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Biomedical subjects

Y Hayasi

Publications and source records attributed to Y Hayasi.

5 recordsLinked to original sources
PubMed2000

[Crescent moon-type tracheobronchial malacia alleviated by placement of stents in trachea and main bronchi].

We encountered a case of crescent-type tracheobronchomalacia in a 54-year-old male smoker. The patient experienced extreme obstructive pulmonary changes but his FVC and DLco findings were within the normal ranges. Plain chest X-ray films indicated tracheal narrowing, a diagnosis that was confirmed by fiberoptic bronchoscopy. Two Z-stents were implanted in the trachea but the patient's symptoms did not subside. Thoracic computed tomography (CT) elucidated stenosis of both main bronchi at end-expiration. The implantation of Z-stents in the main bronchi remarkably alleviated the symptoms and improved peak expiratory flow. Six months after implantation, the tracheal stents broke. A favorable course was obtained by inserting an ultraflex stent inside the broken Z-stents. DLco is important to the diagnosis of tracheobronchomalacia, whereas peak expiratory flow and thoracic CT findings are useful in evaluating the effectiveness of treatment. We concluded that ultraflex stents should be the first choice for treatment of tracheal stenosis, and that Z-stents are appropriate for the treatment of bronchial obstruction.

Bronchi↗
PubMed1994

Sub-kilohertz flash X-ray generator utilising a glass-enclosed cold-cathode triode.

The construction and fundamental studies are described for a sub-kilohertz X-ray generator for producing low-dose rate flash X-rays. The X-ray tube was a glass-enclosed cold-cathode triode, composed of a tungsten plate target, a rod-shaped graphite cathode, a mesh-type trigger electrode made of tungsten wires, and a glass tube body. The coaxial condenser was charged up to 60 kV by a power supply, and the electric charges in the condenser were discharged to the X-ray tube repetitively when a negative high-voltage pulse was applied to the trigger electrode. The maximum tube voltage before the discharging was equivalent to the initial charged voltage of the condenser, and the maximum tube current was about 0.3 kA with a charged voltage of 60 kV. The X-ray durations were about 1 microsecond, and the X-ray intensity was about 0.47 microC kg-1 at 0.5 m per pulse with a charged voltage of 60 kV. The maximum repetition rate of the X-rays was about 0.4 kHz, and high-speed radiography was performed.

Animals↗
PubMed1994

10 kHz microsecond pulsed X-ray generator utilising a hot-cathode triode with variable durations for biomedical radiography.

A 10 kHz pulsed X-ray generator utilising a hot-cathode triode in conjunction with a new type of grid control device for controlling X-ray duration is described. The energy-storage condenser was charged up to 70 kV by a power supply, and the electric charges in the condenser were discharged to the X-ray tube repetitively by the grid control device. The maximum values of the grid voltage (negative value), the tube voltage, and the tube current were -1.5 kV, 70 kV, and 0.4 A, respectively. The duration of the flash X-ray pulse was primarily determined by the time constant of the grid control device and the cut-off voltage of thermoelectrons. The X-ray duration was controlled within a region of less than 1 ms; the X-ray intensity with a pulse width of 0.27 ms, a charged voltage of 70 kV, and a peak tube current of 0.4 A was 0.92 microC kg-1 at 0.5 m per pulse. The maximum repetition rate was about 10 kHz, and the size of the focal spot was about 3.5 x 3.5 mm.

Animals↗