Publications by authors named "Yuichi Aoyama"

The Totten Glacier in East Antarctica, with an ice volume equivalent to >3.5 m of global sea-level rise, is grounded below sea level and, therefore, vulnerable to ocean forcing. Here, we use bathymetric and oceanographic observations from previously unsampled parts of the Totten continental shelf to reveal on-shelf warm water pathways defined by deep topographic features.

View Article and Find Full Text PDF

We have probed the crystalline electric-field ground states of pure |J=7/2,J_{z}=±5/2⟩ as well as the anisotropic c-f hybridization in both valence fluctuating systems α- and β-YbAlB_{4} by linear polarization dependence of angle-resolved core level photoemission spectroscopy. Interestingly, the small but distinct difference between α- and β-YbAlB_{4} was found in the polar angle dependence of linear dichroism, indicating the difference in the anisotropy of c-f hybridization, which may be a key to understanding a heavy Fermi liquid state in α-YbAlB_{4} and a quantum critical state in β-YbAlB_{4}.

View Article and Find Full Text PDF

Aim: This work investigated the dosimetric properties of a 10-MV photon beam emitted from a medical linear accelerator (linac) with no flattening filter (FF). The aim of this study is to analyze the radiation fluence and energy emitted from the flattening filter free (FFF) linac using Monte Carlo (MC) simulations.

Materials And Methods: The FFF linac was created by removing the FF from a linac in clinical use.

View Article and Find Full Text PDF

A 59-year-old woman was admitted with to our hospital with a sudden severe headache that had lasted for 5 days. Neck stiffness was present, but no other neurological deficits were present. Subarachnoid hemorrhage and intra-tumor hemorrhage were not noted on a head computed tomography (HCT).

View Article and Find Full Text PDF

A 51 year old male was admitted to our hospital with sudden consciousness disturbance, global aphagia and right hemiparesis. Magnetic resonance imaging (MRI) revealed fresh infarctions in the territory of the left middle cerebral artery, and MR angiography (MRA) showed occlusion of the left carotid artery and the left middle cerebral artery. We started conservative therapy, including antiplatelet drug and blood pressure control.

View Article and Find Full Text PDF

A 59-year-old employed man was recommended to have surgical treatment for symptomatic left middle cerebral arterial stenosis. He refused surgical treatment for social reasons but was given conservative therapy for the prevention of the recurrence of cerebral infarction. Immediately after he retired, he had severe recurrent cerebral infarction with severe anemia and low blood pressure due to gastroduodenal ulcer bleeding.

View Article and Find Full Text PDF

Image-guided radiation therapy using a gold marker-based tumor tracking technique provides precise patient setup and monitoring. However, the marker consists of high-Z material, and the resulting scattered rays tend to have adverse effects on the dose distribution of radiotherapy. The purpose of this study was to evaluate the dosimetric perturbation due to the use of a gold marker for radiotherapy in the lungs.

View Article and Find Full Text PDF

Background: Intraoperative radiotherapy (IORT) is under evaluation in breast-conserving surgery. We have begun our study with the first step being a phase I-II study. This study was designed to identify the recommended dose and to test the feasibility of and tolerance to IORT in Japanese patients (UMIN000000918).

View Article and Find Full Text PDF

Introduction: The purpose of this study was to evaluate the role of contrast-enhanced fast imaging with steady-state acquisition (CE-FIESTA) for assessing whether dural attachment in intracranial meningiomas is adhesive or not by correlation with intraoperative findings.

Methods: Fourteen consecutive patients who were candidates for surgical treatment of meningiomas were prospectively analyzed with preoperative magnetic resonance imaging, including CE-FIESTA at 3 T. First, two neuroradiologists assessed several characteristics of the attachment of the meningioma to the dura mater or skull base on CE-FIESTA images.

View Article and Find Full Text PDF

To investigate the effects of scattered radiation when a thin titanium plate (thickness, 0.05 cm) used for skull fixation in cerebral nerve surgery is irradiated by a 4-MV photon beam. We investigated the dose distribution of radiation inside a phantom that simulates a human head fitted with a thin titanium plate used for post-surgery skull fixation and compared the distribution data measured using detectors, obtained by Monte Carlo (MC) simulations, and calculated using a radiation treatment planning system (TPS).

View Article and Find Full Text PDF

A 12-month-old girl presented with a rare atypical choroid plexus papilloma manifesting as conscious disturbance and vomiting. Magnetic resonance (MR) imaging revealed a well-delineated 5 x 6-cm lobulate mass in the right lateral ventricle. Only partial removal of the tumor was performed because of excessive intraoperative hemorrhage at the first surgery.

View Article and Find Full Text PDF

Background: The present study was designed to identify the optimal intraoperative radiotherapy (IORT) dose for early breast cancer in Japanese women.

Methods: A phase I study was designed using a scheme of dose-escalation from 19, 20, and 21 Gy at 90% isodose. The primary endpoint was early toxicity.

View Article and Find Full Text PDF

Background Context: Hemangioblastomas in the central nervous system are highly vascular lesions, but have low risk of hemorrhage. In spinal lesions, there are a few rare cases of intramedullary hemorrhages associated with hemangioblastoma, and their prognoses were very severe.

Purpose: This is the first case of an intrasyrinx hemorrhage associated with hemangioblastoma in epiconus.

View Article and Find Full Text PDF

Object: The morphological and functional impairments of neurons and their connections caused by hydrocephalus, and their restoration by ventricular shunt placement were investigated in experimental hydrocephalus by the immunostaining of neurofilaments, which constitute the major component of the neuronal cytoskeleton.

Methods: Progressive hydrocephalus was induced in 15 young mongrel dogs 1 to 2 months of age, 3 to 4 weeks after cisternal injection of kaolin. The dogs were divided into three groups of five animals each, a "preshunt," "post-shunt," and "nonshunt" group, depending on whether the hydrocephalic animals underwent a procedure to insert a ventriculoperitoneal shunt.

View Article and Find Full Text PDF

In the case of total skin electron therapy without the beam guide, the electron beam is scattered just outside the gantry exit, dose uniformity in the field is broken, and dose is spread outside the light field. The aims of this study were to measure the mean energy of the off-axis incident electron beam without the beam guide and to establish a reference for the clinical situation. For the measurement, a 4 MeV electron beam was selected among several energies from the linear accelerator.

View Article and Find Full Text PDF

Normal pressure hydrocephalus (NPH) is a clinical syndrome associated with dementia, gait disturbance and urinary incontinence. Gait disturbance is usually the initial sign and most important symptom, but its objective evaluation has not been established. We analyzed the gait of an idiopathic NPH before and after ventricular shunting with the gait analysis system.

View Article and Find Full Text PDF