Biomedical subjects

Masayuki Kamba

Publications and source records attributed to Masayuki Kamba.

4 recordsLinked to original sources

PubMed2006

Sonographic subcutaneous and visceral fat indices represent the distribution of body fat volume.

BACKGROUND: A reliable method for direct measurement of both subcutaneous and visceral fat volume is the measurement of fat tissue area from tomographic pictures by CT or by MR imaging. However, these are not widely usable because of high cost and/or exposure to radiation. METHODS: We compared sonographic subcutaneous and visceral fat indices with fat distribution by serial-slice MR imaging in 17 subjects. Sonographic subcutaneous or visceral fat index is standardized thickness of subcutaneous fat tissue or the intra-abdominal depth at the level of umbilicus by height. RESULTS: Sonographic visceral fat index and intra-abdominal depth were significantly correlated with visceral fat volume by serial-slice MR imaging (r = 0.746, r = 0.726, respectively). Similarly, sonographic subcutaneous fat index and subcutaneous fat thickness were significantly correlated with subcutaneous fat volume by serial-slice MR imaging (r = 0.825, r = 0.816, respectively). The ratio of sonographic visceral fat index and sonographic subcutaneous fat index was closely correlated with the ratio of the visceral fat volume and the subcutaneous fat volume by single-slice MR imaging, which proves to be related to cardiovascular disease risk (r = 0.722). CONCLUSION: Sonographic subcutaneous or visceral fat index could be an easily measured and inexpensive indicator for the assessment of fat distribution instead of CT or MR imaging.

Adult↗

PubMed2004

A dynamic system model-based technique for functional MRI data analysis.

Signals in functional magnetic resonance imaging (fMRI) are influenced by physiological fluctuations in addition to local brain activity. We have proposed a dynamic system model-based technique for separation of signal changes related to brain activation inputs from those related to physiological fluctuations. We applied this technique to a visual fMRI experiment to determine the validity and feasibility of this technique for fMRI data analyses. Gradient-echo echo planar images were obtained from 12 healthy volunteers with a Siemens ALLEGRA operating at 3 T, with a repetition time of 500 ms, echo time of 20 ms, field of view of 200-210 mm, matrix size of 64 x 64, and slice thickness of 5 mm. Twelve runs with two stimulation periods of varied duration (2-8 s) with 8-Hz flickering illumination were obtained for each subject. Local signal changes were modeled by an autoregressive model with two exogenous inputs, a visual stimulation input and a global reference signal. Local signal changes were appropriately predicted not only for stimulation periods but also resting periods. A significant linear relationship was found between model static gain based on the dynamic system modeling and beta coefficient based on a general linear model (GLM) analysis for active voxels in the primary visual cortex (analysis of covariance [ANCOVA], P < 0.001; estimated parameter, 0.967; 95% confidence interval, 0.734-1.201). This dynamic system model-based technique is sufficiently accurate and feasible for use in extracting signal changes related to brain activation inputs from measured signals with physiological fluctuations.

Adult↗

PubMed2003

Transneuronal degeneration in patients with temporal lobe epilepsy: evaluation by MR imaging.

The aim of this study was to assess the MR imaging findings of transneuronal degeneration of limbic system in the patients with temporal lobe epilepsy, and to detect the influence of surgery on the anatomy of the limbic system. Axial and coronal T1- and T2-weighted MR images were retrospectively analyzed in 34 patients with temporal lobe epilepsy, focusing on transneuronal degeneration. In 17 of the 34 patients, MR images were also analyzed after selective amygdalo-hippocampectomy. Atrophy of the fornix, mamillary body, mamillothalamic tract (MTT), and thalamus ipsilateral to the epileptic focus was demonstrated on MR images in 14.7, 17.6, 8.8, and 11.8% of the 34 patients, respectively. Focal hyperintensity of the thalamus was found on T2-weighted images in 8.8% of the 34 patients. In 17 patients who were evaluated before and after surgery, transneuronal degeneration was seen more frequently after surgery: fornix (11.8 vs 29.4%), mamillary body (11.8 vs 52.9%), MTT (5.9 vs 11.8%), and thalamus (11.8 vs 11.8%). Transneuronal degeneration of the limbic system is clearly demonstrated by MR imaging in patients with temporal lobe epilepsy, and surgical intervention induces transneuronal degeneration more frequently.

Adolescent↗

PubMed2003

Age-related changes in cerebral lactate metabolism in sleep-disordered breathing.

Thirty-one patients, aged 22-71 years, with nocturnal apneic episodes and/or habitual snoring were studied with magnetic resonance spectroscopy (MRS) and diagnostic polysomnography separately to determine whether accumulation of lactate caused by cerebral hypoxia during sleep is associated with sleep-disordered breathing (SDB), aging and co-morbidities related to SDB. Eight proton magnetic resonance spectra for sleep and two for periods of arousal were obtained from the right centrum semiovale. All patients were evaluated for the presence or absence of co-morbidities including hypertension, cardiac disease, diabetes mellitus, and hyperlipidemia. Significant lactate signals were found in seven patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) during sleep periods, and none during periods of arousal. Aging was significantly related to the presence or absence of significant lactate signals during sleep periods as determined by logistic regression analysis (beta=0.2480; 95% confidence interval, 0.0905-0.5094; P=0.0001). Apnea index (AI), apnea-hypopnea index (AHI), and minimum value of peripheral oxyhemoglobin saturation each significantly interacted with age (P=0.0081, 0.0284, and 0.0302, respectively). Our findings suggest that SDB combined with aging is related to accumulation of lactate during sleep.

Adult↗