Koji Sakai

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Magnetic resonance tractography based on diffusion-tensor imaging was first introduced to the medical imaging community a decade ago. It has been successfully applied to a number of neurological conditions and most commonly used for preoperative planning for brain tumors and vascular malformations. Areas of active research include stroke, and dementia,(More)
The mechanism controlling cell-specific Ang II production in the brain remains unclear despite evidence supporting neuron-specific renin and glial- and neuronal-specific angiotensinogen (AGT) expression. We generated double-transgenic mice expressing human renin (hREN) from a neuron-specific promoter and human AGT (hAGT) from its own promoter (SRA mice) to(More)
The subfornical organ (SFO) of the brain has long been considered a critical integrating center for the cardiovascular actions of the renin-angiotensin system (RAS). Early reports of angiotensin II (Ang II) immunoreactivity in the SFO and its neural projections to downstream cardiovascular nuclei raised the possibility that Ang II is produced locally and(More)
Recently, axons have been recognized as computational units in neuronal networks that can change their conduction properties along with their firing. However, little is known about the relationship between spontaneous activity and changes in the conduction velocity due to lack of a suitable method. Here, we studied changes in the conduction velocity during(More)
Diffusion-weight imaging (DWI) has already been incorporated as a regular sequence for patients. If DWI could indicate brain temperature without a complicated procedure, such information may greatly contribute to initial diagnosis. The temperature (T: °C) was calculated using the following equation form the diffusion coefficient (D): T= 2256.74/ln(More)
Among MR methods, the most clinically applicable temperature measurement method at deep brain might be the diffusion-weighted image (DWI) thermometry. Although only applicable to cerebrospinal fluid (CSF), it is thought to be potentially useful in assessing the thermal pathophysiology of the brain in both patients and healthy subjects. The purpose of this(More)
A method for the measurement of temperature in the lateral ventricle using diffusion-weighted imaging (DWI) has been proposed recently. This method uses predetermined arbitrary thresholds, but a more objective method of calculation would be useful. We therefore compared four different calculation methods, two of which were newly created and did not require(More)
Brain metabolism declines with age, but cerebral blood flow (CBF) is less age dependent. We therefore hypothesized that the brain temperature would decline with age, and measured the temperatures of the lateral ventricles in healthy volunteers. Diffusion-weighted imaging (DWI) data from 45 healthy volunteers [mean (± standard deviation) age, 30.6 ± 8.66(More)