White-matter integrity in patients with systemic lupus erythematosus and memory deficits

PURPOSE

Cognitive dysfunction is common in neuropsychiatric systemic lupus erythematosus (SLE). Memory is a commonly affected cognitive domain. Clinically, however, it is difficult to detect memory deficits. The objective of this study is to evaluate whether normal controls and SLE patients with and without memory deficit differ in terms of white-matter integrity.

METHODS

Twenty SLE patients with memory deficit were compared to 47 SLE patients without memory deficit and 22 sex-, age-, and education-matched control individuals. Diffusion tensor imaging (DTI) was performed in a 1.5-Tesla scanner. For tract-based spatial statistics analysis, a white-matter skeleton was created. A permutation-based inference with 5000 permutations with a threshold of p < 0.05 was used to identify abnormalities in fractional anisotropy (FA). The mean diffusivity (MD), radial diffusivity (RD) and axial diffusivity (AD) were also projected onto the mean FA skeleton.

RESULTS

Compared to controls, SLE patients with and without memory deficit had decreased FA in: bilateral anterior thalamic radiation, inferior fronto-occipital fasciculus, superior longitudinal fasciculus, uncinate fasciculus, corticospinal tract, genu, and body of the corpus callosum. SLE patients with and without memory deficit also presented increased MD and RD values compared to controls in these areas. Comparison between SLE patients with and without memory deficit did not present significant differences in DTI parameters.

CONCLUSION

DTI can detect extensive abnormalities in the normal-appearing white matter of SLE patients with and without memory deficit, compared to controls. However, there was no difference, in terms of white-matter integrity, between the groups of SLE patients.

Quantification of diffusion and anisotropy in intracranial epidermoids using diffusion tensor metrics and p: q tensor decomposition

PURPOSE

To quantitatively evaluate the diffusion tensor metrics p, q, L and fractional anisotropy in intracranial epidermoids in comparison with normal white matter in the splenium of the corpus callosum.

METHODS

This retrospective study included 20 consecutive patients referred to our institute. All patients had a magnetic resonance imaging (MRI) study on a 1.5-Tesla MR system. A spin-echo echo-planar DTI sequence with diffusion gradients along 30 non-collinear directions was performed. The eigen values (λ₁, λ₂, λ₃) were computed for each voxel and, using p: q tensor decomposition, the DTI metrics p, q and L-values and fractional anositropy (FA) were calculated. The region of interest (ROI) (6 pixels each) was placed within the lesion in all the cases and in the splenium of the corpus callosum.

RESULTS

The mean FA in the lesion and splenium were 0.50 and 0.88 respectively, with a statistically significant difference between them (P<0.01). On p: q tensor decomposition, the mean p-value in the epidermoid was 1.55±0.24 and 1.35±0.20 in the splenium; the mean q-values in the epidermoid was 0.67±0.13 and 1.27±0.17 in the splenium; the differences were statistically significant (P=0.01 and <0.01 respectively). The significant difference between p- and q-values in epidermoids compared with the splenium of callosum was probably due to structural and orientation differences in the keratin flakes in epidermoids and white matter bundles in the callosum. However, no significant statistical difference in L-values was noted (P=0.44).

CONCLUSION

DTI metrics p and q have the potential to quantify the diffusion and anisotropy in various tissues thereby gaining information about their internal architecture. The results also suggest that significant differences of DTI metrics p and q between epidermoid and the splenium of the corpus callosum are due to the difference in structural organization within them.

Can diffusion tensor metrics help in preoperative grading of diffusely infiltrating astrocytomas? A retrospective study of 36 cases

INTRODUCTION

Diffusion weighted imaging and diffusion tensor imaging (DTI) give information about the amount and directionality of water diffusion occurring in a given tissue. Here we study the role of diffusion tensor metrics including fractional anisotropy (FA) and spherical anisotropy (CS) in preoperative grading of diffusely infiltrating astrocytomas.

METHODS

We performed DTI in 38 patients with pathologically proven diffusely infiltrating astrocytomas, who were classified into two groups, i.e., 15 patients with high-grade astrocytoma (HGAs, WHO grade III and IV) and 23 patients with low-grade astrocytoma (LGAs, WHO grade II). We measured maximum FA and minimum CS values in all cases from tumor. Histopathological diagnosis was established in all cases.

RESULTS

The mean maximum FA values were higher in HGA (0.583 ± 0.104) than LGA (0.295 ± 0.058), while mean minimum CS values were lower in HGA (0.42 ± 0.121) than LGA (0.722 ± 0.061). The difference in the diffusion tensor indices between HGA and LGA was found to be statistically significant with P value of <0.001. Keeping cutoff FA value of 0.4, all HGAs showed higher maximum FA values, and all LGAs showed lower maximum FA values. Also, all HGAs showed minimum CS values less than a cutoff value of 0.6, and all LGAs showed minimum CS values higher than 0.6.

CONCLUSION

Diffusion tensor metrics such as maximum FA and minimum CS can help to differentiate HGA from LGA.

Diffusion tensor and tensor metrics imaging in intracranial epidermoid cysts

PURPOSE

To explore the utility of diffusion tensor imaging (DTI) and diffusion tensor metrics (DTM) in characterizing the structural pathology of epidermoid cysts. DTI gives information about the tissue structure; a high fractional anisotropy (FA) indicates a highly structured orientation of the tissue, fibers, or white matter tracts. Based on the tensor rank, a set of three metrics has been described that can be used to measure the directional dependence of diffusion: linear anisotropy (CL), planar anisotropy (CP), and spherical anisotropy (CS). DTM takes into account the shape of diffusion anisotropy and hence may provide better insight into the orientation of structures than FA.

MATERIALS AND METHODS

DTI was performed in three patients with epidermoid cysts. FA, directionally-averaged mean diffusivity (Dav), exponential apparent diffusion coefficient (eADC), and DTM, such as CL, CP, and CS, were measured from the tumor core as well as from the normal-appearing white matter. Histopathological correlation was obtained.

RESULTS

Epidermoid cysts showed high FA with Dav values similar to that of normal white matter. eADC maps did not show any restriction of diffusion. FA values were high, but not as high as that for the white matter. CP values were higher and CL values were lower than those obtained for the white matter in various regions.

CONCLUSION

High CP values suggest preferential diffusion of water molecules along a two-dimensional geometry, which could be attributed to the well-structured orientation of keratin filaments and flakes within the tumor as demonstrated by histopathology. Advanced imaging modalities like DTI with DTM can provide information regarding the microstructural anatomy of the epidermoid cysts.

Diffusion tensor anisotropy magnetic resonance imaging: a new tool to assess synovial inflammation

OBJECTIVE

Diffusion tensor imaging (DTI) has been used to study the structure of ordered biological tissue. DTI-derived metrics correlate with inflammatory cytokines and adhesion molecules, expressed in the brain abscess. We aimed to study the role of DTI-derived metrics in delineating the synovitis and their correlation with inflammatory proteins expressed in the SF of chronic inflammatory arthritis patients.

METHODS

DTI was performed on 18 patients and 6 healthy controls. A follow-up DTI at 6 months was performed in 10 patients. Quantification of inflammatory cytokines (TNF-alpha, IL-1beta) and soluble intercellular adhesion molecule-1 (sICAM-1) in SF and their correlation with DTI-derived metrics was performed.

RESULTS

DTI-derived metrics, fractional anisotropy (FA), cylindrical isotropy (CL), planar anisotropy (CP) and spherical isotropy (CS), were significantly altered in the inflamed synovium of the patients as compared to the healthy controls. Significant correlation between FA and TNF-alpha (r = 0.68, P = 0.002) and IL-1beta (r = 0.48, P < 0.05) and inverse correlations between mean diffusivity (MD) and TNF-alpha (r = -0.54, P < 0.05) and CS and TNF-alpha (r = -0.53, P < 0.05) and CP and IL-1beta and sICAM (r = 0.48, P < 0.05 and r = 0.49, P < 0.05, respectively) were observed. A significant correlation between post-contrast signal intensity (PCI) and IL-1beta and sICAM-1 (r = 0.61, P = 0.01 and r = 0.46, P = 0.05) and volume and sICAM-1 (r = 0.45, P = 0.05) was observed, respectively.

CONCLUSION

Results of this pilot study suggest that the DTI-derived metrics have the potential to delineate synovial inflammation; however, it is not superior to conventional MRI for its detection and assessment of therapeutic response.

Diffusion tensor mode in imaging of intracranial epidermoid cysts: one step ahead of fractional anisotropy

INTRODUCTION

The signal characteristics of an epidermoid on T2-weighted imaging have been attributed to the presence of increased water content within the tumor. In this study, we explore the utility of diffusion tensor imaging (DTI) and diffusion tensor metrics (DTM) in knowing the microstructural anatomy of epidermoid cysts.

MATERIALS AND METHODS

DTI was performed in ten patients with epidermoid cysts. Directionally averaged mean diffusivity (D(av)), exponential diffusion, and DTM-like fractional anisotropy (FA), diffusion tensor mode (mode), linear (CL), planar (CP), and spherical (CS) anisotropy were measured from the tumor as well as from the normal-looking white matter.

RESULTS

Epidermoid cysts showed high FA. However, D(av) and exponential diffusion values did not show any restriction of diffusion. Diffusion tensor mode values were near -1, and CP values were high within the tumor. This suggested preferential diffusion of water molecules along a two-dimensional geometry (plane) in epidermoid cysts, which could be attributed to the parallel-layered arrangement of keratin filaments and flakes within these tumors.

CONCLUSION

Thus, advanced imaging modalities like DTI with DTM can provide information regarding the microstructural anatomy of the epidermoid cysts.

Can we differentiate true white matter fibers from pseudofibers inside a brain abscess cavity using geometrical diffusion tensor imaging metrics?

High fractional anisotropy (FA) usually reflects the orientation and integrity of white matter (WM) fibers. Other regions of increased FA have been described, such as brain abscesses, developing cortex, and areas of hemorrhage. It may not be possible to differentiate true fibers from the pseudofibers found inside an abscess cavity on the basis of FA and mean diffusivity (MD). The aim of this study was to differentiate true WM fibers from pseudo WM tracts inside the abscess cavity using geometrical diffusion tensor imaging metrics [linear anisotropy (CL), planar anisotropy (CP), and spherical anisotropy (CS)]. Diffusion tensor imaging was performed in 42 patients with brain abscess and 10 age/sex-matched controls. Automated segmentation using Java-based software divided the abscess cavity into two sub-regions with FA < 0.20 and FA > or = 0.20. Quantitation was carried out on the sub-regions of the abscess cavity with FA > or = 0.20. In healthy controls, regions of interest were placed on the corpus callosum, posterior limb of the internal capsule, and periventricular and subcortical WM. Significantly increased CP values were observed inside the abscess cavity compared with various normal WM regions. Significantly increased FA and CL values were observed in the abscess cavity compared with subcortical WM only. However decreased FA and CL values were observed in the cavity compared with the corpus callosum, posterior limb of the internal capsule, and periventricular WM. The 95% confidence intervals of means for the abscess cavity were well separated from those for WM in the case of CL and CP; however, they overlapped in the case of FA, MD, and CS. High CP with low CL inside the abscess cavity suggests that the shape of the diffusion tensor is predominantly planar, whereas it is linear in WM tracts. These geometrical indices may have advantages over FA for differentiating true from pseudo WM tracts inside the abscess cavity.

Comparison of Diffusion-Weighted MR Imaging and T2-Weighted MR Imaging in Patients with Amyotrophic Lateral Sclerosis

The purpose of this study was to compare diffusion-weighted MR imaging with conventional MR sequences in patients with amyotrophic lateral sclerosis (ALS) and controls, and to assess the diagnostic value of diffusion-weighted imaging in the ALS patients. Twelve patients with ALS (ten men and two women, mean age 56 years) and 12 age-matched control subjects were studied with axial diffusion-weighted imaging and conventional MR imaging. Three adjacent slices of diffusion-weighted imaging were obtained at the level of the internal capsule. The diffusion-weighted imaging was performed with a b-value from 165-600 s/mm(2). Identical slices of diffusion-weighted images and conventional MR images were evaluated by a consensus reading. Diffusion-weighted images showed high signal intensity in the corticospinal tract at the level of the internal capsule in 11/12 patients with ALS (92%) and 5/12 control subjects (42%), whereas T2-weighted images (T2WI) revealed high signal intensity in the corticospinal tract in 11/12 patients with ALS (92%) and 8/12 control subjects (67%). The proton-weighted images (PDWI) disclosed the high signal corticospinal tract in 5/12 patients with ALS (42%), but not in any of the control subjects. Considering ALS patients versus control subjects, statistical analysis demonstrated that diffusion-weighted imaging (p=0.027, X(2) test) and proton-weighted imaging (p=0.037) were more specific than T2-weighted imaging. Diffusion-weighted imaging and proton-weighted imaging were more specific than T2-weighted imaging. The combination of diffusion-weighted imaging and T2WI/PDWI seems a promising tool in the diagnosis of amyotrophic lateral sclerosis.

Quantitative diffusion tensor imaging in amyotrophic lateral sclerosis

OBJECTIVE

Aim of present study was to evaluate changes in diffusion tensor imaging (DTI) parameters in the whole brain of 28 patients with amyotrophic lateral sclerosis (ALS) compared to 26 healthy controls.

METHODS

In both fibertracking and voxel-based analysis, quantitative comparisons of the diffusion parameters between ALS patients and controls were performed. Correlation analyses of diffusion parameters and disease duration and disease severity were performed. A second DTI examination was acquired, allowing the evaluation of the effect of disease progression on the diffusion parameters.

RESULTS

Fibertracking analysis revealed that especially the precentral part of the corticospinal tract (CST) was impaired. In the voxel-based analysis, it was shown that changes of diffusion parameters occurred throughout the brain, including frontal, temporal and parietal lobes. Disease severity was inversely correlated with the fractional anisotropy (FA). In the follow-up examination, a further decline of FA over time could be demonstrated in the CST as well as in the whole brain white matter.

INTERPRETATION

This study provides support for the view of ALS as being a multisystem degenerative disease, in which abnormalities of extra-motor areas play an important role in the in vivo physiopathology.

Presurgical planning for tumor resectioning

Since the birth of functional magnetic resonance imaging (fMRI)-a noninvasive tool able to visualize brain function-now 15 years ago, several clinical applications have emerged. fMRI follows from the neurovascular coupling between neuronal electrical activity and cerebrovascular physiology that leads to three effects that can contribute to the fMRI signal: an increase in the blood flow velocity, in the blood volume and in the blood oxygenation level. The latter effect, gave the technique the name blood oxygenation level dependent (BOLD) fMRI. One of the major clinical uses is presurgical fMRI in patients with brain abnormalities. The goals of presurgical fMRI are threefold: 1) assessing the risk of neurological deficit that follows a surgical procedure, 2) selecting patients for invasive intraoperative mapping, and 3) guiding of the surgical procedure itself. These are reviewed here. Unfortunately, randomized trials or outcome studies that definitively show benefits to the final outcome of the patient when applying fMRI presurgically have not been performed. Therefore, fMRI has not yet reached the status of clinical acceptance. The final purpose of this article is to define a roadmap of future research and developments in order to tilt pre-surgical fMRI to the status of clinical validity and acceptance.