Yoshio Yanagihara

A new method for automatic identification of coronary arteries in standard biplane angiograms

A new computerized method for analyzing biplane coronary arteriograms was proposed. The method extracted the vessels in an image, detected branching points, and identified vessel segments according to their anatomical names. The method was applied to a pair of orthogonal projection images acquired in the right anterior oblique and left anterior oblique views. It recognized the corresponding vessel segments in the images and labeled them correctly by their anatomical names. For diameter measurement, a combined first and second derivative filter process was applied to the images along the skeleton lines of the extracted vessel segments. We also designed a method of representation in which vessel diameters measured in the two projection images could be displayed in a single image.

Measurement of distensibility of blood vessels using cineangiograms.

We developed a new, cineangiographic method to accurately measure the dynamic changes in the internal diameter of human arteries in vivo. Cine films were digitized at a spatial resolution of 4 microns/pixel, using a line image sensor. The vessel edges, with a Gaussian fit to a unilateral profile curve of the vessel, were determined with the aid of a computer program. We measured contrast-filled cylinder vessel models (2 to 7 mm in diameter) and evaluated precision, accuracy and linearity of the diameter measurement. A pulsatile vessel model of about 3.9 mm in internal diameter was used to examine the reliability of our method for detecting arterial wall motion. If the coefficient of variation of the vessel diameter determined cineangiographically was less than 2.2% we considered the cineangiograms sufficiently accurate to determine the internal vessel diameter and evaluate arterial distensibility.

Construction of structural edge map on chest radiograph using hough transformation and line connection

For computer diagnosis of a chest radiograph, we propose a method to make a structural edge map consisting of subclaviculars, heart, diagram, and ribs that have been extracted from a chest radiograph. On processing, the intensity of the edges of an input image was calculated by a derivative filter. Next, the possibility of lines and/or arcs was calculated by Hough transformation. This transformation was applied to 13 small areas for each of the organs in the image. A reconnection of lines and arcs representing the edges of the organs was performed, and a structural edge map was then constructed. As a result detection of subclaviculars, heart, diaphragms, and inferior edge lines of ribs was very good (ge; 79 percent). However, detection on superior edge lines was poor (= 55 percent).

A study of color transfer methods with color gradation and distribution of nature picture

The authors proposed a novel color transfer method based on color gradation which may represent human impression. The method has two steps of color transfer with color gradation mainly to transfer hue values and with the color distribution of gradation mainly to transfer saturation values and lightness values. The experiments of substituting or exchanging the color features of images are conducted. From the experimental results, the transferred image might have some similar impression of the reference image, even retaining impression of the object image.

A study of region extraction and system model on an observation system of time-sequenced 3-D CT images

For an observation system assisted for diagnosis of 3-D CT images consisting of time-sequenced multi slice tomograms, the refinement method to obtain the more precise region detection on which noise areas are reduced is proposed. The experimental results show that noise areas are reduced effectively. And also the system model refined by code refactoring is also proposed to be able to make the system having flexibility, also for that the proposed method is implemented.

Algorithm effects on computerized vessel analysis from digitized cine film and a new method of generating the centerline of a vessel

This study concerns methods of accurately measuring vessel diameters using coronary cineangiograms. Various edge detection filters are compared and a new method for determining the centerline of a vessel is developed. Vessel phantoms of different sizes are used to evaluate the precision and accuracy of an entropy filter, a combined first and second derivative filter, a Laplace-Gaussian filter, a first derivative filter and a second derivative filter. The entropy filter is found to yield the most reliable, precise and accurate data. For use in a clinical case with an irregular arterial wall, a new method of determining the centerline is delineated in which the centerline of a vessel (which we define as a set of points having equal distance to each of any two opposite edge lines) is calculated with images called distance maps. We find that this method of detecting the centerline provides an acceptable assessment of the centerline on visual evaluation.

Automatic detection method of stenotic lesions in coronary cineangiograms

A new image processing procedure enabling the automatic detection of coronary artery stenoses by cineangiography was developed. Detection of stenoses was performed using computer image processing by the following procedure. The path of the arteries was extracted by a subtraction method. The thresholding image was obtained from the subtraction image, and converted to a ‘thinning’ image, which represented the center line of the artery. For measurement of the arterial diameter, the vessel edges were determined by unilateral Gaussian fit to profile curves in sections perpendicular to the center line. Stenoses could then be detected on the basis of the normal diameter of artery estimated by Hough transformation. This method facilitates the detection of stenotic lesions from coronary cineangiograms.

A Study on a Method of Effective Memory Utilization on GPU Applied for Neighboring Filter on Image Processing

In this paper, the methods of implementing neighboring filters on newly supplied Graphics Processing Unit (GPU) are described. In general, neighboring filters are always utilized in image processing. Mainly in consideration of memory accesses, four methods implementing neighboring filtering are proposed and compared. The experimental result shows that one of the proposed methods (called “4X-block”) at the block size of 16 is the fastest among them, when loading and processing data in shared memory in GPU. It is also shown that this method is about 1.45X faster than the basic method implemented on GPU.

An Analysis Method of Measurement of Noise Spectrum in the Ultra Low Space Frequencies of a Radiographic Film by MEM.

The noise power spectra of radiographic film have been used to analyze the graininess of radiography. Furthermore, it has recently become clear that graininess analysis, especially at low space frequencies, is needed for quantitative evaluation of a radiographic screen/film system. This paper describes a method for analysis of film at low space frequencies that is based on the maximum entropy method (MEM). This method can determine the basic order of MEM to maximize the ratio of the order to the power spectrum at low space frequencies. Experimental results confirmed that the noise power to express the radiographic influence on films can be precisely measured at ultralow space frequencies.