In vivo precision of bootstrap algorithms applied to diffusion tensor imaging data

Purpose:

To determine the precision for in vivo applications of model and non–model‐based bootstrap algorithms for estimating the measurement uncertainty of diffusion parameters derived from diffusion tensor imaging data.

Materials and Methods:

Four different bootstrap methods were applied to diffusion datasets acquired during 10 repeated imaging sessions. Measurement uncertainty was derived in eight manually selected regions of interest and in the entire brain white matter and gray matter. The precision of the bootstrap methods was analyzed using coefficients of variation and intra‐class correlation coefficients. Comprehensive simulations were performed to validate the results.

Results:

All bootstrap algorithms showed similar precision which slightly varied in dependence of the selected region of interest. The averaged coefficient of variation in the selected regions of interest was 13.81%, 12.35%, and 17.93% with respect to the apparent diffusion coefficient, the fractional anisotropy value, and the cone of uncertainty, respectively. The repeated measurements showed a very high similarity with intraclass‐correlation coefficients larger than 0.96. The simulations confirmed most of the in vivo findings.

Conclusion:

All investigated bootstrap methods perform with a similar, high precision in deriving the measurement uncertainty of diffusion parameters. Thus, the time‐efficient model‐based bootstrap approaches should be the method of choice in clinical practice. J. Magn. Reson. Imaging 2012;36:979–986. © 2012 Wiley Periodicals, Inc.     

Cerebral asymmetry in patients with schizophrenia: A voxel‐based morphometry (VBM) and diffusion tensor imaging (DTI) study

Purpose:

To evaluate the differences in gray‐ and white‐matter asymmetry between schizophrenia patients and normal subjects.

Materials and Methods:

Forty‐eight right‐handed patients with chronic schizophrenia (24 males and 24 females) and 48 right‐handed age‐ and sex‐matched healthy controls (24 males and 24 females) were included in this study. The effects of diagnosis on gray‐matter volume asymmetry and white‐matter fractional anisotropy (FA) asymmetry were evaluated with use of voxel‐based morphometry (VBM) and voxel‐based analysis of FA maps derived from diffusion tensor imaging (DTI), respectively.

Results:

The mean gray‐ and white‐matter volumes were significantly smaller in the schizophrenia group than in the control group. The voxel‐based morphometry (VBM) showed no significant effect of diagnosis on gray‐matter volume asymmetry. The voxel‐based analysis of DTI also showed no significant effect of diagnosis on white‐matter FA asymmetry.

Conclusion:

Our results of voxel‐based analyses showed no significant differences in either gray‐matter volume asymmetry or white‐matter FA asymmetry between schizophrenia patients and normal subjects. J. Magn. Reson. Imaging 2010;31:221–226. © 2009 Wiley‐Liss, Inc.     

Regional atrophy of transcallosal prefrontal connections in cognitively normal APOE ϵ4 carriers

Purpose

To investigate the possible effect of the APOE ?4 allele on age‐related regional volume loss within the corpus callosum (CC) in healthy ?4 allele carriers compared with noncarriers.

Materials and Methods

A total of 211 subjects, ages 27 to 83 years, 51 ?4 carriers and 160 noncarriers underwent T1‐weighted MRI scan. All subjects had normal MRI scan and performed within normal range on a neuropsychological battery of tests. CC was segmented into seven functionally relevant regions using a previously published probabilistic map of the CC connectivity. We measured the volumes of the CC and its subregions. We used a regression model (with volumes as dependent and age as independent variables) and compared the slopes between carriers and noncarriers using an analysis of covariance model. We also carried out voxel‐based‐morphometry analysis to investigate the possible effect of the APOE ?4 gene on the gray matter.

Results

We found that the volume of the CC and all subregions decreased with increasing age in both groups. The slope was steeper in the APOE ?4 carriers compared withthe noncarriers particularly in the prefrontal region (P = 0.02). No gray matter differences were observed between the two groups.

Conclusion

APOE ?4 polymorphism is associated with accelerated age‐related volume loss in the prefrontal callosal tracts without gray matter loss. This result suggests the role of APOE ?4 in the brain aging by primarily affecting white matter structures particularly in the frontal lobe. J. Magn. Reson. Imaging 2009;29:1021–1026. © 2009 Wiley‐Liss, Inc.

     

Validation of functional diffusion maps (fDMs) as a biomarker for human glioma cellularity

Purpose:

To present comprehensive examinations of the assumptions made in functional diffusion map (fDM) analyses and provide a biological basis for fDM classification.

Materials and Methods:

Sixty‐nine patients with gliomas were enrolled in this study. To determine the sensitivity of apparent diffusion coefficients (ADCs) to cellularity, cell density from stereotactic biopsy specimens was correlated with preoperative ADC maps. For definition of ADC thresholds used for fDMs, the 95% confidence intervals (CI) for changes in voxel‐wise ADC measurements in normal appearing tissue was analyzed. The sensitivity and specificity to progressing disease was examined using both radiographic and neurological criteria.

Results:

Results support the hypothesis that ADC is inversely proportional to cell density with a sensitivity of 1.01 × 10^?7 [mm²/s]/[nuclei/mm²]. The 95% CI for white matter = 0.25 × 10^?3 mm²/s, gray matter = 0.31 × 10^?3 mm²/s, a mixture of white and gray matter = 0.40 × 10^?3 mm²/s, and a mixture of white matter, gray matter, and cerebrospinal fluid = 0.75 × 10^?3 mm²/s. Application of these measurements as ADC thresholds produce varying levels of sensitivity and specificity to disease progression, which were all significantly better than chance.

Conclusion:

This study suggests fDMs are valid biomarkers for brain tumor cellularity. J. Magn. Reson. Imaging 2010;31:538–548. ©2010 Wiley‐Liss, Inc.

     

Stimulated echo induced misestimates on diffusion tensor indices and its remedy

Purpose:

To report possible erroneous estimates of diffusion parameters in the twice‐refocused spin‐echo (TRSE) technique, proposed to eliminate eddy‐current‐induced geometric distortions in diffusion‐weighted echo‐planar imaging, when stimulated echo signals are inappropriately included.

Materials and Methods:

Eleven subjects were included for imaging experiments on two 1.5 Tesla systems using the TRSE sequence. Three versions, two with unbalanced crusher gradients inserted to dephase the stimulated echo from the b = 0 images and one with balanced crusher gradients, were implemented. The apparent diffusion coefficients (ADC) and fractional anisotropy (FA) were derived and compared.

Results:

The ADCs obtained with unbalanced crusher gradients were closer to values reported in the literature. Stimulated echo led to ADC over‐estimations by 34.2%, 50.4%, 54.0%, 51.5%, 24.0%, and 41.9% in the genu of corpus callosum, splenium of corpus callosum, bilateral corona radiata, internal capsule, mediofrontal gyrus, and the cuneus, respectively (P < 0.01), with concomitant reduction in FA in highly anisotropic regions. Over‐estimations of diffusion coefficients were found to be roughly equal along all directions.

Conclusion:

Formation of stimulated echo in the TRSE technique can lead to erroneous estimations of the diffusion parameters, even if no prominent morphological artifacts are seen. J. Magn. Reson. Imaging 2010;31:1522–1529. © 2010 Wiley‐Liss, Inc.     

Diffusion tensor spectroscopy (DTS) of human brain.

The diffusion tensor of N-acetyl aspartate (NAA), creatine and phosphocreatine (tCr), and choline (Cho) was measured at 3T using a diffusion weighted STEAM (1)H-MRS sequence in the healthy human brain in 6 distinct regions (4 white matter and 2 cortical gray matter). The Trace/3 apparent diffusion coefficient (ADC) of each metabolite was significantly greater in white matter than gray matter. The Trace/3 ADC values of tCr and Cho were found to be significantly greater than NAA in white matter, whereas all 3 metabolites had similar Trace/3 ADC in cortical gray matter. Fractional anisotropy (FA) values for all 3 metabolites were consistent with water FA values in the 4 white matter regions; however, metabolite FA values were found to be higher than expected in the cortical gray matter. The principal diffusion direction derived for NAA was in good agreement with expected anatomic tract directions in the white matter.     

Preliminary evidence of altered gray and white matter microstructural development in the frontal lobe of adolescents with attention-deficit hyperactivity disorder: a diffusional kurtosis imaging study

Purpose

To investigate non‐Gaussian water diffusion using diffusional kurtosis imaging (DKI) to assess age effects on gray matter (GM) and white matter (WM) microstructural changes in the prefrontal cortex (PFC) of adolescents with attention‐deficit hyperactivity disorder (ADHD) compared to typically developing controls (TDC).

Materials and Methods

In this preliminary cross‐sectional study, T1‐weighted magnetization‐prepared rapid gradient echo (MPRAGE) and DKI images were acquired at 3T from TDC (n = 13) and adolescents with ADHD (n = 12). Regression analysis of the PFC region of interest (ROI) was conducted.

Results

TDC show a significant kurtosis increase of WM microstructural complexity from 12 to 18 years of age, particularly in the radial direction, whereas WM microstructure in ADHD is stagnant in both the axial and radial directions. In ADHD, GM microstructure also lacked a significant age‐related increase in complexity as seen in TDC; only kurtosis measures were able to detect this difference.

Conclusion

These findings support the prevailing theory that ADHD is a disorder affecting frontostriatal WM. Our study is the first to directly quantify an aberrant age‐related trajectory in ADHD within GM microstructure, suggesting that the assessment of non‐Gaussian directional diffusion using DKI provides more sensitive and complementary information about tissue microstructural changes than conventional diffusion imaging methods. J. Magn. Reson. Imaging 2011;33:17–23. © 2010 Wiley‐Liss, Inc.     

Correlation of cognitive dysfunction and diffusion tensor MRI measures in patients with mild and moderate multiple sclerosis

Purpose

To compare the diffusion tensor imaging (DTI) measures of multiple sclerosis (MS) patients and healthy subjects in every brain voxel and to correlate them with Paced Auditory Serial Addition Test (PASAT) scores.

Materials and Methods

Fractional anisotropy (FA), and mean, longitudinal, and transverse diffusivity are compared between control subjects and MS patients, which were subdivided as mildly and moderately impaired. In addition, PASAT scores are correlated for both MS groups with the diffusion measures. An optimized voxel based analysis (VBA) method, in terms of coregistration, atlas construction, and image smoothing, was thereby used.

Results:

Diffusion differences between the control subjects and the patients with MS were found in the corpus callosum, inferior longitudinal fasciculus, cortico spinal tracts, forceps major, superior longitudinal fasciculus, and cingulum. In addition, we observed significant correlations of the FA and PASAT scores in the left inferior longitudinal fasciculus, the forceps minor, the capsula interna and externa, the genu of the corpus callosum, the left cingulum, the superior longitudinal fasciculus, and the corona radiata.

Conclusion:

Diffusion differences were observed between the mildly impaired MS patients and control subjects. In addition, different diffusion measures correlated with PASAT scores for cognitive decline in parietal, frontal, as well as temporal white matter (WM) regions. J. Magn. Reson. Imaging 2010;31:1492–1498. © 2010 Wiley‐Liss, Inc.     

Directional diffusion in relapsing-remitting multiple sclerosis: a possible in vivo signature of Wallerian degeneration

PURPOSE: To examine the role of directional dependence of the apparent diffusion coefficients in the evaluation of normal-appearing brain regions of patients with relapsing-remitting multiple sclerosis. MATERIALS AND METHODS: The role of diffusion tensor eigenvalues was investigated in the normal-appearing brain regions for 18 patients with relapsing-remitting multiple sclerosis and 15 age-matched normal controls. RESULTS: The isotropic apparent diffusion was increased in all regions. However, reduced anisotropy was significant only in regions with high anisotropy, including the corpus callosum and the internal capsule, and was due to increased diffusion tensor eigenvalues corresponding to diffusion transverse to the fibers without significant increase along the fibers. This characteristic pattern of changes in diffusion tensor eigenvalues has been observed previously in cases of Wallerian degeneration. Low-anisotropy regions corresponded to gray matter and gray/white interface regions. Since fiber tract orientations are not determined for regions of low anisotropy, this characteristic pattern of diffusion change is not detectable in these regions. CONCLUSION: Examination of diffusion tensor eigenvectors may provide insight into the changes observed in diffusion and a signature of Wallerian degeneration in the normal-appearing white matter of relapsing-remitting multiple sclerosis patients.     

Whole brain white matter changes revealed by multiple diffusion metrics in multiple sclerosis: a TBSS study

Objective

To investigate whole brain white matter changes in multiple sclerosis (MS) by multiple diffusion indices, we examined patients with diffusion tensor imaging and utilized tract-based spatial statistics (TBSS) method to analyze the data.

Methods

Forty-one relapsing-remitting multiple sclerosis (RRMS) patients and 41 age- and gender-matched normal controls were included in this study. Diffusion weighted images were acquired by employing a single-shot echo planar imaging sequence on a 1.5 T MR scanner. Voxel-wise analyses of multiple diffusion metrics, including fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) were performed with TBSS.

Results

The MS patients had significantly decreased FA (9.11%), increased MD (8.26%), AD (3.48%) and RD (13.17%) in their white matter skeletons compared with the controls. Through TBSS analyses, we found abnormal diffusion changes in widespread white matter regions in MS patients. Specifically, decreased FA, increased MD and increased RD were involved in whole-brain white matter, while several regions exhibited increased AD. Furthermore, white matter regions with significant correlations between the diffusion metrics and the clinical variables (the EDSS scores, disease durations and white matter lesion loads) in MS patients were identified.

Conclusion

Widespread white matter abnormalities were observed in MS patients revealed by multiple diffusion metrics. The diffusion changes and correlations with clinical variables were mainly attributed to increased RD, implying the predominant role of RD in reflecting the subtle pathological changes in MS.     

Analysis of new diffusion tensor imaging anisotropy measures in the three‐phase plot

Purpose:

To evaluate diffusion anisotropy from diffusion tensor imaging using new measures derived from Hellinger divergences and from compositional data distances.

Materials and Methods:

New anisotropy measures obtained from the diffusion tensor imaging were measured and compared with classic ones such as fractional anisotropy (FA) and relative anisotropy (RA). The evaluation was done using the three‐phase plot (3P‐plot). The measures were compared with regard to their sensitivity to detect white and gray matter changes on human DTI data acquired from five normal volunteers. For each volunteer, different volumes of interest located in white matter (WM) and gray matter (GM) were considered.

Results:

The proposed Compositional Kullback‐Leibler (KLA) and the classic FA had a similar behavior, although KLA detected better the transitions between white and gray matter. Moreover, KLA showed a better discrimination in areas with great confluence of fibers.

Conclusion:

KLA detects better than FA the difference between WM and GM. This leads KLA to be a good measure for segmenting WM from GM. J. Magn. Reson. Imaging 2010;31:1435–1444. © 2010 Wiley‐Liss, Inc.     

T2 detection of tumor invasion within segmented components of glioblastoma multiforme

Purpose

To use T2‐weighted images to detect tumor invasion when comparing normal individuals to groups of gliomablastoma multiforme (GBM) patients with varying levels of CXCR4, a chemokine receptor that promotes tumor migration.

Materials and Methods

T2‐weighted images were acquired preoperatively in 22 treatment‐naïve GBM patients. Two groups were formed based on the expression levels of CXCR4. A third group of normal volunteers was used for comparison. Each image was segmented to obtain four different clusters for tissue types identified as white matter, basal ganglia, gray matter/edema and cerebrospinal fluid (CSF)/tumor. Signal intensity histograms were formed for each cluster and compared between groups.

Results

In every cluster the GBM groups displayed significantly higher standard deviations of intensity distributions when compared to normal subjects. Significant differences in skewness were found between normal subjects and GBM patients in the white matter, basal ganglia, and CSF/tumor. Further, when the two groups of GBM patients were compared the CXCR4‐high group was found to have a significant shift in the median intensity values in the cluster containing gray matter and peritumoral edema.

Conclusion

T2 signal intensity histograms in normal subjects differ significantly from those obtained from GBM groups, suggesting widespread dissemination of disease. J. Magn. Reson. Imaging 2009;29:251–257. © 2009 Wiley‐Liss, Inc.     

High B‐value apparent diffusion‐weighted images from CURVE‐ball DTI

Purpose

To investigate the utility of a proposed clinical diffusion imaging scheme for rapidly generating multiple b‐value diffusion contrast in brain magnetic resonance imaging (MRI) with high signal‐to‐noise ratio (SNR).

Materials and Methods

Our strategy for efficient image acquisition relies on the invariance property of the diffusion tensor eigenvectors to b‐value. A simple addition to the conventional diffusion tensor MR imaging (DTI) data acquisition scheme used for tractography yields diffusion‐weighted images at twice and three times the conventional b‐value. An example from a neurosurgical brain tumor is shown. Apparent diffusion‐weighted (ADW) images were calculated for b‐values 800, 1600, and 2400 s/mm², and a map of excess diffusive kurtosis was computed from the three ADWs.

Results

High b‐value ADW images demonstrated decreased contrast between normal gray and white matter, while the heterogeneity and contrast of the lesion was emphasized relative to conventional b‐value data. Kurtosis maps indicated the deviation from Gaussian diffusive behavior.

Conclusion

DTI data with multiple b‐values and good SNR can be acquired in clinically reasonable times. High b‐value ADW images show increased contrast and add information to conventional DWI. Ambiguity in conventional b‐value images over whether hyperintense signal results from abnormally low diffusion, or abnormally long T₂, is better resolved in high b‐value images. J. Magn. Reson. Imaging 2009;30:243–248. © 2009 Wiley‐Liss, Inc.     

Characterization of low‐grade gliomas using RGB color maps derived from ADC histograms

Purpose

To use normalized apparent diffusion coefficient (nADC) histograms from patients with grade II oligodendroglioma (OD) and astrocytoma (AC) to generate RGB color maps that emphasize the differences between normal‐appearing white matter (NAWM), oligo‐like, and astro‐like regions.

Materials and Methods

NAWM and nonenhancing lesion (NEL) ADC values from 19 ODs and 11 ACs were summed to generate oligo‐like (red), NAWM (green), and astro‐like (blue) nADC histograms. These nADC histograms were then used to map nADC values to an RGB matrix.

Results

Color maps of oligodendroglial tumor regions were generally visualized in pink, while color maps of astrocytic tumor regions showed various shades of blue. This technique was also applied to 23 patients with the more mixed subtype, oligoastrocytoma (OA), which showed a mixture of both blue and pink, which in many cases appeared to bleed into each other and were blotchy.

Conclusion

This technique allows for the visualization of biologically different regions within the whole tumor mass, which may aid in directing image‐guided biopsies. This can be used to ensure that the biopsy is directed to regions that can more accurately define the dominant tumor characteristics. J. Magn. Reson. Imaging 2009;30:209–213. © 2009 Wiley‐Liss, Inc.     

MRI‐based thermal dosimetry and diffusion‐weighted imaging of MRI‐guided focused ultrasound thermal ablation of uterine fibroids

Purpose

To investigate tissue changes observed in diffusion‐weighted imaging (DWI) and its relation to contrast imaging, thermal dosimetry, and changes in the apparent diffusion coefficient (ADC) after MRI‐guided focused ultrasound surgery (MRgFUS) of uterine fibroids.

Materials and Methods

Imaging data were analyzed from 45 fibroids in 42 women treated with MRgFUS. The areas of the hyperintense regions in DWI and of nonperfused regions in T1‐weighted contrast enhanced imaging (both acquired immediately after treatment) were compared with each other and to thermal dosimetry based estimates. Changes in ADC were also calculated.

Results

Hyperintense regions were observed in 35/45 fibroids in DWI. When present, the areas of these regions were comparable on average to the thermal dose estimates and to the nonperfused regions, except for in several large treatments in which the nonperfused region extended beyond the treated area. ADC increased in 19 fibroids and decreased in the others.

Conclusion

DWI changes, which includes changes in both in T2 and ADC, may be useful in many cases to delineate the treated region resulting from MRgFUS. However, clear DWI changes were not always observed, and in some large treatments, the extent of the nonperfused region was under estimated. ADC changes immediately after MRgFUS were unpredictable. J. Magn. Reson. Imaging 2009;29:404–411. © 2009 Wiley‐Liss, Inc.     

Quantitation of brain tissue changes associated with white matter hyperintensities by diffusion‐weighted and magnetization transfer imaging: The LADIS (leukoaraiosis and disability in the elderly) study

Purpose

To explore the value of diffusion‐weighted imaging (DWI) and magnetization transfer imaging (MTI) for the improved detection and quantification of cerebral tissue changes associated with ageing and white matter hyperintensities (WMH).

Materials and Methods

DWI (n = 340) and MTI (n = 177) were performed in nine centers of the multinational Leukoaraiosis And DISability (LADIS) study investigating the impact of WMH on 65‐ to 85‐year‐old individuals without prior disability. We assessed the apparent diffusion coefficient (ADC) and magnetization transfer ratio (MTR) of normal appearing brain tissue (NABT) and within WMH and related them to subjects' age and WHM severity according to the Fazekas score.

Results

ADC and MTR values showed a significant inter‐site variation, which was stronger for the MTR. After z‐transformation multiple regression analysis revealed WMH severity and age as significant predictors of global ADC and MTR changes. Only lesional ADC, but not MTR was related to WMH severity.

Conclusion

ADC and MTR are both sensitive for age and WMH related changes in NABT. The ADC is more sensitive for tissue changes within WMH and appears to be more robust for multicenter settings. J. Magn. Reson. Imaging 2009;29:268–274. © 2009 Wiley‐Liss, Inc.     

多发性硬化患者弥散张量成像及其与认知功能的关系

目的: 探讨多发性硬化(MS)患者脑内病灶及脑组织的MR弥散张量成像(DTI)特点及其与认知功能的关系.材料和方法:对7例MS患者进行韦氏智力量表测查及头颅DTI检查.结果:病灶、病灶周围看似正常的组织(PWM)、看似正常的白质(NAWM)及看似正常的灰质(NAGM)较对照组相应部位脑组织的表观扩散系数(ADC)值增高,各向异性(FA)值减低.有智能损害的MS患者的NAWM、NAGM的ADC值高于智能正常的患者;而其NAGM的FA值低于智能正常的患者.结论:PWM、NAWM及NAGM组织内存在结构与功能改变,并影响认知功能.DTI有助于发现认知改变的微小结构和功能的异常.     

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. J. Magn. Reson. Imaging 2009;29:967–970. © 2009 Wiley‐Liss, Inc.     

Diffusion characteristics associated with neuronal injury and glial activation following hypoxia‐ischemia in the immature brain

To identify quantitative MRI indices of injury in the brain following neonatal hypoxic‐ischemic brain injury, we subjected mouse pups to hypoxia‐ischemia on postnatal day 7 and obtained conventional and diffusion‐weighted in vivo images of the brain 24 h later followed by histological assessment. T₂‐weighted images showed increased signal intensity in the CA1 and CA2 regions of the hippocampus ipsilateral to the injury and adjacent white matter. In contrast, diffusion imaging showed reduced apparent diffusion coefficient (ADC) values in CA1 and CA2, but increased values in the adjacent white matter. Histological analysis showed widespread gliosis with degenerating oligodendrocytes in the ipsilateral hippocampus. In addition, white matter areas that were abnormal by MRI showed an increase in the number of activated microglia (CD45 positive cells). Activated caspase‐3 immunostaining showed a marked increase in neurons in the hippocampal regions corresponding to those with reduced ADC, and a quantitative measure of staining showed a statistically significant correlation with the ADC. In contrast, ADC was higher in adjacent white matter, where histology showed activation of microglia and reactive oligodendrocytes but not caspase‐3 activation. These results suggest that the ADC response differs between areas of neuronal injury as compared with those showing glial changes without marked cell death. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Diffusion-weighted imaging improves prediction in cognitive outcome and clinical phases in patients with carbon monoxide intoxication

Introduction

Changes in apparent diffusion coefficient (ADC) values often reflect tissue injury. Use of ADC as a surrogate marker to assess clinical phases has not been systemically applied in patients with carbon monoxide (CO) intoxication.

Methods

Fifty-nine magnetic resonance imaging scans and cognitive evaluations were performed in 47 patients with CO intoxication and compared with 22 sex- and age-matched controls. The patients were further classified into three groups based on the clinical phases, namely, acute (within 2 weeks), delayed neuropsychiatric (2 weeks to 6 months), and chronic (>1 year) groups. The ADC values were measured in 16 regions of interests (ROIs) and correlated with cognitive test scores.

Results

Among the 59 evaluations, 15 were in the acute, 26 in the delayed neuropsychiatric, and 18 in the chronic groups. Among the ROIs, significant elevations of ADC values were found in the corpus callosum and globus pallidus in all three CO phases compared with the controls, and the ADC values were highest in the chronic phases. In contrast, the ADC values in peripheral gray matter and white matter were highest in the delayed neuropsychiatric group. Both globus pallidus and corpus callosum ADC values correlated with multiple cognitive test scores.

Conclusion

Using ADC as a surrogate marker, the globus pallidus and corpus callosum can be considered to be two vulnerable structures in the gray and white matter. Significant differences between ADC values correlated well with clinical phase and cognitive performance.