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We developed an image-shifting subtraction program and carried out embossed radiography (ER) utilizing single- and dual-energy subtractions. In particular, dual-energy subtraction was carried out to decrease the absorption contrast of unnecessary regions. The contrast resolution of a target region was increased using the subtraction program and a linear-contrast system in a flat panel detector (FPD). The X-ray generator had a 100 μm-focus tube, and the subtractions were performed at tube voltages of 40 and 70 kV, a tube current of 0.50 mA, and an X-ray exposure time of 5.0 s. ER was achieved with cohesion imaging using the FPD with pixel sizes of 48×48 μm 2 , and the shifting dimension of an object in the horizontal and vertical directions ranged from 48 to 96 μm. At a shifting distance of 96 μm, the spatial resolutions in the horizontal and vertical directions measured with a lead test chart were both 83 μm. In ER of animal phantoms, we obtained high-contrast embossed images of fine bones, gadolinium oxide particles in blood vessels, iodine-based microspheres in coronary arteries approximately 100 μm in diameter.

An energy-discrimination K-edge X-ray computed tomography (CT) system is useful for increasing the contrast resolution of a target region by utilizing contrast media. The CT system has a cadmium telluride (CdTe) detector, and a projection curve is obtained by linear scanning with use of the CdTe detector in conjunction with an X-stage. An object is rotated by a rotation step angle with use of a turntable between the linear scans. Thus, CT is carried out by repetition of the linear scanning and the rotation of an object. Penetrating X-ray photons from the object are detected by the CdTe detector, and event signals of X-ray photons are produced with use of charge-sensitive and shaping amplifiers. Both the photon energy and the energy width are selected by use of a multi-channel analyzer, and the number of photons is counted by a counter card. For performing energy discrimination, a low-dose-rate X-ray generator for photon counting was developed; the maximum tube voltage and the minimum tube current were 110 kV and 1.0 microA, respectively. In energy-discrimination CT, the tube voltage and the current were 60 kV and 20.0 microA, respectively, and the X-ray intensity was 0.735 microGy/s at 1.0 m from the source and with a tube voltage of 60 kV. Demonstration of enhanced iodine K-edge X-ray CT was carried out by selection of photons with energies just beyond the iodine K-edge energy of 33.2 keV.

An energy-discrimination K-edge x-ray computed tomography (CT) system is useful for controlling the image contrast of a target region by selecting both the photon energy and the energy width. The CT system has an oscillation-type linear cadmium telluride (CdTe) detectror. CT is performed by repeated linear scans and rotations of an object. Penetrating x-ray photons from the object are detected by a CdTe detector, and event signals of x-ray photons are produced using charge-sensitive and shaping amplifiers. Both photon energy and energy width are selected out using a multichannel analyzer, and the number of photons is counted by a counter card. In energy-discrimination CT, the tube voltage and tube current were 80 kV and 20 μA, respectively, and the x-ray intensity was 1.92 μGy/s at a distance of 1.0 m from the source and a tube voltage of 80 kV. The energy-discrimination CT was carried out by selecting x-ray photon energies.

We developed an embossed radiography system utilizing single- and dual-energy subtractions for decreasing the absorption contrast of unnecessary regions, and contrast resolution of a target region was increased using image-shifting subtraction and a linear-contrast system in a flat panel detector (FPD). To carry out embossed radiography, we developed a computer program for two-dimensional subtraction, and a conventional x-ray generator with a 0.5-mm-focus tube was used. Energy subtraction was performed at tube voltages of 42.5 and 70.0 kV, a tube current of 1.0 mA, and an x-ray exposure time of 5.0 s. Embossed radiography was achieved with cohesion imaging by use of the FPD with pixel sizes of 48 ×48 μm, and the shifting dimension of an object in the horizontal and vertical directions ranged from 48 to 144 μm. We obtained high-contrast embossed images of fine bones and coronary arteries approximately 100 μm in diameter.

High-speed photon counting is useful for discriminating photon energy and for decreasing absorbed dose for patients in medical radiography, and the counting is usable for constructing an x-ray computed tomography (CT) system. A photon-counting x-ray CT system is of the first generation type and consists of an x-ray generator, a turn table, a translation stage, a two-stage controller, a multipixel photon counter (MPPC) module, a 1.0-mm-thick LSO crystal (scintillator), a counter card (CC), and a personal computer (PC). Tomography is accomplished by repeating the linear scanning and the rotation of an object, and projection curves of the object are obtained by the linear scanning using the detector consisting of a MPPC module and the LSO. The pulses of the event signal from the module are counted by the CC in conjunction with the PC. The lower level of the photon energy is roughly determined by a comparator circuit in the module, and the unit of the level is the photon equivalent (pe). Thus, the average photon energy of the x-ray spectra increases with increasing the lower-level voltage of the comparator. The maximum count rate was approximately 20 Mcps, and energy-discriminated CT was roughly carried out.

A preliminary experiment for producing narrow-photon-energy cone-beam x-rays using a silicon single crystal is described. In order to produce low-photon-energy x-rays, a 100-µm-focus x-ray generator in conjunction with a (111) plane silicon crystal is employed. The x-ray beams from the source are confined by an x-y diaphragm, and monochromatic cone beams are formed by the crystal and three lead plates. The x-ray generator consists of a main controller and a unit with a high-voltage circuit and a 100-µm-focus x-ray tube. In this experiment, the maximum tube voltage and current were 35 kV and 0.50 mA, respectively, and the x-ray intensity of the microfocus generator was 343 μGy/s at 1.0 m from the source with a tube voltage of 30 kV and a current of 0.50 mA. The effective photon energy is determined by Bragg's angle, and the photon-energy width is regulated by the angle delta. Using this generator in conjunction with a computed radiography system, quasi-monochromatic radiography was performed using a cone beam with an effective energy of approximately 15.5 keV.

A microfocus x-ray tube is useful in order to perform magnification digital radiography including phase-contrast effect. The 100-µm-focus x-ray generator consists of a main controller for regulating the 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 105 kV, 0.5 mA, and 50 W, respectively. Using a 3.0-mm-thick aluminum filter, the x-ray intensity was 26.0 µGy/s at 1.0 m from the source with a tube voltage of 60 kV and a current of 0.50 mA. Because the peak photon energy was approximately 35 keV using the filter with a tube voltage of 60 kV, the bremsstrahlung x-rays were absorbed effectively by iodine-based contrast media with an iodine K-edge of 33.2 keV. Magnification angiography was performed by two-time magnification imaging with a computed radiography system using iodine-based microspheres 15 µm in diameter. In angiography of non-living animals, we observed fine blood vessels of approximately 100 µm with high contrasts.

The samarium-target x-ray tube is useful in order to perform cone-beam K-edge angiography because K-series characteristic x-rays from the samarium target are absorbed effectively by iodine-based contrast media. This generator consists of the following components: a constant high-voltage power supply, a filament power supply, a turbomolecular pump, and an x-ray tube. The x-ray tube is a demountable diode which is connected to the turbomolecular pump and consists of the following major devices: a samarium target, a tungsten hairpin cathode (filament), a focusing (Wehnelt) electrode, a polyethylene terephthalate x-ray window 0.25 mm in thickness, and a stainless-steel tube body. In the x-ray tube, the positive high voltage is applied to the anode (target) electrode, and the cathode is connected to the tube body (ground potential). In this experiment, the tube voltage applied was from 50 to 70 kV, and the tube current was regulated to within 0.10 mA by the filament temperature. The exposure time is controlled in order to obtain optimum x-ray intensity. The electron beams from the cathode are converged to the target by the focusing electrode, and bremsstrahlung x-rays were absorbed using a 50-µm-thick tungsten filter. The x-ray intensity was 1.04 μGy/s at 1.0 m from the x-ray source with a tube voltage of 60 kV and a tube current of 0.10 mA, and angiography was performed using a computed radiography system and iodine-based microspheres 15 µm in diameter. In angiography of non-living animals, we observed fine blood vessels of approximately 100 µm with high contrasts.

A microfocus x-ray tube is useful in order to perform magnification digital radiography. The 100-µm-focus x-ray generator consists of a main controller for regulating the 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 105 kV, 0.5 mA, and 50 W, respectively. Using a 50-µm-thick tungsten filter, the x-ray intensity was 34.0 µGy/s at 1.0 m from the source with a tube voltage of 100 kV and a current of 0.50 mA. Since K-series characteristic x-rays from tungsten targets are absorbed effectively by gadolinium-based contrast media, these x-rays are very useful to perform enhanced angiography. Magnification angiography was performed by two-time magnification imaging with a computed radiography system. In angiography of non-living animals, we observed fine blood vessels of approximately 100 µm with high contrasts.

Novel monochromatic x-ray generators and their applications to high-speed radiography are described. The five generators are as follows: a weakly ionized linear plasma x-ray generator, a monochromatic compact flash x-ray generator, a super-fluorescent plasma generator, a cerium x-ray generator using a 3.0-mm-thick aluminum filter, and a 100micron-focus x-ray generator utilizing the filter. Using the linear plasma generator with a copper target, we observed clean K lines and their harmonics, and soft flash radiography was performed with pulse widths of approximately 500 ns. The compact monochromatic flash x-ray generator produced clean molybdenum K lines easily, and high-speed radiography was performed with pulse widths of approximately 100 ns. Using a steady-state cerium x-ray generator, we performed real-time angiography utilizing an image intensifier and a high-sensitive camera (MLX) made by NAC Image Technology Inc. with a capture time of 1 ms. Finally, real-time magnification radiography was performed by twofold magnification imaging using a 100micron-focus x-ray generator and the high-sensitive camera.

A microfocus x-ray tube is useful in order to perform magnification digital radiography including phase-contrast effect. The 100-µm-focus x-ray generator consists of a main controller for regulating the 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 105 kV, 0.5 mA, and 50 W, respectively. Using a 3.0-mm-thick aluminum filter, the x-ray intensity was 26.0 µGy/s at 1.0 m from the source with a tube voltage of 60 kV and a current of 0.50 mA. Because the peak photon energy was approximately 35 keV using the filter with a tube voltage of 60 kV, the bremsstrahlung x-rays were absorbed effectively by iodine-based contrast media with an iodine K-edge of 33.2 keV. Real-time magnification radiography was performed by twofold magnification imaging with an image intensifier camera, and angiography was achieved with iodine-based microspheres 15 µm in diameter. In angiography of non-living animals, we observed fine blood vessels of approximately 100 µm with high contrasts.

This generator consists of the following components: a constant high-voltage power supply, a filament power supply, a turbomolecular pump, and an x-ray tube. The x-ray tube is a demountable diode which is connected to the turbomolecular pump and consists of the following major devices: a tungsten hairpin cathode (filament), a focusing (Wehnelt) electrode, a polyethylene terephthalate x-ray window 0.25 mm in thickness, a stainless-steel tube body, a pipe target, and a rod target. The pipe and rod targets are useful for forming linear and cone beams, respectively. In the x-ray tube, the positive high voltage is applied to the anode (target) electrode, and the cathode is connected to the tube body (ground potential). In this experiment, the tube voltage applied was from12 to 20 kV, and the tube current was regulated to within 0.10 mA by the filament temperature. The exposure time is controlled in order to obtain optimum x-ray intensity. The electron beams from the cathode are converged to the target by the focusing electrode, and clean K-series characteristic x-rays are produced through the focusing electrode without using a filter. The x-ray intensities of the pipe and rod targets were 1.29 and 4.28 μGy/s at 1.0 m from the x-ray source with a tube voltage of 15 kV and a tube current of 0.10 mA, and quasi-monochromatic radiography was performed using a computed radiography system.

A fundamental study on quasi-monochromatic parallel radiography using a polycapillary plate and a copper-target x-ray tube is described. The x-ray generator consists of a negative high-voltage power supply, a filament (hot cathode) power supply, and an x-ray tube. The negative high-voltage is applied to the cathode electrode, and the anode electrode is connected to the ground. In this experiment, the tube voltage was regulated from 12 to 22 kV, and the tube current was regulated within 3.0 mA by the filament temperature. The exposure time was controlled in order to obtain optimum x-ray intensity, and the maximum focal spot dimensions were approximately 2.0 x 1.5 mm. The polycapillary plate was J5022-16 (Hamamatsu Photonics Inc.), and the plate thickness was 1.0 mm. The outer, effective, and hole diameters were 33 mm, 27 mm, and 10 μm, respectively. Quasi-monochromatic x-rays were produced using a 10 μm-thick copper filter with a tube voltage of 17 kV, and these rays were formed into parallel beams by the polycapillary. The radiogram was taken using a computed radiography system utilizing imaging plates. In the measurement of image resolution, the resolution hadly varied according to increases in the distance between the chart and imaging plate using a polycapillary. We could observe a 50 μm tungsten wire clearly, and fine blood vessels of approximately 100 μm were visible in angiography.

We developed an image-shifting subtraction program and carried out magnification embossed radiography (MER) utilizing single- and dual-energy subtractions. In particular, dual-energy subtraction was carried out to decrease the absorption contrast of unnecessary regions. The contrast resolution of the target region was increased by the use of subtraction software and a linear-contrast system in a flat-panel detector (FPD). The X-ray generator had a 100-µm-focus tube, and the subtractions were performed at tube voltages of 40 and 70 kV, a tube current of 0.50 mA, and an X-ray exposure time of 5.0 s. MER images with threefold magnification were obtained using the FPD with a pixel size of 48×48 µm2, and the shifting dimensions of the imaged object in the horizontal and vertical directions ranged from 48 to 192 µm. At a shifting distance ranging from 48 to 144 µm, the spatial resolutions in the horizontal and vertical directions measured with a lead test chart were both 50 µm. In the MER of nonliving animals, we obtained high-contrast embossed images of fine bones, gadolinium oxide particles in blood vessels, and iodine-based microspheres in coronary arteries of approximately 100 µm diameter.

An energy-discriminating K-edge X-ray computed tomography (CT) system is useful for increasing the contrast resolution of a target region utilizing contrast media and for reducing the absorbed dose for patients. The CT system is of the first-generation type of detector using cadmium telluride (CdTe). CT is performed by repeated translations and rotations of an object. Penetrating X-ray photons from the object are detected by a CdTe detector, and event signals of X-ray photons are produced using charge-sensitive and shaping amplifiers. Both photon energy and energy width are selected out using a multichannel analyzer, and the number of photons is counted by a countercard. To perform energy discrimination, a low-dose-rate X-ray generator for photon counting was developed. Its maximum tube voltage and minimum tube current were 110 kV and 1 µA, respectively. In energy-discriminating CT, the tube voltage and tube current were 100 kV and 20 µA, respectively, and the X-ray intensity was 2.98 µGy/s at a distance of 1.0 m from the source and a tube voltage of 100 kV. The demonstration of enhanced gadolinium K-edge X-ray CT was carried out by selecting photons with energies just beyond the gadolinium K-edge energy of 50.3 keV.

A microfocus x-ray tube is useful to perform magnification digital radiography, including phase-contrast effects. The 100-m-focus x-ray generator consists of a main controller for regulating the 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 are 105 kV, 0.5 mA, and 50 W, respectively. Using a 3-mm-thick aluminum filter, the x-ray intensity is 26.0 Gy/s at 1.0 m from the source, with a tube voltage of 60 kV and a current of 0.50 mA. Because the peak photon energy is approximately 35 keV using the filter with a tube voltage of 60 kV, the bremsstrahlung x-rays are absorbed effectively by iodine-based contrast media with an iodine K-edge of 33.2 keV. Magnification angiography is performed by three-fold magnification imaging with a computed radiography sys-tem using iodine-based microspheres 15 m in diameter. In angiography of nonliving animals, we observe fine blood vessels approximately 100 m with high contrasts.