Kaoru Sumida

Automated subfield volumetric analysis of hippocampus in temporal lobe epilepsy using high-resolution T2-weighed MR imaging.

Background and purpose Automated subfield volumetry of hippocampus is desirable for use in temporal lobe epilepsy (TLE), but its utility has not been established. Automatic segmentation of hippocampal subfields (ASHS) and the new version of FreeSurfer software (ver.6.0) using high-resolution T2-weighted MR imaging are candidates for this volumetry. The aim of this study was to evaluate hippocampal subfields in TLE patients using ASHS as well as the old and new versions of FreeSurfer. Materials and methods We recruited 50 consecutive unilateral TLE patients including 25 with hippocampal sclerosis (TLE-HS) and 25 without obvious etiology (TLE-nonHS). All patients and 45 healthy controls underwent high-resolution T2-weighted and 3D-volume T1-weighted MRI scanning. We analyzed all of their MR images by FreeSurfer ver.5.3, ver.6.0 and ASHS. For each subfield, normalized z-scores were calculated and compared among groups. Results In TLE-HS groups, ASHS and FreeSurfer ver.6.0 revealed maximal z-scores in ipsilateral cornu ammonis (CA) 1, CA4 and dentate gyrus (DG), whereas in FreeSurfer ver.5.3 ipsilateral subiculum showed maximal z-scores. In TLE-nonHS group, there was no significant volume reduction by either ASHS or FreeSurfer. Conclusions ASHS and the new version of FreeSurfer may have an advantage in compatibility with existing histopathological knowledge in TLE patients with HS compared to the old version of FreeSurfer (ver.5.3), although further investigations with pathological findings and/or surgical outcomes are desirable.

Computed-tomography-guided anatomic standardization for quantitative assessment of dopamine transporter SPECT

PurposeFor the quantitative assessment of dopamine transporter (DAT) using [123I]FP-CIT single-photon emission computed tomography (SPECT) (DaTscan), anatomic standardization is preferable for achieving objective and user-independent quantification of striatal binding using a volume-of-interest (VOI) template. However, low accumulation of DAT in Parkinson’s disease (PD) would lead to a deformation error when using a DaTscan-specific template without any structural information. To avoid this deformation error, we applied computed tomography (CT) data obtained using SPECT/CT equipment to anatomic standardization.MethodsWe retrospectively analyzed DaTscan images of 130 patients with parkinsonian syndromes (PS), including 80 PD and 50 non-PD patients. First we segmented gray matter from CT images using statistical parametric mapping 12 (SPM12). These gray-matter images were then anatomically standardized using the diffeomorphic anatomical registration using exponentiated Lie algebra (DARTEL) algorithm. Next, DaTscan images were warped with the same parameters used in the CT anatomic standardization. The target striatal VOIs for decreased DAT in PD were generated from the SPM12 group comparison of 20 DaTscan images from each group. We applied these VOIs to DaTscan images of the remaining patients in both groups and calculated the specific binding ratios (SBRs) using nonspecific counts in a reference area. In terms of the differential diagnosis of PD and non-PD groups using SBR, we compared the present method with two other methods, DaTQUANT and DaTView, which have already been released as software programs for the quantitative assessment of DaTscan images.ResultsThe SPM12 group comparison showed a significant DAT decrease in PD patients in the bilateral whole striatum. Of the three methods assessed, the present CT-guided method showed the greatest power for discriminating PD and non-PD groups, as it completely separated the two groups.ConclusionCT-guided anatomic standardization using the DARTEL algorithm is promising for the quantitative assessment of DaTscan images.

Graph Theoretical Analysis of Structural Neuroimaging in Temporal Lobe Epilepsy with and without Psychosis

Purpose Psychosis is one of the most important psychiatric comorbidities in temporal lobe epilepsy (TLE), and its pathophysiology still remains unsolved. We aimed to explore the connectivity differences of structural neuroimaging between TLE with and without psychosis using a graph theoretical analysis, which is an emerging mathematical method to investigate network connections in the brain as a small-world system. Materials and Methods We recruited 11 TLE patients with unilateral hippocampal sclerosis (HS) presenting psychosis or having a history of psychosis (TLE-P group). As controls, 15 TLE patients with unilateral HS without any history of psychotic episodes were also recruited (TLE-N group). For graph theoretical analysis, the normalized gray matter images of both groups were subjected to Graph Analysis Toolbox (GAT). As secondary analyses, each group was compared to 14 age- and gender-matched healthy subjects. Results The hub node locations were found predominantly in the ipsilateral hemisphere in the TLE-N group, and mainly on the contralateral side in the TLE-P group. The TLE-P group showed significantly higher characteristic path length, transitivity, lower global efficiency, and resilience to random or targeted attack than those of the TLE-N group. The regional comparison in betweenness centrality revealed significantly decreased connectivity in the contralateral temporal lobe, ipsilateral middle frontal gyrus, and bilateral postcentral gyri in the TLE-P group. The healthy subjects showed well-balanced nodes/edges distributions, similar metrics to TLE-N group except for higher small-worldness/modularity/assortativity, and various differences of regional betweenness/clustering. Conclusion In TLE with psychosis, graph theoretical analysis of structural imaging revealed disrupted connectivity in the contralateral hemisphere. The network metrics suggested that the existence of psychosis can bring vulnerability and decreased efficiency of the whole-brain network. The sharp differences in structural networks between morphologically homogeneous groups are remarkable and may contribute to a better understanding of psychosis in TLE.

White matter abnormalities in patients with temporal lobe epilepsy and amygdala enlargement: Comparison with hippocampal sclerosis and healthy subjects

PURPOSE Cases of temporal lobe epilepsy (TLE) with ipsilateral amygdala enlargement (AE) have increasingly been reported. However, the white matter (WM) abnormalities of TLE patients with AE remain poorly investigated. Here we explored macrostructural and microstructural WM abnormalities in TLE patients with AE compared to normal controls and TLE patients with hippocampal sclerosis (HS). MATERIAL AND METHODS We selected 17 patients with unilateral TLE with AE (TLE-AE) based on automated amygdala volumetry using FreeSurfer software, and 34 healthy controls and 35 patients with unilateral TLE with HS (TLE-HS) were also recruited. Subsequently, differences in gray matter (GM) and WM volumes and fractional anisotropy (FA) among the three groups were analyzed using SPM8 software. RESULTS The volume analysis of GM obtained results that are consistent with the structural characteristics of TLE with AE and with HS (i.e. amygdala increase in the TLE-AE, and mesial temporal atrophy in the TLE-HS). In the volume of WM, only the TLE-HS patients had WM reductions mainly in the ipsilateral temporal lobe. Compared to the controls, the TLE-AE group showed a significant FA decrease in the ipsilateral anterior cingulum and the corpus callosum, whereas an extended FA decrease in the whole cerebrum was observed in the TLE-HS group. CONCLUSION Our findings regarding the WM of TLE patients with AE may reflect characteristic pathophysiology such as the anatomical and functional connection between the amygdala and medial prefrontal cortex, and our results may thus provide insights into TLE with AE.

Intraventricular cerebrospinal fluid temperature analysis using MR diffusion-weighted imaging thermometry in Parkinson's disease patients, multiple system atrophy patients, and healthy subjects

We examined the temperature of the intraventricular cerebrospinal fluid (Tv) in patients with Parkinsons disease (PD) and those with multiple system atrophy (MSA) in comparison with healthy subjects, and we examined normal changes in this temperature with aging.

Effects of pure and hybrid iterative reconstruction algorithms on high-resolution computed tomography in the evaluation of interstitial lung disease

OBJECTIVES To compare image quality characteristics of high-resolution computed tomography (HRCT) in the evaluation of interstitial lung disease using three different reconstruction methods: model-based iterative reconstruction (MBIR), adaptive statistical iterative reconstruction (ASIR), and filtered back projection (FBP). METHODS Eighty-nine consecutive patients with interstitial lung disease underwent standard-of-care chest CT with 64-row multi-detector CT. HRCT images were reconstructed in 0.625-mm contiguous axial slices using FBP, ASIR, and MBIR. Two radiologists independently assessed the images in a blinded manner for subjective image noise, streak artifacts, and visualization of normal and pathologic structures. Objective image noise was measured in the lung parenchyma. Spatial resolution was assessed by measuring the modulation transfer function (MTF). RESULTS MBIR offered significantly lower objective image noise (22.24±4.53, P<0.01 among all pairs, Students t-test) compared with ASIR (39.76±7.41) and FBP (51.91±9.71). MTF (spatial resolution) was increased using MBIR compared with ASIR and FBP. MBIR showed improvements in visualization of normal and pathologic structures over ASIR and FBP, while ASIR was rated quite similarly to FBP. MBIR significantly improved subjective image noise (P<0.01 among all pairs, the sign test), and streak artifacts (P<0.01 each for MBIR vs. the other 2 image data sets). CONCLUSION MBIR provides high-quality HRCT images for interstitial lung disease by reducing image noise and streak artifacts and improving spatial resolution compared with ASIR and FBP.

Intraventricular temperature measured by diffusion-weighted imaging compared with brain parenchymal temperature measured by MRS in vivo

We examined and compared the temperatures of the intraventricular cerebrospinal fluid (Tv) and the brain parenchyma (Tp) using MRI, with reference to the tympanic membrane temperature (Tt) in healthy subjects. We estimated Tv and Tp values from data gathered simultaneously by MR diffusion‐weighted imaging (DWI) and MRS, respectively, in 35 healthy volunteers (17 males, 18 females; age 25–78 years). We also obtained Tt values just before each MR examination to evaluate the relationships among the three temperatures. There were significant positive correlations between Tv and Tp (R = 0.611, p < 0.001). The correlation was also significant after correction for Tt (R = 0.642, p < 0.001). There was no significant correlation between Tv and Tt or between Tp and Tt in the men or the women. Negative correlations were found between Tv and age and between Tp and age in the males but not females. DWI thermometry seems to reflect the intracranial environment as accurately as MRS thermometry. An age‐dependent decline in temperature was evident in our male subjects by both DWI and MRS thermometry, probably due to the decrease in cerebral metabolism with age. Copyright

Noninvasive evaluation of the correlation between regional cerebral blood flow and intraventricular brain temperature in temporal lobe epilepsy

INTRODUCTION In temporal lobe epilepsy (TLE), an uncoupling of cerebral blood flow (CBF) and metabolism is indicated. The aim of this study was to clarify this relationship by investigating intraventricular brain temperature (BT) and CBF in TLE using a noninvasive MRI technique. MATERIAL AND METHODS We recruited 38 subjects with left TLE and 39 subjects with right TLE. All patients underwent an MRI examination including diffusion-weighted imaging (DWI) and pseudo-continuous arterial spin labeling (pCASL). Intraventricular BT was calculated by a DWI thermometric technique, and regional CBF was obtained from pCASL images, and we analyzed the relationship between them using the statistical parametric mapping 8 software (SPM8). RESULTS In only the left TLE group, there was a significant negative correlation between CBF and BT in the left inferior frontal gyrus. Positive correlations in the bilateral posterior poles were also found at the trend level in left TLE group. The patients with right TLE showed no significant correlation. CONCLUSION Our results may reflect a regional uncoupling of blood flow and metabolism in those brain areas, and they may indicate that TLE has different metabolic regulation systems in the brain.

Noninvasive detection of focal brain hyperthermia related to continuous epileptic activities using proton MR spectroscopy

Recent studies using rat models suggested that epileptic discharges (EDs) can induce focal brain hyperthermia, but such ED-related hyperthermia has not been confirmed in humans. We examined hyperthermia of the focus of epilepsy using noninvasive proton magnetic resonance spectroscopy (1H-MRS) thermometry. We recruited six pediatric patients with refractory daily seizures, continuous interictal epileptic discharges, and concordant focus lesions on MRI who had undergone comprehensive presurgical exams. 1H-MRS thermometry calculated the temperatures of the presumed epileptogenic lesions, and we examined the contralateral counterparts in each patient as controls. As a result, the mean temperature of the epileptogenic foci (36.81°C) was significantly higher than that of the controls (36.01°C). The mean difference was 0.81°C (95%CI: 0.22-1.39, p=0.017). 1H-MRS thermometry may have the ability to noninvasively detect focal brain hyperthermia related to continuous EDs in human subjects, and to contribute to a better understanding and focus detection of epilepsy.