Yoshiharu Tamakawa

The circuit of Papez in mesial temporal sclerosis: MRI.

Abstract We looked at abnormalities in the circuit of Papez in patients with the mesial temporal sclerosis (MTS). We reviewed the MRI studies of 15 patients with probable MTS, seeking changes in the fornix, mamillary body, mamillothalamic tract, thalamus and cingulate and parahippocampal gyri. We correlated any abnormalities with each other and with clinical severity. Atrophy and/or signal change in one or more structures in the circuit of Papez were found in five patients. They involved the parahippocampal gyri in all five, the fornices in four, mamillary bodies in three, the thalamus in two and the cingulate gyrus in one. Changes in the fornix, mamillary body, thalamus or cingulate gyrus were always accompanied by hippocampal and parahippocampal atrophy. The patients with abnormalities of the circuit of Papez did not have more severe epilepsy than those without. Changes in the parahippocampal gyrus, including the entorhinal cortex and subiculum, in which forniceal fibres originate, may be crucial in causing abnormalities more distally in the circuit.

Repetitive flash x‐ray generator utilizing a simple diode with a new type of energy‐selective function

The construction and the fundamental studies of a repetitive flash x‐ray generator having a simple diode with an energy‐selective function are described. This generator consisted of the following components: a constant high‐voltage power supply, a high‐voltage pulser, a repetitive high‐energy impulse switching system, a turbo molecular pump, and a flash x‐ray tube. The circuit of this pulser employed a modified two‐stage surge Marx generator with a capacity during main discharge of 425pF. The x‐ray tube was of the demountable‐diode type which was connected to the turbo molecular pump and consisted of the following major devices: a rod‐shaped anode tip made of tungsten, a disk cathode made of graphite, an aluminum filter, and a tube body made of glass. Two condensers inside of the pulser were charged from 40 to 60 kV, and the output voltage was about 1.9 times the charging voltage. The peak tube voltage was primarily determined by the anode‐cathode (A‐C) space, and the peak tube current was less than 0.6 k...

Repetitive flash x‐ray generator having a high‐durability diode driven by a two‐cable‐type line pulser

The fundamental studies of a repetitive soft flash x‐ray generator having a high‐durability diode for high‐speed radiography in biomedical and technological fields are described. This generator consisted of the following essential components: a constant negative high‐voltage power supply, a line‐type high‐voltage pulser with two 10 m coaxial‐cable condensers, each with a capacity of 1.0 nF, a thyratron pulser as a trigger device, an oil‐diffusion pump, and a flash x‐ray tube. The x‐ray tube was of a diode type which was evacuated by an oil‐diffusion pump with a pressure of approximately 6.7×10−3 Pa and was composed of a planar tungsten anode, a planar ferrite cathode, and a polymethylmethacrylate tube body. The space between the anode and cathode electrodes (AC space) could be regulated from the outside of the tube. The two cable condensers were charged from −40 to −60 kV by a power supply, and the output voltage was about −1.5 times the charged voltage. Both the first peak voltage and current increased a...

Fundamental Study on a Long-Duration Flash X-Ray Generator with a Surface-Discharge Triode

Fundamental studies on a long-duration flash X-ray generator are described. This generator consisted of the following components: a high-voltage power supply with a maximum voltage of 100 kV, an energy-storage condenser of 500 nF, a main discharge condenser of 10 nF, a turbo molecular pump, a thyratron pulser as a trigger device, and a surface-discharge triode. The effective pulse width was less than 30 µs, and the X-ray intensity approximately had a value of 0.6 µC/kg at 1.0 m per pulse with a charged voltage of 60 kV. The maximum tube voltage was equivalent to the initial charged voltage of the condenser, and the peak tube current was less than 40 A. With this generator, we could obtain stable X-ray intensity maximized by preventing damped oscillations of the tube voltage and current.

Pasteurized intercalary autogenous bone graft: radiographic and scintigraphic features.

Abstract  Objective. Pasteurized autogenous bone graft sterilized at a low temperature (60°C) is one option for reconstruction after resection of bone and soft tissue tumors. The purpose of this investigation was to assess the normal and abnormal radiographic and scintigraphic findings of pasteurized intercalary autogenous bone graft after resection of bone and soft tissue sarcomas. Design. This was a retrospective evaluation of the radiography and bone scintigraphy findings in patients after treatment of bone and soft tissue sarcomas using an intercalary pasteurized autogenous bone graft. Patients. Among 10 consecutive patients, eight had intercalary grafts, and they constitute the subjects of this study. All available radiography and bone scintigraphy findings were reviewed for the healing process and the possibility of complications. Results and conclusions. Healing and incorporation of the graft were observed in five patients during the follow-up, but the other three did not heal satisfactorily. Rapid incorporation of pasteurized autogenous bone graft can be demonstrated by means of radiography and bone scintigraphy.

Virtual CT endoscopy of ossicles in the middle ear

The purpose of this study is to evaluate how virtual computed tomography (CT) endoscopy may help in assessing ossicles in the middle ear. Our series consisted of 96 ears of 68 consecutive patients with conducting hearing loss. All examinations were performed with a high-resolution spiral CT using axial and direct coronal planes of the temporal bone. Perspective virtual endoscopy was processed using the virtual endoscopic software. Superstructure of the stapes was difficult to evaluate on the virtual endoscopy; however, virtual endoscopy of the middle ear provides further information on the pathological conditions including congenital anomaly, posttraumatic, and inflammatory processes.

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

The construction and fundamental studies are described for a subkilohertz 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 μs, and the X-ray intensity was about 0.47 μC 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.

High-speed soft x-ray techniques

The construction and the characteristics of recent high- speed soft x-ray generators designed by the authors are described. The flash x-ray generators having cold-cathode radiation tubes are three types as follows: (1) soft generator utilizing an ignitron, (2) plasma generator for producing high-intensity characteristic x rays, and (3) water-window generator having a high-durability fermite capillary. In general, when we employed the flash x-ray generators with diodes, the pulse widths had values of less than 200 ns. Next, the x-ray duration was almost equivalent to the durations of the tube voltage and current during their damped oscillations when the water-window generator was employed. The maximum tube voltage was increased up to 100 kV, and the tube currents achieved with high-intensity generators were more than 10 kA. In order to obtain kilohertz-range repetition rates, we have developed two types of stroboscopic x-ray generators having hot-cathode tubes as follows: (4) low-photon-energy generator utilizing and triode and (5) high-photon-energy generator with a diode. As the duration was controlled in a microsecond range by using the low-photon-energy generator, sufficient x-ray intensifier for the normal radiography were obtained. The maximum photon energy could be increased up to about 200 keV by the high-photon-energy generator having a double transformer. Using these generation, we performed high-speed soft radiography.

MRI of myositis ossificans circumscripta

Myositis ossificans circumscripta (or pseudomalignant osseous tumor of soft tissue) may be confused with malignant neoplasms if there is no clear history of trauma. Two cases are presented in which magnetic resonance imaging (MRI) clearly demonstrates disproportionally extensive abnormal signal intensity along the course of muscle fibers. Although the specificity of this finding is uncertain, MRI enhances the level of confidence in diagnosing myositis ossificans.

Kilohertz‐range flash x‐ray generator utilizing a triode in conjunction with an extremely hot cathode

The construction and the fundamental studies of a kilohertz‐range flash x‐ray generator having a triode in conjunction with an extremely hot cathode are described. This generator consisted of the following components: a constant‐high voltage power supply, an energy storage condenser of 100 nF, a constant high‐voltage power supply for regulating an initial grid voltage of −1.6 kV, a grid pulser, and an x‐ray tube. The x‐ray tube was of an enclosed‐triode type and consisted 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 of tungsten, a grid made from tungsten wire, and a glass tube body. The energy storage condenser was charged from 50 to 70 kV, and the electric charges in the condenser were discharged repetitively to the x‐ray tube by the grid electrode driven by the grid pulser. The temperature of the filament was about 2000 K, and the cathode current was primarily controlled by the gri...