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This study was conducted in order to develop a novel noninvasive system for measurement and imaging of the arterial oxygen density ratio (ODR) in the retinal microcirculation. We developed a system composed of two digital cameras with two different filters, which were attached to a fundus camera capable of simultaneously obtaining two images. Actual measurements were performed on healthy volunteer eyes (n = 61). A new algorithm for ODR measurement and pixel-level imaging of erythrocytes was constructed from these data. The algorithm was based on the morphological closing operation and the line convergence index filter. For system calibration, we compared and verified the ODR values in arterioles and venules that were specified in advance for 56 eyes with reproducibility. In 10 additional volunteers, ODR measurements and imaging of the arterial phase in the retinal microcirculation corresponding to changes in oxygen saturation of the peripheral arteries at normal breathing and breath holding were performed. Estimation of incident light to erythrocytes and pixel-level ODR calculation were achieved using the algorithm. The mean ODR values of arterioles and venules were 0.77 ± 0.060 and 1.02 ± 0.067, respectively. It was possible to separate these regions, calibrate at the pixel level, and estimate the arterial phase. In each of the 10 volunteers, changes in the arterial phase ODR corresponding to changes in oxygen saturation of the peripheral arteries were observed before and after breath holding on ODR images. The mean ODR in 10 volunteers was increased by breath holding (p

We developed a new artificial image enhancement system and evaluated its usefulness in controlling intraoperative reflection and enhancing of Brilliant Blue G (BBG) staining.The system was composed of three kinds of filters (a polarizing filter, a blue-enhancing filter, and a sharp-cut filter Y) and attached to the inferior surface of the operating microscope. Twenty-seven post-mortem extracted porcine eyes were used for a series of examinations. We performed surgery using the 23G-vitrectomy system with a halogen light and xenon lights and compared the reduction of intraoperative reflection under air condition and visibility and BBG contrast with and without this system. The evaluation of images was calculated in CIE 1976 (L*, a*, b*) color space (CIELAB) carried out by ImageJ software. The transmission of each filter and absorbance of BBG was measured by a spectrophotometer. We measured spectral irradiance at each wavelength about each filter from each light source with a spectroradiometer.Under both light sources, intraoperative reflection was controlled using a polarizing (PL) filter or combination of filters under air condition. Evaluation of the value of L* within the cutter surface was changed by 37.8 % under the halogen light, and 61.6 % (averaged) under the xenon light with inserted filters versus no filter. The BBG intensity difference was obtained with sharp-cut Y filter under both light source and PL with blue enhancing filter under the halogen light using each L*, a*, b* parameter with statistically significant (p0.01, 0.05). However, there was a relative decrease in the observation illuminance when the filter inserted according to the attenuation total spectral irradiance.This system can reduce intraoperative reflections under the air condition and obtain an excellent BBG staining intensity induced by various light sources.

This paper proposes a new method of extracting lines characterized as long and narrow bright regions, or curvilinear convex regions, in images. Generally, the contrast and the line width cause difficulty in extraction of ridgelines and skeletons. Therefore, this paper proposes the line convergence vector field model based on the intensity gradient vector field for a model of the curvilinear convex region. This model is independent of the contrast and the scale. Next, we propose the line convergence degree as a value of model evaluation for realizing the extraction of the curvilinear convex regions on the basis of this model. Then, we propose the Gradient-Angle-Weighted Hough Transform (GAWHT) for calculation of the evaluation value. Moreover, we obtain the theoretical value for the line convergence degree, as well as show its effectiveness in extraction of the curvilinear convex regions. We applied our method to artificial and practical images in experiment. The results show successfully extracted lines with a normalized index of the shape of the curvilinear convex region, demonstrating the effectiveness in extracting such regions free from the contrast and the scale. © 2000 Scripta Technica, Syst Comp Jpn, 31(3): 49–58, 2000

We proposed a new visualization procedure for oxygen saturation in retinal capillary vessels by spectroscopic imaging. Four-wavelength spectroscopic imaging was used for a mesurement of capillary vessel region.

We have proposed a new automatic visualization procedure based the ratio of optical densities (ODs) obtained at two different wavelength for the oxygen saturation imaging in human retinal vessels. This method utilized the morphological processing and the line convergence index filter to estimate the reflection image of outside vessels and extract the vessel structure from retinal image, respectively. In the experimental measurement, clear difference between retinal arteries and veins has been observed. In this study, the data processing technique of the line convergence index filter was applied to a color fundus image to investigate the ability of vessel extraction. In addition, four-wavelength imaging was proposed to evaluate oxygen saturation of the retinal capillary vessels and to decrease the influence of the melanin pigmentation.

We proposed a new visualization procedure for oxygen saturation of retinal blood vessels by spectroscopic imaging of two-wavelength images. Morphological processing and line convergence index filter were used for the calculating processing.

A new automatic visualization procedure for the oxygen saturation imaging from multi-spectral imaging of human retinal vessels has been proposed. Two-wavelength retinal fundus images at 545 and 560 nm, which were oxygen insensitive and oxygen sensitive, respectively, were captured by CCD cameras simultaneously through a beam splitter and interference filters. We applied a morphological processing technique to presume a distribution of incident light including the vessel parts and an optical density (OD) image of each wavelength image. And the OD ratio (OD 560 /OD 545 ) image was calculated as a relative indicator of oxygen saturation. Furthermore, processing of line convergence index filter was adopted to identify the retinal vessels. Clear diffe rence between retinal arteries and veins was observed in the automated imaging method. In addition, th e decrease of oxygen saturati on in the retinal artery without breathing could be monitored by the ODR. This method is possible to be applied to real-time monitoring for oxygen saturation of retinal vessels. Keywords: Oxygen saturation, Spectroscopic imaging, Retinal fundus image, Line convergence index filter

The temporal image subtraction technique was applied to bone scintigraphy, using Photoshop (commercially available image processing software) and Morpher (public domain warping software). For the temporal subtraction images, 81 subtraction images (19 cases) were prepared by a method used to subtract the previous images from the current ones. Registration of the current and previous images was performed by manual operation using Photoshop, and warping was done using the warping function of Morpher. In addition, difference images prepared after correcting the distributions of radioactive isotopes of the current and previous images using the count of the pelvic region were also examined. Compared with manual operation, alignment of images by warping improved registration and reduced the generation of pseudo-images of subtraction images. The rate of identification of abnormal accumulation-enhanced regions and subjective evaluation by doctors was improved for warping more than for manual operation. Furthermore, abnormal hot regions, which are difficult to find in film images, could be found in three subtraction images. In addition, it was confirmed that abnormal hot regions become more visible in many cases by preparing subtraction images after correcting the count between images using the count of the pelvic region. Thus, it is suggested that the temporal image subtraction technique in bone scintigraphy enables more accurate observation of enhancement of or changes in abnormal hot regions, which will support diagnostic reading. It is considered that enhancement of or changes in abnormal hot regions will be more accurately understood through further detailed discussion in the future.

In this work, we propose a new filter to detect and enhance lines in real images with varying contrast. It is robust against noise disturbances and also its output does not depend on the contrast. We first define the line-convergence vector field model based on the distribution of gradient vector orientation. Next we define a criterion index called the line-convergence degree to evaluate the likelihood of the existence of a line. The output of the proposed filter is defined as the average of line-convergence degrees in a region which is adapted to the gradient vector distribution. The filter output is a function of only gradient vector orientation and it is free from absolute intensity and relative contrast variations. Experimental results using artificial images and real images show the effectiveness of the proposed filter.