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Biomedical subjects

F Toyofuku

Publications and source records attributed to F Toyofuku.

10 recordsLinked to original sources
PubMed1993

A study of the effects of lead foil in dental X-ray film packets on radiographic image quality.

The role of lead foil in protecting film from image degradation due to back-scattered radiation was studied. The effects of low-scattering (polystyrene foam) and tissue-equivalent (Lucite) materials on relative speed and modulation transfer factor (MTF) of the front and back films from Kodak DF-57 double film packets were evaluated. The relative speed of the back film with polystyrene foam behind the film was about 10% faster with lead foil. However, when Lucite was placed behind the film, lead foil eliminated the effect of scattered radiation on film density, MTF, was decreased by the presence of lead foil when polystyrene foam was placed behind the film. With Lucite, however, lead foil improved the MTF value, which was decreased by the scattered radiation at spatial frequencies over 5 cycle mm-1. These results suggest that lead foil itself causes scattered or secondary radiation and affects film speed and resolution. However, it also protects the film from scattered radiation from tissue behind the film and results in improvement in resolution.

Analysis of Variance↗
PubMed1990

Image analysis of microsialograms of the mouse parotid gland: a study of the effect of contrast medium in experimentally induced sialoadenitis.

Quantitative image analysis of mouse parotid gland sialograms was achieved by conversion of the digital image to a histogram. The relationships between histogram pattern, microsialographic appearance and the amount of contrast medium infused were compared in normal glands and in experimentally induced sialoadenitis. Differences in the pattern enabled a distinction to be drawn between poor sialographic technique and genuine pathology.

Animals↗
PubMed1986

Synchrotron radiation at the Photon Factory for non-invasive coronary angiography: experimental studies.

Synchrotron radiation available at the Photon Factory, National Laboratory for High Energy Physics, provides a new X-ray source which is highly suitable for K-edge subtraction. This is due to its high intensity, its parallelism and its monochromaticity, available in a monochromator system. Experiments were performed using wiggler synchrotron radiation. Since the beam size is relatively-small for in-vivo imaging, a phantom coupled with a detector was moved horizontally using a scanning table. K-edge subtraction was successfully applied both to the coronary artery phantom filled with barium sulphate, and to rat angiography using iodine contrast material. The potential use and value of energy subtraction was successfully demonstrated.

Animals↗
PubMed1985

Whole-body irradiation inhibits the escape phenomenon of osteoclasts in bones of calcitonin-treated rats.

The escape phenomenon is characteristic of osteoclastic bone resorption in organ cultures, and calcitonin only transiently inhibits parathyroid hormone (PTH)-stimulated resorption. The present study demonstrated that the transient inhibition of osteoclastic bone resorption, a phenomenon reminiscent of escape, occurs in the bones of calcitonin (ECT)-treated rats and that whole-body irradiation inhibits this escape. Rats were treated with daily subcutaneous injections of ECT for 72 h. At 24 h ECT decreased the incidence of osteoclast profiles with ruffled borders both in the growth plate-metaphysis junction (GPMJ) and the metaphyseal trabecular bone region (MT). However, by 72 h the incidence in the MT had been restored to the level of the control. The trabecular bone volume in the ECT-treated bone did not differ significantly from the control value. Whole-body irradiation (600 rad) before the first injections of ECT prevented the re-activation of the ruffled border formation and increased the trabecular bone volume at 72 h. Irradiation diminished the number of osteoclasts in the ECT-treated bones to the level of the control. ECT-treated bones contained a greatly increased number of macrophage-like cells (MO). Irradiation prevented this ECT-induced increase in the number of MO. These results strongly suggest that the escape phenomenon in vivo involves the calcitonin-induced proliferation of cells in the mononuclear phagocyte system, with resultant increases in the number of osteoclasts and in the bone resorption activity of osteoclasts.

Animals↗
PubMed1984

[The applicability of pions to cancer radiotherapy. III. Measurement of x-ray and gamma-rays by NaI detector for the determination of the peak-region in pi- meson exposure].

A method of externally observing the stop-region of pi- meson for monitoring during exposure to a patient is discussed. Negative pi mesic X-rarys, gamma-rays and neutrons are emitted from the region where pi- mesons stop and produce stars. These radiations can be detected outside the exposed patient. Water phantom as normal tissue equivalent material was exposed by pi- mesons at various depths. The resulting gamma-ray yields were determined by counting the gamma-rays in coincidence with incident pi- mesons using a sodium iodide (NaI) detector. This type of gamma-ray measuring system is useful to make sure that the peak position of the depth-dose distribution in the patient is exactly situated at the desired one during exposure. It is suggested that the scintillation camera with a multiholecollimator is a powerful and convenient tool for the two dimensional peak positioning.

Gamma Rays↗
PubMed1979

[Microdosimetry of in-flight pi-beams (author's transl)].

Microdosimetry of in-flight pi-beams was performed at the T1 channel of National Laboratory for High Energy Physics (KEK), Tsukuba, Japan. Distributions of lineal energy (y) in-flight pi-beams having six momentum values from 120 MeV/c to 1000 MeV/c were measured with an LET counter which simulates 2 micron sphere of soft tissue filled with the methane base tissue equivalent gas. Frequency spectra were obtained in the range of 1.6 less than y less than 430 keV/micron. Fractional dose y . d(y), cumulative dose D(y), and mean lineal energy were calculated from these spectra; then momentum dependences were investigated. These absolute values have little physical application because of the lack of data for y less than 1.6 keV/micron. However, the general trends of y distribution in momentum dependence were found, qualitatively. As the momentum becomes smaller, the rate of high y component in the dose increased.

Elementary Particles↗