Takashi Obi

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This study was performed to examine the usefulness of medical endoscopic imaging utilizing narrow-band illumination. The contrast between the vascular pattern and the adjacent mucosa of the underside of the human tongue was measured using five narrow-band illuminations and three broadband illuminations. The results demonstrate that the pathological features(More)
True three-dimensional (3-D) volume reconstruction from fully 3-D data in positron emission tomography (PET) has only a limited clinical use because of its large computational burden. Fourier rebinning (FORE) of the fully 3-D data into a set of 2-D sinogram data decomposes the 3-D reconstruction process into multiple 2-D reconstructions of decoupled 2-D(More)
The range of the reproducible color, i.e., color gamut, of the conventional display devices such as CRTs (cathode ray tubes) and LCDs (liquid crystal displays) is sometimes insufficient for reproducing the natural color of an object through color imaging systems. In this paper, six-primary color display is presented to reproduce the expanded color gamut, by(More)
A high-performance brain PET scanner, jPET-D4, which provides four-layer depth-of-interaction (DOI) information, is being developed to achieve not only high spatial resolution, but also high scanner sensitivity. One technical issue to be dealt with is the data dimensions which increase in proportion to the square of the number of DOI layers. It is,(More)
Nonlinear estimation method of spectral reflectance from camera responses is proposed. The proposed method minimizes the mean square error of spectral reflectance when the reflectance can be regarded as a random sequence of Gaussian mixture distribution. In computer simulations, 168 samples of spectral reflectance from a color chart are estimated from their(More)
The projection X-ray microscope utilises a very small X-ray source emitted from a thin (0.1-3 microm) target metal film excited by the focused electron beam of a scanning electron microscope. When an object is placed just below the target metal film, the diverging X-rays enlarge the shadow of the object. Because no X-ray optics such as a zone-plate is used,(More)
To reproduce the natural color of an object through color imaging systems, the range of the reproducible color, i.e., the color gamut, of the color display devices must be expanded, because the color gamut of current display devices such as cathode ray tubes (CRTs) and liquid crystal displays (LCDs) is insufficient. We present a new method to enlarge the(More)
In the conventional color reproduction based on the colo-rimetric match for a standard observer, color mismatch can be perceived if the color matching functions of the observer deviate from those of the standard observer; this phenomenon is known as observer metamerism. Recently, multi-primary display, using more than three-primary colors, has attracted(More)