3-D analysis of microvascular architecture of the spleen with ultra-high-resolution for partial splenic embolization

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.