3D gradient echo sequence with isotropic resolution of (0.2 mm)(3). Experimental studies in small rodents requiring high spatial resolution can be performed by using a clinical 3 T scanner with appropriate dedicated coils.

Lesion detection at seven Tesla in multiple sclerosis using magnetisation prepared 3D-FLAIR and 3D-DIR

ObjectivesTo examine the feasibility and value of 7 T 3D T2-weighted Fluid Attenuated Inversion Recovery (FLAIR) and Double Inversion Recovery (DIR) MR sequences for lesion detection in multiple sclerosis (MS).MethodsHigh-resolution 3D-FLAIR and 3D-DIR MR sequences at 7 T were obtained using magnetisation preparation (MP), and compared with 2D-T2-weighted and 3D-T1-weighted sequences in 10 MS patients and five healthy controls. We determined contrast ratios and counted lesions according to anatomical location.ResultsMR imaging at 7 T was safe and allowed multi-contrast imaging within clinically acceptable imaging times. Lesion to white matter (WM) and grey matter (GM) contrast ratios were higher in 3D-MP-FLAIR and 3D-MP-DIR compared with 2D-T2 and 3D-T1. Cortical (mixed+intra-cortical) and total lesion counts were 97/592 on 3D-MP-FLAIR and 100/558 on 3D-MP-DIR compared with 84/384 on 2D-T2 and 42/442 on 3D-T1. More juxta-cortical lesions were seen with 3D-MP-FLAIR (205) and 3D-MP-DIR (133) than with 2D-T2 (125) and 3D-T1 (70). Finally, higher numbers of lesions were found for deep WM lesions: 176 for 3D-MP-FLAIR and 196 for 3D-MP-DIR vs. 155 for 2D-T2 and 131 for 3D-T1.ConclusionsNear isotropic 3D-MP-FLAIR and 3D-MP-DIR allows high quality T2-weighted MR imaging in MS at 7 T, improving (cortical) lesion detection. Key Points • Magnetization prepared 3D-FLAIR and 3D-DIR 7 T MRI provide high quality isotropic images. • MS lesions are well demonstrated by 3D-MP-FLAIR and 3D-MP-DIR at 7 T MRI. • 3D-MP-FLAIR and 3D-MP-DIR at 7 T MRI show many more Virchov-Robin spaces.

7 tesla MRI of microbleeds and white matter lesions as seen in vascular dementia

To evaluate 7T MRI in the assessment of cerebrovascular alterations as seen in vascular dementia by means of detection of cerebral microbleeds (CMB) and depiction of white matter lesions (WML). 7T imaging was evaluated with respect to 1.5T. Ten healthy volunteers and 10 patients with CMBs and/or WMLs were examined at 1.5T and 7T using gradient-echo (T2*, SWI) and turbo-spin-echo sequences (FLAIR). Comparisons of image quality, CMB and WML detection rates between sequences and field strengths were performed. Using high-resolution SWI at 7T 129 CMBs were detected compared to 75 at 1.5T using clinical SWI. With T2* at 7T 101 CMBs could be detected (33 CMBs at 1.5T). Lesion sizes were significantly larger for higher field strength. FLAIR images at 7T highlighted WMLs known from 1.5T with comparable extent. Gray and white matter contrast in FLAIR was slightly better at 1.5T, whereas image resolution and contrast of the WMLs to surrounding tissue was higher at 7T. By means of higher sensitivity for CMBs, 7T (SWI, T2*) might have significant impact on the early detection, diagnosis, and optimized antithrombotic therapy of cerebrovascular patients (eg, vascular dementia) in the future. Given the current state of technical development, 7T is approximately on par with 1.5T in the depiction of WMLs and their distribution, but holds the potential for future improvements.

Detection of Epileptogenic Cortical Malformations with Surface-Based MRI Morphometry

Magnetic resonance imaging has revolutionized the detection of structural abnormalities in patients with epilepsy. However, many focal abnormalities remain undetected in routine visual inspection. Here we use an automated, surface-based method for quantifying morphometric features related to epileptogenic cortical malformations to detect abnormal cortical thickness and blurred gray-white matter boundaries. Using MRI morphometry at 3T with surface-based spherical averaging techniques that precisely align anatomical structures between individual brains, we compared single patients with known lesions to a large normal control group to detect clusters of abnormal cortical thickness, gray-white matter contrast, local gyrification, sulcal depth, jacobian distance and curvature. To assess the effects of threshold and smoothing on detection sensitivity and specificity, we systematically varied these parameters with different thresholds and smoothing levels. To test the effectiveness of the technique to detect lesions of epileptogenic character, we compared the detected structural abnormalities to expert-tracings, intracranial EEG, pathology and surgical outcome in a homogeneous patient sample. With optimal parameters and by combining thickness and GWC, the surface-based detection method identified 92% of cortical lesions (sensitivity) with few false positives (96% specificity), successfully discriminating patients from controls 94% of the time. The detected structural abnormalities were related to the seizure onset zones, abnormal histology and positive outcome in all surgical patients. However, the method failed to adequately describe lesion extent in most cases. Automated surface-based MRI morphometry, if used with optimized parameters, may be a valuable additional clinical tool to improve the detection of subtle or previously occult malformations and therefore could improve identification of patients with intractable focal epilepsy who may benefit from surgery.

Phase contrast imaging in neonates

Magnetic resonance phase images can yield superior gray and white matter contrast compared to conventional magnitude images. However, the underlying contrast mechanisms are not yet fully understood. Previous studies have been limited to high field acquisitions in adult volunteers and patients. In this study, phase imaging in the neonatal brain is demonstrated for the first time. Compared to adults, phase differences between gray and white matter are significantly reduced but not inverted in neonates with little myelination and iron deposits in their brains. The remaining phase difference between the neonatal and adult brains may be due to a different macromolecule concentration in the unmyelinated brain of the neonates and thus a different frequency due to water macromolecule exchange. Additionally, the susceptibility contrast from brain myelination can be separately studied in neonates during brain development. Therefore, magnetic resonance phase imaging is suggested as a novel tool to study neonatal brain development and pathologies in neonates.

可変フリップ角を用いた３Ｄ−Ｔ２強調像（３Ｄ−ＳＰＡＣＥ）におけるコントラスト特性の検討

Sampling perfection with application optimized contrasts using different flip angle evolution (3D-SPACE) sequence enables one to decrease specific absorption rate (SAR) by using variable flip angle refocusing pulse. Therefore, it is expected that the contrast obtained with 3D-SPACE sequences is different from that of spin echo (SE) images and turbo spin echo (TSE) images. The purpose of this study was to evaluate the characteristics of the signal intensity and central nervous system (CNS) image contrast in T(2) weighted 3D-SPACE. Using 3 different sequences (SE, 3D-TSE and 3D-SPACE) with TR/TE=3500/70, 90 and 115 ms, we obtained T(2) weighted magnetic resonance (MR) images of inhouse phantom and five healthy volunteers' brain. Signal intensity of the phantom which contains various T(1) and T(2) value was evaluated. Tissue contrasts of white/gray matter, cerebrospinal fluid (CSF)/subcutaneous fat and gray matter/subcutaneous fat were evaluated for a clinical image study. The phantom study showed that signal intensity in 3D-SPACE significantly decreased under a T(1) value of 250 ms. It was markedly decreased in comparison to other sequences, as effective echo time (TE) was extended. White/gray matter contrast of 3D-SPACE was the highest in all sequences. On the other hand, CSF/fat and gray matter/fat contrast of 3D-SPACE was higher than TSE but lower than SE. CNS image contrasts of 3D-SPACE were comparable to that of SE. Signal intensity had decreased in the range where T(1) and T(2) values were extremely short.

Cervical spinal cord multiple sclerosis: evaluation with 2D multi-echo recombined gradient echo MR imaging

Objective: The two-dimensional multi-echo recombined gradient echo (MERGE) technique automatically acquires and sums multiple gradient echoes at various echo times in cervical spine magnetic resonance (MR) imaging. This technique increases the grey–white matter contrast within the spinal cord and should also improve the depiction of cervical cord lesions. The aim of this study was to qualitatively and quantitatively evaluate MERGE imaging compared with T2-weighted fast spin-echo (T2WFSE) imaging for depicting multiple sclerosis (MS) lesions in the cervical cord.Methods: Nineteen consecutive patients (10 males and 9 females; age range 22–62 years, mean age 43.6 years) with clinically diagnosed MS were examined with cervical spinal cord MR imaging at 3 T including both MERGE and T2WFSE imaging. Qualitative evaluation for MS lesion conspicuity was performed. The quantitative criterion utilized to compare MERGE imaging with T2WFSE imaging was the lesion-to-background contrast-to-noise ratio (CNR).Results: MERGE imaging showed 79 lesions and missed 1 that was depicted on T2WFSE imaging. T2WFSE imaging showed 46 lesions and missed 34 that were depicted on MERGE imaging. MERGE imaging was markedly superior to T2WFSE imaging in rendering greater lesion conspicuity. In the quantitative evaluation, the lesion-to-background CNR upon MERGE imaging was significantly higher than that upon T2WFSE imaging (P < 0.001, paired t-test).Conclusions: MERGE imaging in the cervical spinal cord increases detection and conspicuity of MS lesions. Strong consideration should be given to utilizing axial MERGE images in the diagnosis and follow-up study of cervical cord MS.

Human imaging at 9.4 T using T2*‐, phase‐, and susceptibility‐weighted contrast

The effect of susceptibility differences on an MR image is known to increase with field strength. Magnetic field inhomogeneities within the voxels influence the apparent transverse relaxation time T(2) *, while effects due to different precession frequencies between voxels caused by local field variations are evident in the image phase, and susceptibility-weighted imaging highlights the veins and deep brain structures. Here, these three contrast mechanisms are examined at a field strength of 9.4 T. The T(2) * maps generated allow the identification of white matter structures not visible in conventional images. Phase images with in-plane resolutions down to 130 μm were obtained, showing high gray/white matter contrast and allowing the identification of internal cortical structures. The susceptibility-weighted images yield excellent visibility of small venous structures and attain an in-plane resolution of 175 μm.

Parapharyngeal space neuroglial heterotopia with tumoral differentiation

For safe 3T-MRI of patients with VNS (vagus nerve stimulator), specific conditions are mandatory. However, application of these conditions can lead to a loss of image quality. In this work, we evaluated the diagnostic value of 3T-MRI in VNS patients with pharmacoresistant epilepsy.Using a transmit-and-receive head coil and adapting our sequences to allow for low SAR (specific absorption rate), we examined 15 patients with pharmacoresistant epilepsy. Diagnostic quality was assessed by comparison of the SNR (signal to noise ratio) and CNR (contrast to noise ratio) of the hippocampus, the grey-white matter contrast and epileptogenic lesions to images of patients without VNS acquired with our routine 3T-MRI protocol and the 32-channel head coil.3T-MRI is feasible in VNS-patients. Image quality is adequate for detection and follow-up of epileptogenic lesions such as ganglioglioma or PNH (periventricular nodular heterotopia). Due to a significant reduction of SNR and CNR, the diagnostic value for subtle lesions may be decreased. Overall, the feasibility of 3T-MRI is beneficial in the diagnostic workup and follow-up of epilepsy-patients with VNS.

Streptococcus suisMeningitis, Hawaii

<i>Streptococcus suis</i>Meningitis, Hawaii

Impact Speed Does Not Determine Severity of Spinal Cord Injury in Mice with Fixed Impact Displacement

The speed of three leading rodent SCI impacting devices—0.1 m/s (Infinite Horizon), 0.2 m/s (Ohio State University), and 0.4 m/s (New York University)—were investigated using a custom-fabricated impactor to determine its effect on mouse spinal cord injury severity. The spared white matter was examined at 7 and 21 days post-injury with in vivo diffusion tensor imaging (DTI) and post-mortem histology, respectively. The neurological outcome of the injured mice was longitudinally evaluated using the Basso mouse scale. In vivo DTI derived diffusion anisotropy maps provided excellent gray-white matter contrast enabling objective and noninvasive quantification of normal appearing white matter. In vivo DTI estimated spared white matter content correlated well with those determined using post-mortem histology. No significant difference in BMS was observed among injury groups of various impact speeds. The present results suggest that injury severity can be reproduced using speeds from 0.1 to 0.4 m/s at the fixed impact displacement.

Age-associated alterations in cortical gray and white matter signal intensity and gray to white matter contrast

Prior studies have focused on patterns of brain atrophy with aging and age-associated cognitive decline. It is possible that changes in neural tissue properties could provide an important marker of more subtle changes compared to gross morphometry. However, little is known about how MRI tissue parameters are altered in aging. We created cortical surface models of 148 individuals and mapped regional gray and white matter T1-weighted signal intensities from 3D MPRAGE images to examine patterns of age-associated signal alterations. Gray matter intensity was decreased with aging with strongest effects in medial frontal, anterior cingulate, and inferior temporal regions. White matter signal intensity decreased with aging in superior and medial frontal, cingulum, and medial and lateral temporal regions. The gray/white ratio (GWR) was altered throughout a large portion of the cortical mantle, with strong changes in superior and inferior frontal, lateral parietal, and superior temporal and precuneus regions demonstrating decreased overall contrast. Statistical effects of contrast changes were stronger than those of cortical thinning. These results demonstrate that there are strong regional changes in neural tissue properties with aging and tissue intensity measures may serve as an important biomarker of degeneration.

Isotropic Sub-Millimeter fMRI of V5 in Human at 7T

Introduction: Recently a combination of a zoomed approach (reduced FOV) with parallel imaging was proposed, to improve the image quality of single-shot EPI acquisitions [1]. For high resolution single-shot EPI at high field strength the use of parallel imaging is mandatory to address the problems of susceptibility induced geometric distortions and blurring due to T2* decay. However, imperfect parallel image reconstruction can result in remaining aliasing artifacts. The combination of parallel imaging with a zoomed approach can eliminate this specific problem, enabling high resolution fMRI acquisitions at ultra-high field strength [2]. Since human cortex is convoluted, the use of isotropic resolution is essential to identify specific areas, as for example V5, within the layer structure. The goal of this study is to demonstrate the feasibility of sub-millimeter isotropic resolution fMRI at ultra-high field strength. Methods: All experiments were performed on a 7T whole-body MR scanner (MAGNETOM 7T, Siemens Healthcare Sector, Erlangen, Germany). An 8element phased array head coil (RAPID, Wurzburg, Germany) was used. Eight healthy volunteers were included in the study; informed consent was obtained before each study. A functional paradigm with blocks of 40s stimulus-on and stimulus-off was used with 8 epochs for a total acquisition time of 20 min. For stimulus-on an expanding and contracting star field and for stimulus-off a static star field was shown to the subjects to activate the motion sensitive area V5. The experiments were performed with a zoomed EPI sequence (TR=5000ms, TE=27, FOV=43x128mm, 15 slices, voxel size=0.7x0.7x0.7mm) with OVS using a SKEWED pulse as proposed in [3,4] and a GRAPPA reconstruction with a 2D convolution kernel [5] with 3 source points along the readout direction and four source points along phase encoding direction and an acceleration factor of three. Results and Discussion: Fig.1 shows the mean EPI image from two different fMRI acquisitions, acquired within a time frame of one month from the same subject. The activation pattern is overlaid onto the mean EPI images. The zoomed EPI acquisition with an isotropic resolution of 0.8 mm is shown in Fig. 1a, while Fig. 1b shows nearly the same slice with an isotropic resolution of 0.7 mm acquired a month later. Enlarged sections of those images are shown in Fig. 2 with the activation pattern (Fig. 2a and 2b) and without the activation pattern (Fig. 2c and 2d). Normally the activation pattern is overlaid onto an anatomical scan with good gray/white matter contrast. In this study the activation pattern is overlaid onto the mean images from the EPI raw images. Due to this, there is no potential error in the registration as might occur whenever the activation pattern is overlaid onto anatomical images from a separate scan. As can be seen in Fig. 2, the activation is mostly concentrated above and below the vein but not within the vein. Conclusion: Sub-millimeter isotropic resolution fMRI is feasible at ultra-high field strength using a combination of parallel imaging and a zoomed approach. The open question, whether gradient echo EPI acquisitions at ultra-high field strength mostly show activations arising from oxygenation changes in larger veins, is not fully answered. However, in this case it is clear that the V5 activation does not come from the big adjacent vein. Further studies should allow studying cortical layer-specific activations.

Investigating the sources of phase contrast: iron oxide nanoparticle study to exclude deoxyhemoglobin as a major source for the gray/white matter phase contrast

Introduction Recently, the benefits of image phase for the study of brain anatomy at high field (> 7 T) have been demonstrated [1]. In some brain regions, the improved contrast to noise ratio (over the magnitude images) between and within grey and white matter structures has provided the opportunity to study the laminar structure of the cortex. Several sources such as iron [1,2], myelin [3], deoxy-hemoglobin [4], and macromolecular concentration [5] have been suggested to contribute to the phase contrast. However, the relative contribution of these sources is not well understood. Recently, Marques et al. [6] used an oxygen challenge in rat to demonstrate a relatively small contribution of deoxy-hemoglobin. However, quantitative interpretation of this result was compromised by the limited contrast modulation introduced by this challenge and potential confounds such as associated blood volume changes. Therefore, the result did not fully eliminate deoxy-hemoglobin as a substantial contributor to gray/white matter phase contrast. Here, we administered iron oxide nanoparticles that induce a relatively large increase in vascular susceptibility to further confirm that deoxy-hemoglobin is not a major source for the gray/white matter contrast. Methods All scans were performed at a 7 Tesla (Bruker BioSpin) animal system with a 4 channel surface coil. The scan sequence for phase images was a 2D multi-echo GRE sequence with FOV = 2.56 x 2.56 cm, resolution = 67 x 67 x 500 μm, flip angle = 60o, TR = 1 sec, TE = 8 / 20 / 32 msec, 4 average, and total scan time = 27 min. After coil-combining, phase images were unwrapped and filtered by a 2D Gaussian high-pass filter (FWHM = 26 voxels) to remove large scale phase variations. The frequency images were calculated from a linear fit to the phase change over the three echoes. T2 * values were also calculated from the multi-echo magnitude data. Scans were performed on an isoflurane anesthetized rat before and after various intravascular administrations of an iron oxide nanoparticle solution (Molday ION, BioPAL). Cumulative doses of 0.5, 0.8, and 3 mg/kg (adjusted for half life) were used. Images were acquired 5 min. after each injection.

Time-efficient fast spin echo imaging at 4.7 T with low refocusing angles

An implementation of fast spin echo at 4.7 T designed for versatile and time-efficient T(2)-weighted imaging of the human brain is presented. Reduced refocusing angles (alpha < 180 degrees) were employed to overcome specific absorption rate (SAR) constraints and their effects on image quality assessed. Image intensity and tissue contrast variations from heterogeneous RF transmit fields and incidental magnetization transfer effects were investigated at reduced refocusing angles. We found that intraslice signal variations are minimized with refocusing angles near 180 degrees, but apparent gray/white matter contrast is independent of refocusing angle. Incidental magnetization transfer effects from multislice acquisitions were shown to attenuate white matter intensity by 25% and gray matter intensity by 15% at 180 degrees; less than 5% attenuation was seen in all tissues at flip angles below 60 degrees. We present multislice images acquired without excess delay time for SAR mitigation using a variety of protocols. Subsecond half Fourier acquisition single-shot turbo spin echo (HASTE) images were obtained with a novel variable refocusing angle echo train (20 degrees < alpha < 58 degrees) and high-resolution scans with a voxel volume of 0.18 mm(3) were acquired in 6.5 min with refocusing angles of 100 degrees.

DENSITY PERTURBATIONS IN DECAYING HOLOGRAPHIC DARK ENERGY MODELS

We study cosmological perturbations in the context of an interacting dark energy model, where the holographic dark energy with IR cutoff decays into the cold dark matter (CDM). For this purpose, we introduce three IR cutoffs of Hubble horizon, particle horizon, and future event horizon. Here we present small perturbations under the case that effective equation of state (EOS: ωeff) for the holographic energy density is determined to be the same negative constant as that for the CDM. Such new matter productions tend to dilute the density perturbations of CDM (matter contrast). For a decelerating universe of ωeff&gt; -1/3, the matter contrast is growing as the universe evolves, while for an accelerating universe of ωeff&lt; -1/3, the matter contrast is decaying, irrespective of the choice of IR cutoff. This shows clearly that the acceleration suppresses the growing of the density perturbations at the early universe.

Changes in Relative Glucose Metabolic Rate Following Cortisol Administration in Aging Veterans with Posttraumatic Stress Disorder: An FDG-PET Neuroimaging Study

Changes in Relative Glucose Metabolic Rate Following Cortisol Administration in Aging Veterans with Posttraumatic Stress Disorder: An FDG-PET Neuroimaging Study

Spin-echo T1-weighted Imaging of the Brain with Interleaved Acquisition and Presaturation Pulse at 3 T: A Feasibility Study Before Clinical Use

Although spin-echo (SE) sequence has some advantages over gradient-echo sequence in brain imaging, gradient-echo sequence is commonly used for T1-weighted imaging (T1WI) at 3 T because contrast on SE T1WI is widely believed to be poor at 3 T. Recently, gray-white matter contrast on single-slice and multi-slice SE imaging with interslice gap was reported as better at 3 T than at 1.5 T. This study examined the feasibility of interleaved SE T1WI of the brain at 3 T. This study also examined whether presaturation pulse (PP) sufficiently suppresses intra-arterial signals because these signals tend to be hyperintense due to longer T1 at 3 T.Subjects consisted of 18 healthy volunteers. Two sets of T1WI were performed using SE sequence. One set consisted of imaging without PP, and the other consisted of imaging with PP. Each set contained three types of gapless imaging as follows; sequential, 100% interleaved, and 200% interleaved imaging. In each subject, contrast-to-noise ratio between gray-matter and white-matter (CNR(GM-WM)) and intra-arterial signals were evaluated.CNR(GM-WM) was significantly higher on interleaved images than on sequential images, regardless of PP (P < .0001). PP sufficiently suppressed intra-arterial signals (P < .0001).CNR(GM-WM) on SE T1WI at 3 T can be improved by interleaved acquisition, and PP sufficiently suppressed intra-arterial signals. Interleaved SE T1WI with PP appears clinically feasible at 3 T.

Techniques for in utero, longitudinal MRI of fetal brain development in baboons at 3 T

Magnetic Resonance Imaging (MRI) is a promising tool for the noninvasive, longitudinal study of developing primate brains. We developed a protocol to scan pregnant baboons serially at 3 T for up to 3 h per session. This protocol includes procedures for animal preparation, anesthesia, MRI scanning, and post-scan animal care. We applied this protocol to scan 5 baboons multiple times across the latter 70% of gestation—from as early as 56 days post-conceptional age to as late as 185 days (term ∼180 days). We successfully acquired high-resolution anatomical images and maps of relaxation times ( T 1 and T 2) of the fetal brains at multiple time points across gestation. These images and maps demonstrated the convergence of gray and white matter contrast near term, and furthermore demonstrated that the convergence of contrast is a consequence of the continuous change in relaxation times during fetal brain development. We estimated the rates of decrease of T 1 and T 2 in white matter and gray matter, respectively. In addition, we measured the volumes of fetal brain at different gestational ages and calculated the growth rates of whole brain (0.91 ± 0.08 cm 3/day) and cortical gray matter (0.40 ± 0.04 cm 3/day). We also measured the mean diffusivity in white matter and deep gray matter using diffusion tensor imaging. In conclusion, in utero MRI of fetal baboon brains greatly enhances the use of nonhuman primate models to study fetal brain development longitudinally.

Impact speed does not determine severity of spinal cord injury in mice with fixed impact displacement

The speed of three leading rodent SCI impacting devices-0.1 m/s (Infinite Horizon), 0.2 m/s (Ohio State University), and 0.4 m/s (New York University)-were investigated using a custom-fabricated impactor to determine its effect on mouse spinal cord injury severity. The spared white matter was examined at 7 and 21 days post-injury with in vivo diffusion tensor imaging (DTI) and post-mortem histology, respectively. The neurological outcome of the injured mice was longitudinally evaluated using the Basso mouse scale. In vivo DTI derived diffusion anisotropy maps provided excellent gray-white matter contrast enabling objective and noninvasive quantification of normal appearing white matter. In vivo DTI estimated spared white matter content correlated well with those determined using post-mortem histology. No significant difference in BMS was observed among injury groups of various impact speeds. The present results suggest that injury severity can be reproduced using speeds from 0.1 to 0.4 m/s at the fixed impact displacement.