PubMed Health⌕ Search

Biomedical subjects

Shunji Mugikura

Publications and source records attributed to Shunji Mugikura.

7 recordsLinked to original sources
PubMed2006

Malignant astrocytic tumors: clinical importance of apparent diffusion coefficient in prediction of grade and prognosis.

PURPOSE: To retrospectively assess the apparent diffusion coefficient (ADC) for prediction of malignancy and prognosis of malignant astrocytic tumors. MATERIALS AND METHODS: The institutional review board approved this study and did not require patient informed consent. Findings from 37 consecutive patients (21 men, 16 women; mean age, 43 years) with pathologically proved malignant astrocytic tumors that included 22 glioblastomas (GBMs) and 15 anaplastic astrocytomas (AAs) were retrospectively evaluated. The minimum ADC value of each tumor was preoperatively determined from several regions of interest defined in the tumor, preferably with avoidance of cystic or necrotic components, on ADC maps derived from isotropic diffusion-weighted images. Surgical intervention, followed by radiation therapy, was undertaken in all cases according to hospital protocol. Immunohistologically, Ki-67 labeling index (LI), indicating cell proliferation, was also determined. The patients were classified into two groups, progressive and stable, according to the 2-year observation after the initial treatment. Correlation analysis (Pearson product moment correlation), Student t test, Welch test, receiver operating characteristic analysis, and Kaplan-Meier method with log-rank test were used for statistical evaluation. RESULTS: There was a significant negative correlation between minimum ADC and Ki-67 LI (r = -0.562, P < .001). The mean minimum ADC (0.834 x 10(-3) mm2 x sec(-1)) of GBM was significantly lower than that (1.06 x 10(-3) mm2 x sec(-1)) of AA (P < .001, Student t test). The mean minimum ADC (0.80 x 10(-3) mm2 x sec(-1)) of the progressive group was significantly lower than that (1.037 x 10(-3) mm2 x sec(-1)) of the stable group (P < .001). The cutoff value of 0.90 x 10(-3) mm2 x sec(-1) for minimum ADC for differentiation of patients with a favorable prognosis from those with a poor prognosis provided the best combination of sensitivity (79%) and specificity (81%) (receiver operating characteristic analysis). The significant difference in the prognosis between two groups classified by using this cutoff value of minimum ADC was noted (P = .002, log-rank test). CONCLUSION: The minimum ADC of malignant astrocytomas can provide additional information about their clinical malignancy related to posttreatment prognosis.

Adult↗
PubMed2006

[Diagnostic value of perfusion-weighted MRI for evaluating postoperative alteration of cerebral hemodynamics following STA-MCA anastomosis in patients with moyamoya disease].

OBJECTIVE: Surgical revascularization for moyamoya disease prevents cerebral ischemic attacks by improving cerebral blood flow (CBF). But little is known about the changes of CBF and its effect on neurological status during the acute stage after direct bypass for moyamoya disease. METHODS AND RESULTS: Perfusion-weighted magnetic resonance imaging (PWI) by the SE-EPI method was performed 4 and 10 days after superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis on 11 sides of 9 patients (male:female = 2:7, 24-61 years old) with moyamoya disease. All patients underwent single-photon emission computed tomography (SPECT) 1 and 7 days after surgery. The time-to-peak (TTP) by PWI showed focal decrease at the site of the anastomosis 4 days after STA-MCA anastomosis compared to preoperative TTP, and was further decreased in larger territory 10 days after surgery in all patients. Postoperative cerebral blood volume (CBV) by PWI showed significant increase compared to preoperative CBV in four patients who suffered symptomatic cerebral hyperperfusion after surgery. Postoperative SPECT revealed apparent increase of CBF in all patients and the patency of the STA-MCA bypass was confirmed by MRA. All patients were discharged without neurological deterioration compared to preoperative neurological status, and none of them suffered ischemic attack after surgery. CONCLUSION: Postoperative decrease in TTP by PWI could be a sensitive parameter for the normalization of CBF after STA-MCA anastomosis in patients with moyamoya disease. Postoperative increase in CBV may suggest cerebral hyperperfusion and could be the optimal predictor for hyperperfusion syndrome after STA-MCA anastomosis in patients with moyamoya disease.

Adult↗
PubMed2004

Changes in brain activation associated with use of a memory strategy: a functional MRI study.

It has been confirmed that some kinds of what are called memory strategies dramatically improve the performance of memory recall. However, there has been no direct research to examine changes in brain activity associated with the use of the method of loci within individuals. In the present study, using fMRI, we compared brain activations before and after instruction in the method of loci during both the encoding and recall phases. The resulting behavioral data showed that the use of the method of loci significantly increased scores for memory recall. The imaging data showed that encoding after instruction in the method of loci, relative to encoding before it, was associated with signal increases in the right inferior frontal gyrus, bilateral middle frontal gyrus, left fusiform gyrus, and bilateral lingual gyrus/posterior cingulate gyrus. Comparison of recall after instruction in the method of loci with that before it showed significant activation in the left parahippocampal gyrus/retrosplenial cortex/cingulate gyrus/lingual gyrus, left precuneus, left fusiform gyrus, and right lingual gyrus/cingulate gyrus. The present study demonstrated the changes in brain activation pattern associated with the use of the method of loci; left fusiform and lingual activity was associated with both the encoding and recall phases, bilateral prefrontal activity with the encoding phase, and activity of the posterior part of the parahippocampal gyrus, retrosplenial cortex, and precuneus with the recall phase. These findings suggest that brain networks mediating episodic encoding and retrieval vary with how individuals encode the same stimuli.

Adult↗
PubMed2002

Neural basis of temporal context memory: a functional MRI study.

Temporal context information is crucial to understanding human episodic memory. Human lesion and neuroimaging data indicate that prefrontal regions are important for retrieving temporal context memory, although the exact nature of their involvement is still unclear. We employed functional magnetic resonance imaging (fMRI) to elucidate the neural basis of two kinds of temporal context memory: the temporal order of items between lists and within a list. On the day of the fMRI experiment, subjects memorized a list of 30 pictures in the morning and another list of 30 pictures in the afternoon. During the scanning session, the subjects performed three tasks. In a between-lists task, they were asked to judge the temporal order between two items that had been presented in different lists. In a within-list task, they were asked to judge the temporal order between two items that had been presented in a single list. We found bilateral prefrontal activities during these two temporal context memory tasks compared with a simple item-recognition task. Furthermore, in direct comparison between these two tasks, we found differential prefrontal activities. Thus, right prefrontal activity was associated with temporal order judgment of items between lists, whereas left prefrontal activity was related to temporal order judgment of items within a list. These results indicate that retrieval processes of two kinds of temporal context memory are supported by different, but overlapping, sets of cerebral regions. We speculate that this reflects different cognitive processes for retrieving temporal context memory between separate episodes and within a single episode.

Adult↗
PubMed2002

Predominant involvement of ipsilateral anterior and posterior circulations in moyamoya disease.

BACKGROUND AND PURPOSE: We encountered several patients with childhood onset of moyamoya disease in whom the ipsilateral anterior and posterior circulations were predominantly involved. This study investigated whether this is an angiographic characteristic of this disease. METHODS: We evaluated steno-occlusive lesions on angiograms of 85 patients with pediatric onset of moyamoya disease, using two 4-stage angiographic classification scales for the internal carotid artery and posterior cerebral artery systems (ICA and PCA staging, respectively) and determined whether lesions with more advanced ICA and PCA stages were on ipsilateral sides. RESULTS: When positive laterality was defined as the presence of a difference by > or =1 stage between the stages on both sides, lateralities in the ICA stages and in the PCA stages were present in 40 (47%) and 27 patients (32%), respectively. Lesions with more advanced ICA and PCA stages were on the same side, with significant probability (P=0.024, Fisher's exact test). Lateralities in both ICA and PCA lesions were found in 17 patients. In 14 (82%) of the 17 patients, the more advanced side of ICA lesions was the same as that of PCA lesions, while it was contralateral in 3 patients (18%). CONCLUSIONS: In pediatric-onset moyamoya disease, asymmetrical involvement of bilateral ICAs and PCAs was common, and the ipsilateral ICA and PCA tended to be predominantly involved.

Adolescent↗
PubMed2002

Conspicuity and evolution of lesions in Creutzfeldt-Jakob disease at diffusion-weighted imaging.

BACKGROUND AND PURPOSE: Diffusion-weighted imaging can disclose distinct hyperintense lesions in Creutzfeldt-Jakob disease (CJD). However, these findings and chronologic changes of CJD at diffusion-weighted imaging have not been fully investigated. Our purpose was to assess the diagnostic value of diffusion-weighted imaging in depicting CJD-related lesions and in tracking the evolution of these lesions. We also compared the sensitivity of diffusion-weighted imaging in depicting CJD-related lesions to that of fluid-attenuated inversion recovery (FLAIR) imaging. METHODS: We reviewed findings in 13 patients with a diagnosis of CJD who underwent MR imaging, including diffusion-weighted imaging. Nine patients were initially examined within 4 months of onset of symptoms (early stage), and eight were examined 4 months or later (late stage). We evaluated four items: 1) distribution of lesions at diffusion-weighted imaging, 2) conspicuity of lesions at diffusion-weighted imaging and FLAIR imaging, 3) chronologic changes in lesions at diffusion-weighted imaging, and 4) chronologic changes in lesions revealed by apparent diffusion coefficient (ADC) maps. RESULTS: Patients had striatal lesions or cerebral cortical lesions or both. The thalamus was involved in only one patient, and the globus pallidus was spared in all patients. The sensitivity of diffusion-weighted imaging in depicting lesions was superior or at least equal to that of FLAIR imaging. Hyperintense lesions at diffusion-weighted imaging changed in extent and intensity over time. Unlike infarction, lesional ADC decreased for 2 weeks or longer. CONCLUSION: The progressively hyperintense changes in the striata and cerebral cortices at diffusion-weighted imaging are considered characteristic of CJD. Diffusion-weighted imaging may be useful for the early diagnosis of CJD.

Aged↗