Hiroyasu Arima

Kilohertz to megahertz soft flash x-ray generators utilizing hot-cathode radiation tubes

Six kinds of repetitive flash x-ray generators having hot-cathode radiation tubes with maximum repetition rates of kilohertz (kHz) to megahertz (MHz) are described. These generators were primarily designed in order to increase the repetition rate of flash x rays and to perform cine or multiple-shot radiography. The temperatures of the filament (cathode) had values of about 2000 K for increasing tube currents. Because the hot-cathode triode was quite useful for high-voltage switching with high-repetition rates, four types of generators in conjunction with the grid pulsers were developed.

Kilohertz-range flash x-ray generator utilizing a hot-cathode triode

The construction and the fundamental studies of a kilohertz-range flash x-ray generator utilizing a hot-cathode triode for high-speed radiography are described. This generator consisted of the following components: a constant high-voltage power supply, an energy- storage main condenser of 97 nF, a grid pulser, and an x-ray tube. The x-ray tube was of an enclosed-triode type and was composed of the following major parts: an anode rod made of copper, a plane anode tip (target) made of tungsten, a focusing electrode made of iron, a hot cathode (filament) made from a tungsten wire, a tungsten grid, and a glass tube body. The main condenser was charged from 50 to 70 kV, and the electric charges in the condenser were discharged repetitively by the grid pulser. The temperature of the cathode was about 2,000 K, and the cathode current was primarily controlled by the grid voltage at a constant filament temperature. The pulse width was less than 2 microsecond(s) , and the maximum repetition rate was about 30 kHz. The x-ray intensity was 67.3 nC/kg at 0.5 m per pulse with a peak grid voltage of 1.2 kV and a charged voltage of main condenser of 70 kV.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A Flash Radiographic System For Biomedical Use

A flash radiographic system utilizing a single flash x-ray generator having a new kind of combined x-ray tube and a computed radiography (CR) system is described. This system consisted of the following components: two types of delay switches (i. e. (a) direct switching and (b) laser switching), a delayed pulse generator, a CR system, and a high-intensity single flash x-ray generator. This generator consisted of the following components: a high-voltage generator, a high-voltage pulser, a vacuum pump, and a new type of combined remote x-ray tube with two sets of anode and cathode electrodes. When the radiographic object triggered the timing switch, a short electric pulse was produced and was transmitted to the delayed pulse generator. An accurate delayed flash x-ray was produced when the delayed pulse was transmitted to the high-speed impulse switching system inside of the high-voltage pulser. Next, when the radiographic object was exposed to the controlled x-rays under the optimum radiographic conditions, the permeating x-rays produced the digital image. The FX pulse widths were less than 10Ons with a photon energy of less than 120keV. Since the time resolutions for the two types of delay switches were less than 2Ons, the total time resolution for the FX production was less than 1ps. Various kinds of high-speed biomedical radiography, e. g., the continuous delayed radiographs and the continuous three-dimensional analysis could be performed by controlling the radiographic conditions.

Flash Energy Subtraction Technique Using a Thin Metal Filter

The flash energy subtraction technique, its principle of operation, and the control methods concerning the FX spectrum distribution are described. This technique was performed by using a high intensity soft flash x-ray (FX) generator having spectrum control functions, Fuji computed radiography (FCR) achieved with a subtraction function, a thin metal filter of copper, and two or three imaging plates. The FX generator was a single exposure type and consisted of the following components: a high voltage generator, a simple low impedance coaxial transmission line with a high voltage coaxial condenser (0.2μF, 100kV), a gas gap switch having a high energy trigger device, a turbo molecular pump, and two types of demountable FX tubes, each of a different type. The FX distribution was controlled to the wide energy latitude from very soft to slightly hard in order to perform the single exposure (flash) energy subtraction radiography. The peak intensity of the FX spectrum rapidly shifted the high photon energy region according to insertion of metal filters. Various single exposure subtraction images were obtained by the subtraction between the soft image (no filter) and the hard image (after filtering).

Flash X-Ray Apparatus With Spectrum Control Functions For Medical Use And Fuji Computed Radiography

Flash radiographic bio-medical studies at sub-microsecond intervals were performed by using both a new type of flash X-ray(FX) apparatus with spectrum control functions and Fuji Computed Radiography(FCR). This single flasher tends to have a comparatively long exposure time and the electric pulse width of the FX wave form is about 0.3,usec. The maximum FX dose is about 50mR at 1m per pulse, and the effective focal spot varies according to condenser charging voltage, A-C distance, etc., ranging from 1.0 to 3.0mm in diameter, but in the low dose rate region it can be reduced to less than 1.0mm in diameter. The FX dose is determined by the condenser charging voltage and the A-C distance, while the FX spectrum is determined by the average voltage of the FX tube and filters. Various clear FX images were obtained by controlling the spectrum and dose. FCR is a new storage medium for medical radiography developed by the Fuji Photo Film Co., Ltd. and this apparatus has various image forming functions: low dose radiography, film density control, image contrast control, subtraction management and others. We have used this new apparatus in conjunction with our FX radiography and have obtained some new and interesting biomedical radiograms: the edge enhancement image, the instantaneous enlarged image, and the single exposure energy subtraction image using the FX spectrum distribution.