Biomedical subjects

Norihiro Sadato

Publications and source records attributed to Norihiro Sadato.

64 records · Page 4Linked to original sources

PubMed2002

Age-related differences in the medial temporal lobe responses to emotional faces as revealed by fMRI.

Age-related differences involved in the neural substrates of emotional face perception were investigated in young and old healthy volunteers. The subjects were scanned using functional magnetic resonance imaging while they were judging the gender of faces with negative, positive, or neutral emotional valence. The results showed that both the predominant activation in young subjects and reduced activity in old subjects contributed to a significant age difference in the left amygdala during the perception of negative faces. Activity in the right parahippocampal gyrus during the perception of positive faces diminished with advancing age. Neural activity in the angular gyrus and lingual gyrus of the right hemisphere was reduced in the old subjects during the perception of positive faces. There was no region where old subjects had greater activity than young subjects during the task. In old subjects, the overall activity in the right hippocampus during the task correlated negatively with age, whereas the activity in the right parahippocampal gyrus correlated positively with neuropsychological performance. There was no significant correlation between subjects' characteristics and signal change in young subjects. These results indicate the age-associated vulnerability of the medial temporal lobe structures including the amygdala, hippocampus, and parahippocampal gyrus during face perception. The dissociation with reduced activity in the left amygdala and the right parahippocampal gyrus may suggest that aging differentially affects neural responses to faces with negative or positive emotional valence. The parieto-occipital lobe, which has been found to be involved in face processing, also showed a functional decline associated with aging.

Adult↗

PubMed2002

Critical period for cross-modal plasticity in blind humans: a functional MRI study.

The primary visual cortex (V1) in congenitally blind humans has been shown to be involved in tactile discrimination tasks, indicating that there is a shift in function of this area of cortex, but the age dependency of the reorganization is not fully known. To investigate the reorganized network, we measured the change of regional cerebral blood flow using 3.0 Tesla functional MRI during passive tactile tasks performed by 15 blind and 8 sighted subjects. There was increased activity in the postcentral gyrus to posterior parietal cortex and decreased activity in the secondary somatosensory area in blind compared with sighted subjects during a tactile discrimination task. This suggests that there is a greater demand for shape discrimination processing in blind subjects. Blind subjects, irrespective of the age at onset of blindness, exhibited higher activity in the visual association cortex than did sighted subjects. V1 was activated in blind subjects who lost their sight before 16 years of age, whereas it was suppressed in blind subjects who lost their sight after 16 years of age during a tactile discrimination task. This suggests that the first 16 years of life represent a critical period for a functional shift of V1 from processing visual stimuli to processing tactile stimuli. Because of the age-dependency, V1 is unlikely to be the "entry node" of the cortex for the redirection of tactile signals into visual cortices after blinding. Instead, the visual association cortex may mediate the circuitry by which V1 is activated during tactile stimulation.

Adult↗

PubMed2002

Effect of postprandial hyperglycaemia in non-invasive measurement of cerebral metabolic rate of glucose in non-diabetic subjects.

The aim of this study was to determine the effect of postprandial hyperglycaemia (HG) on the non-invasive measurement of cerebral metabolic rate of glucose (CMRGlc). Five patients who had a meal within an hour before a fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) examination were recruited in this study. They underwent intermittent arterial blood sampling (measured input function), and, based on this sampling, CMRGlc was calculated using an autoradiographic method (CMRGlc(real)). Simulated input functions were generated based on standardised input function, body surface area and net injected dose of FDG, and simulated CMRGlc (CMRGlc(sim)) was also calculated. Percent error of the area under the curve (AUC) between measured (AUC(real)) and simulated input function (AUC(IFsim)) and percent error between CMRGlc(real) and CMRGlc(sim) were calculated. These values were compared with those obtained from a previous study conducted under fasting conditions (F). The serum glucose level in the HG group was significantly higher than that in the F group (165+/-69 vs 100+/-9 mg/dl, P=0.0007). Percent errors of AUC and CMRGlc in grey matter and white matter in HG were significantly higher than those in F (12.9%+/-1.3% vs 3.5%+/-2.2% in AUC, P=0.0015; 18.2%+/-2.2% vs 2.9%+/-1.9% in CMRGlc in grey matter, P=0.0028; 24.0%+/-4.6% vs 3.4%+/-2.2% in CMRGlc in white matter, P=0.0028). It is concluded that a non-invasive method of measuring CMRGlc should be applied only in non-diabetic subjects under fasting conditions.

Brain↗

PubMed2002

Differentiation of prostate cancer from benign prostate hypertrophy using dual-echo dynamic contrast MR imaging.

OBJECTIVE: To investigate the usefulness of dynamic contrast magnetic resonance (MR) imaging in the differentiation of prostate cancer (PC) from benign prostate hypertrophy (BPH). MATERIALS AND METHODS: Eleven PC patients and 13 BPH patients were entered into the analysis. The mean gradient (MG) was calculated from the T2* term-eliminated time-signal intensity curve obtained from dynamic contrast MR data, and the MG of PC and that of BPH were compared. RESULTS: The MG of PC was significantly higher than that of BPH. When the threshold value was set to 1.88% per s for discriminating PC from BPH, the sensitivity, specificity, and accuracy were 100, 85, and 92%, respectively. CONCLUSION: The MG, which is derived from the T2* term-eliminated time-signal intensity curve, may be a useful index for differentiating PC from BPH.

Adult↗

PubMed2002

Prognostic value of 2-deoxy-2-[F-18]fluoro-D-glucose positron emission tomography imaging for patients with prostate cancer.

PURPOSE: The purpose of this study was to investigate the prognostic value of measuring glucose metabolism of primary prostate cancer lesions, using 2-Deoxy-2-[F-18]Fluoro-D-Glucose positron emission tomography (FDG-PET). PROCEDURES: Forty-two patients with prostate cancer were investigated with FDG-PET, and standardized uptake value (SUV) of the prostate was calculated. After PET study, radical prostatectomy was performed in 17 patients (RPT group), and endocrine therapy in 25 patients (ET group). Relapse-free survival curves were created by the Kaplan-Meier method. RESULTS: In the RPT group, the patients with high SUV had a poorer prognosis compared to those with low SUV (P = 0.033). In the ET group, the patients with high SUV were likely to have a poorer prognosis with low significance at a level of P = 0.087. CONCLUSIONS: FDG-PET appeared to have a defined prognostic value for patients with prostate cancer undergoing radical prostatectomy, and more patients need to be studied for patients undergoing endocrine therapy.

Journal Article↗

PubMed2002

Whole-body (18)F-fluorodeoxyglucose positron emission tomography in patients with head and neck cancer.

OBJECTIVE: Because of the high risk of secondary primary malignancies in addition to possible distant metastases, whole-body evaluation is critically important in patients with head and neck cancer. We evaluated the clinical usefulness of whole-body (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) before initial treatment. STUDY DESIGN: We performed whole-body FDG PET in 26 patients with head and neck cancer (squamous cell carcinoma, n = 20; salivary gland carcinoma, n = 6) before initial treatment. FDG images were prospectively evaluated, and further imaging studies were performed if required. Final diagnosis for the presence or absence of distant lesions was made by analysis of the pathologic findings of surgical specimens or by analysis of the clinical follow-up data for more than 1 year. RESULTS: PET images showed FDG avid lesions distant from the head and neck area in 3 of 26 patients (11.5%). Two patients were confirmed to have secondary primary cancer (one with colon cancer in the early stage and another with small lung metastasis from postoperative colon cancer). They were diagnosed and treated properly both for the head and neck cancer and the secondary primary cancer. One patient was confirmed to have large lung metastasis from head and neck cancer, and appropriate treatment was selected. CONCLUSIONS: Whole-body FDG PET has a clinical impact on the management of patients with head and neck cancer by detecting secondary primary malignancies as well as distant metastases.

Adult↗

PubMed2002

Measurement of the vascularity and vascular leakage of gliomas by double-echo dynamic magnetic resonance imaging: a preliminary study.

RATIONALE AND OBJECTIVE: To evaluate the vascularity and vascular leakage of well-enhanced gliomas by double-echo dynamic magnetic resonance (MR) imaging. MATERIALS AND METHODS: Eight patients with glioblastoma multiforme (GBM) and two patients with juvenile pilocytic astrocytoma (JPA) were studied. Double-echo dynamic MR imaging was utilized to separate the T2* shortening effect and the T1 shortening effect. The former was represented by the vascularity index, and the latter was represented by the leakage index. These indexes were compared with histopathologic data. RESULTS: The mean vascularity index of the GBM was higher than that of the JPA (mean +/- SD, 3.48 +/- 1.57 [GBM] versus 0.51 +/- 0.29 [JPA]), and the mean leakage index of the JPA was higher than that of the GBM (1.35 +/- 0.87 [JPA] versus 0.27 +/- 0.15 [GBM]). Abundant vascularity was noted in the tight interstitial space in the pathologic specimen of GBM. Conversely, sparse vasculature was observed in the wide interstitial space in the pathologic specimen of JPA. CONCLUSION: This method may enable better characterization of grade in well-enhanced glioma by providing the information on the vascularity and leakage indexes.

Adult↗

PubMed2002

11C-acetate PET imaging of prostate cancer.

UNLABELLED: 11C-Acetate can act as a probe of tissue metabolism through entry into catabolic or anabolic metabolic pathways as mediated by acetyl-coenzyme A. The uptake of (11)C-acetate in prostate cancer was investigated to determine whether this tracer has potential in tumor identification. METHODS: Twenty-two patients with prostate cancer underwent PET after intravenous administration of 740 MBq (11)C-acetate. Eighteen of the 22 patients were also investigated with (18)F-FDG PET. Standardized uptake values (SUVs) for each tumor were investigated for tracer activity at 10-20 min after (11)C-acetate and 40-60 min after (18)F-FDG administration. RESULTS: Adenocarcinoma of the prostate showed variable uptake of (11)C-acetate, with SUVs ranging from 3.27 to 9.87. In contrast, SUVs for (18)F-FDG ranged from 1.97 to 6.34. By visual inspection, (11)C-acetate accumulation in primary prostate tumors was positive in all patients, whereas (18)F-FDG accumulation was positive in only 15 of 18 patients. (11)C-Acetate PET in a patient with lymph node metastasis showed high intrapelvic accumulation corresponding to metastatic sites. Similarly, 2 patients with bone metastases were (11)C-acetate avid. CONCLUSION: (11)C-Acetate shows marked uptake in prostate cancer and is more sensitive in detection of prostate cancer than is (18)F-FDG PET. (11)C-Acetate represents a new tracer for detection of prostate cancer with PET, measuring radiopharmaceutical uptake pathways that are different from those measured by (18)F-FDG.

Acetates↗

PubMedDate not supplied

H(2) (15)0 positron emission tomography validation of semiquantitative prostate blood flow determined by double-echo dynamic MRI: a preliminary study.

PURPOSE: Information regarding prostate blood flow as determined by positron emission tomography (PET) with H 0 may provide useful information about tumor diagnosis; however, PET requires a cyclotron for the production of an extremely short half-life (2 minutes) tracer. Therefore, the aim of this study was to propose a complementary index for blood flow as determined by MRI to validate the results and compare them with PET, especially for prostate tissue. METHODS: Six consecutive patients with prostate disease were studied. The two semiquantitative indices for tumor blood flow were calculated from the time-concentration curve measured from double-echo MR images. The theory of nondiffusible tracers by means of indicator dilution theory was applied to MR data. The relative regional blood flow (rrBF) was calculated as the ratio of the relative regional blood volume to relative regional mean transit time. Another proposed index was the maximum height of the time-concentration curve. PET studies were also performed, and absolute blood flow values were calculated for each subject. These indices calculated from different modalities were then compared. RESULTS: A significant correlation was found between the rrBF and the absolute blood flow as determined by PET (r = 0.69, p < 0.005). A significant correlation was also found between the maximum height of the time-concentration curve and the absolute blood flow (r = 0.85, p < 0.0001). CONCLUSIONS: The semiquantitative tumor blood flow indices measured with MRI have a good correlation with the corresponding measurements by PET; therefore, these indices may provide useful information about tumor diagnosis in clinical settings.

Aged↗

PubMedDate not supplied

Age-dependent change in metabolic response to photic stimulation of the primary visual cortex in infants: functional magnetic resonance imaging study.

The blood oxygen level-dependent (BOLD) response to photic stimulation in the primary visual cortex (V1) reverses from positive to negative around 8 weeks of age. This phenomenon may be caused by increased oxygen consumption during stimulation as the result of a rapid increase of synaptic density at this age. To test this hypothesis, we applied existing mathematic models of BOLD signals to the experimental data from infants. When the stimulus-related increments of cerebral blood flow and cerebral blood volume were fixed at 60% and 20%, respectively, the mean estimated increment of the cerebral metabolic rate of oxygen of the V1 in the elder infant group (57.1% +/- 8.8%) was twice as large as that in the younger infant group (32.2% +/- 4.7%), which corresponds to the reported difference in synaptic density. The present data confirmed that a change in oxygen consumption could explain a transition from a positive to a negative BOLD response.

Age Factors↗