Yuichi Sato

Iwate Medical University, Morioka, Iwate, Japan

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Publications (11)15.54 Total impact

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    ABSTRACT: To perform dual-energy X-ray imaging, we developed a dual-energy silicon X-ray diode (DE-Si-XD) consisting of two ceramic-substrate silicon X-ray diodes (Si-XD) and a 0.2-mm-thick copper filter. The Si-XD is a high-sensitivity Si photodiode selected for detecting X-rays. In the front Si-XD, X-ray photons from an X-ray tube are directly detected. Because low-energy photons are absorbed by the front Si-XD and the filter, the average photon energy increases when the back Si-XD is used. In the front Si-XD, the photocurrents flowing through the Si-XD are converted into voltages and amplified using current-voltage and voltage-voltage (V-V) amplifiers. The output from the V-V amplifier is input to an analog-digital converter through an integrator for smoothing the voltage. The same amplification method is also used in the back Si-XD. Dual-energy computed tomography (DE-CT) is accomplished by repeated linear scans and rotations of the object, and two projection curves of the object are obtained simultaneously by linear scanning at a tube voltage of 90 kV and a current of 1.0 mA. In the DE-CT, the exposure time for obtaining a tomogram is 10 min with scan steps of 0.5 mm and rotation steps of 1.0°. Using gadolinium-based contrast media, energy subtraction was performed.
    Radiation Measurements 04/2015; 77. DOI:10.1016/j.radmeas.2015.04.003 · 1.14 Impact Factor
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    ABSTRACT: An energy-dispersive (ED) X-ray computed tomography (CT) system is useful for carrying out monochromatic imaging by selecting optimal energy photons. CT is performed by repeated linear scans and rotations of an object. X-ray photons from the object are detected by the cadmium telluride (CdTe) detector, and event pulses of X-ray photons are produced using charge-sensitive and shaping amplifiers. The lower photon energy is determined by a comparator, and the maximum photon energy of 70 keV corresponds to the tube voltage. Logical pulses from the comparator are counted by a counter card through a differentiator to reduce pulse width and rise time. In the ED-CT system, tube voltage and current were 70 kV and 0.30 mA, respectively, and X-ray intensity was 18.2 μGy/s at 1.0 m from the source at a tube voltage of 70 kV. Demonstration of gadolinium K-edge CT for cancer diagnosis was carried out by selecting photons with energies ranging from 50.4 to 70 keV, and photon-count energy subtraction imaging from 30 to 50.3 keV was also performed.
    Japanese Journal of Applied Physics 10/2012; 51(10):2402-. DOI:10.1143/JJAP.51.102402 · 1.06 Impact Factor
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    ABSTRACT: BACKGROUND: We report a case of an uncommon association of pituitary adenoma with neuronal choristoma that usually is diagnosed at initial surgery. CASE DESCRIPTION: A 50-year-old woman with acromegaly and bitemporal hemianopsia underwent removal of a pituitary adenoma via the transsphenoidal approach. Histologic examination of the first surgical specimen demonstrated only adenoma, which was eosinophilic and expressed growth hormone. Fourteen years later, bitemporal hemianopsia recurred, and magnetic resonance imaging revealed regrowth of the residual tumor. DISCUSSION: The patient underwent removal of the regrown tumor via the transsphenoidal approach. Histologic examination of the second surgical specimen revealed gangliocytoma and a small component of pituitary adenoma. CONCLUSIONS: The present case report supports the theory that pituitary adenoma with neuronal choristoma might represent the result of neuronal differentiation from pituitary adenoma.
    World Neurosurgery 06/2012; 80(3-4). DOI:10.1016/j.wneu.2012.06.031 · 2.42 Impact Factor
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    ABSTRACT: A 54-year-old man with a pulsatile mass on the right side of his neck suffered left hemiparesis due to cerebral infarction in the right cerebral hemisphere. Three-dimensional computed tomographic angiography revealed an aneurysm located at the origin of the right cervical internal carotid artery (ICA). On magnetic resonance (MR) imaging, the aneurysm included fresh and organized thrombi. Under intraoperative monitoring of transcranial Doppler (TCD), transcranial cerebral oxygen saturation (cSO2) and electroencephalogram (EEG), the aneurysm was removed and the right common carotid artery (CCA) and ICA were anastomosed using interposition graft of expanded polytetrafluoroethylene. Attempts were made to keep systolic blood pressure during surgery above a +10% increase. Microembolic signals developed on TCD during dissection of the aneurysm, and then the CCA was early clamped. Transcranial cSO2 on the right forehead and EEG showed no abnormal change throughout surgery. Postoperatively, MR imaging revealed two asymptomatic spotty ischemic lesions, and the patient had only hoarseness. The present case suggests that intentional hypertension and monitoring of TCD, transcranial cSO2 and EEG during surgery might minimize development of intraoperative ischemic events due to embolism from the surgical site and carotid clamping.
    Surgery for Cerebral Stroke 01/2012; 40(4):267-272. DOI:10.2335/scs.40.267
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    ABSTRACT: X-ray fluorescence (XRF) analysis is useful for mapping various atoms in objects, and XRF is emitted by absorbing X-ray photons with energies beyond the K-edge energy of the target atom. Narrow-energy-width bremsstrahlung X-rays are selected using a 3.0-mm-thick aluminum filter. These rays are absorbed by iodine media in objects, and iodine XRF is produced from the iodine atoms. Next, iodine Kα photons are discriminated by a multichannel analyzer and the number of photons is counted by a counter card. CT is performed by repeated linear scans and rotations of an object. The X-ray generator has a 100μm focus tube with a 0.5-mm-thick beryllium window, and the tube voltage and the current for XRF were 80kV and 0.50mA, respectively. The demonstration of XRF-CT for mapping iodine atoms was carried out by selection of photons in an energy range from 27.5 to 29.5keV with a photon-energy resolution of 1.2keV.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 05/2011; 638(1):187-191. DOI:10.1016/j.nima.2011.02.073 · 1.32 Impact Factor
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    ABSTRACT: X-ray fluorescence (XRF) analysis is useful for mapping various molecules in objects, and XRF is irradiated by absorbing X-ray photons with energies beyond the K-edge energy of the target molecule. Quasi-monochromatic bremsstrahlung X-rays are selected out using a 3.0-mm-thick aluminum filter. These rays are absorbed effectively by iodine media in objects, and iodine XRF is produced from the iodine molecules. Next, the iodine Kα rays are discriminated out by a multichannel analyzer, and the number of photons is counted by a counter card. The CT system is a first-generation type, and CT is performed by repeated linear scans and rotations of an object. The X-ray generator has a 100-μm-focus tube with a 0.5-mm-thick beryllium window, and the tube voltage and the current for XRF were 50kV and 0.5A, respectively. The demonstration of XRF CT was carried out by selection of photons in an energy range from 27.5 to 29.5keV with a photon-energy resolution of 1.2keV.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 10/2010; DOI:10.1016/j.nima.2010.10.108 · 1.32 Impact Factor
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    ABSTRACT: Phosphorylation of histone H2AX is a sensitive marker of DNA damage, particularly of DNA double strand breaks. Using multiparameter cytometry we explored effects of etoposide and temozolomide (TMZ) on three glioblastoma cell lines with different p53 status (A172, T98G, YKG-1) and on normal human astrocytes (NHA) correlating the drug-induced phosphorylated H2AX (gammaH2AX) with cell cycle phase and induction of apoptosis. Etoposide induced gammaH2AX in all phases of the cell cycle in all three glioblastoma lines and led to an arrest of T98G and YKG-1 cells in S and G(2)/M. NHA cells were arrested in G(1) with no evidence of gammaH2AX induction. A172 responded by rise in gammaH2AX throughout all phases of the cycle, arrest at the late S- to G(2)/M-phase, and appearance of senescence features: induction of p53, p21(WAF1/CIP1), p16(INK4A) and beta-galactosidase, accompanied by morphological changes typical of senescence. T98G cells showed the presence of gammaH2AX in S phase with no evidence of cell cycle arrest. A modest degree of arrest in G(1) was seen in YKG-1 cells with no rise in gammaH2AX. While frequency of apoptotic cells in all four TMZ-treated cell cultures was relatively low it is conceivable that the cells with extensive DNA damage were reproductively dead. The data show that neither the status of p53 (wild-type vs. mutated, or inhibited by pifithrin-alpha) nor the expression of O(6)-methylguanine-DNA methyltransferase significantly affected the cell response to TMZ. Because of diversity in response to TMZ between individual glioblastoma lines our data suggest that with better understanding of the mechanisms, the treatment may have to be customized to individual patients.
    Cancer biology & therapy 04/2009; 8(5):452-7. DOI:10.4161/cbt.8.5.7740 · 3.63 Impact Factor
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    ABSTRACT: A microfocus X-ray tube is useful for performing magnification digital radiography. The 100-mum-focus X-ray generator consists of a main controller, for regulating tube voltage and current, and a tube unit with a high-voltage circuit and a fixed anode X-ray tube. The maximum tube voltage, current, and electric power were 106 kV, 0.5 mA, and 50 W, respectively. Using a 100-mum-thick tungsten filter, the X-ray intensity was 19.8 muGy/s at 1.0 m from the source with a tube voltage of 100 kV and a current of 0.50 mA. Since Kalpha rays from tungsten targets are absorbed effectively by gadolinium-based contrast media, these rays are useful for performing enhanced angiography. Magnification angiography was performed by threefold magnification imaging using a computed radiography system and the filter at a tube voltage of 100 kV. In angiography of nonliving animals, we observed fine blood vessels of approximately 100 mum with high contrasts.
    Japanese Journal of Applied Physics 06/2008; 47:4772-4776. DOI:10.1143/JJAP.47.4772 · 1.06 Impact Factor
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    ABSTRACT: A desmoplastic infantile astrocytoma (DIA) is an extremely rare tumor that comprises a solid astrocytic tumor accompanied by a large cyst and involves the superficial cerebral cortex and leptomeninges in infants. The solid part of this type of tumor has been well described in various reports and books, but characteristics of the cystic portion have remained unclear. Because adequate resection is required to ensure a favorable prognosis, information about the cyst is very important for diagnostic purposes and surgical planning. The authors report on the clinical and histological features of the cyst in a case of a DIA. A 12-month-old boy presented with vomiting. Contrast-enhanced magnetic resonance imaging revealed a strongly enhancing single-lobed large cyst located in the deep white matter, under the solid part of the tumor attached to the dura mater of the left frontal lobe. Both the solid and cystic portions of the tumor were surgically removed. The border between the cyst wall and surrounding white matter was unclear. Histologically, the cyst wall was composed of gliosis representing a rough accumulation of reactive astrocytes, lymphocytes, and small capillary vessels in edematous parenchyma, but no tumor cells. The present case and previous reports suggest that the cyst does not contain tumor cells, even if strongly depicted on contrast-enhanced neuroimaging, and that a thickly enhancing cyst wall indicates gliosis with accumulation of numerous small vessels.
    Journal of Neurosurgery Pediatrics 03/2008; 1(2):148-51. DOI:10.3171/PED/2008/1/2/148 · 1.37 Impact Factor
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    ABSTRACT: A 53-year-old man presented with subarachnoid hemorrhage (SAH) in the left sylvian fissure. Preoperative computed tomography angiography revealed symmetrical aneurysms located at the bifurcations of the right and left middle cerebral arteries (MCAs). The left MCA aneurysm responsible for the SAH was clipped. The patient received post-surgical volume expansion treatment that did not induce hypertension. His systolic blood pressure ranged from 170 to 225 mmHg between the day of the first surgery and the 11th postoperative day. The postoperative course was uneventful until the 11th postoperative day when the patient suffered another SAH in the right sylvian fissure. The right MCA aneurysm was responsible for the second SAH and was clipped. The patient had multiple risk factors for rupture of concomitant unruptured aneurysm including a large, multilobed aneurysm, hypertension, smoking, and a family history of aneurysmal SAH. The present case suggests that all aneurysms should be simultaneously treated using endovascular coil embolization or several craniotomies if the patient has multiple risk factors.
    Neurologia medico-chirurgica 02/2008; 48(11):512-4. DOI:10.2176/nmc.48.512 · 0.65 Impact Factor
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    ABSTRACT: Reported herein is a case of central neurocytoma with differentiation toward ganglion cells, considered to be a typical case of ganglioneurocytoma. Tumor cells of various degree of differentiation toward ganglion cells were intermingled with typical neurocytoma cells in a fibrillary background, with transition of tumor cells from typical neurocytoma cells to differentiated ganglion cells evident throughout the tumor. The tumor cell nuclei were positive for NeuN. Fine granular positivity for synaptophysin was seen in the cytoplasm of the tumor cells, and background fibrils and the cytoplasm of some ganglioid cells were positive for neurofilament. Several cases of central neurocytoma with ganglioid cells have been reported, with some diagnosed as ganglioneurocytoma. However, histopathological details and persuasive figures have been lacking. It is considered that the diagnosis of ganglioneurocytoma should be applied to tumors displaying the following characteristics: (i) clinical aspects such as location, demarcation and growth rate consistent with neurocytoma; (ii) transition between neurocytoma cells and ganglion cells; and (iii) ganglioid cells distributed throughout the tumors.
    Pathology International 01/2008; 57(12):799-803. DOI:10.1111/j.1440-1827.2007.02177.x · 1.59 Impact Factor