Eiki Nagao

Perfusion Imaging of Brain Tumors Using Arterial Spin-Labeling : Correlation with Histopathologic Vascular Density

BACKGROUND AND PURPOSE: We investigated the relationship between tumor blood-flow measurement based on perfusion imaging by arterial spin-labeling (ASL-PI) and histopathologic findings in brain tumors. MATERIALS AND METHODS: We used ASL-PI to examine 35 patients with brain tumors, including 11 gliomas, 9 meningiomas, 9 schwannomas, 1 diffuse large B-cell lymphoma, 4 hemangioblastomas, and 1 metastatic brain tumor. As an index of tumor perfusion, the relative signal intensity (SI) of each tumor (%Signal intensity) was determined as a percentage of the maximal SI within the tumor per averaged SI within normal cerebral gray matter on ASL-PI. Relative vascular attenuation (%Vessel) was determined as the total microvessel area per the entire tissue area on CD-34–immunostained histopathologic specimens. MIB1 indices of gliomas were also calculated. The differences in %Signal intensity among different histopathologic types and between high- and low-grade gliomas were compared. In addition, the correlations between %Signal intensity and %Vessel or MIB1 index were evaluated in gliomas. RESULTS: Statistically significant differences in %Signal intensity were observed between hemangioblastomas versus gliomas (P < .005), meningiomas (P < .05), and schwannomas (P < .005). Among gliomas, %Signal intensity was significantly higher for high-grade than for low-grade tumors (P < .05). Correlation analyses revealed significant positive correlations between %Signal intensity and %Vessel in 35 patients, including all 6 histopathologic types (rs = 0.782, P < .00005) and in gliomas (rs = 0.773, P < .05). In addition, in gliomas, %Signal intensity and MIB1 index were significantly positively correlated (rs = 0.700, P < .05). CONCLUSION: ASL-PI may predict histopathologic vascular densities of brain tumors and may be useful in distinguishing between high- and low-grade gliomas and in differentiating hemangioblastomas from other brain tumors.

Simultaneous measurement of arterial transit time, arterial blood volume, and cerebral blood flow using arterial spin-labeling in patients with Alzheimer disease

BACKGROUND AND PURPOSE: Cerebral hemodynamics abnormality in Alzheimer disease (AD) is not fully understood. Our aim was to determine whether regional hypoperfusion due to AD is associated with abnormalities in regional arterial blood volume (rABV) and regional arterial transit time (rATT) as measured by quantitative arterial spin-labeling (ASL) with multiple-delay time sampling. MATERIALS AND METHODS: Nineteen patients with AD (9 men and 10 women; mean age, 74.5 ± 8.6 years) and 22 cognitively healthy control subjects (11 men and 11 women; mean age, 72.8 ± 6.8 years) were studied by using a quantitative ASL method with multiple-delay time sampling. From the ASL data, maps of regional cerebral blood flow (rCBF), rABV, and rATT were generated. A region of hypoperfusion due to AD was determined by statistical parametric mapping (SPM) analysis. Mean rCBF, rABV, and rATT values within the hypoperfused region were compared between the AD and control groups. RESULTS: Despite the significantly lower rCBF (P = .0004) in patients with AD (27.8 ± 7.1 mL/100 g/min) in comparison with control subjects (36.7 ± 6.3 mL/100 g/min), no significant difference in rATT was observed between the control (0.48 ± 0.09 seconds) and AD (0.47 ± 0.10 seconds) groups. Mean rABV was lower in the AD group (0.22 ± 0.10%) than in the control group (0.27 ± 0.12%), though the difference did not reach the level of statistical significance. CONCLUSIONS: Our results revealed that regional hypoperfusion in AD is not associated with rATT prolongation, suggesting that the mechanism of hypoperfusion is distinct from that in cerebrovascular diseases.

Arterial spin labelling at 3-T MR imaging for detection of individuals with Alzheimer’s disease

The purpose of this study was to determine whether arterial spin labelling (ASL) at 3-T MR imaging can be used to discriminate individuals with Alzheimer’s disease (AD) from cognitively normal subjects. Twenty AD patients and 23 cognitively normal control subjects were studied using ASL on a 3-T MR imager. Absolute regional cerebral blood flow (rCBF) maps were calculated. In addition, normalized rCBF maps were obtained using CBF in the sensorimotor cortex for normalization. A voxel-wise comparison of these rCBF maps between the AD and control groups was performed using the two-sample t test. Individuals with AD were discriminated from control subjects based on mean rCBF values within a region-of-interest defined by the t test, and the discriminating performance was evaluated by the receiver operating characteristic (ROC) analysis. Comparisons of both absolute and normalized rCBF maps revealed areas of significant hypoperfusion caused by the effects of AD in the bilateral precunei and posterior cingulate gyri. ROC analyses resulted in area under the curve (AUC) values of 0.861 to 0.877 for absolute and 0.910 to 0.932 for normalized rCBF. Our results suggest that ASL at 3-T MR imaging can be used to help discriminate individuals with AD from normal subjects.

Regional gray and white matter volume abnormalities in obsessive-compulsive disorder: A voxel-based morphometry study

Previous studies have demonstrated both functional and structural abnormalities in the frontal-striatal-thalamic circuits in obsessive-compulsive disorder (OCD). The purpose of this study was to assess volume abnormalities not only of gray matter (GM), but also of white matter (WM) in patients with OCD using voxel-based morphometry (VBM). Subjects consisted of 23 patients with OCD and 26 normal control subjects. All patients were drug-free for at least 2 weeks before the study. Three-dimensional T1-weighed MR images were obtained in all subjects. Optimized voxel-based morphometry was performed to detect structural difference between the two groups. The patients with OCD demonstrated a significant reduction of GM volume in the bilateral medial prefrontal cortex, right premotor area, right orbitofrontal cortex (OFC), right dorsolateral prefrontal cortex, and bilateral temporal and occipital regions. The OCD patients also showed a significant WM volume increase in the right anterior limb of the internal capsule, right orbitofrontal region, and a significant WM volume reduction in the left anterior cingulate gyrus. Our findings are consistent with previous studies implicating dysfunction of the frontal cortex including the OFC. The results suggested that WM volume abnormalities in the orbitofrontal region, anterior limb of the internal capsule, and anterior cingulate gyrus would imply abnormalities in the pathways of frontal-striatal circuits.

CT and MRI findings of human herpesvirus 6-associated encephalopathy: comparison with findings of herpes simplex virus encephalitis.

OBJECTIVE It is important to differentiate human herpesvirus 6 (HHV-6)-associated encephalopathy from herpes simplex encephalitis (HSE). Although these conditions are similar with regard to involvement of the mesial temporal lobe, HSE is sensitive to acyclovir but HHV-6 encephalopathy is not. We compared the imaging findings of the two conditions. MATERIALS AND METHODS We encountered eight cases of HHV-6 encephalopathy and nine cases of HSE. We divided an observation time into early, middle, and late periods defined as 0-2, 3-30, and more than 30 days from the onset of neurologic symptoms. Differences between HHV-6 encephalopathy and HSE on CT scans in the early period and in distribution and temporal changes in the affected regions on MR images in the three periods were analyzed. RESULTS At MRI in the early and middle periods, all eight patients with HHV-6 encephalopathy had exclusive involvement of the mesial temporal lobes, and all nine patients with HSE had involvement of both the mesial temporal lobes and the extratemporal regions (p < 0.01). Among patients who underwent head MRI, six of six with HHV-6 encephalopathy but none of six with HSE had resolution of high signal intensity on T2-weighted and FLAIR images (p < 0.01). Among patients who underwent head CT in the early period, none of the four with HHV-6 encephalopathy and six of the seven with HSE had abnormal findings, including parenchymal swelling, decreased attenuation of affected regions, and abnormal gyral enhancement (p < 0.05). CONCLUSION Serial MRI showed transient abnormal signal intensity in the mesial temporal lobes in patients with HHV-6 encephalopathy but persistent abnormal signal intensity in both the mesial temporal lobes and the extratemporal regions in patients with HSE. CT in the early period showed no abnormality in patients with HHV-6 encephalopathy but definite abnormal findings in patients with HSE. These differences may be useful in the differential diagnosis of the two conditions.

Volumetric Asymmetry and Differential Aging Effect of the Human Caudate Nucleus in Normal Individuals: A Prospective MR Imaging Study

The purpose of this study was to examine interhemispheric asymmetry in volume of the caudate nucleus and its age dependency.

Intra- and interhemispheric variations of diffusivity in subcortical white matter in normal human brain

Our purpose was to reveal potential regional variations in water molecular diffusivity within each cerebral hemisphere and across the right and left hemispheres. Diffusion-weighted images of 44 healthy right-handed adult male subjects were obtained using a diffusion tensor imaging sequence. Mean diffusivity (MD) values in subcortical white matter (WM) within 39 regions in each hemisphere were measured using an automated method. Intrahemispheric comparisons of MDs in subcortical WM were performed among six brain regions (frontal, parietal, occipital and temporal lobes and pre- and postcentral gyri). Interhemispheric comparisons of MDs were performed between the right and left counterparts of the 39 regions. In both hemispheres, diffusivity in the precentral gyrus was lower than those in other regions, while diffusivity in the parietal lobe was higher than others. MD asymmetry in which the left was lower than the right was found in the parietal lobe, middle occipital gyrus, and medial and orbital aspects of the frontal lobe. The converse asymmetry was revealed in the frontal operculum, supplementary motor cortex, temporal lobe, limbic cortices, precuneus and cuneus. Our results revealed significant intra- and interhemispheric regional variations in MD in subcortical WM, which may be related to different densities of axons and myelin sheaths.

Accelerated territorial arterial spin labeling based on shared rotating control acquisition: an observer study for validation

IntroductionShared rotating control acquisition can shorten the imaging time of territorial arterial spin labeling (tASL) by 33% compared with the normal control acquisition scheme but potentially results in an inaccurate estimate of vascular territories due to imperfect magnetization transfer compensation. Our purpose was to validate the accuracy of the shared rotating control acquisition method in evaluation of vascular territories.MethodsTwenty-four patients underwent tASL at a 3.0-T MRI with the conventional normal control acquisition method. Composite vascular territory maps, in which the blood flows from the right and left internal carotid arteries and the posterior circulation were encoded in red–green–blue, were generated as a normal averaged control-label scheme and as a simulated shared rotating control scheme. Two observers independently reported the most dominant territorial flow in 26 brain regions corresponding to the arterial segments at three post-labeling time points. Inter-reader and inter-method agreements were analyzed using κ statistics.ResultsOverall inter-reader agreements were excellent for both the normal control and the shared rotating control methods (κ = 0.98, respectively). Overall inter-method agreement was also excellent (κ = 0.98), although relatively low agreement was noted in the bilateral posterior cerebral artery territories (κ = 0.79 to 0.93).ConclusionOur results suggested that tASL using shared rotating control acquisition can provide information on the vascular territories comparable to that obtained using the normal control acquisition while substantially shortening the imaging time.

Age-related microstructural changes in subcortical white matter during postadolescent periods in men revealed by diffusion-weighted MR imaging.

Continuous maturation of cerebral white matter (WM) in the postadolescent period is not fully understood. To elucidate the time course and location of possible postadolescent maturational changes in cerebral WM, we studied 60 healthy male subjects who were in their second to seventh decade using diffusion‐weighted imaging. Mean diffusivity (MD) in subcortical WM was measured in 78 cortical regions in each subjects brain using an automated method. Regression analysis was used to model the age‐related change in MD by either a linear or a quadratic function in each region. Age‐related changes in subcortical MD were best modeled by either a linear function or a quadratic function in 27 regions including language‐related regions, visual or multimodal areas in the bilateral occipital and temporal lobes, limbic areas including the bilateral parahippocampal gyri, and the bilateral postcentral and left precentral gyri. In these regions, the MD rapidly decreased until middle age and thereafter reached a plateau. Our results revealed microstructural changes in local subcortical WM and suggests a continuing maturational process in postoadolescent periods. Hum Brain Mapp 2009.

Transcatheter arterial embolization for chest wall metastasis of hepatocellular carcinoma

Hemothorax due to rupture of metastatic hepatocellular carcinoma (HCC) is a very rare complication with high mortality because of uncontrollable hemorrhage. A 71-year-old man treated by transcatheter arterial embolization for HCC with massive bleeding from chest wall metastasis is reported. Enhanced computed tomography and selective intercostal angiogram showed a hypervascular mass in the right chest wall and extravasation of contrast agent. After successful transcatheter arterial embolization with gelatin sponge particles and metallic coils, the patient recovered from shock without major complication. To our knowledge, a successfully treated case of hemothorax due to rupture of metastatic HCC has not previously been described.