KEYWORDS: Spleen, Image segmentation, Data acquisition, 3D image processing, Data processing, 3D acquisition, Distance measurement, Synchrotron radiation, X-rays, Visualization
The purpose of this study is to clarify embolic effects of embolic agents for partial splenic embolization. Partial splenic
embolization is a minimally invasive technique for splenomegaly. However, embolic agents have been empirically
chosen because embolic effects have never been studied quantitatively. We have constructed a quantitative 3-D analysis
system of microvascular architecture. The system has consisted of data acquisition, segmentation, and measurement of
diameters of end arterioles. 3-D volumetric data of samples with ultra-high resolution was acquired using a synchrotron
radiation CT constructed in SPring-8. Segmented microvascular architecture was obtained applying an adaptive region
growing method. This method is a kind of dynamic thresholding to cope with nonuniformity of the voxel intensity. To
recognize end of arterioles, distance map from initial point placed at the root of the major trunk have been generated
applying single-seeded coding. Diameters of vasculature are measured using single-seeded clusters which are formed
from the same single-seeded code in the distance map and Euclidean distance transform which measures the minimum
distances between each voxel and vascular boundary. Diameters of end arterioles are obtained choosing the maximum
value in the result of Euclidian distance transform in the most distant cluster. In this study, we found diameters of
embolized end arterioles were ranging from 48 to 72 micrometers with the analysis system. We have concluded that a
quantitative 3-D analysis system have been successfully developed for microvascular architecture. A new approach to
establish theoretical basis of embolization therapy with microspheres have been provide owing to the system.
We have previously reported a synchrotron radiation (SR) microtomography system constructed at the bending magnet beamline at the SPring-8. This system has been applied to the lungs obtained at autopsy and inflated and fixed by Heitzman’s method. Normal lung and lung specimens with two different types of pathologic processes (fibrosis and emphysema) were included. Serial SR microtomographic images were stacked to yield the isotropic volumetric data with high-resolution (12 μm3 in voxel size). Within the air spaces of a subdivision of the acinus, each voxel is segmented three-dimensionally using a region growing algorithm (“rolling ball algorithm”). For each voxel within the segmented air spaces, two types of voxel coding have been performed: single-seeded (SS) coding and boundary-seeded (BS) coding, in which the minimum distance from an initial point as the only seed point and all object boundary voxels as a seed set were calculated and assigned as the code values to each voxel, respectively. With these two codes, combinations of surface rendering and volume rendering techniques were applied to visualize three-dimensional morphology of a subdivision of the acinus. Furthermore, sequentially filling process of air into a subdivision of the acinus was simulated under several conditions to visualize the ventilation procedure (air flow and diffusion). A subdivision of the acinus was reconstructed three-dimensionally, demonstrating the normal architecture of the human lung. Significant differences in appearance of ventilation procedure were observed between normal and two pathologic processes due to the alteration of the lung architecture. Three-dimensional reconstruction of the microstructure of a subdivision of the acinus and visualization of the ventilation procedure (air flow and diffusion) with SR microtomography would offer a new approach to study the morphology, physiology, and pathophysiology of the human respiratory system.
We have applied a synchrotron radiation computed tomography (SRCT) system to the lung specimens and evaluated its resolving power compared with the histopathologic appearances, precisely. An SRCT system has been constructed in the bending magnet beamline at the SPring-8. The system consists of a double-crystal monochromator, a rotating sample stage, a fluorescent screen, and a charge-coupled device (CCD) array detector (1024 X 1024 pixels with 12 X 12 micrometers 2 pixel size). The energy of the x-ray beam was tuned to 9 - 12 keV. The lungs obtained at autopsy were inflated and fixed by Heitzman's method. A cylindrical specimen (diameter, approximately 8 mm; height, 15 - 25 mm) was rotated in the plane parallel to the beam. The detected signal was transferred to a workstation; then, SRCT images (matrix size, 800 X 800 pixels) were reconstructed by a filtered back- projection. Finally, 6 - 12 micrometer-thick microscopic sections were obtained and stained with hematoxylin and eosin for histopathologic examination. SRCT images well depicted the terminal bronchiole, respiratory bronchiole, alveolar duct, alveolar sac, and alveolar septum. Different pathologic processes (alveolar hemorrhage, alveolitis) demonstrated on SRCT images were well correlated with the histopathologic appearances.
We have designed an image compression scheme based on multiresolution decomposition using the quadrature mirror filters (QMFs), and applied it to chest radiographs. In order to assess the preservation of diagnostic image quality, we performed image review study using a diagnostic workstation. From the result of review by diagnostic radiologists, our method may be available in clinical practice.
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